Burkert 1110 series Operating Instructions Manual

Operating Instructions

Bedienungsanleitung

Instructions de Service

Type 1110

Digital Industrial Controller

Digitaler Industrieregler

We reserve the right to make technical changes without notice.
Technische Änderungen vorbehalten.

© 2002 Bürkert Werke GmbH & Co. KG

Operating Instructions 0507/10_EU-ML_00801137

DIGITAL INDUSTRIAL CONTROLLER

CONTENTS:

1 GENERAL SAFETY INSTRUCTIONS .......................................................................... 3

2 CHARACTERISTICS AND POSSIBILITIES OF USE

(OVERVIEW) .............................................................................................................................. 4

3 INSTALLING THE CONTROLLER .................................................................................. 6

4 CONNECTIONS ....................................................................................................................... 6

4.1 Pin assignments ........................................................................................................................ 6

4.2 Supply voltages ......................................................................................................................... 7

4.2.1 115/230 V and 24/48 V Changeover

4.2.2 24V DC/AC Converter for operation at 24 V DC

................................................................................

........................................................

4.3 Signal inputs ............................................................................................................................... 9

4.4 Signal outputs ........................................................................................................................... 11

5 CONTROLLER STRUCTURES...................................................................................... 13

5.1 Overall Structure of the Digital Industrial regulator ................................................. 13

5.2 Controller for single control loop ......................................................................................15

5.2.1 Single control loop

5.2.2 Standard controller structure

..................................................................................................................

.............................................................................................

15
15

5.3 Controller with additional functions for feed forward control ............................... 17

5.3.1 Single control loop with feed forward control

5.3.2 Feed forward controller structure

.....................................................................................

.............................................................

17
17

5.4 Controller with additional functions for follow-up control ...................................... 19

5.4.1 Servo-control (external set-point input)

5.4.2 External setpoint controller structure

........................................................................

.............................................................................

19
19

5.5 Controller with additional functions for ratio control ................................................21

5.5.1 Ratio control

5.5.2 Ratio controller structure

..............................................................................................................................

.....................................................................................................

21
22

5.6 Controller with additional functions for cascade control ....................................... 23

5.6.1 Cascade control

5.6.2 Cascade controller structure

......................................................................................................................

.............................................................................................

23
24

5.7 Explanations of the controller structures' function blocks .................................... 26

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8
8

1110 - 1

DIGITAL INDUSTRIAL CONTROLLER

6 OPERATION ............................................................................................................................. 38

6.1 Operating levels....................................................................................................................... 38

6.2 Operator controls and indicators ..................................................................................... 39

6.3 Process operation .................................................................................................................. 40

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6.4 Setting numeric values

6.5 Configuration ............................................................................................................................ 43

6.5.1 Operation during configuration

6.5.2 Main menu of the configuration level

6.5.3 Configuration menus

6.5.4 Meanings of the symbols in the configuration menus

6.6 Parameter definition .............................................................................................................. 68

6.6.1 Operation during parameter definition

6.6.2 Parameter definition menus

7 SELF-OPTIMISATION ......................................................................................................... 72

......................................................................................................... 42

.............................................................................................................

.........................................................................................

.............................................................................

...........................................

..........................................................................

...............................................................................................

43
44
46
54

68
68

7.1 Stability and control quality ................................................................................................ 72

7.2 Principle of self-optimisation by adaption ....................................................................72

7.3 Principle of self-optimisation by tuning ......................................................................... 72

7.4 Operating principle of the tuning and adaption modules ...................................... 74

7.5 Notes on using the tuning and adaption module ..................................................... 75

7.6 Operating the tuning and adaption functions ............................................................. 79

8 ERROR MESSAGES AND WARNINGS .................................................................... 81

9 ANNEX ........................................................................................................................................ 84

9.1 Characteristics of PID controllers ....................................................................................84

9.2 Rules for adjusting PID controllers ................................................................................. 88

9.3 List of abbreviations ............................................................................................................... 91

9.4 Index ............................................................................................................................................. 92

9.5 Userconfiguration .................................................................................................................... 93

2 - 1110

DIGITAL INDUSTRIAL CONTROLLER

1 GENERAL SAFETY INSTRUCTIONS

To ensure that the device functions correctly, and will have a long service life, please
comply with the information in these Operating Instructions, as well as in the
application conditions and the additional data given in the data sheet:

• When planning the application of the device, and during its operation, observe
the general technical rules!

• Installation and maintenance work should only be carried out by specialist staff
using the correct tools!

• Observe the relevant accident prevention and safety regulations for electrical
equipment during the operation and maintenance of the unit!

• If the controller is part of a complex automation system, a defined and controlled
re-start must be carried out following an interruption of operation.

• Always switch off the voltage before carrying out work on the device!

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• Take suitable measures to prevent unintentional operation or impermissible
impairment.

• If these instructions are ignored, no liability will be accepted from our side, and
the guarantee on the device and on accessory parts will become invalid!

1110 - 3

DIGITAL INDUSTRIAL CONTROLLER

2 CHARACTERISTICS AND POSSIBILITIES OF USE

(OVERVIEW)

The digital industrial controller is designed as a PID controller for controlling tasks in
the process control technology. It represents a new controller generation based on a
microprocessor.

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Either standard
scaleable controller inputs or resistance thermometers and thermocouples can be
connected.

Outputs for continuous standard signals or relay outputs can now be used as
controller outputs.

In addition, outputs for error reports and a binary input and output for additional
functions are available.

RS 232 or RS 485 / PROFIBUS serial interfaces are available as connection
options.

The following control tasks can be realised with the controller:

• Fixed setpoint control (single control loop)

• Fixed setpoint with feed forward control

• Follow-up control (external set-value)

• Ratio control

• Cascade control

The controller is characterised by user-friendly operation and has a backlit, easily
legible LCD plain language display.
The following operator actions can be carried out with menu support in various
operator control levels:

current/voltage

and frequency-analog signals can be applied to the

4 - 1110

• Configuration (defining the controller structure),

• Parameter definition (setting controller parameters),

• Process operation (manual interventions).

Configuration and parameter definition data is stored in an EEPROM to protect
against power failures.

NOTE

The digital industrial regulator complies with the 73/23/EWG
Low Voltage Regulations and the EMC 89/2338/EWG
Regulations.

DIGITAL INDUSTRIAL CONTROLLER

Unauthorized operation of the individual operator control levels can be rendered
impossible by a free choice of user codes. Regardless of this, a permanently
programmed and invariable master code exists which allows access to all levels.
This 4-digit master code can be found on the bottom margin of this page. It
can be cut out and stored separately from the instruction manual.

Self-optimization algorithms (for self-adjustment and adaption) are implemented in
the controller and ensure automatic adaption of the controller’s parameters to the
process in the closed control loop.
Figure 1 shows an overview of the controller.

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Figure 1: Overview diagram

✂

Mastercode for digital
industrial controller:

8575

1110 - 5

DIGITAL INDUSTRIAL CONTROLLER

3 INSTALLING THE CONTROLLER

The controller was conceived for installation in switch panels. On the controller,
first of all remove the retaining elements engaged on both sides by swivelling in
anticlockwise direction. Insert the controller, including the enclosed rubber seal, into
the insertion opening from the front. Then again engage the two retaining elements
in the bolts on the sides of the housing and screw in the threaded pin inside from the
rear.

Switch panel insertion opening (W x H): 92 x 92 mm2 (+0,8 mm)
Outer controller dimensions (W x H x D): 96 x 96 x 173 mm

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Controller weight: 960 g
Degree of protection: IP 65 (front when using the

Operating temperature: 0 bis +50 °C
Storage temperature: -20 bis +60 °C

ATTENTION!

4 CONNECTIONS

4.1 Pin assignments

3

enclosed seal)

To ensure the electromagnetic compatibility (EMC) the screw
terminal TE (Technical Earth) must be connected to the earth
potential by a cable that is as short as possible (30 cm, 2.5 mm2)

Figure 2: Rear side of controller

6 - 1110

TE connection
(Technical Earth)

Relay 3
(Alarm)

Relay 3
(Alarm)

Relay 1
(Output)

DIGITAL INDUSTRIAL CONTROLLER

Controller input 2 Controller input 1

Position acknow­ledgement

Binary
output

Controller output

Standard signal
Current

Standard signal
Voltage

Relay 2
(Output)

Binary
input

Power

supply

Fig. 3: Allocation of the terminal strip

NOTE When connecting the sensor lines:

• Lay the lines separate from the power lines (lines in which large
currents flow) and high frequency lines. Never under any
circumstances use multi-pole cables to carry both power and
sensor lines.

• When using screened cables, only connect the screen at one
end. Never under any circumstances connect the screen to both
the protective conductor and the earth of the regulator input.

Resistance
thermometer
PT100

Thermo
couples

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4.2 Supply voltages

Power supply for the Connect to terminals 14
controller: and 15.
Model 1: 115 / 230V 50 ... 60 Hz
Model 2: 12 / 24V 50 ... 60 Hz
Power supply for 24 V DC Accessible on terminals 23

transducers: and 24.

ATTENTION!

To ensure the electro-magnetic compatibility (EMC), the screw
terminal TE (Technical Earth) must be connected to the earth
potential with a short cable (30 cm, 2.5 mm2).

1110 - 7

DIGITAL INDUSTRIAL CONTROLLER

4.2.1 115/230 V and 24/48 V Changeover

By means of a jumper inside the unit, the supply voltage can be changed from 230 V
to 115 V, or from 12 V to 24 V respectively. This adaptation must take place before
installing the unit.

Procedure:

Î Insert all connection and supply lines

Î Remove the connecting screw for the Technical Earth

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Î Remove the optionally-installed interface card (if present)

Î Undo the four screws on the rear plate, and remove the rear plate

Î Pull the unit one third of the way out of the housing

Î The jumper is easily accessible on the power supply printed-circuit board,

positioned immediately in front of one of the relays and identified by the numbers
1-4 on the board.

Î At delivery, the connector is positioned between contacts 2 and 4

Î To change the unit to 115V or 12 V respectively, contacts 1 and 3 must be

bridged with the connector. Proceed identically when changing from 24V to 12V.

Î Finally, push the unit back into the housing, and screw on the rear plate.

NOTE

If the unit is to be set to the lower voltage, please ensure that the
voltage does not exceed the quoted tolerances, and make a note
on the wiring diagram.

4.2.2 24V DC/AC Converter for operation at 24 V DC

The 12/24V AC controller model can also be operated at 24 VDC using an optional
DC/AC converter. Up to 3 controllers can be supplied from a single converter. (Order
number: 19139J)

Supply voltage 16V - 26V DC

Output voltage 16V-26V AC (50 Hz)

Efficiency > 95%

Switch-on delay max. 5 secs

Dimensions (WxHxD) 23 x 75 x 110 mm

8 - 1110

3

4.3 Signal inputs

All signal inputs are short-circuit proof, are voltage-stable to 41 volts and are
galvanically isolated with regard to the outputs and the supply voltage.

Controller input 1:

The following input configurations are available:

• Input for standard signal (voltage) 0 ... 10 V Terminals 30 and 31

Input resistance: > 400 kΩ

Measuring error: < 0,2 %

Temperature influence: < 0.2 % / 10 degrees

• Input for standard signal (current) 0 (4) ... 20 mA Terminals 29 and 31

Input resistance: < 300 Ω in accordance with DIN IEC 381 (typically 200)

DIGITAL INDUSTRIAL CONTROLLER

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Measuring error: < 0,2 %

Temperature influence: < 0.2 % / 10 degrees

Nominal temperature: 22 °C

Wire breakage and short-circuit detection within the range from 4 to 20 mA

• Input for frequency-analog signal 5 ... 1000 Hz Terminals 28 and 31

Input resistance: > 10 kΩ

Measuring error: < 0,1 %

Signal types: Sine wave, square wave, delta ( > 300 mVpp)

• Input for connection of Pt 100 resistance Terminals 35, 36, 37, 38
thermometers

(in accordance with DIN 43760 for 3 and 4-wire connection)

Measurement range - 200 to + 850 °C

Measurement current max. 0,5 mA

Measuring error ± 0.2 % ± 2 digits

1110 - 9

DIGITAL INDUSTRIAL CONTROLLER

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NOTE

• Input for connection of thermocouples Terminals 38 and 39

For the following thermocouples, the characteristics are linearised internally:

Type Thermocouple pair Measurement range Accuracy

J Fe - CuNi -200 to +1200 °C < ± 0.3 % ± 1 Digit

K NiCr - Ni -200 to +1370 °C < ± 0.3 % ± 1 Digit

T Cu - CnNi 0 to +400 °C < ± 0.3 % ± 2 Digit

R Pt 13Rh - Pt 0 to 1760 °C < ± 0.3 % ± 1 Digit

S Pt 10Rh - Pt 0 to 1760 °C < ± 0.3 % ± 1 Digit

NOTE

If the displayed values are fluctuating, set the limit frequency of the
digital filter to a lower value in the Inputs menu and check the TE
connection.

If the displayed values are fluctuating, set the limit frequency of the
digital filter to a lower value in the Inputs menu and check the TE
connection.

Input impedance: > 1 MΩ
Comparison point compensation:

• internal with integrated NTC thermistor
Comparison point compensation error: 0.5 K ± 1 digit

• external with Pt 100 resistance thermometer

Controller input 2

• Input for standard signal (voltage) 0 ... 10 V Terminals 18 and 19

(same technical data as for controller input 1)

• Input for standard signal (current) 0 (4) ... 20 mA Terminals 17 and 19

(same technical data as for controller input 1)

• Input for frequency-analog signal 5 ... 1000 Hz Terminals 16 and 19

(same technical data as for controller input 1)

Configurable for:

• Feed forward control

• Follow-up control (external setpoint)

• Ratio control

• Cascade control

10 - 1110

DIGITAL INDUSTRIAL CONTROLLER

• Input for the connection of a potentiometer Terminals 19, 20 and 27

for position feedback (1 ... 10 kΩ)
for position regulation

• Binary inputs Terminals 25 and 26

Input resistance: > 25 kΩ

Configurable line of action:

Logical value Voltage not inverted inverted

0 0 ... 4,5 V nactive active

1 13 ... 35 V active inactive

Configurable functions:

• Changeover between manual and automatic mode

• Changeover between external and internal setpoint *)

• Triggering alarms

• Safety value output

*) Available only if controller input 2 has been configured for an external setpoint.

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4.4 Signal outputs

Controller output

The following output configurations are available:

Controller output for continuous signals

• Output for standard signal 0 ... 10 V Terminals 33 and 34

max. load current: 5 mA
Accuracy: 0,5 %

• Output for standard signal 0 (4) ... 20 mA Terminals 32 and 33

max. load resistance: 600 Ω
Accuracy: 0,5 %

Controller outputs for discontinuous signals

2 relays with one potential free changeover contact each:

Relay 1 Terminals 7, 8 and 9

Relay 2 Terminals 10, 11 and 12

1110 - 11

DIGITAL INDUSTRIAL CONTROLLER

The following output signals are configurable (cf. Sections 5.7 and 6.5.4):

• 2-point PWM signal (PWM: Pulse width modulation)

• 3-point PWM signal

• 3-point step signal

• 3-point step signal with external feedback (position control)

Electrical data of the relay AC DC

Max. switched voltage 250 V 300 V

Max. switched current 5A 5A

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Max. switched power 1250 VA 100 W at 24V, 30 W at 250V

• Binary output Terminals 21 and 22

max. load current: 20 mA

Configurable line of action (not inverted / inverted):

Logical value Output not inverted inverted

0 high resistance inactive active

1 17.5 ... 24 V active inactive

Configurable functions:

• Signal:

• Signal:

• Signal:

Outputs for alarms

2 relays with one potential free changeover contact and internal connected bose
(see connection diagram):

Relay 3 Terminals 1, 2 and 3
Relay 4 Terminals 3, 4 and 5

Configurable alarms:

• Alarm, absolute

• Alarm, relative

• Alarm, ratio

Alarm has occurred
Error has occurred
MANUALmode

Electrical data of the relay AC DC

Max. switched voltage 250 V 300 V

Max. switched current 5A 5A

Max. switched power 1250 VA 100 W at 24V, 30 W at 250V

12 - 1110

DIGITAL INDUSTRIAL CONTROLLER

5 CONTROLLER STRUCTURES

5.1 Overall Structure of the Digital Industrial Controller

Figure 4 shows the overall structure of the digital industrial controller in the form of a
signal flow chart. In addition to function blocks, it contains function selectors which
are used to set a concrete controller structure when configuring the controller.

The following concrete controller structures can be configured on the basis of the
overall structure:

• Controller for single control loop
(

Standard controller

• Controller with additional functions for feed forward control
(

Feed forward controller

• Controller with additional functions for follow-up control
(

External setpoint controller

• Controller with additional functions for ratio control
(

Ratio controller

• Controller with additional functions for cascade control
(

Cascade controller

The function blocks contained in the overall structure are explained in Section 5.7.

structure)

structure)

structure)

structure)

structure)

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1110 - 13

DIGITAL INDUSTRIAL CONTROLLER

Filter 1

PV1

Input 1

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Ramp

13

5

6

14

Root extraction Scaling

1

Linearisation

SP1

23

4

Setpoint
limiting

COs

CO

10

Controller 2

7

11

Line of action

Multiplier

CO2

Manipulated
variable limiting

12

27

SP

PV1

Alarm abs.

Alarm ratio

Alarm rel.

Continuous
signal

2-point­PWM signal

3-point­PWM signal

3-point­step signal

8

Aabs

28

Averh

9

Arel

15

16

17

RA

18

SP2

22

20

29

21

CO1

Controller 1

Input 2

23 24

PV2

Filter 2 Root extraction

Line of action

Scaling

Manipulated
variable limiting

25

ext.SP

off

ratio

cascade

Feed forward

Figure 4: Overall structure of the Digital Industrial Regulator

Refer to Page 122 ff for a description of the function blocks

3-point-step
signal with
ext. p. a.

26

PDT1

Feed forward
control

19

Controller
output

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DIGITAL INDUSTRIAL CONTROLLER

5.2 Controller for single control loop

5.2.1 Single control loop

If a control task consists of keeping a quantity (e.g. a temperature) at a fixed setpoint
SP (constant), a fixed setpoint control configuration is used for this purpose. The
control variable PV (temperature) is measured and compared against the setpoint
SP (Figure 5).

Z

Setpoint
generator

SP

PVd

F

R

Controller

CO

Controlled system

PV

F

S

Figure 5: Single control loop

If it deviates from the setpoint as the result of a disturbance Z, for example, the
controller generates a manipulated variable CO according to this deviation, which is
referred to as the system deviation PVd = SP-PV, in such a way that the controlled
variable PV is adapted as exactly as possible to the setpoint.
A PID controller can be used for this purpose. With regard to its parameters, it must
be configured so as to arrive at a control response that does justice to the task in
hand (see Annex).

Example:

Let us look at control of a room’s temperature as an example of a fixed setpoint
control configuration in a single control loop. The aim is to compensate all
disturbances that cause the room temperature to deviate from the temperature
setpoint. The room temperature is compared against the setpoint SP. According to
the system deviation PVd, the controller adjusts the fuel supply until the required
room temperature has been reached.

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5.2.2

Standard controller

The

standard controller

overall structure appropriately. It is based on PID controller 2. PID controller 1 is not
used. Input 1 is used for the controlled variable PV1, while input 2 is not used. SP1
is the setpoint that has to be set.

structure

structure shown in Figure 6 is obtained by configuring the

1110 - 15

DIGITAL INDUSTRIAL CONTROLLER

Filter 1

PV1

Input 1

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5

Ramp

6

13

14

Root extraction Scaling

213

Linearisation

SP1

4

Setpoint
limiting

COs

CO

10

Controller 2

7

11

Line of action

CO2

Multiplier

12

Manipulated
variable limiting

8

Aabs

Alarm abs.

PV1

28

Averh

SP

27

Alarm ratio

Alarm rel.

Continuous
signal

2-point­PWM signal

3-point­PWM signal

3-point­step signal

9

Arel

15

16

17

RA

18

SP2

22

20

29

CO1

Controller 1

Line of action

Manipulated
variable limiting

Input 2

PV2

Filter 2

23

Root extraction

24

Scaling

25

ext.SP

off

Figure 6: Structure of the Standard Controller

Description of the functional blocks from Page 122

21

ratio

cascade

Feed forward

3-point-step
signal with
ext. p. a.

PDT1

Feed forward
control

19

Controller
output

26

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DIGITAL INDUSTRIAL CONTROLLER

5.3 Controller with additional functions for feed forward control

5.3.1 Single control loop with feed forward control

The control response of a single control loop can be improved substantially in most
cases by feed forward control. The precondition for this is that the disturbance
variable can be measured and recorded.
The disturbance can be fed either to the controller's input or output via a
compensator Fk (Fig. 7). In the digital controller, the disturbance is fed forward to the
controller's output. The compensator Fk consists of a PDT-1 element. This element's
P component feeds forward in proportion to the disturbance. The D component feeds
a value that is proportional to changes in the disturbance. Both components can be
chosen freely when configuring or defining the parameters.

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Z

F

Z

PV

F

S2

Partial controlled
system 2

Setpoint
generator

SP PVd

F

R

Controller

Compensation element

F

K

CO

F

S1

Partial controlled
system 1

Figure 7: Single control loop with feed forward control
a) to the controller’s input
b) to the controller’s output

Example:

Let us take water level control in a steam boiler as an example of fixed setpoint
control with feed forward control. The water level is measured and controlled by way
of the supply of feed water. Here, the outgoing quantity of steam manifests itself in
the form of the principal disturbance. If it is measured and additionally fed forward to
the controller. The controller's response can be improved in this way.

5.3.2

Feed forward controller

The

feed forward

configuring the overall structure accordingly. It is based on PID controller 2.
PID controller 1 is not used. Input 1 is used for the controlled variable PV1, while
input 2 serves to feed the disturbance forward to the controller’s output. SP1 is the
setpoint that has to be set.

structure

controller structure highlighted in Figure 8 is obtained by

1110 - 17

DIGITAL INDUSTRIAL CONTROLLER

Filter 1

PV1

Input 1

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Ramp

Root extraction

1

Linearisation

5

SP1

6

4

Setpoint
limiting

13

COs

CO

14

10

Controller 2

Scaling

2

11

Line of action

3

8

Aabs

Alarm abs.

PV1

7

Multiplier

12

CO2

SP

27

Alarm ratio

Alarm rel.

Continuous
signal

2-point­PWM signal

3-point­PWM signal

Manipulated
variable limiting

3-point­step signal

28

Averh

9

Arel

15

16

17

RA

18

SP2

22

20

29

CO1

Controller 1

Line of action

Manipulated
variable limiting

Input 2

PV2

23

Filter 2 Root extraction

24

Scaling

25

ext.SP

off

Figure 8: Structure of the feed forward control

Description of the functional blocks from Page 122

21

ratio

cascade

Feed forward

3-point-step
signal with
ext. p. a.

PDT1

Feed forward
control

19

Controller
output

26

18 - 1110

DIGITAL INDUSTRIAL CONTROLLER

5.4 Controller with additional functions for follow-up control

5.4.1 Follow-up control (external set-point input)

The purpose of a follow-up control is to slave the controlled variable PV1 as exactly
as possible to another variable, the command variable, which varies in time. Either a
process variable PV2 originating from a system FS2 or a different variable with a
given time progression can be used as the command variable (Figure 9).

Z

SP=
PV2

F

S2

PVd

CO

F

R

F

S

PV1

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5.4.2

Setpoint
generator

Controller

Controlled system

Figure 9: Follow-up control

The controller of a follow-up control configuration must be designed so as to arrive
at a good response to setpoint changes with a short settling time and well­attenuated stabilisation.

Example:

Let us take a power steering system as an example of a follow-up control. The
command variable PV2 for the angle of the wheel (controlled variable PV1) is
specified by the position of the steering wheel.

External setpoint controller

The

external setpoint

controller structure highlighted in Figure 10 is obtained by

structure

appropriately configuring the overall structure. It is based on PID controller 2. PID
controller 1 is not used. Input 1 is used for the control variable PV1, while the
command variable is applied to input 2 as the external setpoint.
In this controller structure, the binary input can be used to switch between the
external setpoint and the setpoint SP1.

1110 - 19

DIGITAL INDUSTRIAL CONTROLLER

Filter 1

PV1

Input 1

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5

Ramp

6

13

14

22

Root extraction

SP1

COs

CO

Controller 2

SP2

Linearisation

10

20

Scaling

213

4

7

SP

Alarm abs.

PV1

Alarm ratio

Setpoint
limiting

Line of action

Multiplier

11

CO2

Manipulated
variable limiting

29

21

27

Alarm rel.

Continuous
signal

2-point-

12

PWM signal

3-point­PWM signal

3-point­step signal

3-point-step
signal with
ext. p. a.

8

Aabs

28

Averh

9

Arel

15

16

17

RA

18

19

Controller
output

CO1

Controller 1

Input 2

PV2

23

Filter 2 Root extraction

Line of action

24

Scaling

Manipulated
variable limiting

25

ext.SP

off

Figure 10: Structure for External Set-Point

Description of the functional blocks from Page 122

20 - 1110

ratio

cascade

Feed forward

26

PDT1

Feed forward
control

DIGITAL INDUSTRIAL CONTROLLER

5.5 Controller with additional functions for ratio control

5.5.1 Ratio control

A ratio control is a special type of follow-up control and/or external set-point input.
The task of a ratio control is to cause a controlled variable (PV1) to track another
process variable (PV2) within a specific ratio.
PV1 is described as the dependent variable, and PV2 as the command variable.

In the regulated condition of the ratio control, the following equation applies:

SPr = PV1 / PV2

SPr: ratio set-point
PV1: dependent variable (controlled variable)
PV2: command variable

This gives the internal set-point for the channel X1 that is to be controlled:

PV1set = PV2*SPr
SP = X2*SPr

Controller

Ratio
setpoint
SPr

Command
variable
PV2

Multiplier

Setpoint
SP

Reference
system

PID Controller

PV1

Regulated
variable CO

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Controlled system

Figure 11: Ratio control

Example:

Let us take mixture control of an acid/alkali flow as an example of a ratio control
system. The internal setpoint SP for the supply of acid (PV1 set) is generated by
multiplying the flow rate of the alkali (command variable PV2) with the ratio setpoint
SPr.

Follow-up
system

1110 - 21

DIGITAL INDUSTRIAL CONTROLLER

5.5.2

Ratio controller

Filter 1

PV1

Input 1

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structure

The

ratio controller

configuring the overall structure. It is based on PID controller 2. PID controller 1 is
not used. Input 1 is used for the control variable PV1 and the process variable PV2
is applied to input 2. SP1 is the ratio setpoint that has to be set.

Root extraction

13

Linearisation

5

SP1

Ramp

6

13

COs

CO

14

Controller 2

structure highlighted in Figure 12 is obtained by appropriately

2

4

Setpoint
limiting

Scaling

7

1110

Line of action

CO2

Multiplier

12

Manipulated
variable limiting

8

Aabs

Alarm abs.

PV1

28

Averh

SP

27

Alarm ratio

Alarm rel.

Continuous
signal

2-point­PWM signal

3-point­PWM signal

3-point­step signal

9

Arel

15

16

17

18

RA

SP2

22

20

29

21

CO1

Controller 1

Line of action

Manipulated
variable limiting

Input 2

PV2

Filter 2

23

Root extraction

24

Scaling

25

ext.SP

ratio

Figure 12: Ratio controller structure

See Page 25 ff for a description of the function blocks

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cascade

Feed forwardoff

3-point-step
signal with
ext. p. a.

PDT1

Feed forward
control

19

Controller
output

26

DIGITAL INDUSTRIAL CONTROLLER

5.6 Controller with additional functions for cascade control

5.6.1 Cascade control

In a cascade control, two control loops are interlinked so that one control loop (the
main control loop) is superimposed on the other (the auxiliary control loop). We
therefore speak of a double control loop (Figure 13).

Z1Z2

CO2

R1

Subsystem 2

Auxiliary control loop

PV2

F

S2

F

R1

Subsystem 1

PV1

Setpoint
generator

SP1

PVd 1

Main controller

CO1

F

R1

Main control loop

PVd2

F

Auxiliary
controller

Figure 13: Cascade control

The controlled system is split into the two subsystems FS1 and FS2. The controlled
variable PV1 is measured on the subsystem FS1 and the auxiliary controlled variable
PV2 is measured on the subsystem FS2.

The auxiliary control loop consists of the auxiliary controller FR2 and the subsystem
FS2. The setpoint for the auxiliary control loop is given by the output variable CO1 of
the main controller FR1, which constitutes the main control loop together with the
auxiliary control loop and the subsystem FS1. The setpoint of the main control loop is
specified as SP1.

A prerequisite for interaction between the two control loops is that the auxiliary
control loop must have a faster time response than the main control loop, i.e. the
essential delays are encountered in the sub-loop FS1. Disturbances Z2 influencing
the subsystem FS2 are balanced out by the faster auxiliary control loop and
disturbances Z1 influencing the subsystem FS1 are balanced out by the main control
loop.

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Example:

Control of the temperature in a tank heated with hot steam can be mentioned as an
example of a cascade control. A fast auxiliary control loop for control of the
hot steam flow rate is superimposed on the slow temperature control loop with the
main controller FR1.

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DIGITAL INDUSTRIAL CONTROLLER

5.6.2

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Cascade controller

The

cascade controller

appropriately configuring the overall structure.

PID controller 1 is used as the main controller and PID controller 2 as the auxiliary
controller. Input 1 is used for the controlled variable PV1 of the main control loop and
input 2 is used for the auxiliary controlled variable PV2.

SP1 is the setpoint for the main control loop. When the main controller is in AUTO
mode, it specifies the setpoint for the auxiliary control loop. When the main controller
is in MANUAL mode, a setpoint SP2 for the auxiliary control loop can be set on the
keyboard.

structure

structure highlighted in Figure 14 is obtained by

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DIGITAL INDUSTRIAL CONTROLLER

PV1

Filter 1

Input 1

5

Ramp

6

13

14

Root extraction Scaling

Linearisation

SP1

213

4

Setpoint
limiting

COs

CO

10

Controller 2

7

11

Line of action

CO2

Multiplier

12

Manipulated
variable limiting

8

Aabs

Alarm abs.

PV1

28

Averh

-

SP

+

27

Alarm ratio

Alarm rel.

Continuous
signal

2-point­PWM signal

3-point­PWM signal

3-point­step signal

9

Arel

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15

16

17

RA

18

SP2

22

20

29

21

CO1

Controller 1

Line of action

Manipulated
variable limiting

Input 2

PV2

Filter 2

2423

Root extraction

Scaling

25

ext.SP

off

ratio

cascade

Feed forward

Figure 14: Cascade controller structure

See Page 122 ff for a description of the function blocks.

3-point-step
signal with
ext. p. a.

PDT1

Feed forward
control

19

Controller
output

26

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DIGITAL INDUSTRIAL CONTROLLER

5.7 Explanations of the controller structures' function blocks

Functional Block 1: Filter at Input 1

Using the filter, the disturbance signals superimposed on the measured signal can
be damped. The filter is designed as a 1st order low-pass filter.

The limiting frequency of the filter can be set up within the range 0.1 to 20.0 Hz via
the parameters Fg1 (1st input) and Fg2 (2nd input) in Parameter (Filter menu) and
Configure (Input 1 and Input 2 menus).

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• 0.1 Hz (strong damping, time constant 1.6 seconds)

• 20.0 Hz (weak damping, time constant 0.01 seconds)

ATTENTION!

Adjustable parameters:

Fg1: Limiting frequency (- 3 dB) of the filter at input 1.

Function block 2: Root extraction at input 1

This function serves to extract the square root of the input signal. It is needed
whenever the flow rate is measured as a pressure difference on a nozzle or
diaphragm (effective pressure method).

As, in some cases, the filter constant can have an effect on the
regulation parameters, the settings of the limiting frequency of
the filter should always be carried out before setting the
regulation parameters.

Function block 3: Scaling at input 1

Scaling assigns a numeric value to the measured electrical value that corresponds
to the physical measured quantity (Figure 15).

Adjustable parameters:

PVh: High scaling value, which is assigned to the maximum current,

voltage or frequency value.

PVl: Low scaling value, which is assigned to the minimum current,

voltage or frequency value.

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Scaling value

PVh

DIGITAL INDUSTRIAL CONTROLLER

PVl

0

Fmin (0 Hz)

4 mA

20 mA
10 V

Fmax

Standard signal

Frequency-analog signal

Figure 15: Scaling

Function block 4: Linearisation

The characteristics of the various thermocouples and of the Pt 100 are linearised
internally.

Function block 5: Setting the setpoint SP1

Setting the set point using the regulator keyboard

Function block 6: Ramp

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The set point can be continually increased or decreased using the ramp function.

Options:

Ramp on: Setpoint ramp active. An entered setpoint is initialised by way of the

Ramp off: Setpoint ramp not active.

ramp.
In a cascade control, the setpoint ramp is only available for the main
controller. The ramp is only started when the controller is in
Automatic mode.

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DIGITAL INDUSTRIAL CONTROLLER

Adjustable parameters:

D: Pitch of the setpoint ramp

SP

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∆SP

∆t

Figure 16: Ramp function

Function block 7: Setpoint limiting

A low and a high limit can be entered for the setpoint. The setpoint can only be
adjusted within this range.

Adjustable parameters:

SPh: High setpoint limit
SPl: Low setpoint limit

D=∆SP / ∆t

t

Function block 8: Alarm, absolute

With this function, the alarm relay is operated if the controlled variable PV exceeds
an upper limit or falls below a lower limit. The limits can be adjusted within the
scaling range PVl .. PVh, or within the measurement range of the temperature
inputs.

High limit violation: Alarm via relay 3

Low limit violation: Alarm via relay 4

Adjustable parameters:

PV+ : High alarm limit
PV- : Low alarm limit
Hy : Switching hysteresis

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