Mitsubishi QCPU, Q Mode, QnACPU Programming Manual

• SAFETY PRECAUTIONS •

(You must read these cautions before using the product)

As for the use of the product, please carefully read this manual and the related manuals introduced later. Also, please pay attention to safety adequately and manage the product correctly. The safety cautions shown in this manual apply to the product only. In this manual, the safety precautions are ranked as "DANGER" and "CAUTION".

DANGER

CAUTION

Note that the !CAUTION level may lead to a serious consequence according to the circumstances. Always follow the instructions of both levels because they are important to personal safety.

Please store this manual in order to read whenever it is necessary. Also, always forward this manual to the end users.

Indicates that incorrect handling may cause hazardous conditions, resulting in death or severe injury.

Indicates that incorrect handling may cause hazardous conditions, resulting in medium or slight personal injury or physical damage.

[Design Precautions]

DANGER

• Install a safety circuit external to the programmable controller that keeps the entire system safe

even when there are problems with the external power supply or the programmable controller. Otherwise, it may cause an output error or an operating error, resulting in an accident. (1) Configure a circuit such as an emergency stop circuit and a protective circuit on the outside

of the programmable logic controller.

(2) When the programmable controller detects the following problems, it will stop calculation

and turn off all outputs.

• An overcurrent protective device or an overvoltage protective device in a power supply module start running.

• A watchdog timer error or others is detected with self-checking function in the programmable controller CPU.

All outputs may be turned on, when an error occurs in the part of I/O controlling or others

that the programmable controller CPU cannot detect. Build a fail safe circuit exterior to the programmable controller to keep the entire system safe. As for the fail safe circuit, refer to a CPU module User’s Manual.

• Configure a circuit that turns on an external power supply when the main power of

programmable controller is turned on. If the external power supply is turned on first, it could result in an output error or an operating error.

A - 1

[Design Precautions]

DANGER

• When connecting a peripheral device to the CPU module or connecting a personal computer or

others to an intelligent function module, always configure an interlock circuit in the sequence program to ensure that the whole system always operate safely. Also, make sure to read this manual carefully and check all operations for safety first before executing other control (program changes, changes of operation status (and status control)) of the operating sequence. Especially for the control described above on the remote sequence from an external device, an immediate action may not be taken for a programmable controller’s trouble due to a data communication fault. Configure the interlock circuit in the sequence program. Simultaneously a recovery method for system, in which a data communications fault occurs, should be determined between the external device and the programmable controller CPU.

[Startup/Maintenance Precaution]

CAUTION

• Make sure to read this manual carefully and check all operations for safety first before

connecting a peripheral device to an operating CPU module online (particularly program changes, forced outputs, and changes of operation status). Otherwise, an operating error may cause damage or problems with the modules.

A - 2

REVISIONS

* The manual number is given on the bottom left of the back cover.

Print Date * Manual Number Revision

Dec., 1999 SH (NA) 080040-A First edition

Jun., 2001 SH (NA) 080040-B

Partial addition About Manuals, Chapter 1, Chapter 2, Section 2.1, 3.1, 3.2, 3.3, 3.3.1,

4.2.3, 4.3.2, 4.3.5, Chapter 5, Section 5.1, 5.2, Chapter 6, Chapter 7, Section 8.1, 8.2

Apr., 2002 SH (NA) 080040-C

Correction Chapter 1, Chapter 7, Section 8.1, 8.2, 8.3, 8.4, 8.5

Jan., 2003 SH (NA) 080040-D • Addition of use of Basic model QCPU

• Addition of explanation of incomplete derivative

Overall reexamination

Mar., 2003 SH (NA) 080040-E • Addition of explanation of incomplete derivative to High Performance

model QCPU

Dec., 2003 SH (NA) 080040-F

Jun., 2004 SH (NA) 080040-G

Sep., 2006 SH (NA) 080040-H

Apr.,2007 SH (NA) 080040-I

Mar.,2008 SH (NA) 080040-J

Correction Chapter 1

Addition of Redundant CPU

Partial addition About Manuals, Chapter 1, Chapter 2, Section 2.1, 3.1.1, 3.1.3, 3.2.1,

3.2.3, 4.3.5, 5.1, 5.2, Chapter 6, Chapter 7, Section 8.1.1 to 8.1.4, Section 9.1.1 to 9.1.5, 9.2, Appendix 1

Partial addition

Section 4.2.5, Appendix 2

Addition of Universal model QCPU

Addition module

Q02UCPU, Q03UDCPU, Q04UDHCPU, Q06UDHCPU

Partial correction GENERIC TERMS AND ABBREVIATIONS USED IN THIS MANUAL, Chapter 1, Chapter 2, Section 2.1, 3.1.1, 3.1.3, 3.2.1, 3.2.3, 5.1, Chapter 6, Chapter 7, 8.1.1 to 8.1.5, 9.1.1 to 9.1.5, Appendix 1

Addition of Universal model QCPU

Addition module

Q13UDHCPU, Q26UDHCPU

Partial correction

GENERIC TERMS AND ABBREVIATIONS USED IN THIS MANUAL, Section 2.1, Appendix 1

A - 3

* The manual number is given on the bottom left of the back cover.

Print Date * Manual Number Revision May,2008 SH (NA) 080040-K

Revision due to the addition of Process CPU and Universal model QCPU

Addition module

Q03UDECPU, Q04UDEHCPU, Q06UDEHCPU, Q13UDEHCPU, Q26UDEHCPU

Q02PHCPU, Q06PHCPU

Partial correction

GENERIC TERMS AND ABBREVIATIONS USED IN THIS MANUAL,

Section 2.1, Appendix 1

Japanese Manual Version SH-080022-K

This manual confers no industrial property rights or any rights of any other kind, nor does it confer any patent licenses. Mitsubishi Electric Corporation cannot be held responsible for any problems involving industrial property rights which may occur as a result of using the contents noted in this manual.

A - 4

INTRODUCTION

Thank you for choosing the Mitsubishi MELSEC-Q/QnA Series of Programmable Logic Controllers. Please read this manual carefully so that the equipment is used to its optimum. A copy of this manual should be forwarded to the end User.

SAFETY CAUTIONS ......................................................................................................................................A- 1

REVISIONS .....................................................................................................................................................A- 3

CONTENTS.....................................................................................................................................................A- 5

About Manuals ................................................................................................................................................A- 8

Generic Terms and Abbreviations Used in This Manual ..............................................................................A-11

1. GENERAL DESCRIPTION 1 – 1 to 1 - 3

1.1 PID Processing Method ........................................................................................................................... 1 - 3

2. SYSTEM CONFIGURATION FOR PID CONTROL 2 - 1 to 2 - 2

2.1 Applicable PLC CPU ................................................................................................................................ 2 - 2

3. PID CONTROL SPECIFICATIONS 3 - 1 to 3 - 14

3.1 PID Control by Incomplete derivative ...................................................................................................... 3 - 1

3.1.1 Performance specifications............................................................................................................... 3 - 1

3.1.2 PID operation block diagram and operation expressions ................................................................ 3 - 2

3.1.3 PID control instruction list.................................................................................................................. 3 - 3

3.2 PID Control by Complete Derivative........................................................................................................ 3 - 8

3.2.1 Performance specifications............................................................................................................... 3 - 8

3.2.2 PID operation block diagram and operation expressions ................................................................ 3 - 9

3.2.3 PID control instruction list................................................................................................................ 3 - 10

4. FUNCTIONS OF PID CONTROL 4 - 1 to 4 - 14

4.1 Outline of PID Control .............................................................................................................................. 4 - 1

4.2 Functions of PID Control.......................................................................................................................... 4 - 2

4.2.1 Operation method.............................................................................................................................. 4 - 2

4.2.2 Forward operation and reverse operation ........................................................................................ 4 - 2

4.2.3 Proportionate operation (P operation) .............................................................................................. 4 - 4

4.2.4 Integrating operation (I operation) .................................................................................................... 4 - 5

4.2.5 Differentiating operation (D operation) ............................................................................................. 4 - 6

4.2.6 PID operation..................................................................................................................................... 4 - 8

4.3 Other Functions........................................................................................................................................ 4 - 9

4.3.1 Bumpless changeover function ........................................................................................................ 4 - 9

4.3.2 MV higher/lower limit control function ............................................................................................. 4 - 10

4.3.3 Monitorning PID control with the AD57(S1) (QnACPU only)......................................................... 4 - 11

4.3.4 Function for transfer to the SV storage device for the PV in manual mode .................................. 4 - 12

4.3.5 Changing the PID control data or input/output data setting range (QCPU only) ......................... 4 – 13

A - 5

5. PID CONTROL PROCEDURE 5 - 1 to 5 - 24

5.1 PID Control Data ...................................................................................................................................... 5 - 4

5.1.1 Number of loops to be used and the number of loops to be executed in a single scan ............... 5 - 15

5.1.2 Sampling cycle ................................................................................................................................5 - 16

5.2 I/O Data .................................................................................................................................................. 5 - 18

6. PID CONTROL INSTRUCTIONS 6 - 1 to 6 - 2

7. HOW TO READ EXPLANATIONS FOR INSTRUCTIONS 7 - 1 to 7 - 2

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES 8 - 1 to 8 - 16

8.1 PID Control Instructions ........................................................................................................................... 8 - 1

8.1.1 PID control data settings S.PIDINIT,SP.PIDINIT .......................................... 8 - 2

8.1.2 PID operation S.PIDCONT,SP.PIDCONT................................... 8 - 3

8.1.3 Operation stop/start of designated loop no. S.PIDSTOP,SP.PIDSTOP,S.PIDRUN,SP.PIDRUN

.................................................................................................................................................................... 8 - 5

8.1.4 Parameter change at designated loop S.PIDPRMW,SP.PIDPRMW ................................8 - 6

8.2 PID Control Program Examples .............................................................................................................. 8 - 8

8.2.1 System configuration for program examples.................................................................................... 8 - 8

8.2.2 Program example for automatic mode PID control.......................................................................... 8 - 9

8.2.3 Program example for changing the PID control mode between automatic and manual .............. 8 - 13

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES 9 - 1 to 9 - 28

9.1 PID Control Instructions ........................................................................................................................... 9 - 1

9.1.1 PID control data settings PIDINIT,PIDINITP................................................. 9 - 2

9.1.2 PID control PIDCONT,PIDCONTP.......................................... 9 - 3

9.1.3 Monitoring PID control status (QnACPU only) PID57,PID57P....................................................... 9 - 5

9.1.4 Operation stop/start of designated loop no. PIDSTOP,PIDSTOPP,PIDRUN,PIDRUNP ......... 9 - 8

9.1.5 Parameter change at designated loop PIDPRMW,PIDPRMWP ....................................... 9 - 9

9.2 PID Control Program Examples (QCPU only) ...................................................................................... 9 - 11

9.2.1 System configuration for program examples.................................................................................. 9 - 11

9.2.2 Program example for automatic mode PID control........................................................................ 9 - 12

9.2.3 Program example for changing the PID control mode between automatic and manual .............. 9 - 15

9.3 PID Control Program Examples (QnACPU only).................................................................................. 9 - 19

9.3.1 System configuration for program examples.................................................................................. 9 - 19

9.3.2 Program example for automatic mode PID control........................................................................ 9 - 20

9.3.3 Program example for changing the PID control mode between automatic and manual ............. 9 – 24

A - 6

APPENDIX APP - 1 to APP - 3

Appendix 1 Processing Time List .............................................................................................................APP - 1

Appendix 2 Anti-Reset Windup Measure .................................................................................................APP - 3

A - 7

About Manuals

Related Manuals

The following manuals are also related to this product. In necessary, order them by quoting the details in the tables below.

Manual Name

Manual Number

(Model Code)

QCPU User's Manual (Function Explanation, Program Fundamentals)

Describes the functions, programming procedures, devices, etc. necessary to create programs.

(Sold separately)

QnACPU Programming Manual (Fundamentals)

Describes how to create programs, the names of devices, parameters, and types of program.

(Sold separately)

QCPU (Q mode) /QnACPU Programming Manual (Common Instructions)

Describes how to use sequence instructions, basic instructions, and application instructions.

(Sold separately)

QnACPU Programming Manual (Special Function)

Describes the dedicated instructions for special function modules available when using the

Q2ACPU(S1), Q3ACPU, and Q4ACPU. (Sold separately)

QnACPU Programming Manual (AD57 Instructions)

Describes the dedicated instructions for controlling an AD57(S1) type CRT controller module available

when using the Q2ACPU(S1), Q3ACPU, or Q4ACPU. (Sold separately)

SH-080484ENG

(13JR73)

IB-66614

(13JF46)

SH-080039

(13JF58)

SH-4013

(13JF56)

IB-66617

(13JF49)

A - 8

Before reading this manual, refer to the user's manual of the used CPU module or the QnACPU Programming Manual (Fundamentals), and confirm which programs, I/O processing, and devices can be used with the used CPU module.

(1) When QCPU is used

QCPU (Q mode)/ QnACPU Programming Manual (Common Instructions)

Describes the instructions other than those given on the ri

ht.

This manual

QCPU (Q mode)/ QnACPU Programming Manual (PID Control Instructions)

Describes the instructions used for PID control.

QCPU User's Manual (Function Explanation, Program Fundamentals)

QCPU (Q mode)/ QnACPU Programming Manual (SFC)

Describes SFC.

Describes the functions, executable programs, I/O processing and device names of the QCPU.

QCPU (Q mode) Programming Manual (MELSAP-L)

Describes MELSAP-L.

QCPU (Q mode) Programming Manual (Structured Text)

Describes the structured text.

A - 9

(2) When QnACPU is used

QCPU (Q mode)/ QnACPU Programming Manual (Common Instructions)

Describes the instructions other than those given on the right.

QnACPU Programming Manual (Special Function Modules)

Describes the instructions for the special function modules such as the AJ71QC24 and AJ71PT32-S3.

QnACPU Programming Manual (Fundamentals)

QnACPU Programming Manual (AD57 Commands)

Describes the AD57 commands for controlling the AD57/AD58.

Describes the programs, I/O processing, device names, etc. that can be executed by the QnACPU.

This manual

QCPU (Q mode)/ QnACPU Programming Manual (PID Control Instructions)

Describes the instructions used for PID control.

QCPU (Q mode)/ QnACPU Programming Manual (SFC)

Describes SFC.

Q4ARCPU only

Q4ARCPU Programming Manual (Application PID Instructions)

Describes the instructions used for applied PID control.

A - 10

Generic Terms and Abbreviations Used in This Manual

This manual uses the following generic terms and abbreviations unless otherwise described.

Generic term/abbreviation Description of generic term/abbreviation

CPU module

QnACPU

QnA

Q4AR Abbreviation of Q4ARCPU

QCPU

QnCPU Abbreviation of Q02CPU

QnHCPU Abbreviation of Q02HCPU, Q06HCPU, Q12HCPU, Q25HCPU

QnPHCPU Abbreviation of Q02PHCPU, Q06PHCPU, Q12PHCPU, Q25PHCPU

QnPRHCPU Abbreviation of Q12PRHCPU, Q25PRHCPU

QnUD(H)CPU

Basic model QCPU

Basic

High Performance model QCPU

High Performance

Process CPU Generic term of Q02PHCPU, Q06PHCPU, Q12PHCPU, Q25PHCPU

Redundant CPU Generic term of Q12PRHCPU, Q25PRHCPU

Universal model QCPU

Universal

Generic term of Basic model QCPU, High Performance model QCPU,

Redundant CPU, Universal model QCPU, QnACPU

Abbreviation of Q2ASCPU, Q2ASCPU-S1, Q2ASHCPU, Q2ASHCPU-S1,

Q2ACPU, Q2ACPU-S1, Q3ACPU, Q4ACPU, Q4ARCPU

Abbreviation of Q2ASCPU, Q2ASCPU-S1, Q2ASHCPU, Q2ASHCPU-S1,

Q2ACPU, Q2ACPU-S1, Q3ACPU, Q4ACPU

Abbreviation of Q00CPU, Q01CPU, Q02CPU, Q02HCPU, Q06HCPU,

Q12HCPU, Q25HCPU, Q12PRHCPU, Q25PRHCPU, Q02UCPU,

Q03UDCPU, Q04UDHCPU, Q06UDHCPU, Q13UDHCPU, Q26UDHCPU,

Q03UDECPU, Q04UDEHCPU, Q06UDEHCPU, Q13UDEHCPU,

Q26UDEHCPU

Abbreviation of Q03UDCPU, Q04UDHCPU, Q06UDHCPU,

Q13UDHCPU, Q26UDHCPU, Q03UDECPU, Q04UDEHCPU,

Q06UDEHCPU, Q13UDEHCPU, Q26UDEHCPU

Generic term of Q00JCPU, Q00CPU, Q01CPU

Generic term of Q02CPU, Q02HCPU, Q06HCPU, Q12HCPU, Q25HCPU

Generic term of Q02UCPU, Q03UDCPU, Q04UDHCPU, Q06UDHCPU,

Q13UDHCPU, Q26UDHCPU, Q03UDECPU, Q04UDEHCPU,

Q06UDEHCPU, Q13UDEHCPU, Q26UDEHCPU

A - 11

MEMO

A - 12

1. GENERAL DESCRIPTION

MELSEC-Q/Qn

1. GENERAL DESCRIPTION

This manual describes the sequence program instructions used to implement PID control with any of the following CPU modules.

• Basic model QCPU (first five digits of serial No. are 04122 or later)

• High Performance model QCPU

• Redundant CPU

• Universal model QCPU

• QnACPU

The Basic model QCPU, High Performance model QCPU, Redundant CPU, and Universal model QCPU have the instructions used to perform PID control by incomplete derivative (PID control instructions) and the instructions used to perform PID control by complete derivative (PID control instructions) as standard features.

The QnACPU has the instructions used to perform PID control by complete derivative (PID control instructions) as standard features.

Since the incomplete derivative PID control instructions and complete derivative PID control instructions are independent of each other, they can be executed at the same time.

The following table indicates the CPU modules that can use the incomplete derivative PID control instructions and complete derivative PID control instructions.

CPU Module Model Name

First five digits of serial No. are

Basic model QCPU

High Performance model QCPU

Redundant CPU Universal model QCPU QnACPU

"04121" or earlier First five digits of serial No. are "04122" or later First five digits of serial No. are "05031" or earlier First five digits of serial No. are "05032" or later

*1: Version 7 or earlier version of GX Developer issues an “instruction code alarm” if it

loads a new CPU instruction realized with GX Developer Version 8.

Incomplete

Derivative

: Usable, : Unusable

Complete Derivative

1 - 1

1. GENERAL DESCRIPTION

MELSEC-Q/Qn

There are the following PID control instructions.

Classification Incomplete Derivative Complete Derivative PID control data setting PID operation PID control status monitor Specified loop No. operation stop Specified loop No. operation start Specified loop No. parameter change

S(P).PIDINIT PIDINIT(P)

S(P).PIDCONT PIDCONT(P)

PID57(P)

S(P).PIDSTOP PIDSTOP(P)

S(P).PIDRUN PIDRUN(P)

S(P).PIDPRMW PIDPRMW(P)

PID control via PID control instructions is implemented by combining the CPU module with the A/D converter module and D/A converter module. In the case of the QnACPU, the PID control status can be monitored using the AD57(S1) CRT controller module.

POINT

(1) The Process CPU is not compatible with the PID control instructions described

in this manual. To implement PID control using the Process CPU, use the process control instructions described in the QnPHCPU/QnPRHCPU Programming Manual (Process Control Instructions).

(2) The Redundant CPU can use the PID control instructions and process control

instructions.

1 - 2

1. GENERAL DESCRIPTION

1.1 PID Processing Method

This section describes the processing method for PID control using PID control

Set value

instructions. (For details on PID operations, see Chapter 4.)

Execute PID control with PID control instructions by loading an A/D converter module and a D/A converter module, as shown in Figure 1.1.

CPU module

PID control instructions

PID operation

Automatic MV

Manual MV

Manual/automatic changeover

D/A conversion module

A/D conversion module

MELSEC-Q/Qn

Controlled system

Sensor

Sequence program

SV: Set Value PV: Process Value MV: Manipulated Value

Figure 1.1 Overview of PID Control Processing

In the PID control processing method, as shown in Figure 1.1, the PID operation is executed using the set value (SV) and the process value (PV) read from the A/D converter module, and the manipulated value (MV) is then calculated. The calculated MV (manipulated value) is output to the D/A converter module.

When a PID operation instruction* is executed in a sequence program, the sampling cycle is measured and a PID operation is performed. PID operation in accordance with the PID operation instruction is executed in preset sampling cycles.

PID operation instruction execution

Step 0

Measurement of sampling cycle

Sampling cycle

PID operation instruction execution

Step 0 Step 0

END END END END

PID operation instruction execution

Measurement of sampling cycle

PID operation instruction execution

Step 0 Step 0

Measurement of sampling cycle

Sampling cycle

PID operation instruction execution

Measurement of sampling cycle PID operation

Figure 1. 2 Operation when PID Operation Instruction Executed

REMARK

*: There are the following PID operation instructions.

S.PIDCONT (incomplete derivative)

PIDCONT (complete derivative)

1 - 3

1. GENERAL DESCRIPTION

MEMO

MELSEC-Q/Qn

1 - 4

2. SYSTEM CONFIGURATION FOR PID CONTROL

MELSEC-Q/Qn

2. SYSTEM CONFIGURATION FOR PID CONTROL

This chapter describes the system configuration for PID control using the PID control instructions. For the modules that can be used to configure a system, refer to the following manual.

• Basic model QCPU, High Performance model QCPU, Universal model QCPU: MELSEC-Q DATA BOOK

CPU module

• QnACPU: User's manual (details) of the used CPU module

Main base unit

Extension cable

For PV (process value) input

A/D conversion module

For MV (manipulated value) output

D/A conversion module

Extension base unit

For PID control monitoring (Only QnACPU)

CRT control module

AD57 or AD57-S1 only

CRT

Operation panel

2 - 1

2. SYSTEM CONFIGURATION FOR PID CONTROL

POINT

SV, PV and MV used with the PID control instructions may be set either with the fixed values of 0 to 2000 or to any values according to the used module. Refer to Section 4.3.5 for details.

Basic model QCPU High Performance model QCPU Redundant CPU Universal model QCPU QnACPU

*: When the resolution of the A/D converter module or D/A converter module used for

I/O of PID control is other than 0 to 2000, convert the digital values into 0 to 2000.

CPU Module Type

2.1 Applicable PLC CPU

SV, PV, MV

0 to 2000 fixed *

: Can be set, : Cannot be set

MELSEC-Q/Qn

Any setting

Component Module

Basic model QCPU

High Performance model QCPU Q02CPU, Q02HCPU, Q06HCPU, Q12HCPU, Q25HCPU Redundant CPU Q12PRHCPU, Q25PRHCPU

Universal model QCPU

QnACPU

Q00JCPU, Q00CPU, Q01CPU (First 5 digits of serial No. are 04122 or later)

Q02UCPU, Q03UDCPU, Q04UDHCPU, Q06UDHCPU, Q13UDHCPU, Q26UDHCPU, Q03UDECPU, Q04UDEHCPU, Q06UDEHCPU, Q13UDEHCPU, Q26UDEHCPU Q2ASCPU, Q2ASCPU-S1, Q2ASHCPU, Q2ASHCPU-S1 Q2ACPU, Q3ACPU, Q4ACPU, Q4ARCPU

2 - 2

3. PID CONTROL SPECIFICATIONS

MELSEC-Q/Qn

3. PID CONTROL SPECIFICATIONS

This section gives the specifications PID operation using PID control instructions.

3.1 PID Control by incomplete derivative

3.1.1 Performance specifications

Number of PID control loops —

Sampling cycle TS 0.01 to 60.00 s

PID operation method —

PID

constant

setting

range

SV (set value) setting range SV 0 to 2000 -32768 to 32767

PV (process value) setting range

MV (manipulated value) output range

Proportional constant KP 0.01 to 100.00

Integral constant TI 0.1 to 3000.0 s

Derivative constant TD 0.00 to 300.00 s

Derivative gain KD 0.00 to 300.00

The performance specifications for PID control are tabled below.

Specifications

With PID limits Without PID limits

High Performance

Item

Basic model

QCPU

8 loops

(maximum)

-50 to 2050 -32768 to 32767

model QCPU,

Redundant CPU,

Universal model

QCPU

32 loops

(maximum)

Process value differentiation incomplete derivative

(forward operation/reverse operation)

Basic model

QCPU

8 loops

(maximum)

High Performance

model QCPU,

Redundant CPU,

Universal model

QCPU

32 loops

(maximum)

: Unusable

QnA

CPU

3 - 1

3. PID CONTROL SPECIFICATIONS

3.1.2 PID operation block diagram and operation expressions

MELSEC-Q/Qn

Name Operation Expressions Meanings of Symbols

Process

value

differentiation

Incomplete

derivative

Forward

operation

Reverse

operation

(1) The PID operation block diagram for incomplete derivative is shown below.

SV +

Set value

Disturbance

(P)

TD S

+(TD/KD) s

(D)

(I)

Kp P

Gain

Manipulated value

Control objective

(2) The operation expressions for PID control using PID control instructions are

indicated below.

n=PVfn*-SV

MV=Kp{(EVn-EV

TS+

Dn= (PVfn-2PV

MVn= MV

)+ EVn+Dn}

n-1

+PV

fn-1

fn-2

n-1

n : Deviation in the present sampling cycle

n-1 : Deviation in the preceding sampling

cycle

SV : Set value

fn : Process value of the present sampling

cycle (after filtering)

fn-1 : Process value of the preceding

sampling cycle (after filtering)

PVfn-2 : Process value of the sampling cycle

two cycles before (after filtering)

n=SV-PVfn*

MV=Kp{(EVn-EV

TS+

Dn= (-PVfn+2PV

MVn= MV

POINT

)+ EVn+Dn}

n-1

-PV

fn-1

fn-2

n-1

MV : Output change value

n : Present manipulation value

n : Present derivative term

D D

n-1 : Derivative term of the preceding

sampling cycle

P : Proportional constant

K T

S : Sampling cycle I : Integral constant

D : Derivative constant

T K

D : Derivative gain

(1) *:PVfn is calculated using the following expression.

Therefore, it is the same as the PV (process value) of the input data as long as the filter coefficient is not set for the input data.

Process Value after Filtering PV

fn= PVn+ (PVfn-1-PVn)

PVn : Process value of the present sampling cycle

: Filter coefficient

fn-1 : Process value of the preceding sampling cycle (after filtering)

fn is stored in the I/O data area. (See Section 5.2)

(2) PV

Process value

Detected noise

3 - 2

3. PID CONTROL SPECIFICATIONS

3.1.3 PID control instruction list

MELSEC-Q/Qn

Name

S.PIDINIT Sets the reference data for PID operation. * ×

S.PIDCONT

S.PIDSTOP

S.PIDRUN

S.PIDPRMW

A list of the instructions used to execute PID control is given below.

Processing Details

Executes PID operation with the SV (set value)

and the PV (process value).

Stops or starts PID operation for the set loop No.

Changes the operation parameters for the

designated loop number to PID control data.

QCPU QnACPU

* ×

CPU Instruction

Usable, ×: Unusable

*: The Basic model QCPU, High Performance model QCPU, Redundant CPU and

Universal model QCPU allow selection of "with/without PID limits". Refer to Sections 5.1 and 5.2 for details of the setting range when "with/without PID limits" has been selected.

3 - 3

3. PID CONTROL SPECIFICATIONS

(1) PID control instruction list

The PID control instruction list has the format indicated below:

Table 3.1 How to Read the PID control Instruction List

Category

Contril data setting

Instruction

Symbol

S.PIDINIT 7

Ladder Format Processing Details

S.PIDINIT

SP.PIDINIT

Sets the PID control data stored in the word device (designated by )

+ 0

Common data

+ 1

+ 2

+ 15

+ 16

+ 29

setting area

For loop 1

For loop 2

For loop n

+ (m+0)

+ (m+13)

m=(n-1) 14+2

Excution

Condition

MELSEC-Q/Qn

Number of Basic

Steps

Subset

Processing

Page

8-2

(4)(3)(2)(1)

(5)

(8)(7)(6)

Explanation

(1) Classification of instructions according to their application. (2) Instruction names written in a sequence program. (3) Symbols used in the ladder diagram. (4) Processing for each instruction.

16-bit data 16-bit data

+ 1S

+ 2S

+ 3S

Four consecutive device numbers (beginning with the device number designated for )

D + 1

+ 2

+ 3

Four consecutive device numbers (beginning with the device number designated for )

Fig. 3.1 Processing for Each Instruction

3 - 4

3. PID CONTROL SPECIFICATIONS

(5) The execution condition for each instruction. Details are given below.

Symbol Execution Condition

(6) Number of instruction steps

For details on the number of steps, refer to the QCPU (Q mode) /QnACPU Programming Manual (Common Instructions).

(7)

A circle

indicates that subset processing is possible.

indicates that subset processing is impossible. For details on subset processing, refer to the QCPU (Q mode) /QnACPU Programming Manual (Common Instructions).

(8) Indicates the page number in this manual where a detailed description for the

instruction can be found.

MELSEC-Q/Qn

Indicates an instruction that is executed for the duration that the

condition for its execution is ON.

When the condition before the instruction is OFF, the instruction is

not executed and no processing is carried out.

Indicates an instruction that is executed once only at the leading

edge (OFF to ON) of the condition for its execution; thereafter the

instruction will not be executed, and no processing will be carried

out, even if the condition is ON.

3 - 5

3. PID CONTROL SPECIFICATIONS

A PID control instruction list is given in Table 3.2.

Table 3.2 PID Control Instruction List

MELSEC-Q/Qn

Category

PID

Control

data

setting

PID

operation

Instruction

Symbol

S.PIDINIT

S.PIDCONT

Ladder Format Processing Details

Sets the PID control data stored in the word device (designated

+ 0

S.PIDINIT S

SP.PIDINIT

+ (m+0)

+ (m+13)

Common data

+ 1

+ 2

+ 15

+ 16

+ 29

setting area

For loop 1

For loop 2

For loop n

m=(n-1) 14+2

Executes PID operation with the SV (set value) and the PV (process value) designated by

and stores the PID

operation results in the MV

S.PIDCONT S

SP.PIDCONT

(manipulated value) area of the word device designated by

Common data

+ (m+0)

+ (m+22)

m=(n-1) 23+10

setting area

+ 9

SV setting area

+ 10

PV setting area

MV value stor age area

+ 32

SV setting area

+ 33

PV setting area

MV value stor age area

+ 55

SV setting area

PV setting area

MV value stor age area

For loop 1

For loop 2

For loop n

Execution

Condition

Number of Basic

Steps

Subset

Processing

Page

8-2

8-3

Operation

stop

Operation

start

Parameter

change

S.PIDSTOP

S.PIDRUN

S.PIDPRMW

S.PIDSTOP

SP.PIDSTOP

S.PIDRUN

SP.PIDRUN

S.PIDPRMW

SP.PIDPRMW

Stops the PID operation at the loop number designated by n.

Starts the operation at the loop

number designated by

8-5

Changes the operation

parameter for the loop number

designated by n to the PID control data stored in the word device designated by S

8-6

3 - 6

3. PID CONTROL SPECIFICATIONS

POINT

(1) "PID operation by incomplete derivative" and "PID operation by complete

derivative" can be executed simultaneously since they are independent.

(2) When the S(P).PIDINIT instruction has been used to make initialization, use the

S(P).PIDCONT instruction to perform PID operation. To stop and start the PID operation of the specified loop No. and to change the PID control data, use the S(P).PIDSTOP, S(P).PIDRUN and S(P).PIDPRMW instructions accordingly.

MELSEC-Q/Qn

3 - 7

3. PID CONTROL SPECIFICATIONS

3.2 PID Control by Complete Derivative

3.2.1 Performance specifications

MELSEC-Q/Qn

Number of PID control loops —

Sampling cycle TS 0.01 to 60.00 s

PID operation method —

PID

constant

setting

range

SV (set value) setting range SV 0 to 2000 -32768 to 32767 0 to 2000

PV (process value) setting range

MV (manipulated value) output range

Proportional constant KP 0.01 to 100.00

Integral constant TI 0.1 to 3000.0 s

Derivative constant T

The performance specifications for PID control are tabled below.

Specification

With PID limits Without PID limits

High

Performance

Item

Basic model

QCPU

8 loops

(maximum)

D 0.00 to 300.00 s

model QCPU,

Redundant

CPU,

Universal model

QCPU

32 loops

(maximum)

Process value differentiation complete derivative

(forward operation/reverse operation)

-50 to 2050 -32768 to 32767 -50 to 2050

Basic model

QCPU

Universal model

8 loops

(maximum)

High

Performance

model QCPU,

Redundant

CPU,

QCPU

32 loops

(maximum)

QnACPU

32 loops

(maximum)

3 - 8

3. PID CONTROL SPECIFICATIONS

3.2.2 PID operation block diagram and operation expressions

MELSEC-Q/Qn

Name Operation Expressions Meanings of Symbols

Process

value

differentiation

Complete

derivative

Forward

operation

Reverse

operation

(1) The PID operation block diagram for complete derivative is shown below.

SV +

Set value

Disturbance

(P)

(D)

I S

(I)

D S

Kp P

Gain

Manipulated value

Control objective

(2) The operation expressions for PID operation using PID control instructions are

indicated below.

EVn=PVfn*-SV

fn-1

T T

+PV

fn-2

MV=Kp{(EVn-EVn-1)+ EVn+Dn}

Dn= (PVfn-2PV

MVn= MV

)

n : Deviation in the present sampling cycle

n-1 : Deviation in the preceding sampling cycle

SV : Set value

fn : Process value of the present sampling cycle

(after filtering)

PVfn-1 : Process value of the preceding sampling

cycle (after filtering)

PVfn-2 : Process value of the sampling cycle two

cycles before (after filtering)

EVn=SV-PVfn*

fn-1

-PV

fn-2

MV=Kp{(EVn-EVn-1)+ EVn+Dn}

Dn= (-PVfn+2PV

MVn= MV

POINT

)

MV : Output change value

n : Present manipulation value

n : Present derivative term

P : Proportional constant

K T

S : Sampling cycle I : Integral constant

D : Derivative constant

(1) *:PVfn is calculated using the following expression.

Therefore, it is the same as the PV (process value) of the input data as long as the filter coefficient is not set for the input data.

Process Value after Filtering PV

fn= PVn+ (PVfn-1-PVn)

PVn : Process value of the present sampling cycle

: Filter coefficient

fn-1 : Process value of the preceding sampling cycle (after filtering)

(2) PV

fn is stored in the I/O data area. (See Section 5.2)

Process value

Detected noise

3 - 9

3. PID CONTROL SPECIFICATIONS

3.2.3 PID control instruction list

MELSEC-Q/Qn

Name

PIDINIT Sets the reference data for PID operation. *

PIDCONT

PID57

PIDSTOP

PIDRUN

PIDPRMW

A list of the instructions used to execute PID control is given below.

Processing Details

Executes PID operation with the SV (set value)

and the PV (process value).

Used to monitor the results of PID operation at an

AD57(S1).

Stops or starts PID operation for the set loop No.

Changes the operation parameters for the

designated loop number to PID control data.

QCPU QnACPU

CPU Instruction

Usable, ×: Unusable

*: The Basic model QCPU, High Performance model QCPU, Redundant CPU and

Universal model QCPU allow selection of "with/without PID limits". Refer to Sections 5.1 and 5.2 for details of the setting range when "with/without PID limits" has been selected.

3 - 10

3. PID CONTROL SPECIFICATIONS

(1) The PID control instruction list

The PID control instruction list has the format indicated below:

Table 3.3 How to Read the PID control Instruction List

Category

PID control data setting

Instruction

Symbol

PIDINIT 29-2

Ladder Format Processing Details

PIDINIT

PIDINITP

Sets the PID control data stored in the word device (designated by )

+ 0

Common data

+ 1

+ 2

+ 11

+ 12

+ 21

setting area

For loop 1

For loop 2

For loop n

+ (m+0)

+ (m+9)

m=(n-1) 10+2

Excution

Condition

MELSEC-Q/Qn

Number of Basic

Steps

Subset

Processing

Page

(8)(7)(6)(5)(4)(3)(2)(1)

Explanation

(1) Classification of instructions according to their application. (2) Instruction names written in a sequence program. (3) Symbols used in the ladder diagram. (4) Processing for each instruction.

16-bit data 16-bit data

+ 1S

+ 2S

+ 3S

Four consecutive device numbers (beginning with the device number designated for )

D + 1

+ 2

+ 3

Four consecutive device numbers (beginning with the device number designated for )

Fig. 3.2 Processing for Each Instruction

3 - 11

3. PID CONTROL SPECIFICATIONS

(5) The execution condition for each instruction. Details are given below.

Symbol Execution Condition

(6) Number of instruction steps

For details on the number of steps, refer to the QCPU (Q mode) /QnACPU Programming Manual (Common Instructions).

(7)

A circle

indicates that subset processing is possible.

indicates that subset processing is impossible. For details on subset processing, refer to the QCPU (Q mode) /QnACPU Programming Manual (Common Instructions).

(8) Indicates the page number in this manual where a detailed description for the

instruction can be found.

MELSEC-Q/Qn

Indicates an instruction that is executed for the duration that the

condition for its execution is ON.

When the condition before the instruction is OFF, the instruction is

not executed and no processing is carried out.

Indicates an instruction that is executed once only at the leading

edge (OFF to ON) of the condition for its execution; thereafter the

instruction will not be executed, and no processing will be carried

out, even if the condition is ON.

3 - 12

3. PID CONTROL SPECIFICATIONS

A PID control instruction list is given in Table 3.4.

Table 3.4 PID Control Instruction List

MELSEC-Q/Qn

Category

Instruction

Symbol

PID

control

data

PIDINIT

setting

PID

operation

PIDCONT

Monitoring PID57

Ladder Format Processing Details

Sets the PID control data stored in the word device (designated by

PIDINIT

PIDINITP

+ (m+0)

+ (m+9)

m=(n-1) 10+2

+ 0

+ 1

+ 2

+ 11

+ 12

+ 21

Common data

setting area

For loop 1

For loop 2

For loop n

Executes PID operation with the SV (set value) and the PV (process value) designated by

and stores the PID

operation results in the MV

PIDCONT

(manipulated value) area of the word device designated by

+ 0

Common da ta

setting area

+ 9

SV setting area

+ 10

PV setting area

MV value star age area

+ 27

SV setting area

+ 28

PV setting area

MV value star age area

+ 45

PIDCONTP S

SV setting area

+ (m+0)

PV setting area

MV value star age area

+ (m+17)

m=(n-1) 18+10

Monitors the PID operation results for the AD57 (S1)

PID57

(designated by

: First I/O number of the

AD57(S1)

: Monitor screen number

1:Loop 1 to loop 8

2:Loop 9 to loop16

PID57P

3:Loop17 to loop24 4:Loop25 to loop32

: Initial screen display

request

For loop 1

For loop 2

For loop n

Execution

Condition

Number of Basic

Steps

Subset

Processing

Page

9-2

9-3

9-5

3 - 13

3. PID CONTROL SPECIFICATIONS

Table 3.4 PID Control Instruction List

MELSEC-Q/Qn

Category

Operation

stop

Operation

start

Parameter

change

Instruction

Symbol

PIDSTOP

PIDRUN

PIDPRMW

Ladder Format Processing Details

PIDSTOP

PIDSTOPP

PIDRUN

PIDRUNP

PIDPRMW

PIDPRMWP

POINT

Stops the PID operation at the loop number designated by n.

Starts the operation at the loop

number designated by

Changes the operation

parameter for the loop number

designated by control data stored in the word device designated by

to the PID

Execution

Condition

Number of Basic

Steps

Subset

Processing

(1) "PID operation by incomplete derivative" and "PID operation by complete

derivative" can be executed simultaneously since they are independent.

(2) When the PIDINIT(P) instruction was used to make initialization, use the

PIDCONT(P) instruction to perform PID operation. To stop and start the PID operation of the specified loop No. and to change the PID control data, use the PIDSTOP(P) instruction, PIDRUN(P) instruction and PIDPRMW(P) instruction.

Page

9-8

9-9

3 - 14

4. FUNCTIONS OF PID CONTROL

MELSEC-Q/Qn

4. FUNCTIONS OF PID CONTROL

This chapter describes PID control performed using the PID control instructions.

4.1 Outline of PID Control

PID control is applicable to process control in which factors such as flowrate, velocity, air flow volume, temperature, tension, mixing ratio, etc. must be controlled. The control

Set value

for maintaining the control object at the preset value is shown in the diagram below:

CPU module

PID control instructions

Manual MV

PID operation

Manual/automatic changeover

Fig. 4.1 Application of PID Control Process Control

During PID control, the value measured by the sensor (process value) is compared with the preset value (set value). The output value (manipulated value) is then adjusted in order to eliminate the difference between the process value and the set value. The MV (manipulated value) is calculated by combining the proportional operation (P), the integral operation (I), and the derivative operation (D) so that the PV is brought to the same value as the SV quickly and precisely. The MV is made large when the difference between the PV and the SV is large so as to bring the PV close to the SV quickly. As the difference between the PV and the SV gets smaller, a smaller MV is used to bring the PV to the same value as the SV gradually and accurately.

D/A conversion module

A/D conversion module

SV: Set Value PV: Process Value MV: Manipulated Value

Controlled system

Sensor

4 - 1

4. FUNCTIONS OF PID CONTROL

4.2 Functions of PID Control

The operation methods for PID control with the PID control instructions are the velocity type and process value derivative type. The following describes the control executed for both of these methods:

4.2.1 Operation method

(1) Velocity type operation

The velocity type operation calculates amounts of changes in the MVs (manipulated values) during PID operation.The actual MV is the accumulated amount of change of the MV calculated for each sampling cycle.

(2) Process value derivative type operation

The process value derivative type operation executes PID operations by differentiating the PV (process value). Because the deviation is not subject to differentiation, sudden changes in the output due to differentiation of the changes in the deviation generated by changing the set value can be reduced.

4.2.2 Forward operation and reverse operation

MELSEC-Q/Qn

Either forward operation or reverse operation can be selected to designate the direction of PID control.

(1) In forward operation, the MV (manipulated value) increases as the PV (process

value) increases beyond the SV (set value).

(2) In reverse operation, the MV increases as the PV decreases below the SV.

(3) In forward operation and reverse operation, the MV becomes larger as the

difference between the SV and the PV increases.

(4) The figure below shows the relationships among forward operation and reverse

operation and the MV, the PV, and the SV.

(MV)

Reverse operation

(SV)

(PV)

Forward operation

4 - 2

)

4. FUNCTIONS OF PID CONTROL

(5) The figure below shows examples of process control with forward operation and

reverse operation:

Process value

MELSEC-Q/Qn

Set value

Temperature

Forward operation (for cooling)

Set value

Time

Temperature

Reverse operation (for heating

Process value

Time

4 - 3

4. FUNCTIONS OF PID CONTROL

4.2.3 Proportional operation (P operation)

The control method for proportional operation is described below.

(1) In proportional operation, an MV (manipulated value) proportional to the deviation

(the difference between the set value and process value) is obtained.

(2) The relationship between E (deviation) and the MV is expressed by the following

formula:

MV=Kp • E

Kp is a proportional constant and is called the "proportional gain".

Condition

When proportional gain Kp is smaller

When proportional gain Kp is larger

(3) The proportional operation in step response with a constant E (deviation) is

illustrated in Fig. 4.2.

MELSEC-Q/Qn

Proportional Operation

Control operation gets slower.

Control operation gets faster. However, hunting is more likely to occur.

DeviationMV

Time

Fig. 4.2 Proportional Operation with a Constant Deviation

(4) A certain error produced relative to a set value is called an offset.

An offset is produced in proportional operation.

Set value Offset Set value Offset

t t

4 - 4

4. FUNCTIONS OF PID CONTROL

4.2.4 Integral operation (I operation)

The control method for integral operation is described below.

(1) In the integral operation, the MV (manipulated value) changes continuously to

zero deviation when it occurs. This operation can eliminate the offset that is unavoidable in proportional operation.

(2) The time required for the MV in integral operation to reach the MV for proportional

operation after the generation of deviation is called the integral time. Integral time is expressed as T

Condition

When integral time TI is shorter

When integral time TI is longer Integrating effect decreases and the time to

(3) The integral operation in step response with a constant E (deviation) is illustrated

in Fig. 4.3.

MELSEC-Q/Qn

Integral Operation

Integrating effect increases and the time to eliminate the offset becomes shorter. However, hunting is more likely to occur.

eliminate the offset becomes longer.

Deviation

Time

MV in "P + I" operations

Time

MV value in I operation

MV value in P operation

Fig. 4.3 Integral Operation with a Constant Deviation

(4) Integral operation is always used in combination with proportional operation (PI

operation) or with proportional and derivative operations (PID operation). Integral operation cannot be used independently.

4 - 5

4. FUNCTIONS OF PID CONTROL

4.2.5 Derivative operation (D operation)

The control method for derivative operation is described below.

(1) In derivative operation, an MV (manipulated value) proportional to the deviation

change rate is added to the system value to zero deviation when it occurs. This operation prevents significant fluctuation at the control objective due to external disturbances.

(2) The time required for the MV in the derivative operation to reach the MV for the

proportional operation after the generation of deviation is called the derivative time. Derivative time is expressed as T

Condition

When derivative time TD is shorter

When derivative time TD is longer

(3) The derivative operation when the deviation is a constant value stepped response

is shown in Fig. 4.4.

MELSEC-Q/Qn

Derivative Operation

Differentiating effect decreases.

Differentiating effect increases. However, hunting of short cycle is more likely to occur.

Time

K DV

Manipulated value for proportional operation

Deviation

Manipulated

value

Fig. 4.4 Derivative operation when the deviation is a constant

(4) Derivative operation is always used in combination with proportional operation

(PD operation) or with proportional and integral operations (PID operation). Derivative operation cannot be used independently.

4 - 6

4. FUNCTIONS OF PID CONTROL

REMARK

About the differences between complete derivative and incomplete derivative [Incomplete derivative]

Incomplete derivative is PID control that has a primary delay filter in the input of a derivative term. The S.PIDCONT instruction is the incomplete derivative PID control instruction. Incomplete derivative is effective for the following cases.

• Control susceptible to high-frequency noise

• When energy effective to actuate an operation end is not given when a step change occurs in a complete derivative system

[Complete derivative]

Complete derivative is PID control that uses the input of a derivative term as it is. The PIDCONT instruction is the complete derivative PID control instruction.

Input

Incomplate derivative

Primary delay filter

Derivative term

TD s

1 TD s

MELSEC-Q/Qn

PV 1/

1/ Derivative gain

Time

Complete derivative

Derivative term

TD s

Larger

Time

4 - 7

4. FUNCTIONS OF PID CONTROL

4.2.6 PID operation

The control method when proportional operation (P operation), integral operation (I operation), and derivative operation (D operation) are used in combination is described below.

(1) During PID operation, the system is controlled by the MV (manipulated value)

calculated in the (P + I + D) operation.

(2) PID operation in step response with a constant E (deviation) is illustrated in Fig.

Deviation

4.5.

Deviation

MELSEC-Q/Qn

PID

Time

Incomplete derivative

Complete derivative

Time

Fig. 4.5 PID Operation with Constant Deviation

4 - 8

4. FUNCTIONS OF PID CONTROL

4.3 Other Functions

During PID control using the PID control instructions, MV upper/lower limit control is automatically executed by the bumpless changeover function explained below.

4.3.1 Bumpless changeover function

(1) This function controls the MV (manipulated value) continuously when the control

mode is changed between manual and automatic.

(2) When the mode is changed (between manual and automatic), data is transferred

between the "MV area for automatic mode (automatic MV)" and "MV area for

manual mode (manual MV)" as described below. The control mode is changed in the I/O data area (see Section 5.2).

(a) Changing from the manual ...........

mode to the automatic mode

(b) Changing from the automatic .......

mode to the manual mode

POINT

(1) Manual and automatic modes of PID control:

1) Automatic mode PID operation is executed with a PID control instruction. The control object is controlled according to the calculated MV.

2) Manual mode PID operation is not executed. The MV is calculated by the user and the

(2) The loop set in the manual mode stores the PV (process value) in the set value

control object is controlled according to the user-calculated MV.

area every sampling cycle.

MELSEC-Q/Qn

The MV in the manual mode is transmitted to the MV area for the automatic mode. The MV in the automatic mode is transmitted to the MV area for the manual mode.

4 - 9

4. FUNCTIONS OF PID CONTROL

4.3.2 MV upper/lower limit control function

(1) The MV upper/lower limit control function controls the upper or lower limit of the MV

calculated in the PID operation. This function is only effective in the automatic mode. It cannot be executed in the manual mode.

(2) By setting the MV upper limit (MVHL) and the MV lower limit (MVLL), the MV

calculated in the PID operation can be controlled within the range between the limits.

EV (deviation)

MVHL

(MV upper limit)

MVLL

(MV lower limit)

Fig. 4.6 Operation in Accordance with the MV Upper/Lower limit

MELSEC-Q/Qn

without limit

AUTO

control

AUTO

(3) When the MV upper/lower limit control is used, the MV is controlled as illustrated

above. A MVHL (MV upper limit) and MVLL (MV lower limit) takes on a value between -50 and 2050 or a user-defined value (except the QnACPU). The following are the default settings:

• Upper limit ..................2000 (Or user-defined value)

• Lower limit ..................0 (Or user-defined value)

The value set for the upper limit must not be smaller than the value set for the lower limit. An error will occur if it is.

4 - 10

4. FUNCTIONS OF PID CONTROL

4.3.3 Monitoring PID control with the AD57(S1) (QnACPU only)

The PID control operation results can be monitored in a bar graph with an AD57(S1) CRT controller unit.

(1) The monitor screen displays the monitored information of eight loops beginning

Bar graph display The SV, PV, and MV of each loop

are displayed as percentages in a bar graph. If the MV percentage is in the range of -2.5% MV 0%, a " " will bedisplayed at the 0% position. If the MV percentage is between 100% and 102.5%, a " " will be displayed above the bar graph.

Limit operation status display

If an SV, PV, and/or MV limiter is activated, the corresponding character is highligted.

with the designated loop number.

Loop number display

Display the loop number (1 to 32).

LOOP 1 LOOP 2 LOOP 3 LOOP 4 LOOP 5 LOOP 6 LOOP 7 LOOP 8

SP SV 50 % PV 40 % MV 73 % PV MV

100

80 60 40 20

SP SV 91 % PV 95 % MV 21 % PV MV

100

80 60 40 20

Device display

Display the device in which the PID data (SV and PV) are stored.

100

80 60 40 20

SP SV 30 % PV 60 % MV 50 % PV MV

100

80 60 40 20

P SV 88 % PV 10 % MV 100 % PV MV

100

80 60 40 20

SP SV 40 % PV 15 % MV 83 % PV MV

MELSEC-Q/Qn

Device number display

Display the first device number of the devices in which the PID value (SV and PV) are stored.

DEVICE R NO. 80

100

80 60 40 20

SPM SV 100 % PV 45 % MV 100 % PV MV

100

80 60 40 20

SPM SV 61 % PV 0 % MV 92 % PV MV

100

80 60 40 20

SP SV 5 % PV 1 % MV 25 % PV MV

Present value display

The SV, PV, and MV present values for each loop are displayed as percentages.

Alarm status display

If the PV exceeds the preset PVL and/or the MV exceeds the preset

MVL, the corresponding character

is highlighted.

POINT

The SV, PV, and MV present value are displayed as percentages of 2000.

100 (%)

1) SV percentage display ...............

2) PV percentage display ...............

3) MV percentage display...............

2000

(2) Use the PID57 instruction to execute monitoring with an AD57(S1).

See Section 9.1.3 for details on the PID57 instruction.

4 - 11

4. FUNCTIONS OF PID CONTROL

MELSEC-Q/Qn

4.3.4 Function for transfer to the SV storage device for the PV in manual mode

When using the PID control instruction to perform PID control, execute the PID

PID Bumpless Processing Flag

SM794

(Incomplete derivative)

operation instruction also in the manual mode.

In the manual mode, it is possible to select whether the PV imported from the A/D converter module is transferred to the SV storage device or not when the PID operation instruction is executed, depending on the ON/OFF status of the PID bumpless processing flag (SM774, SM794).

SM774

(Complete derivative)

OFF

POINT

• The PV is transferred to the SV storage device when the PID operation instruction is executed.

• When the manual mode is switched to the automatic mode, the MV output in the manual mode is continued.

• When the SV is changed after switching to the automatic mode, control is performed to achieve the SV, starting from the MV output in the manual mode.

• The PV is not transferred to the SV storage device when the PID operation instruction is executed.

• When the manual mode is switched to the automatic mode, control is performed to achieve the SV, starting from the MV output in the manual mode.

• Before switching to the automatic mode, store the SV into the SV storage device.

Operation

Depending on whether SM774/SM794 is ON or OFF, there are the following differences in control when the manual mode is switched to the automatic mode.

• When SM774/SM794 is OFF, the PV is transferred to the SV storage device. Therefore, there is no difference between the PV and SV when the manual mode is switched to the automatic mode. Hence, an abrupt change does not occur in MV at the time of mode switching. Instead, since the SV after mode switching differs from the target value in the automatic mode, the user should change the SV to the target value step by step in the sequence program.

• When SM774/SM794 is ON, the PV is not transferred to the SV storage device. Therefore, there is a difference between the PV and SV when the manual mode is switched to the automatic mode. If the difference is large at the time of mode switching, an abrupt change may occur in MV. Use this method in a system where the mode is switched when the PV has fully neared the SV. PID control in the automatic mode can be executed immediately without the SV being changed step by step in the sequence program.

REMARK

The SV and PV are stored into the devices specified in the I/O data area with the

PID operation instruction.

4 - 12

4. FUNCTIONS OF PID CONTROL

MELSEC-Q/Qn

4.3.5 Changing the PID control data or input/output data setting range (QCPU only)

The setting ranges of the following data of the PID control data (refer to Section 5.1) and I/O data (refer to Section 5.2) can be changed as desired by user setting.

Item Set Data

MV lower limit value

PID control data

I/O data

To make the user setting valid, turn the bit corresponding to the relevant loop of the PID limit setting special register (SD774, SD775, SD794, SD795) to "1".

PID Limit Setting Special Register

Incomplete derivative Complete derivative

SD794 SD774

SD795 SD775

POINT

The Basic model QCPU has 8 loops. b0 to b7 of SD774 and SD794 are valid.

b15

0/1

b15

0/1

MV upper limit value

MV change rate limit value

PV change rate limit value

Automatic MV

PV after filtering

Manual MV

Setting Range

b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2

0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1

0/1

LOOP 15 LOOP 16

b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2

0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1

0/1

LOOP 31 LOOP 32

LOOP 8

0: With PID limit (system fixed value) 1: Without PID limit (user setting)

0/1b10/1

LOOP 1 LOOP 2

LOOP 17 LOOP 18

4 - 13

4. FUNCTIONS OF PID CONTROL

MEMO

MELSEC-Q/Qn

4 - 14

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

5. PID CONTROL PROCEDURE

Changing the PID control data

Changing the SV (set value)

Automatic/manual mode change of MV (manipulated value)

The programming procedure required to execute PID control is shown below.

Programming Procedure

Setting the PID control data

Set the PID control data in the word devices.

Executing the PID control data setting instruction *

Enter in the CPU module the PID control data set in the word devices by executing the PID control data setting instruction.

Setting the initial processing flag

Set the initial processing flag in the I/O data.

Setting the SV (set value)

Set the SV (set value) in the I/O data.

See Section 5.1 for details on the setting items and setting procedure.

See Section 8.1.1/9.1.1 for details on the instruction.

See Section 5.2 for details on I/O data.

Select manual mode?

NO (automatic mode)

Selecting automatic MV control

Set the manual/automatic selection for I/O data to automatic

Reading/setting the PV

After reading the data from the A/D converter module, set it in the PV area of the I/O data area.

(1)

(2)

YES (manual mode)

Selecting manual MV control

Set the manual/automatic selection for I/O data to manual.

Setting the manually controlled MV (MV

Set the manual MV(MV the I/O data.

MAN

See Section

5.2 for details on I/O data.

)

) in

MAN

REMARK

*: The following instructions are available as the PID control data setting instructions.

S.PIDINIT (incomplete derivative) PIDINIT (complete derivative)

5 - 1

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

(2)(1)

Executing the PID operation instruction

Using the PID operation instruction, execute PID operation based on the PID control data set in the word devices and the I/O data.

Outputting the MV (manipulated value)

The MV obtained from the PID operation result is read, and written to the D/A converter module.

Mounitoring with the AD57(S1) (QnACPU only)

Using an AD57(S1) monitor the controlled conditions by executing a PID57 instruction.

See Section 8.1.2/9.1.2 for details on the instruction.

The MV, obtained from the PID operation result, is stored in the I/O data area. See Section 5.2 for details on I/O data.

See Section 9.1.3 for details on the instruction. Thus step is not necessary when monitoring with an AD57(S1) is not required.

POINT

• Registering or changing the PID control data per sequence program scan will present no problem. However, execute the the PID control data setting instructions *

when you registered or changed the PID control data. If you do not execute the PID control data setting instructions instruction, the data registered or the correction made to the PID control data will not be reflected at the execution of the the PID operation instructions.

• You need not execute the PID control data setting instructions when using the parameter change instruction *

to change the PID control data per loop.

REMARK

*1: The following instructions are available as the PID operation instructions.

S.PIDCONT (incomplete derivative) PIDCONT (complete derivative)

*2: The following instructions are available as the PID control data setting

instructions.

S.PIDINIT (incomplete derivative) PIDINIT (complete derivative)

*3: The following instructions are available as the parameter change instructions.

S. PIDPRMW (incomplete derivative) PIDPRMW (complete derivative)

5 - 2

5. PID CONTROL PROCEDURE

MEMO

MELSEC-Q/Qn

5 - 3

5. PID CONTROL PROCEDURE

5.1 PID Control Data

MELSEC-Q/Qn

Common

setting

data

Data for

each loop

Data

No.

(1) PID control data is used to set the reference values for PID operation.

Store the PID control data into the CPU module with the PID control data setting instruction before executing PID operation instruction

The PID control data is classified into two types, "common data for all loops" and "data for individual loops".

(a) For Basic model QCPU

Table 5.1 PID Control Data List

Data Item Description

Number of

loops

Number of

loops in one

scan

Selection of

operational

expression

Sampling

cycle (T

Proportional

constant (K

Integral

constant (T

Derivative

constant (T

Filter coefficient (

Sets the number of loops for

which PID operation will be

executed.

Sets the number of loops for

which single PID operation

will be executed when the

multiple loops reaches the

sampling cycle time.

Selects the PID operational

expression indicated in

Section 3.1.2/Section 3.2.2.

Sets the cycle of PID

operation.

PID operation Proportional

gain

This constant expresses the

magnitude of the integral

operation (I operation) effect.

Increasing the integral

constant slows down the

manipulated value change.

This constant expresses the

magnitude of the derivative

operation

(D operation) effect.

Increasing the derivative

constant causes a significant

change in the manipulated

value even with slight

change of the control

objective.

Sets the degree of filtering

applied to the process value.

)

The filtering effect decreases

as the value gets closer to 0.

Incomplete derivative

With PID limits Without PID limits

User

Setting Range

1 to 8 1 to 8 1 to 8 1 to 8

Forward

operation: 0

Reverse

operation: 1

0.01 to 60.00 s

0.01 to 100.00

0.1 to 3000.0 s 0.1 to 3000.0 s

Infinite(

If the setting

exceeds

for T

3000.0 s

0.00 to 300.00 s

0 to 100 % 0 to 100 0 to 100 % 0 to 100

)

Specification

Range

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

Setting Range

Forward

operation: 0

Reverse

operation: 1

0.01 to 60.00 s

0.01 to 100.00

Infinite(

If the setting for T

3000.0 s

0.00 to 300.00 s

)

exceeds

User

Specification

Range

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

5 - 4

5. PID CONTROL PROCEDURE

REMARK

*1: The following are available as the PID operation instructions.

S.PIDCONT (incomplete derivative) PIDCONT (complete derivative)

*2: The following are available as the PID control data setting instructions.

S.PIDINIT (incomplete derivative) PIDINIT (complete derivative)

Complete derivative

With PID limits Without PID limits

Setting

Range

1 to 8 1 to 8 1 to 8 1 to 8

Forward operation :

Reverse operation: 1

0.01 to 60.00s

0.01 to 100.00

0.1 to 3000.0 s 0.1 to 3000.0 s

Infinite(

If the setting for T

3000.0 s

0.00 to 300.00 s

0 to 100% 0 to 100 0 to 100% 0 to 100

)

exceeds

User

Specification

Range

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

Setting

Range

Forward operation : 0

Reverse operation: 1

0.01 to 60.00 s

0.01 to 100.00

Infinite(

If the setting for T

3000.0 s

0.00 to 300.00 s

)

exceeds

User

Specification

Range

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

MELSEC-Q/Qn

Processing when Set Data is

Outside the Allowable Setting Range

An error occurs and PID operation is

not executed for all loops.

An error occurs and PID operation

for the corresponding loop is not

executed.

An error occurs and PID operation

for the corresponding loop is not

executed.

An error occurs and PID operation

for the corresponding loop is not

executed.

5 - 5

5. PID CONTROL PROCEDURE

Table 5.1 PID Control Data List

Data for

each

loop

Data

No.

Data Item Description

In the automatic mode, sets the

lower limit for the MV (manipulated

MV Lower

limit (MVLL)

MV Upper

limit (MVHL)

MV change

rate limit

MVL)

(

PV change

rate limit

PVL)

(

Derivative

gain (K

value) calculated in PID operation.

When the MV is less than the MV

lower limit, the MVLL is used as

the MV.

In the automatic mode, sets the

upper limit for the MV calculated in

PID operation.

When the MV is greater than the

MV upper limit, the MVHL is used

as the MV.

Sets the limit for variation between

the previous MV and present MV.

When the MV variation is greater

than the limit value, 1 is set for bit

1 (b1) of the alarm device.

Does not limit the MV variation.

(If the MV variation is greater than

the limit value, it is used

unchanged as the MV variation to

calculate the MV.)

Sets the limit for variation between

the previous PV and present PV.

When the PV variation is greater

than the limit value, 1 is set for bit

0 (b0) of the alarm device.

Does not limit the PV variation.

(If the PV variation is greater than

the limit value, it is used

unchanged as the PV variation to

perform the PID operation.)

Sets a time period (operation

delay) for derivative operation.

As the value is greater, the time

period decreases and operation

becomes closer to complete

derivative.

MELSEC-Q/Qn

Incomplete derivative

With PID limits Without PID limits

User

Setting Range

-50 to 2050 -50 to 2050

0 to 2000 0 to 2000

0.00 to 300.00

(Ideal value is

8.00)

Infinite(

If the setting

exceeds

for K

300.00

)

Specification

Range

0 to 32767

(unit: 0.01)

Setting Range

-32768 to

32767

-32768 to

32767

-32768 to

32767

-32768 to

32767

0.00 to 300.00

(Ideal value is

8.00)

Infinite(

If the setting for K

300.00

exceeds

)

Specification

Range

-32768 to

0 to 32767

(unit: 0.01)

User

32767

5 - 6

5. PID CONTROL PROCEDURE

Complete derivative

With PID limits Without PID limits

Setting

Range

-50 to 2050 -50 to 2050 -32768 to 32767 -32768 to 32767

0 to 2000 0 to 2000 -32768 to 32767 -32768 to 32767

User Specification

Range

Setting Range

User Specification

Range

MELSEC-Q/Qn

Processing when Set Data is

Outside the Allowable Setting Range

In the case of "with PID limits", PID

operation is performed after

conversion into the following value.

When the MVLL or MVHL value is

less than -50, "-50" is used.

When the MVLL or MVHL value is

greater than 2050, "2050" is used.

In the case of "with PID limits", PID

operation is performed after

conversion into the following value.

When the MVL value is less

than -50, it is converted into -50.

When the MVL value is greater

than 2050, it is converted into

2050.

In the case of "with PID limits", PID

operation is performed after

conversion into the following value.

When the PVL value is less

than -50, it is converted into -50.

When the PVL value is greater

than 2050, it is converted into

2050.

An error occurs and PID operation

for the corresponding loop is not

executed.

5 - 7

5. PID CONTROL PROCEDURE

(b) For High Performance model QCPU, Redundant CPU,

Data

No.

Data Item Description

Universal model QCPU

Table 5.2 PID Control Data List

MELSEC-Q/Qn

Incomplete derivative

With PID limits Without PID limits

User

Setting Range

Specification

Range

Setting Range

Specification

Range

User

Common

setting

data

Data for

each loop

Number of

loops

Number of

loops in one

scan

Selection of

operational

expression

Sampling

cycle (T

Proportional

constant (K

Integral

constant (T

Derivative

constant (T

Filter

coefficient (

Sets the number of loops for which

PID operation will be executed.

Sets the number of loops for which

single PID operation will be

executed when the multiple loops

reaches the sampling cycle time.

Selects the PID operational

expression indicated in Section

3.1.2/Section 3.2.2.

Sets the cycle of PID operation. 0.01 to 60.00 s

PID operation proportional gain 0.01 to 100.00

This constant expresses the

magnitude of the integral operation

(I operation) effect. Increasing the

integral constant slows down the

manipulated value change.

This constant expresses the

magnitude of the derivative

operation

(D operation) effect.

Increasing the derivative constant

causes a significant change in the

manipulated value even with slight

change of the control objective.

Sets the degree of filtering applied

to the process value.

)

The filtering effect decreases as the

value gets closer to 0.

1 to 32 1 to 32 1 to 32 1 to 32

Forward

operation: 0

Reverse

operation: 1

0.1 to 3000.0 s 0.1 to 3000.0 s

Infinite(

If the setting for T

3000.0 s

300.00 s

0 to 100 % 0 to 100 0 to 100 % 0 to 100

exceeds

0.00 to

)

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

Forward

operation: 0

Reverse

operation: 1

0.01 to 60.00 s

0.01 to 100.00

Infinite(

If the setting for T

3000.0 s

exceeds

0.00 to

300.00 s

)

0 or 1

1 to 6000

(unit: 10 ms)

1 to 10000

(unit: 0.01)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

5 - 8

5. PID CONTROL PROCEDURE

Complete derivative

With PID limits Without PID limits

Setting Range

1 to 32 1 to 32 1 to 32 1 to 32

Forward

operation : 0

Reverse

operation: 1

0.01 to 60.00 s

0.01 to 100.00

0.1 to 3000.0 s 0.1 to 3000.0 s

User Designation

Range

0 or 1

1 to 6000

(units: 10 ms)

1 to 10000

(units: 0.01)

Setting Range

Forward

operation : 0

Reverse

operation: 1

0.01 to 60.00 s

0.01 to 100.00

User Designation

Range

0 or 1

1 to 6000

(units: 10 ms)

1 to 10000

(units: 0.01)

MELSEC-Q/Qn

Processing if Set Data is Outside the

Allowable Setting Range

An error occurs and PID operation is not

executed for all loops.

An error occurs and PID operation for the

corresponding loop is not executed.

Infinite(

If the setting for T

3000.0 s

0.00 to 300.00 s

0 to 100 % 0 to 100 0 to 100 % 0 to 100

)

exceeds

1 to 32767

(units: 100 ms)

0 to 30000

(units: 10 ms)

Infinite(

If the setting for T

3000.0 s

0.00 to 300.00 s

)

exceeds

1 to 32767

(units: 100 ms)

0 to 30000

(units: 10 ms)

An error occurs and PID operation for the

corresponding loop is not executed.

An error occurs and PID operation for the

corresponding loop is not executed.

5 - 9

5. PID CONTROL PROCEDURE

Table 5.2 PID Control Data List

Data for

each

loop

Data

No.

Data Item Description

In the automatic mode, sets the

lower limit for the MV (manipulated

MV Lower

limit (MVLL)

MV Upper

limit (MVHL)

MV change

rate limit

MVL)

(

PV change

rate limit

PVL)

(

Derivative

gain (K

value) calculated in PID operation.

When the MV is less than the MV

lower limit, the MVLL is used as

the MV.

In the automatic mode, sets the

upper limit for the MV calculated in

PID operation.

When the MV is greater than the

MV upper limit, the MVHL is used

as the MV.

Sets the limit for variation between

the previous MV and present MV.

When the MV variation is greater

than the limit value, 1 is set for bit

1 (b1) of the alarm device.

Does not limit the MV variation.

(If the MV variation is greater than

the limit value, it is used

unchanged as the MV variation to

calculate the MV.)

Sets the limit for variation between

the previous PV and present PV.

When the PV variation is greater

than the limit value, 1 is set for bit

0 (b0) of the alarm device.

Does not limit the PV variation.

(If the PV variation is greater than

the limit value, it is used

unchanged as the PV variation to

perform the PID operation.)

Sets a time period (operation

delay) for derivative operation.

As the value is greater, the time

period decreases and operation

becomes closer to complete

derivative.

MELSEC-Q/Qn

Incomplete derivative

With PID limits Without PID limits

User

Setting Range

-50 to 2050 -50 to 2050 -32768 to 32767

0 to 2000 0 to 2000 -32768 to 32767

0.00 to 300.00

(Ideal value is

8.00)

Infinite(

If the setting

exceeds

for K

300.00

)

Specification

Range

0 to 32767

(unit: 0.01)

Setting Range

0.00 to 300.00

(Ideal value is

8.00)

Infinite(

If the setting for K

300.00

exceeds

)

Specification

Range

-32768 to

0 to 32767

(unit: 0.01)

User

32767

5 - 10

5. PID CONTROL PROCEDURE

Complete derivative

With PID limits Without PID limits

Setting

Range

-50 to 2050 -50 to 2050 -32768 to 32767 -32768 to 32767

0 to 2000 0 to 2000 -32768 to 32767 -32768 to 32767

User Specification

Range

Setting Range

User Specification

Range

MELSEC-Q/Qn

Processing when Set Data is

Outside the Allowable Setting Range

For the High Performance model

QCPU "with PID limits" or the

QnACPU, PID operation is

performed after conversion into the

following value.

When the MVLL or MVHL value is

less than -50, it is converted into -

50.

When the MVLL or MVHL value is

greater than 2050, it is converted

into 2050.

In the case of "with PID limits", PID

operation is performed after

conversion into the following value.

When the MVL value is less

than 0, it is converted into 0.

When the MVL value is greater

than 2000, it is converted into

2000.

In the case of "with PID limits", PID

operation is performed after

conversion into the following value.

When the PVL value is less

than 0, it is converted into 0.

When the PVL value is greater

than 2000, it is converted into

2000.

An error occurs and PID operation

for the corresponding loop is not

executed.

5 - 11

5. PID CONTROL PROCEDURE

Table 5.3 PID Control Data List

Data

Commo n setting data

Data for each loop

Data Item Description

No.

Number of

loops

Number of

loops in one scan

Selection of operational

expression

Sampling

cycle (T Proportional

constant (K

Integral

constant (T

Derivative

constant (T

Filter coefficient

(

MV Lower

limit (MVLL)

MV Upper

limit (MVHL)

MV change

rate limit (

PV change

rate limit (

)

MVL)

PVL)

Sets the number of loops for which PID operation will be executed. Sets the number of loops for which single PID operation will be executed when the multiple loops reaches the sampling cycle time.

Selects the PID operational expression indicated in Section 3.2.2.

Sets the cycle of PID operation. 0.01 to 60.00 s

PID operation ratio 0.01 to 100.00

This constant expresses the magnitude of the integral operation (I operation) effect.

Increasing the integral constant slows down the manipulated value change.

This constant expresses the magnitude of the derivative operation (D operation) effect. Increasing the derivative constant causes a

significant change in the manipulated value even with slight change of the control objective.

Sets the degree of filtering applied to the process value. The filtering effect decreases as the value gets closer to 0.

In the automatic mode, sets the lower limit for the MV (manipulated value) calculated in PID operation. When the MV is less than the MV lower limit, the MVLL is used as the MV. In the automatic mode, sets the upper limit for the MV calculated in PID operation. When the MV is greater than the MV upper limit, the MVHL is used as the MV. Sets the limit for variation between the previous MV and present MV. When the MV variation is greater than the limit value, 1 is set for bit 1 (b1) of the alarm device. Does not limit the MV variation. (If the MV variation is greater than the limit value, it is used unchanged as the MV variation to calculate the MV.) Sets the limit for variation between the previous PV and present PV. When the PV variation is greater than the limit value, 1 is set for bit 0 (b0) of the alarm device. Does not limit the PV variation. (If the PV variation is greater than the limit value, it is used unchanged as the PV variation to perform the PID operation.)

Setting Range

1 to 32 1 to 32

Forward

operation: 0

Reverse

operation: 1

0.1 to 3000.0 s

Infinite(

If the setting

exceeds

for T

3000.0 s

0.00 to 300.00 s

0 to 100 % 0 to 100

-50 to 2050 -50 to 2050

0 to 2000 0 to 2000

User Specifi-

cation Range

1 to 6000

(unit: 10 ms)

1 to 10000 (unit: 0.01)

)

1 to 32767

(unit: 100 ms)

0 to 30000

(unit: 10 ms)

0 or 1

MELSEC-Q/Qn

Processing when Set Data is

Outside the Allowable Setting

An error occurs and PID operation is not executed for all loops.

An error occurs and PID operation for the corresponding loop is not executed.

PID operation is performed after conversion into the following value.

When the MVLL or MVHL value is less than -50, it is converted into -50. When the MVLL or MVHL value is greater than 2050, it is converted into 2050.

PID operation is performed after conversion into the following value.

When the MVL value is less than 0, it is converted into 0. When the MVL value is greater than 2000, it is converted into 2000.

PID operation is performed after conversion into the following value.

When the PVL value is less than 0, it is converted into 0. When the PVL value is greater than 2000, it is converted into 2000.

Range

5 - 12

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

Specified device number +0

(2) PID control data can be set in any word device number.

However, all the data used for the corresponding loops must be set in devices with consecutive numbers.

(3) The PID control data allocations are shown below.

(a) For incomplete derivative

Number of loops

Number of loops in 1 scan

Selection of operational expression

Sampling cycle (T

Proportional constant (K

Integral constant (T

Derivative constant (T

Filter coefficient ( )

MV lower limit (MVLL)

MV upper limit (MVHL)

+10

MV change rate limit ( MVL)

+11

PV change rate limit ( PVL) 0 *

+12

Derivative gain (K

+13

0 *

+14

0 *

+15 +16

Selection of operational expression Sampling cycle (T

+17

Proportional constant (K

+18

Integral constant (T

+19

Derivative constant (T

+20

Filter coefficient (

+21

MV lower limit (MVLL)

+22

MV upper limit (MVHL)

+23

MV change rate limit ( MVL)

+24

PV change rate limit (

+25 +26

0 * Derivative gain (K

+27

0 *

+28

0 *

+29

)

PVL)

)

Conmon to all loops

For loop No.1 (14 words)

For loop No.2 (14 words)

For the total number of loops to be used

+(m + 0) +(m + 1) +(m + 2) +(m + 3) +(m + 4) +(m + 5) +(m + 6) +(m + 7) +(m + 8) +(m + 9) +(m + 10) +(m + 11)

+(m + 12) +(m + 13)

Selection of operational expression Sampling cycle (T Proportional constant (K Integral constant (T Derivative constant (T Filter coefficient ( MV lower limit (MVLL) MV upper limit (MVHL) MV change rate limit ( MVL) PV change rate limit ( PVL)

0 * Derivative gain (K

0 * 0 *

)

POINT

)

For loop No.n (14 words)

m=(n-1) 14+2

Store 0 into the " * " marked area of the PID control data. If other than 0 is stored into the " * " marked area, an error occurs and processing is not performed. (Error code: 4100)

5 - 13

5. PID CONTROL PROCEDURE

(a) Use the following formula to calculate the number of device points to be

used when setting the PID control data:

Number of device points = 2 + 14 n (n: Number of loops to be used)

(b) Set each data as a binary value.

last device number of the specified device, an error occurs and processing

Specified device number +0

+1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 +13 +14 +15 +16 +17 +18 +19 +20 +21 +22 +23

is not performed. (Error code: 4101)

(b) For complete derivative

Number of loops Number of loops in 1 scan Selection of operational expression Sampling cycle (T Proportional constant (K Integral constant (T Derivative constant (T Filter coefficient ( ) MV lower limit (MVLL) MV upper limit (MVHL) MV change rate limit ( MVL) PV change rate limit ( PVL) Selection of operational expression Sampling cycle (T Proportional constant (K Integral constant (T Derivative constant (T Filter coefficient ( ) MV lower limit (MVLL) MV upper limit (MVHL) MV change rate limit ( MVL) PV change rate limit ( Selection of opperational expression Sampling cycle (T

MELSEC-Q/Qn

Conmon to all loops

)

PVL)

For loop No.1 (10 words)

For loop No.2 (10 words)

For loop No.3 (10 words)

For the total number of loops to be used

+(m + 0) +(m + 1) +(m + 2) +(m + 3) +(m + 4) +(m + 5) +(m + 6) +(m + 7) +(m + 8) +(m + 9)

Selection of opperational expression Sampling cycle (T Proportional constant (K Integral constant (T Derivative constant (T Filter coefficient ( MV lower limit (MVLL) MV upper limit (MVHL) MV change rate limit ( MVL) PV change rate limit ( PVL)

)

m=(n-1) 10+2

For loop No.n (10 words)

(a) Use the following formula to calculate the number of device points to be

used when setting the PID control data:

Number of device points = 2 + 10 n (n: Number of loops to be used)

(b) Set each data as a binary value.

the last device number of the specified device, an error occurs and processing is not performed. (Error code: 4101)

5 - 14

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

5.1.1 Number of loops to be used and the number of loops to be executed in a single scan

(1) The number of loops to be used means the number of loops for which PID

operation is executed. The sampling cycle time is measured for the set number of loops when the PID operation instruction

executed for the loop for which the sampling cycle time reaches or exceeds the set sampling cycle.

(2) Processing time increases in proportion to the number of loops for which PID

operation is executed when the PID operation instruction is executed.

A : Fixed time for measuring sampling time

Processing time = A + B n

B : Time required to execute PID operation for a

loop

n = Number of loops

(3) The number of loops to be executed in a single scan means the number of loops

for which PID operation is executed in one scan when there is more than one loop for which sampling cycle time reaches or exceeds the set sampling cycle when the PID operation instruction is executed. If the number of loops to be executed in a single scan is set, PID operation is only executed for the set number of loops even if there are a greater number of loops for which the sampling cycle time reaches or exceeds the set sampling cycle when the PID operation instruction is executed. PID operation is executed for the rest of the loops in the next scan.

Execution of PID operation instruction

* is executed. PID operation is

Next PID operation instruction step

Sequence program

Execution of the PID operation

POINT

Processing time = A + B n

END 0

Processing time = A + B n

Scan time

END 0

If the number of loops for which sampling cycle time reaches or exceeds the set sampling cycle is greater than the number of loops to be executed in a single scan, the PID operation execution priority is as follows: (1) The lowest numbered loop is given the highest priority. (2) If there are loops in the preceding scan for which PID operation has not been

executed, they are given the highest priority.

REMARK

*: The following instructions are available as the PID operation instructions.

S.PIDCONT (incomplete derivative) PIDCONT (complete derivative)

5 - 15

5. PID CONTROL PROCEDURE

5.1.2 Sampling cycle

(1) A sampling cycle is the cycle in which PID operation is executed.

The measurement time for one scan is added to the measurement time of up to the preceding scan each time a PID operation instruction* When the cumulative value reaches or exceeds the set sampling cycle, the PID operation of the corresponding loop is performed.

(2) The measured value of the sampling time used for PID operation is truncated to

units of 10 ms. For example, if the sampling cycle setting is 50 ms and the measured value is 57 ms, PID operation is executed with a sampling time of 50 ms.If the measured value is 64 ms, PID operation is executed with a sampling time of 60 ms.

When sampling cycle = 50 ms

Power ON

Sequence program

Measured value

PID operation instruction

PID control data setting instruction

0 ms

END

PID operation instruction

19 ms

END

PID operation instruction

19 ms

19+19=38 ms

END

PID operation instruction

19 ms

38+19=57 ms

PID operation instruction

END

19 ms 19 ms

7+19=26 ms

PID operation instruction

END

19 ms 19 ms

26+19=45 ms

MELSEC-Q/Qn

is executed.

PID operation instruction

END

45+19=64 ms

PID operation instruction

4+19=23 ms

END

Measured value < Set value

PID operation is executed with set values.

Measured value < Set value

Measured value is changed to 57 - 50 = 7 ms

Measured value > Set value

PID operation is executed with 50 ms sampling time.

Measured value < Set value

Measured value is changed to 64 - 60 = 4 ms

Measured value > Set value

PID operation is executed with 60 ms sampling time.

Measured value < Set value

POINT

The sampling cycle is measured when the PID operation instruction is executed. Therefore, a value smaller than the sequence program scan time cannot be set for the sampling cycle. If a value smaller than the scan time is set, PID operation will be executed in accordance with the scan time.

REMARK

*1: The following instructions are available as the PID operation instructions.

S.PIDCONT (incomplete derivative) PIDCONT (complete derivative)

*2: The following instructions are available as the PID control data setting

instructions.

S.PIDINIT (incomplete derivative) PIDINIT (complete derivative)

5 - 16

5. PID CONTROL PROCEDURE

MEMO

MELSEC-Q/Qn

5 - 17

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

5.2 I/O Data

(1) The I/O data consists of input data, such as the SV (set value) and PV (process

value), which are set to execute PID operation, and output data, such as operation results.

(2) The I/O data area is divided into the "data area where data are allocated loop-by-

loop" and "work area used by the system to perform PID operation".

Data Name Description

Set value SV PID control target value 0 to 2000 -32768 to 32767

Process value PV

Automatic

manipulated

value

Process value

after filtering

Manual

manipulated

value

Manual/

automatic

selection

Alarm ALARM

PVf

MAN/

AUTO

Feedback data from controlled system objective to

A/D converter module

The manipulated value calculated by PID

operation.

Output from the D/A converter module to the

controlled system.

Process value calculated using the operation

formula in POINT(1) in Section 3.1.2/ POINT(1) in

Section 3.2.2.

In the manual control mode, the data output from

MAN

the D/A converter module is stored.

Selects whether the output data to the D/A

converter module is shown as a manual

manipulated value or an automatic manipulated

value.

In manual control mode, the automatic

manipulated value remains unchanged.

Used to determine if the change rate of the MV

(manipulated value) and the PV (process value) is

within or outside the allowable range.

Once set, the alarm data is retained until the user

resets it.

If the MV is outside the limit range, "1" is set for bit 1

(b1).

If the PV is outside the limit range, "1" is set for bit 0

(b0).

Table 5.4 I/O Data List

0: Manual manipulated value

1: Automatic manipulated

value

b15tob2b0b1

Setting Range

QCPU

With PID limits Without PID limits

-50 to 2050 -32768 to 32767

0: Manual manipulated value

1: Automatic manipulated

value

b15tob2b0b1

If the PV is outside the limit range, '1' is set for bit 0. If the MV is outside the limit range, '1' is set for bit 1.

5 - 18

5. PID CONTROL PROCEDURE

MELSEC-Q/Qn

0: Manual manipulated

1: Automatic manipulated

value

QnACPU

0 to 2000

-50 to 2050

QCPU "with PID limit", or QnACPU, PID operation is performed after

conversion into the following value.

QCPU "with PID limit", or QnACPU, PID operation is performed after

conversion into the following value.

QCPU "with PID limit", or QnACPU, PID operation is performed after

conversion into the following value.

An error occurs if the setting is neither 0 nor 1, and PID operation of the

corresponding loop will not be executed.

Processing when Set Data is Outside the Specified Range

When SV is less than 0, SV must be 0.

When SV is greater than 2000, SV must be 2000.

When PV is less than -50, PV must be -50.

When PV is greater than 2050, PV must be 2050.

When MVMAN is less than -50, MVMAN must be -50.

When MVMAN is greater than 2050, MVMAN must be 2050.

b15tob2b0b1

If the PV is outside the limit range, '1' is set for bit 0. If the MV is outside the limit range, '1' is set for bit 1.

5 - 19

5. PID CONTROL PROCEDURE

(3) For the I/O data, any word device number can be specified. However, all the data

used for the corresponding loops must be set in devices with consecutive numbers.

(4) The I/O data allocations are shown below.

(a) For incomplete derivative

Designated device number +0

Initial processing flag

Work area for PID control

(cannot be used)

Set value (SV)

+10

Process value (PV)

+11

Automatic manipulated value (MV)

+12

Process value after filtering (PVf)

+13

Manual manipulated value (MV

+14

Manual/automatic selection (MAN/AUTO)

+15

Alarm (ALARM)

+16

+17

Work area for No. 1 loop

(cannot be used)

+32

Set value (SV)

+33

Process value (PV)

+34

Automatic manipulated value (MV)

+35

Process value after filtering (PVf)

+36

Manual manipulated value (MV

+37 +38

Manual/automatic selection (MAN/AUTO)

+39

Alarm (ALARM)

+40

Work area for No. 2 loop

(cannot be used)

+55 +56

Set value (SV)

+57

Process value (PV) Automatic manipulated value (MV)

+58

+59

MELSEC-Q/Qn

Write

Read/write disabled

Write

Read

)

MAN

)

MAN

Write

Read/write

Read/write disabled

Write

Read

Write

Read/write

Read/write disabled

Write

Read

I/O data area for loop 1 (23 words)

I/O data area for loop 2 (23 words)

Number of loops to be used

I/O data area for loop 3 (23 words)

+ (m + 0) + (m + 1)

+ (m + 2) + (m + 3) + (m + 4) + (m + 5) + (m + 6)

+ (m + 7)

+ (m + 22)

Set value (SV) Process value (PV) Automatic manipulated value (MV) Process value after filtering (PVf) Manual manipulated value (MV Manual/automatic selection (MAN/AUTO) Alarm (ALARM)

Work area for No. n loop

(cannot be used)

)

MAN

m=(n-1) 23+10

Write

Read

Write

Read/write

Read/write disabled

I/O data area for loop n (23 words)

1) Use the following formula to calculate the number of device points to be used when setting the input/output data:

Number of device points = 10 + 23 n (n: Number of loops to be used)

2) Set each data as a binary value.

5 - 20

5. PID CONTROL PROCEDURE

3) The initial processing flag sets the processing method at the start of PID

•) In the initial PID operation processing cycle, operation is executed

•) The initial processing flag is set in the following manner:

4) Where "write" is designated for a data area, it indicates that the data should be written with a user sequence program. Where "read" is designated for a data area, it indicates that the data should be read with a user sequence program. Never attempt to write data to a data area designated "read/write disabled" or "read". If this is attempted, correct PID operation will not be possible.

5) If the number of device points used for the corresponding loops exceeds the last device number of the specified device, an error occurs and processing is not performed. (Error code: 4101)

MELSEC-Q/Qn

operation.

assuming that the set sampling cycle is reached or exceeded.

0......................... PID operation is batch processed in a single scan for

the number of loops to be used.

Other than 0 ......PID operation is processed in several scans for the

number of loops to be used. Sampling begins sequentially from the loop for which the initial processing has been completed. The number of processing loops per scan is the set number of loops to be executed per scan.

5 - 21

5. PID CONTROL PROCEDURE

(b) For complete derivative

Designated device number +0

Initial processing flag

Work area for PID control

(cannot be used)

Set value (SV)

+10

Process value (PV)

+11

Automatic manipulated value (MV)

+12

Process value after filtering (PVf)

+13

Manual manipulated value (MV

+14

Manual/automatic selection (MAN/AUTO)

+15

Alarm (ALARM)

+16

+17

Work area for No. 1 loop

(cannot be used)

+27

Set value (SV)

+28

Process value (PV)

+29

Automatic manipulated value (MV)

+30

Process value after filtering (PVf)

+31

Manual manipulated value (MV

+32 +33

Manual/automatic selection (MAN/AUTO)

+34

Alarm (ALARM)

+35

Work area for No. 2 loop

(cannot be used)

+45 +46

Set value (SV)

+47

Process value (PV) Automatic manipulated value (MV)

+48

+49

MELSEC-Q/Qn

Write

Read/write disabled

Write

Read

)

MAN

)

MAN

Write

Read/write

Read/write disabled

Write

Read

Write

Read/write

Read/write disabled

Write

Read

I/O data area for loop 1 (18 words)

I/O data area for loop 2 (18 words)

Number of loops to be used

I/O data area for loop 3 (18 words)

+ (m + 0) + (m + 1)

+ (m + 2) + (m + 3) + (m + 4) + (m + 5) + (m + 6)

+ (m + 7)

+ (m + 17)

Set value (SV) Process value (PV) Automatic manipulated value (MV) Process value after filtering (PVf) Manual manipulated value (MV Manual/automatic selection (MAN/AUTO) Alarm (ALARM)

Work area for No. n loop

(cannot be used)

)

MAN

m=(n-1) 18+10

Write

Read

Write

Read/write

Read/write disabled

I/O data area for loop n (18 words)

1) Use the following formula to calculate the number of device points to be used when setting the I/O data:

Number of device points = 10 + 18 n (n: Number of loops to be used)

2) Set each data as a binary value.

5 - 22

5. PID CONTROL PROCEDURE

3) The initial processing flag sets the processing method at the start of PID

operation.

•) In the initial PID operation processing cycle, operation is executed

•) The initial processing flag is set in the following manner:

4) Where "write" is designated for a data area, it indicates that the data

should be written with a user sequence program. Where "read" is designated for a data area, it indicates that the data should be read with a user sequence program. Never attempt to write data to a data area designated "read/write disabled" or "read". If this is attempted, correct PID operation will not be possible. Note that when control is to be started from the initial status, data must be cleared with a sequence program.

5) If the number of device points for the number of used loops exceeds the

last device number of the specified device, an error occurs and processing is not performed. (Error code: 4101)

MELSEC-Q/Qn

assuming that the set sampling cycle is reached or exceeded.

0......................... PID operation is batch processed in a single scan for

the number of loops to be used.

Other than 0 ......PID operation is processed in several scans for the

5 - 23

5. PID CONTROL PROCEDURE

MEMO

MELSEC-Q/Qn

5 - 24

6. PID CONTROL INSTRUCTIONS

MELSEC-Q/Qn

6. PID CONTROL INSTRUCTIONS

PID control instructions are defined in the same configuration as High Performance model QCPU, Redundant CPU, Universal model QCPU and QnACPU control instructions.

For details on the configuration of control instructions, see the QCPU (Q mode)/ QnACPU Programming Manual (Common Instructions.)

6 - 1

6. PID CONTROL INSTRUCTIONS

MEMO

MELSEC-Q/Qn

6 - 2

7. HOW TO READ EXPLANATIONS FOR INSTRUCTIONS

MELSEC-Q/Qn

7. HOW TO READ EXPLANATIONS FOR INSTRUCTIONS

The explanations for instructions presented in the next section take the following form.

Device

Classification

Usable

devices*

(1)

(2)

(3)

(4)

(5)

Internal Device

(system, user) Bit Word

X, Y, M,

L, SM, F,

B, SB,

FX*

, FY*2

T* C*

SD,SW,

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

QCPU

Process CPU

Universal

*1: First five digits of serial No. are 04122 or later *2: First five digits of serial No. are 05032 or later

Special Function

Module U

S.PIDCONT

SP.PIDCONT

8.1.2 PID Operation

Bit Word

Instruction mnemonic

S.PIDCONT

SP.PIDCONT

Internal Devices

(System, User)

Set Data

Execution

condition

Applicable

CPU

File Register

Command

Basic

PLC CPU

High Performance

MELSECNET/10 (H)

Usable Devices

Bit Word

[SET DATA]

[FUNCTION]

Set Data Description Data Type

First number of devices allocated to I/O device area 16-bi t binary

(1) When the S.PIDCONT instruction is executed, the sampling cycle is measured

and PID operation is performed.

(2) With the S.PIDCONT instruction, PID operation is carried out on the basis of the

set value (SV) and process value (PV) in the I/O data area set to the device number specified by S or later, and the operation result is stored into the automaticall y manipulated value (MV) area of the I/O data area.

(3) PID operation is executed in response to the execution of the S.PIDCONT

instruction appearing first after the set time for sampling cycle has elapsed (see Section 5.1.2).

(4) During PID control, turn ON the control command to execute the S.PIDCONT

instruction in every scan. If not, PID operation in a normal sampling cycle will not available. It is not possible to execute the S.PIDCONT instruction more than once in one

scan.

If it is executed more than once in one scan, PID operation cannot be performed

in a normal sampling cycle.

(5) The S.PIDCONT instruction is not available for use in an interrupt program, fixed

scan execution type program or low speed execution type program.

If the S.PIDCONT instruction has been used in an interrupt program, fixed scan execution type program or low speed execution type program, PID operation cannot be performed in a normal sampling cycle.

8 - 3

(1) Section number and general description of the instruction (2) "O" is appended to those devices that can be used with the instruction.

The classes of use into which the devices that can be used are divided are as follows.

, ST*5,

,D, W,

File

R, ZR

MELSECNET/10 (H)

\ *3

Bit Word

\Y \B

\SB

Special Function Module U

\SW

\G Z

*1 : The devices that can be set are indicated in the "Constant" and "Other" columns. *2 : FX and FY can only be used with bit data, and FD can only be used with word data. *3 : Can be used with MELSECNET/G,MELSECNET/H and MELSECNET/10. *4 : For the explanation of the corresponding devices, refer to the QCPU User's Manual

(Function Explanation, Programming Fundamentals) or the QnACPU Programming Manual (Basics).

*5 : T, ST and C can be used as the word devices only.

Index

Constant*1 Other*1

Decimal number

Hexadecimal number

Real number constant

Character string constant

Index Register

MELSEC-Q/Qn

Redundant

QnA Q4AR

CPU

Constant Other

U,DX, DY, N, BL, TR,

P, I, J,

BLY\S

(6)

7 - 1

7. HOW TO READ EXPLANATIONS FOR INSTRUCTIONS

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

(6) For S, designate the first number of the device numbers that are designated in the I/O

data area. If file registers (R) are designated for the I/O data area, do not set memory protect ON for the file registers (R). If memory protect is set ON, correct P ID operation will be precluded, although no error will occur. See Section 5.2 for details on the I/O data area.

(7) Execute the S.P IDCONT instruction in every scan even while the manual manipulated

value (MVMAN) is being output in the manual control mode.

The bumpless switching cannot be executed if the S.PIDCONT instruction has not been

executed.

See Section 4.3.1 for details on the bumpless switching.

(8) Use the READY signal to establish an interlock with respect to the individual modules,

so that the S.PIDCONT instruction is executed only when both the A/D converter module for reading the PV (process value) and the D/A converter module for outputting the MV (manipulated value) are normal.*

READY signal for the A/D converter module

Control command

READY signal for the D/A converter module

If the S.PIDCONT instruction is executed while either or both of the modules are faulty, PID operation cannot be executed correctly because the PV (process value) cannot be

(7)

[OPERATION ERRORS]

read correctl y and/or the MV (manipulated value) cannot be output correctly.

(1) An operation error will occur, the error flag (S M0) will be turned ON, and an error code

will be stored in SD0, in the following cases.

• When the S.PIDINIT instruction is executed before executing the S.PIDCONT instruction. (Error code: 4103)

• When the value set as the PID control data is outside the allowable range.

(Error code: 4100)

• When the device range allocated to the PID control data area, designated with exceeds the last device number of the corresponding device. (Error code: 4101)

REMARK

*: For details on the READY signals of the A/D converter module and D/A converter module,

refer to the manual for the relevant module.

8 - 4

(3) Indicates the expressions and instruction execution conditions in the ladder

mode.

Execution Condition Executed while ON Executed once at OFF ON

Symbol used on the

explanation page

(4) Explains the set data for each instruction and indicates the data type.

Data Type Description

16-bit binary

Indicates that binary 16-bit data or the first number of a word device can be used.

(5) Indicates the function of the instruction. (6) This shows a CPU module to which instructions are given.

: Usable, : Usable on condition, : Unusable

(7) Indicates the conditions that will cause errors and the error numbers.

7 - 2

MELSEC-Q/Qn

S.PIDCONT D100

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

This section explains how to use the PID control instructions for PID control and shows some programming examples.

8.1 PID Control Instructions

8 - 1

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Applicable

CPU

Basic

8.1.1 PID control data settings

Instruction

mnemonic

Internal Devices

(System, User)

Bit Word

Execution

condition

S.PIDINIT

SP.PIDINIT

File Register

Command

Set Data Description Data Type

First number of devices in which data for PID control is set 16-bit binary

(1) The PID control data for the number of loops to be used, which are set to the

device number specified by thereby making the PID control possible. See section 5.1 for details on PID control data

(2) When the S.PIDINIT instruction is executed at more than one point within a scan,

the setting value of the S.PIDINIT instruction closest to the S.PIDCONT instruction is effective.

(3) The S.PIDINIT instruction must be executed before the S.PIDCONT instruction.

PID control is not possible if the S.PIDINIT instruction has not been executed.

(1) An operation error will occur, the error flag (SM0) will be turned ON, and an error

code will be stored in SD0, in the following cases.

• When the value set as the PID control data is outside the allowable range. (Error code: 4100)

• When (MV upper limit) < (MV lower limit). (Error code: 4100)

• When (Number of loops used) < (Number of loops executed in one scan). (Error code:4100)

• When the device range allocated to the PID control data area, designated by exceeds the last device number of the corresponding device.

(Error code: 4101)

• When the "*" area of the PID control data that is mentioned in section 5.1 (3) is not 0. (Error code: 4100)

Set Data

[SET DATA]

[FUNCTIONS]

[OPERATION ERRORS]

PLC CPU

High Performance

MELSECNET/10 (H)

Direct J

Bit Word

Universal

Usable Devices

or later, are entered in the CPU module in a batch,

QCPU

Process CPU

*1: First five digits of serial No. are 04122 or later *2: First five digits of serial No. are 05032 or later

Special Function

Module U

S.PIDINIT

SP.PIDINIT

Redundant

CPU

Index Register

Constant Other

QnA Q4AR

8 - 2

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Applicable

CPU

8.1.2 PID operation

Instruction

mnemonic

Internal Devices

(System, User)

Bit Word

Execution

condition

S.PIDCONT

SP.PIDCONT

(1) When the S.PIDCONT instruction is executed, the sampling cycle is measured

(2) With the S.PIDCONT instruction, PID operation is carried out on the basis of the

(3) PID operation is executed in response to the execution of the S.PIDCONT

(4) During PID control, turn ON the control command to execute the S.PIDCONT

(5) The S.PIDCONT instruction is not available for use in an interrupt program, fixed

Set Data

[SET DATA]

[FUNCTION]

QCPU

Basic

File Register

Command

PLC CPU

High Performance

MELSECNET/10 (H)

Direct J

Bit Word

Universal

Usable Devices

Process CPU

*1: First five digits of serial No. are 04122 or later *2: First five digits of serial No. are 05032 or later

Special Function

Module U

S.PIDCONT

SP.PIDCONT

Redundant

CPU

Index Register

QnA Q4AR

Constant Other

Set Data Description Data Type

First number of devices allocated to I/O device area

16-bit binary

and PID operation is performed.

set value (SV) and process value (PV) in the I/O data area set to the device number specified by S or later, and the operation result is stored into the automatically manipulated value (MV) area of the I/O data area.

instruction appearing first after the set time for sampling cycle has elapsed (see Section 5.1.2).

instruction in every scan. If not, PID operation in a normal sampling cycle will not available. It is not possible to execute the S.PIDCONT instruction more than once in one scan. If it is executed more than once in one scan, PID operation cannot be performed in a normal sampling cycle.

scan execution type program or low speed execution type program. If the S.PIDCONT instruction has been used in an interrupt program, fixed scan execution type program or low speed execution type program, PID operation cannot be performed in a normal sampling cycle.

8 - 3

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

(6) For

(7) Execute the S.PIDCONT instruction in every scan even while the manual

(8) Use the READY signal to establish an interlock with respect to the individual

, designate the first number of the device numbers that are designated in the I/O data area. If file registers (R) are designated for the I/O data area, do not set memory protect ON for the file registers (R). If memory protect is set ON, correct PID operation will be precluded, although no error will occur. See Section 5.2 for details on the I/O data area.

manipulated value (MV The bumpless switching cannot be executed if the S.PIDCONT instruction has not been executed. See Section 4.3.1 for details on the bumpless switching.

modules, so that the S.PIDCONT instruction is executed only when both the A/D converter module for reading the PV (process value) and the D/A converter module for outputting the MV (manipulated value) are normal.*

READY signal for the A/D converter module

Control command

MAN) is being output in the manual control mode.

S.PIDCONT D100

MELSEC-Q/Qn

[OPERATION ERRORS]

(1) An operation error will occur, the error flag (SM0) will be turned ON, and an error

REMARK

READY signal for the D/A converter module

If the S.PIDCONT instruction is executed while either or both of the modules are faulty, PID operation cannot be executed correctly because the PV (process value) cannot be read correctly and/or the MV (manipulated value) cannot be output correctly.

code will be stored in SD0, in the following cases.

• When the S.PIDINIT instruction is executed before executing the S.PIDCONT

instruction. (Error code

: 4103)

• When the value set as the PID control data is outside the allowable range.

(Error code

: 4100)

• When the device range allocated to the PID control data area, designated with

, exceeds the last device number of the corresponding device.

(Error code

: 4101)

*: For details on the READY signals of the A/D converter module and D/A converter

module, refer to the manual for the relevant module.

8 - 4

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Applicable

CPU

Basic

PLC CPU

High Performance

Universal

8.1.3 Operation stop/start of designated loop no.

Usable Devices

Set Data

Internal Devices

(System, User)

Bit Word

Instruction

mnemonic

S.PIDSTOP S.PIDRUN

SP.PIDSTOP SP.PIDRUN

Execution

condition

[SET DATA]

Set Data Description Data Type

[FUNCTION]

(1) S.PIDSTOP, SP.PIDSTOP

(2) S.PIDRUN, SP.PIDRUN

[OPERATION ERRORS]

(1) An operation error will occur and the error flag (SM0) will be turned ON in the

File Register

Command

Loop number at which start/stop is to be executed 16-bit binary

(a) Stops the PID operation for the loop number designated by

The loop stopped by the S.PIDSTOP instruction does not resume PID operation even if the S.PIDINIT instruction is executed.

(b) Retains the operation data during the stop.

(a) Starts the PID operation of the loop No. specified by

This instruction is designed to re-execute PID operation of the loop No. that has stopped with the S.PIDSTOP instruction.

(b) This instruction will be ignored if the instruction is executed for the loop No.

that is currently running PID operation.

following cases.

• When the loop number designated by

• When

• When Redundant CPU, Universal model QCPU) (Error code: 4100)

• When the S.PIDINIT and S.PIDCONT instructions have not been executed before execution of the S.PIDSTOP instruction. (Error code: 4103)

• When the S.PIDINIT and S.PIDCONT instructions have not been executed before execution of the S.PIDRUN instruction. (Error code: 4103)

MELSECNET/10 (H)

Direct J

Bit Word

Special Function

Module U

is outside the range 1 to 8. (Basic model QCPU) (Error code: 4100)

is outside the range 1 to 32. (High Performance model QCPU,

QCPU

Process CPU

*1: First five digits of serial No. are 04122 or later *2: First five digits of serial No. are 05032 or later

SP.

Redundant

CPU

Index Register

indicates PIDSTOP/PIDRUN

QnA Q4AR

Constant

K, H

does not exist. (Error code: 4100)

Other

8 - 5

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

QCPU

Applicable

CPU

Basic

PLC CPU

High Performance

Universal

Process CPU

*1: First five digits of serial No. are 04122 or later *2: First five digits of serial No. are 05032 or later

Redundant

CPU

8.1.4 Parameter change at designated loop

Usable Devices

Set Data

Internal Devices

(System, User)

Bit Word

File Register

Instruction

mnemonic

S.PIDPRMW

SP.PIDPRMW

Execution

condition

Command

[SET DATA]

Set Data Description Data Type

Loop number for which change is to be made

First number of devices in which PID control data to be

changed is stored

[FUNCTIONS]

(1) Changes the operation parameter for the loop number designated by

PID control data stored in the devices starting with the device number designated

(2) The configuration of the data for PID control which starts from the device number

designated by

Selection of operational expression

Sampling cycle (T

Proportional constant (K

Integral constant (T

Derivative constant (T

Filter coefficient ( )

MV lower limit (MVLL)

MV upper limit (MVHL)

MV change rate limit ( MVL)

PV change rate limit ( PVL)

+10

Derivative gain (K

+11

+12

+13

MELSECNET/10 (H)

Direct J

Bit Word

Special Function

Module U

S.PIDPRMW

SP.PIDPRMW

Index Register

Constant

K, H

16-bit binary

is shown below.For details on PID control data, see Section 5.1.

)

QnA Q4AR

Other

to the

8 - 6

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

[OPERATION ERRORS]

(1) An operation error will occur and the error flag (SM0) will be turned ON, and error

code will be stored in SD0, in the following cases.

• When the loop number designated by

• When

• When Redundant CPU, Universal model QCPU) (Error code: 4100)

• When the PID control data is outside the setting range. (Error code: 4100)

• When any of

(Error code: 4100)

• When the device range assigned to the PID control data area by last device number of the applicable range. (Error code: 4101)

• When the S.PIDINIT instruction has not been executed before execution of the S.PIDPRMW instruction. (Error code: 4100)

is outside the range 1 to 8.(Basic model QCPU) (Error code: 4100)

is outside the range 1 to 32.(High Performance model QCPU,

+10, S+12 and S+13 in the PID control data is not 0.

does not exist. (Error code: 4100)

MELSEC-Q/Qn

exceeds the

8 - 7

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

8.2 PID Control Program Examples

This section describes examples of sequence programs that execute PID control.

8.2.1 System configuration for program examples

The following illustrates the system configuration for the program examples in Sections

8.2.2 and 8.2.3

CPU module

MELSEC-Q/Qn

PID operation

Loop 1

PID operation

Loop 2

Q62DA

CH.1

CH.2

External device

Q64AD I/O numbers ...........X/Y80 to X/Y8F

Q62DA I/O numbers ...........X/YA0 to X/YAF

Q64AD

CH.1

CH.2

8 - 8

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

8.2.2 Program example for automatic mode PID control

This section gives a program example in which PID operation is performed using the digital values imported from the Q64AD as PV and the MV obtained as a result of PID operation are output from the Q62DA to control external devices.

[PROGRAMMING CONDITIONS]

(1) Refer to Section 8.2.1 for details on the system configuration.

(2) PID operation is executed for 2 loops.

(3) The sampling cycle is 1 second.

(4) The PID control data is set in the following devices:*

Common data ..................................D500 and D501

Loop 1 data ......................................D502 to D515

Loop 2 data ......................................D516 to D529

(5) The I/O data is set in the following devices:*

Common data ..................................D600 to D609

Loop 1 data ......................................D610 to D632

Loop 2 data ......................................D633 to D655

(6) The following SV are set for loop 1 and loop 2 using a sequence program:

Loop 1 ..............................................600

Loop 2 ..............................................1000

(7) The following devices are used for PID control start/stop commands.

PID control start command ..............X0

PID control stop command ..............X1

(8) The digital values of the Q64AD and Q62DA are set within the range 0 to 2000.

MELSEC-Q/Qn

REMARK

*1: For details on PID control data, see Section 5.1. *2: For details on I/O data, see Section 5.2.

8 - 9

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

[PROGRAM EXAMPLE]

MELSEC-Q/Qn

Sets the number of loops to be used to 2.

Sets the number of loops to be executed per scan to 2.

Sets the operation expression to forward operation.

Sets the sampling cycle to 1s.

Sets the proportional constant to 1.

Sets the integral constant to 3000s.

Sets the derivative constant to 0s.

Sets the filter coefficient to 0%.

Sets the MV lower limit to 0.

Sets the MV upper limit to

2000.

Sets the MV change rate limit to 2000.

Sets the PV change rate limit to 2000.

Sets 0.

Setting of common data of PID control data

Setting of PID control data for loop 1

Sets the derivative gain to 8.

Sets 0.

8 - 10

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Sets the operation expression to reverse operation.

Sets the sampling cycle to 1s.

Sets the proportional constant to 1.

Sets the integral constant to 3000s.

Sets the derivative constant t o 0s.

Sets the filter coeffic ent to 0%.

Sets the MV lower limit to 0.

Sets the MV upper limit to 2000.

Sets the MV change rate limit to 2000.

Sets the PV change rate limit to 2000.

Setting of PID control data for loop 2

Sets 0.

Sets the derivative gain to 8.

Sets 0.

Sets the PID control data that are set in D500 to D529.

Sets the Q62DA to output enable.

Sets the initial processing flag to 0.

Sets the SV to 600.

Sets the automatic mode.

Sets the SV to 1000.

Sets the automatic mode.

PID opera tion start command

Setting of common data of I/O data

Setting of I/O data for loop 1

Setting of I/O data for loop 2

8 - 11

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Sets the PV from the Q64AD to the I/O data area (for loop 1).

Sets the PV from the Q64AD to the I/O data area (for loop 2).

PID operation

Turns ON the output enable of CH. 1 of the Q62DA.

Turns ON the output enable of CH. 2 of the Q62DA.

Writes the MV of loop 1 to CH. 1 of the Q62DA.

Writes the MV of loop 2 to CH. 2 of the Q62DA.

PID operation stop

8 - 12

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

8.2.3 Program example for changing the PID control mode between automatic and manual

An example program for switching between automatic and manual modes while executing PID operation is described below.

[PROGRAMMINGCONDITIONS]

(1) Refer to Section 8.2.1 for details on the system configuration.

(2) PID operation is executed for 1 loop.

(3) The sampling cycle is 1 second.

(4) The PID control data is set in the following devices:

Common data ............................................................ D500 and D501

Loop 1 data ................................................................ D502 to D515

(5) The I/O data is set in the following devices:

Common data ............................................................ D600 to D609

Loop 1 data ................................................................ D610 to D630

(6) The SV and MV in manual mode are set with external digital switches as follows:

SV............................................................................... X30 to X3F

MV (manual control mode) ........................................ X20 to X2F

(7) The following devices are used to start and stop PID control and the

automatic/manual changeover command:

PID control start command ........................................ X0

PID control stop command ........................................ X1

SV setting command.................................................. X3

MV setting command in manual mode ..................... X4

Automatic/manual mode changeover command ...... X6

(OFF: Automatic mode, ON: Manual mode)

(8) The digital values of the Q64AD and Q62DA are set within the range 0 to 2000.

8 - 13

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

(9) The PID bumpless processing flag, SM794, is set to OFF. In the manual mode,

the SV is automatically rewritten to the PV when PID operation is performed. Therefore, when the manual mode is returned to the automatic mode, the SV must be rewritten to the one used in the automatic mode before switching to the manual mode. The SV is rewritten step-by-step 10 times as illustrated below:

SV value in manual mode

Manual to automatic mode change command

SV value in automatic mode

1 s

1 s 1 s 1 s

10 s

The SV is rewritten using the operation method illustrated below:

SV value in manual mode

SV value in

automatice mode

Incremental

value

The incremental value obtained with the formula above is added to SV every second. The remainder is added in the first addition operation.

MELSEC-Q/Qn

Remainder

8 - 14

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

[PROGRAM EXAMPLE]

MELSEC-Q/Qn

Sets the n umber of loops to be used to 1.

Sets the nu mber of lo ops to be execu ted per scan to 1. Sets the operation expression to forward operation.

Sets the sampling cycle to 1s.

Sets the proportional constant to 1.

Sets the integral constant to 3000s.

Sets the derivati ve constant to 0s.

Sets the filter coefficient to 0%.

Sets the MV lower limit to 0.

Sets the MV upper limit to 2000.

Sets the MV change rate limit to 2000.

Sets the PV change rate limit to 2000.

Setting of common data of PID control data

Setting of PID control da ta for loop 1

Sets 0.

Sets the derivative gain to 8.

Sets 0.

Sets the PID control data that are set in D500 to D515.

Sets the Q62DA to output enable.

Sets the initial processing flag to 0.

Inputs the SV externally.

Saves the SV for manual to automatic mode change processing.

PID operation start command

Sets the PV value from the Q64AD to the I/O data area.

I/O data setting

8 - 15

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Sets the manual mode.

Resets the devices used for manual to automatic mode change processing.

Sets the MV externally.

Sets the automatic mode.

Manual to automatic mode change command

Since the manual mode is not switched to the automatic mode until PID operation is performed after the manual to automatic mode change command has turned ON, executes the manual to automatic change command processing (step 115 to step 151) with a delay in switching time taken into consideration.

Processing in manual mode

(Present SV value)

is calculated; the quotient is stored in D215 and the remainder in D216.

Command to execute processing at 1 second intervals

Counts the number of times.

Subtracts the quotient from the SV.

Subtracts the remainder from the SV only at the first time.

End of manual to automatic mode change processing

Executes the S.PIDCONT instruction in either the manual mode or automatic mode.

Turns ON the output enable of CH.1 of the Q62DA.

Writes the MV value to CH.1 of the Q62DA.

PID operation stop

(SV value in

automatic mode)

Processing to return the SV to the value used in the automatic mode.

8 - 16

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

This chapter explains the PID control instruction usage and program examples for implementing PID control.

9.1 PID Control Instructions

9 - 1

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Applicable

CPU

9.1.1 PID control data settings

Instruction

mnemonic

Internal Devices

(System, User)

Bit Word

Execution

condition

PIDINIT

PIDINITP

File Register

Set Data

[SET DATA]

Set Data Description Data Type

[FUNCTIONS]

(1) The PID control data for the number of loops to be used, which are set to the

device number specified by thereby making the PID control possible. Refer to Section 5.1 for details of the PID control data.

(2) When the PIDINIT instruction is executed at more than one point within a scan,

the setting value of the PIDINIT instruction closest to the PIDCONT instruction is effective.

(3) The PIDINIT instruction must be executed before the PIDCONT instruction.

PID control is not possible if the PIDINIT instruction has not been executed.

[OPERATION ERRORS]

(1) An operation error will occur, the error flag (SM0) will be turned ON, and an error

code will be stored in SD0, in the following cases.

• When the value set as the PID control data is outside the allowable range.

• When (Number of loops used) < (Number of loops executed in one scan).

• When (MV upper limit value) < (MV lower limit value).

• When the device range allocated to the PID control data area, designated by exceeds the last device number of the corresponding device.

QCPU

Basic

Command

PLC CPU

High Performance

MELSECNET/10 (H)

Direct J

Bit Word

Universal

Usable Devices

Process CPU

*1: First five digits of serial No. are 04122 or later

Special Function

Module U

PIDINIT

PIDINITP

Redundant

CPU

Index Register

QnA Q4AR

Constant Other

First number of devices in which data for PID control is set 16-bit binary

or later, are entered in the CPU module in a batch,

(Error code: 4100)

(Error code: 4101)

9 - 2

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

9.1.2 PID control

Instruction

mnemonic

Internal Devices

(System, User)

Bit Word

PIDCONT

PIDCONTP

Set Data

[SET DATA]

[FUNCTION]

QCPU

Applicable

CPU

Execution

condition

Basic

File Register

Control command

PLC CPU

High Performance

MELSECNET/10 (H)

Direct J

Bit Word

Universal

Usable Devices

Process CPU

*1: First five digits of serial No. are 04122 or later

Special Function

Module U

PIDCONT

PIDCONTP

Redundant

CPU

Index Register

QnA Q4AR

Constant Other

Set Data Description Data Type

First number of devices allocated to I/O device area

16-bit binary

(1) When the PIDCONT instruction is executed, the sampling cycle is measured and

PID operation is performed.

(2) With the PIDCONT instruction, PID operation is carried out on the basis of the set

value (SV) and process value (PV) in the I/O data area set to the device number specified by S or later, and the operation result is stored into the automatically manipulated value (MV) area of the I/O data area.

(3) PID operation is executed in response to the execution of the PIDCONT

instruction appearing first after the set time for sampling cycle has elapsed (see Section 5.1.2).

(4) During PID control, turn ON the control command to execute the PIDCONT

instruction in every scan. If not, PID operation in a normal sampling cycle will not available. It is not possible to execute the PIDCONT instruction more than once in one scan. If it is executed more than once in one scan, PID operation cannot be performed in a normal sampling cycle.

(5) The PIDCONT instruction is not available for use in an interrupt program, fixed

scan execution type program or low speed execution type program. If the PIDCONT instruction has been used in an interrupt program, fixed scan execution type program or low speed execution type program, PID operation cannot be performed in a normal sampling cycle.

9 - 3

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

(6) For

, designate the first number of the device numbers that are designated as the I/O data area. If file registers (R) are designated for the I/O data area, do not set memory protect ON for the file registers (R). If memory protect is set ON, correct PID operation will be precluded, although no error will occur. See Section 5.2 for details on the I/O data area.

(7) Execute the PIDCONT instruction in every scan even while the manual

manipulated value (MV

MAN) is being output in the manual control mode.

The bumpless function cannot be executed if the PIDCONT instruction has not been executed. See Section 4.3.1 for details on the bumpless function.

(8) Use the READY signal to establish an interlock with respect to the individual

modules, so that the PIDCONT instruction is executed only when both the A/D converter module for reading the PV (process value) and the D/A converter module for outputting the MV (manipulated value) are normal.*

READY signal for the A/D converter module

Control command

READY signal for the D/A converter module

PIDCONT D100

If the PIDCONT instruction is executed while either or both of the modules are faulty, PID operation cannot be executed correctly because the PV (process value) cannot be read correctly and/or the MV (manipulated value) cannot be output correctly.

[OPERATION ERRORS]

(1) An operation error will occur, the error flag (SM0) will be turned ON, and an error

code will be stored in SD0, in the following cases.

• When the PIDINIT instruction is executed before executing the PIDCONT

instruction. (Error code

• When the value set as the PID control data is outside the allowable range.

• When the device range allocated to the PID control data area, designated with

, exceeds the last device number of the corresponding device.

(Error code

MELSEC-Q/Qn

: 4103)

(Error code

: 4100)

: 4101)

REMARK

*: For details on the READY signals of the A/D converter module and D/A converter

module, refer to the manual for the relevant module.

9 - 4

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

QCPU

CPU

Basic

PLC CPU

High Performance

Universal

Process CPU

Redundant

CPU

9.1.3 Monitoring PID control status (QnACPU only)

Usable Devices

Set Data

Internal Devices

(System, User)

Bit Word

File Register

MELSECNET/10 (H)

Direct J

Bit Word

Special Function

Module U

Index Register

Constant

K, H

Instruction

mnemonic

PID57

PID57P

Execution

condition

Command

PID57

PID57P

S1 S2

[SET DATA]

Set Data Description Data Type

First I/O number of the AD57(S1) used to monitor the PID

control status

Screen number corresponding to the loop number to be

monitored

Initial screen display request

[FUNCTION]

(1) The display unit of the AD57(S1) designated by

of the loop number designated by

in a bar graph. By executing the initial screen display request, designated by in the still portion of the monitor screen (with the exception of bar graphs and numerical data) are displayed in the initial state of PID control monitoring.

(2) Addresses 0 to 1599 in the VRAM area of the AD57(S1) are used for the PID

control monitor. Therefore, these addresses cannot be used by the user if PID control status monitoring is executed; if they are, the data stored in them will be lost.

(3) Execute the CMODE instruction (AD57 command) to monitor the PID control

status before executing the PID57 instruction. If the CRT standard display mode, set with the CMODE instruction, has not been set for the AD57(S1), the display unit will not be able to display anything.

displays the PID control status

, the characters

QnA Q4ARApplicable

Other

16-bit binary

9 - 5

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

(4) Execute the PID57 instruction only after the PIDINIT and PIDCONT instructions

have been executed. An error will occur if the PID57 instruction is executed before the PIDINIT and PIDCONT instructions.

(5) Designate the loop number indicated by

with a screen number from "1" to "4",

as shown below:

Screen Number

Loop Numbers to be Monitored

1 Loop 1 to loop 8

Loop 9 to loop 16

Loop 17 to loop 24

Loop 25 to loop 32

(6) The initial screen display request, designated by

, displays the characters in the still portion of the monitor screen. To make the initial screen display request, set "0" for Characters besides the bar graphs and numeric data will be not displayed unless the initial screen display request is executed.

(7) After the initial screen is displayed, the value designated by

stored in If the device designated by

and then the PID control monitor function is executed.

is a file register, do not set the memory protect function for the file register ON. If the memory protect function is ON, the screen cannot display the monitor data correctly.

(8) The initial screen display request should only be executed once in response to

the first PID57 instruction after the start of QnACPU operation. If it is executed every scan, the bar graphs and numeric data will not be displayed, although the characters in the still portion are displayed.

(9) To monitor PID control status with the AD57(S1), a character generator ROM and

canvas ROM must be loaded to the AD57(S1). The characters shown in Figure 9.1, corresponding to character codes 000 to 00B

H, must be created in the character generator ROM.

If these characters are not created, bar graphs cannot be displayed. Refer to the following manuals for details on creating the character generator ROM and canvas ROM.

• SW1GP-AD57P Operating Manual

MELSEC-Q/Qn

is automatically

9 - 6

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

76543210 76543210 76543210 76543210 76543210 76543210

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

000H

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

001H

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

002H

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

003H

Address where a character should be created

7654321076543210

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

007H006H

Address where a character should be created

76543210

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

008H

76543210

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

009H 00BH

Fig. 9.1 Characters for PID Control Status Monitor

MELSEC-Q/Qn

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

004H

76543210

9 10 11 12 13 14 15 16 17 18 19

0 1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17 18 19

005H

76543210

9 10 11 12 13 14 15 16 17 18 19

00AH

[OPERATION ERRORS]

(1) An operation error will occur and the error flag (SM0) will be turned ON, and an

error code will be stored in SD0, in the following cases.

• When the CMODE instruction has not been executed for AD57(S1). (Error code: 2110)

• When the PIDINIT instruction has not been executed before the PID57

instruction. (Error code: 4103)

• When the PIDCONT instruction has not been executed before the PID57

instruction. (Error code: 4103)

• When the screen number designated with

is outside the range of 1 to 4.

(Error code

: 4100)

9 - 7

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

MELSEC-Q/Qn

Applicable

CPU

Basic

PLC CPU

High Performance

9.1.4 Operation stop/start of designated loop no.

Usable Devices

Set Data

Internal Devices

(System, User)

Bit Word

File Register

MELSECNET/10 (H)

Direct J

Bit Word

Instruction

mnemonic

PIDSTOP PIDRUN

PIDSTOPP PIDRUNP

Execution

condition

Command

[SET DATA]

Set Data Description Data Type

Loop number at which start/stop is to be executed 16-bit binary

[FUNCTION]

(1) PIDSTOP, PIDSTOPP

(a) Stops the PID operation for the loop number designated by

The loop stopped by the PIDSTOP instruction does not resume PID operation even if the PIDINIT instruction is executed.

(b) Retains the operation data during the stop.

(2) PIDRUN, PIDRUNP

(a) Starts the PID operation of the loop No. specified by

This instruction is designed to re-execute PID operation of the loop No. that has stopped with the PIDSTOP instruction.

(b) This instruction will be ignored if the instruction is executed for the loop No.

that is currently running PID operation.

[OPERATION ERRORS]

(1) An operation error will occur and the error flag (SM0) will be turned ON in the

following cases.

• When the loop number designated by

• When n is outside the range 1 to 8. (Basic model QCPU) (Error code: 4100)

• When CPU, Universal model QCPU, QnACPU) (Error code: 4100)

is outside the range 1 to 32.(High Performance model QCPU, Redundant

• When the PIDINIT and PIDCONT instructions have not been executed before execution of the PIDSTOP instruction. (Error code: 4103)

• When the PIDINIT and PIDCONT instructions have not been executed before execution of the PIDRUN instruction. (Error code: 4103)

Universal

Special Function

Module U

QCPU

Process CPU

*1: First five digits of serial No. are 04122 or later

Redundant

CPU

Index Register

indicates PIDSTOP/PIDRUN

QnA Q4AR

Constant

K, H

does not exist. (Error code: 4100)

Other

9 - 8

Mitsubishi QCPU, Q Mode, QnACPU Programming Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

• SAFETY PRECAUTIONS •

REVISIONS

INTRODUCTION

CONTENTS

About Manuals

Generic Terms and Abbreviations Used in This Manual

1. GENERAL DESCRIPTION

1.1 PID Processing Method

2. SYSTEM CONFIGURATION FOR PID CONTROL

2.1 Applicable PLC CPU

3. PID CONTROL SPECIFICATIONS

3.1 PID Control by incomplete derivative

3.1.1 Performance specifications

3.1.2 PID operation block diagram and operation expressions

3.1.3 PID control instruction list

3.2 PID Control by Complete Derivative

3.2.1 Performance specifications

3.2.2 PID operation block diagram and operation expressions

3.2.3 PID control instruction list

4. FUNCTIONS OF PID CONTROL

4.1 Outline of PID Control

4.2 Functions of PID Control

4.2.1 Operation method

4.2.2 Forward operation and reverse operation

4.2.3 Proportional operation (P operation)

4.2.4 Integral operation (I operation)

4.2.5 Derivative operation (D operation)

4.2.6 PID operation

4.3 Other Functions

4.3.1 Bumpless changeover function

4.3.2 MV upper/lower limit control function

4.3.3 Monitoring PID control with the AD57(S1) (QnACPU only)

4.3.4 Function for transfer to the SV storage device for the PV in manual mode

4.3.5 Changing the PID control data or input/output data setting range (QCPU only)

5. PID CONTROL PROCEDURE

5.1 PID Control Data

5.1.1 Number of loops to be used and the number of loops to be executed in a single scan

5.1.2 Sampling cycle

5.2 I/O Data

6. PID CONTROL INSTRUCTIONS

7. HOW TO READ EXPLANATIONS FOR INSTRUCTIONS

8. INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

8.1 PID Control Instructions

8.1.1 PID control data settings

8.1.2 PID operation

8.1.3 Operation stop/start of designated loop no.

8.1.4 Parameter change at designated loop

8.2 PID Control Program Examples

8.2.1 System configuration for program examples

8.2.2 Program example for automatic mode PID control

8.2.3 Program example for changing the PID control mode between automatic and manual

9. COMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES

9.1 PID Control Instructions

9.1.1 PID control data settings

9.1.2 PID control

9.1.3 Monitoring PID control status (QnACPU only)

9.1.4 Operation stop/start of designated loop no.