Beckhoff EP7047-1032 User Manual
Documentation | EN
EP7047-1032
Stepper motor box with incremental encoder and vector control
2020-12-22 | Version: 1.0
Table of contents
Table of contents
1 Foreword ....................................................................................................................................................5
1.1 Notes on the documentation..............................................................................................................5
1.2 Safety instructions .............................................................................................................................6
1.3 Documentation Issue Status..............................................................................................................7
2 Product overview.......................................................................................................................................8
2.1 Introduction........................................................................................................................................8
2.2 Technical data ...................................................................................................................................9
2.3 Scope of supply ...............................................................................................................................10
2.4 Process image.................................................................................................................................11
2.4.1 "Predefined PDO Assignments" ...................................................................................... 11
2.4.2 Process data objects ....................................................................................................... 13
2.5 Technology ......................................................................................................................................18
2.5.1 Stepper motor .................................................................................................................. 19
2.5.2 Selecting a stepper motor................................................................................................ 22
2.5.3 Standard mode ................................................................................................................ 23
2.5.4 Field-oriented control ....................................................................................................... 25
3 Mounting and connections.....................................................................................................................27
3.1 Mounting..........................................................................................................................................27
3.1.1 Dimensions ...................................................................................................................... 27
3.1.2 Fixing ............................................................................................................................... 28
3.1.3 Functional earth (FE) ....................................................................................................... 28
3.2 Connections.....................................................................................................................................29
3.2.1 Connector overview ......................................................................................................... 29
3.2.2 EtherCAT: X40 and X41 .................................................................................................. 30
3.2.3 Supply voltages: X60 and X61......................................................................................... 32
3.2.4 Incremental encoders: X03 or X04 .................................................................................. 34
3.2.5 Limit switch: X05.............................................................................................................. 35
3.2.6 Latch input: X06............................................................................................................... 36
3.2.7 Motor brake: X07 ............................................................................................................. 37
3.2.8 Stepper motor: X08.......................................................................................................... 38
4 Commissioning and configuration ........................................................................................................40
4.1 Integrating EP7047 into a TwinCAT project ....................................................................................40
4.2 Parameterizing EP7047...................................................................................................................41
4.2.1 Open the parameter directory (CoE) ............................................................................... 41
4.2.2 Setting important motor parameters ................................................................................ 42
4.2.3 Setting other important parameters ................................................................................. 44
4.3 Setting the operating mode .............................................................................................................45
4.3.1 Operating modes ............................................................................................................. 46
4.4 Parameterizing the NC axis.............................................................................................................52
4.4.1 Parameterizing the encoder............................................................................................. 54
4.4.2 Parameterizing the controller........................................................................................... 56
4.5 Performing a test run .......................................................................................................................58
4.5.1 Test run with TwinCAT NC .............................................................................................. 58
EP7047-1032 3Version: 1.0
Table of contents
4.5.2 Test run without the TwinCAT NC ................................................................................... 59
4.6 Further applications .........................................................................................................................60
4.6.1 Using the "Positioning Interface" ..................................................................................... 60
4.6.2 Linking an NC axis with EP7047...................................................................................... 75
4.6.3 Determining the voltage constant of a motor experimentally........................................... 76
4.6.4 Restoring the delivery state ............................................................................................. 77
4.7 Decommissioning ............................................................................................................................78
5 Diagnosis..................................................................................................................................................79
5.1 Diagnostics – basic principles of diag messages ............................................................................79
5.2 Diag Messages of EtherCAT devices for drive technology .............................................................88
6 CoE parameters .......................................................................................................................................89
6.1 Object directory ...............................................................................................................................89
6.2 Data format of CoE parameters.......................................................................................................91
6.3 Object description............................................................................................................................92
6.3.1 Objects for parameterization............................................................................................ 92
6.3.2 Status objects .................................................................................................................. 96
6.3.3 Standard objects.............................................................................................................. 97
7 Appendix ..................................................................................................................................................99
7.1 General operating conditions...........................................................................................................99
7.2 Accessories ...................................................................................................................................100
7.3 Version identification of EtherCAT devices ...................................................................................101
7.3.1 Beckhoff Identification Code (BIC)................................................................................. 105
7.4 Support and Service ......................................................................................................................107
EP7047-10324 Version: 1.0
Foreword
1 Foreword
1.1 Notes on the documentation
Intended audience
This description is only intended for the use of trained specialists in control and automation engineering who
are familiar with the applicable national standards.
It is essential that the documentation and the following notes and explanations are followed when installing
and commissioning these components.
It is the duty of the technical personnel to use the documentation published at the respective time of each
installation and commissioning.
The responsible staff must ensure that the application or use of the products described satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.
Disclaimer
The documentation has been prepared with care. The products described are, however, constantly under
development.
We reserve the right to revise and change the documentation at any time and without prior announcement.
No claims for the modification of products that have already been supplied may be made on the basis of the
data, diagrams and descriptions in this documentation.
Trademarks
Beckhoff®, TwinCAT®, EtherCAT®, EtherCATG®, EtherCATG10®, EtherCATP®, SafetyoverEtherCAT®,
TwinSAFE®, XFC®, XTS® and XPlanar® are registered trademarks of and licensed by Beckhoff Automation
GmbH. Other designations used in this publication may be trademarks whose use by third parties for their
own purposes could violate the rights of the owners.
Patent Pending
The EtherCAT Technology is covered, including but not limited to the following patent applications and
patents: EP1590927, EP1789857, EP1456722, EP2137893, DE102015105702 with corresponding
applications or registrations in various other countries.
EtherCAT® is registered trademark and patented technology, licensed by Beckhoff Automation GmbH,
Germany.
Copyright
© Beckhoff Automation GmbH & Co. KG, Germany.
The reproduction, distribution and utilization of this document as well as the communication of its contents to
others without express authorization are prohibited.
Offenders will be held liable for the payment of damages. All rights reserved in the event of the grant of a
patent, utility model or design.
EP7047-1032 5Version: 1.0
Foreword
1.2 Safety instructions
Safety regulations
Please note the following safety instructions and explanations!
Product-specific safety instructions can be found on following pages or in the areas mounting, wiring,
commissioning etc.
Exclusion of liability
All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH & Co. KG.
Personnel qualification
This description is only intended for trained specialists in control, automation and drive engineering who are
familiar with the applicable national standards.
Description of instructions
In this documentation the following instructions are used.
These instructions must be read carefully and followed without fail!
DANGER
Serious risk of injury!
Failure to follow this safety instruction directly endangers the life and health of persons.
WARNING
Risk of injury!
Failure to follow this safety instruction endangers the life and health of persons.
CAUTION
Personal injuries!
Failure to follow this safety instruction can lead to injuries to persons.
NOTE
Damage to environment/equipment or data loss
Failure to follow this instruction can lead to environmental damage, equipment damage or data loss.
Tip or pointer
This symbol indicates information that contributes to better understanding.
EP7047-10326 Version: 1.0
Foreword
1.3 Documentation Issue Status
Version Comment
1.0 • First release
Firmware and hardware versions
This documentation refers to the firmware and hardware version that was applicable at the time the
documentation was written.
The module features are continuously improved and developed further. Modules having earlier production
statuses cannot have the same properties as modules with the latest status. However, existing properties
are retained and are not changed, so that older modules can always be replaced with new ones.
Documentation Firmware Hardware
1.0 06 00
The firmware and hardware version (delivery state) can be found in the batch number (D-number) printed on
the side of the EtherCAT Box.
Syntax of the batch number (D-number)
D: WW YY FF HH
WW - week of production (calendar week)
YY - year of production
FF - firmware version
HH - hardware version
Further information on this topic: Version identification of EtherCAT devices [}101].
Example with D no. 29 10 02 01:
29 - week of production 29
10 - year of production 2010
02 - firmware version 02
01 - hardware version 01
EP7047-1032 7Version: 1.0
Product overview
2 Product overview
2.1 Introduction
Stepper motor box with incremental encoder and field-oriented control, 48 V DC, 5 A
The EP7047-0032 EtherCAT Box is designed for the medium performance range of stepper motors. The
PWM output stages cover a wide range of voltages and currents. They are housed in the EtherCAT Box,
together with two inputs for limit switches. The EP7047-0032 can be adapted to the motor and the
application with just a few parameters. The torsionally stiff integrated encoder (1024 inc/rev) makes the
AS2000 stepper motor ideal for closed-loop control of the EP7047-0032. Either a 5 V or a 24 V single-ended
version can be used as an encoder.
Quick links
Technical data [}9]
Process image [}11]
Connections [}29]
Commissioning and configuration [}40]
EP7047-10328 Version: 1.0
2.2 Technical data
All values are typical values over the entire temperature range, unless stated otherwise.
EtherCAT
Connection 2x M8 socket, 4-pin, green
Electrical isolation 500V
Supply voltages
Connection Input: 7/8" plug, 5-pin
Downstream connection: 7/8" socket, 5-pin
US nominal voltage 24VDC (-15%/ +20%)
US sum current
Current consumption from U
UP nominal voltage 8…48V
UP sum current
Current consumption from U
1)
S
max. 16Aat 40°C
120mA + current consumption of connected devices:
• encoder
• motor brake
• limit switches
1)
P
max. 16A at 40°C
= current consumption of the stepper motor
DC
Product overview
Stepper motor
Motor type 2-phase stepper motor, unipolar or bipolar
Connection 1x M12 socket, 5-pin
Current per phase max. 5A (overload-proof and short-circuit proof)
Maximum step frequency Adjustable:
1000/ 2000/ 4000/ 8000/ 16000 full steps per second
Microstepping up to 64x
2)
Current controller frequency approx. 30 kHz
Resolution approx. 5000 positions per revolution in typical applications
Encoder input
Number 1
encoder type Incremental encoders
Connection 1x M12 socket, 5-pin
Encoder supply Alternatively:
• 5VDC, max 0.5A, short-circuit proof
• 24V
max. 0.5A, not short-circuit proof
DC,
signals A, B, C; single-ended
(C = reference pulse / zero pulse)
Signal voltage "0" -3…2V
Signal voltage "1" 3.7…28V
Pulse frequency max. 400,000 increments per second (4-fold evaluation)
1)
This value corresponds to the current carrying capacity of the connections for the supply voltages.
2)
automatic switching, speed-dependent.
EP7047-1032 9Version: 1.0
Product overview
Digital inputs for limit switches
Number 2
Nominal voltage high level 24V
DC
Digital output for the motor brake
Nominal voltage 24VDC from the control voltage U
S
Output current max. 0,5A
Environmental conditions
Ambient temperature during operation -25…+60°C
Ambient temperature during storage -40…+85°C
Vibration/ shock resistance conforms to EN60068-2-6/ EN60068-2-27
EMC immunity/ emission conforms to EN61000-6-2/ EN61000-6-4
Protection class IP65, IP66, IP67 conforms to EN60529
Housing data
Dimensions Wx Hx D 60mmx 150mmx 26,5mm (without connectors)
Weight approx. 440g
Material PA6 (polyamide)
Installation position variable
Approvals
Approvals CE, UL in preparation
2.3 Scope of supply
Make sure that the following components are included in the scope of delivery:
• 1x EP7047-1032 EtherCAT Box
• 1x Protective cap for supply voltage output, 7/8”, black (pre-fitted)
• 2x protective cap for EtherCAT socket, M8, green (pre-assembled)
• 10x labels, blank (1 strip of 10)
Pre-assembled protective caps do not ensure IP67 protection
Protective caps are pre-assembled at the factory to protect connectors during transport. They may
not be tight enough to ensure IP67 protection.
Ensure that the protective caps are correctly seated to ensure IP67 protection.
EP7047-103210 Version: 1.0
Product overview
2.4 Process image
The scope of the process image is adjustable.
EP7047-1032 has several predefined variants of the process image: "Predefined PDO Assignments". Select
the "Predefined PDO Assignment" according to the operating mode [}45].
The factory default setting is "Velocity control compact" [}12].
2.4.1 "Predefined PDO Assignments"
Name Process image Process data objects
Position control
ENC Status [}13]
STM Status [}15]
ENC Control [}16]
STM Control [}17]
STM Position [}17]
Positioning interface
Positioning interface (Auto
start)
Positioning interface (Auto
start) with info data
ENC Status [}13]
STM Status [}15]
POS Status [}14]
ENC Control [}16]
STM Control [}17]
POS Control [}16]
ENC Status [}13]
STM Status [}15]
POS Status [}14]
ENC Control [}16]
STM Control [}17]
POS Control [}16]
POS Control 2 [}16]
ENC Status [}13]
STM Status [}15]
EP7047-1032 11Version: 1.0
STM Synchron info data [}15]
POS Status [}14]
ENC Control [}16]
STM Control [}17]
POS Control [}16]
POS Control 2 [}16]
Product overview
Name Process image Process data objects
Positioning interface compact
ENC Status [}13]
STM Status [}15]
POS Status compact [}14]
ENC Control [}16]
STM Control [}17]
POS Control compact [}16]
Velocity control
Velocity control compact
(Factory setting)
Velocity control compact with
info data
ENC Status [}13]
STM Status [}15]
ENC Control [}16]
STM Control [}17]
STM Velocity [}17]
ENC Status compact [}13]
STM Status [}15]
ENC Control compact [}16]
STM Control [}17]
STM Velocity [}17]
ENC Status compact [}13]
STM Status [}15]
STM Synchron info data [}15]
ENC Control compact [}16]
STM Control [}17]
STM Velocity [}17]
EP7047-103212 Version: 1.0
Product overview
2.4.2 Process data objects
2.4.2.1 "ENC status"
"ENC Status" contains the status variables of the encoder input. "ENC" is the abbreviation for "Encoder".
Status
• Latch C valid: A signal edge has been detected at
encoder signal "C". As a result, the "Counter value"
was written to the variable "Latch value" at the time of
the signal edge.
• Latch extern valid: A signal edge was detected at
the latch input X06 [}36]. As a result, the counter
value was written to the variable "Latch value" at the
time of the signal edge.
• Set counter done: The value from "Set counter
value" was written to the variable "Counter value" after
setting of "Set counter" (ENC Control [}16]).
• Counter underflow: The counter value "Counter
value" has fallen below the value 0.
• Counter overflow: The counter value "Counter value"
has exceeded the maximum value.
• Extrapolation stall: The extrapolated part of the
counter is invalid ("Micro increments").
• Status of input A: Current signal level of encoder
signal "A" (X03 / X04 [}34])
• Status of input B: Current signal level of encoder
signal "B" (X03 / X04 [}34])
• Status of input C: Current signal level of encoder
signal "C" (X03 / X04 [}34])
• Status of extern latch: Current signal level at the
latch input (X06 [}36])
• Sync error: Distributed Clocks synchronization error
in the previous cycle.
• TxPDO Toggle: This bit is inverted each time an input
data update occurs.
1)
1)
Counter value: The current counter value.
Latch value: Counter value stored at the time of the last
signal edge at latch input X06 or encoder signal "C".
1)
The latch function is deactivated in the factory setting. You may activate and configure the latch function in
1)
process data object "ENC Control" [}16] or "ENC Control compact" [}16].
2.4.2.2 "ENC Status compact"
This process data object is identical with "ENC status" [}13], see there.
EP7047-1032 13Version: 1.0
Product overview
2.4.2.3 "POS Status"
"POS Status" contains the status variables of the Positioning Interface [}60].
Status
• Busy: A motion command is active.
• In-Target: The target position of the motion command
has been reached.
• Warning: Warning message.
• Error: Error message.
• Calibrated: The motor is calibrated.
• Accelerate: The motor accelerates.
• Decelerate: The motor brakes.
• Ready to execute: Ready for a motion command.
Actual position: current set position
Actual velocity: current set velocity
Actual drive time: the elapsed time of the motion
command.
2.4.2.4 "POS Status compact"
"POS Status compact" contains the status variables of the Positioning Interface [}60].
Status
This variable is identical to the "Status" variable in the
process data object "POS Status [}14]". See there.
EP7047-103214 Version: 1.0
Product overview
2.4.2.5 "STM Status"
„STM Status" contains the status bits of the stepper motor output stage. "STM" is the abbreviation for
"Stepper Motor".
Ready to enable: The output stage can be enabled. See
output variable "Enable" in the process data object STM
Control [}17].
Ready: The output stage is enabled.
Warning: Warning message.
Error: Error message. The output stage was switched
off due to an error. You can acknowledge the error
message with the output variable "Reset" in the process
data object STM Control [}17]
Moving positive: The speed is greater than 0.
Moving negative: The speed is less than 0.
Motor stall: A loss of step has occurred.
2.4.2.6 "STM Synchronous info data"
"STM" is the abbreviation for "Stepper Motor".
Info data n: Additional information from the box.
You can select what information these variables should
contain:
• Parameter 8012:11
• Parameter 8012:19
Select info data 1 [}94]
hex
Select info data 2 [}94]
hex
EP7047-1032 15Version: 1.0
Product overview
2.4.2.7 "ENC Control"
Enable latch C: Activate edge trigger for encoder input
"C".
Enable latch extern on positive edge: Activate edge
trigger for positive signal edges at latch input X06
[}36].
Set counter: Accept the value of the variable "Set
counter value" as the current counter value.
Enable latch extern on negative edge: Activate edge
trigger for negative signal edges at latch input X06
[}36].
Set counter value: Default value for "Set counter".
2.4.2.8 "ENC Control compact"
This process data object is identical with "ENC Control" [}16].
2.4.2.9 "POS Control"
This process data object contains variables for controlling the Positioning Interface [}60].
2.4.2.10 "POS Control 2"
This process data object contains variables for controlling the Positioning Interface [}60].
2.4.2.11 "POS Control compact"
This process data object contains variables for controlling the Positioning Interface [}60].
EP7047-103216 Version: 1.0
Product overview
2.4.2.12 "STM Control"
Enable: Enable output stage.
Reset: Acknowledge error message, reset error status.
See input variable "Error" in the process data object STM
Status [}15]
2.4.2.13 "STM Position"
Position: Position setpoint.
Specify the position setpoint in increments.
Conversion from degrees (°) to increments: See below.
Conversion of position setpoints
The formula for converting a position setpoint from degrees (°) to increments depends on whether you are
using an encoder.
• If you are not using an encoder (feedback type [}94] = "Internal counter" ), use this formula:
Position: Setpoint [increments]
Θ
: Setpoint [°]
set
φ: Step angle of the motor [°]
(for AS10xx stepper motors: φ=1.8°)
• If you are using an encoder (feedback type [}94] = "Encoder" ), use this formula:
Position: Setpoint [increments]
Θ
: Setpoint [°]
set
PPR: Resolution of the encoder [increments/revolution]
(for AS10xx stepper motors: inc = 1024)
2.4.2.14 "STM Velocity"
Velocity: Speed setpoint in % of the parameter "Speed
range" [}44].
32767
-100%.
Conversion of speed setpoints
corresponds to 100%, -32767
dec
Velocity: Setpoint [increments/s]
n
: Setpoint [rpm]
set
φ: Step angle of the motor [°]
(for AS10xx stepper motors: φ=1.8°)
f
: "Speed range" [}44] [full steps/s]
max
corresponds to
dec
The speed setpoint can be positive or negative, depending on the desired direction of rotation of the motor.
EP7047-1032 17Version: 1.0
Product overview
2.5 Technology
EP7047-1032 provides two basic modes of operation.
• In standard mode [}23] all unipolar and bipolar stepper motors that comply with the specifications of
EP7047-1032 can be controlled. Two currents with sine/cosine curve are provided. The current is
clocked with 64 kHz and resolved with up to 64-fold microstepping to achieve a smooth current.
• Extended mode [}25] is based on field-oriented control. This mode can only be used for stepper
motors from Beckhoff. The current is not only provided, but controlled in a comprehensive manner.
Typical stepper motor problems such as pronounced resonance are therefore finally a thing of the past.
Furthermore, the current is adjusted depending on the load, thereby enabling considerable energy
savings and lower thermal loads at the stepper motor.
Realisation of more demanding positioning tasks
More demanding positioning tasks can be realised via the TwinCAT automation software from Beckhoff. Like
other axes, EP7047-1032 is integrated via the TwinCAT System Manager and can be used like standard
servo axes. Special stepper motor features, such as speed reduction in the event of large following errors,
are automatically taken into account via the stepper motor axis option. The effort for changing from a
servomotor to a stepper motor - and back - is no greater than changing from one fieldbus to another one
under TwinCAT.
The output stages of EP7047-1032 have an overload protection in the form of an overtemperature warning
and switch-off. Together with short circuit detection, diagnostic data are accessible in the process image of
the controller. In addition, this status is displayed by LEDs, along with other information. The output stage is
switched on via an Enable-Bit. The motor current can be set and reduced via a parameter value.
Optimum adaptation to the motor and the implementation of energy-saving features require minimum
programming effort. Since all data are set in the form of parameters in the CoE register, it is easily possible
to replace an EtherCAT device or store certain parameters for transfer to the next project. It is therefore no
longer necessary to transfer certain potentiometer settings or to document DIP switch settings.
EP7047-103218 Version: 1.0
Product overview
2.5.1 Stepper motor
Stepper motors are electric motors and are comparable with synchronous motors. The rotor is designed as a
permanent magnet, while the stator consists of a coil package. The frequency of the stator rotary field is
always in a fixed ratio relative to the rotor speed. In contrast to synchronous motors, stepper motors have a
large number of pole pairs. In a minimum control configuration, the stepper motor is moved from pole to pole,
or from step to step.
Stepper motors have been around for many years. They are robust, easy to control, and provide high torque.
In many applications, the step counting facility saves expensive feedback systems. Even with the
increasingly widespread use of synchronous servomotors, stepper motors are by no means "getting long in
the tooth". They are considered to represent mature technology and continue to be developed further in
order to reduce costs and physical size, increase torque and improve reliability. For a standard stepper
motor with 200 full steps, the best possible positioning accuracy is approx. 1.8°.
Today, the most widely used type in industry is the hybrid stepper motor type. In this type of motor the rotor
consists of a toothed iron core with one or a few permanent magnets in the rotor core. The rotor is designed
such that the polarity of successive teeth is inverse. This enables the production of motors with a high
number of steps, which is essential for positioning accuracy, combined with a relatively high torque. The
electrical behaviour of such a hybrid stepper motor is comparable with a multipole synchronous servomotor.
However, thanks to the synchronous toothing of stator and rotor, hybrid stepper motors offer a significantly
higher cogging torque.
Hybrid stepper motors with two or more phases are available on the market. Since EP7047-1032 is designed
for two-phase motors, the description focuses on the two-phase type, with the phases referred as A and B in
this documentation.
Stepper motor parameters
• Mechanical system
Irrespective of the drive and the stepper motor itself, the configuration of the mechanism attached to the
motor shaft has significant influence on the achievable control quality.
Natural resonances, load resonances, gear backlash (loose) and static friction have negative affect on the
controllability of the drive system. This often requires "softer" controller parameterisation, which in turn leads
to a higher position lag in the system. Sliding friction can result in reduced efficiency (due to increased
energy demand), but on the other hand it can have a positive effect on the control stability, due to its
dampening effect.
As a general rule, the "stiffer" the mechanics of a drive system, the easier it is to control, which is beneficial
for achieving a small position lag in the drive system.
• Speed
Stepper motors have low maximum speed, which is usually specified as a maximum step frequency.
• Number of phases
Motors with 2 to 5 phases are common. EP7047-1032 supports 2-phase motors. 4-phase motors are
basically 2-phase motors with separate winding ends. They can be connected directly to EP7047-1032.
• Torque
Refers to the maximum motor torque at different speeds. This parameter is usually represented by a
characteristic curve. Stepper motors have comparatively high torque in the lower speed range. In many
applications, this enables them to be used directly without gearing. Compared with other motors, stepper
motors can quite easily provide a holding moment of the same order of magnitude as the torque.
EP7047-1032 19Version: 1.0
Product overview
• Cogging torque
In many cases the stepper motors design results in high cogging torque, which can lead to relatively strong
natural resonance in a motor- and load-dependent speed range. In relation to the cogging torque, increased
inertia often leads to a less strong resonance and smoother operation.
• Mass moment of inertia
In standard mode, the key parameter of the mechanical system is the mass moment of inertia JΣ. It is
essentially composed of the mass moment of inertia of the stepper motor rotor JM and the mass moment of
inertia of the connected load JL. The friction moment J
and the moment of inertia of the encoder J
fric
can be
Enc
neglected in a first approximation.
JƩ ≈ JM + J
L
The ratio between the load torque and the motor torque is defined by the constant kJ.
kJ ≈ JL / J
M
Fig.1: Simplified representation of the mass moments of inertia
As a first approximation, the coupling of the individual masses over the rotor shaft can be modelled as twomass oscillator. The resonance frequency between the motor and the encoder lies in a relatively high
frequency range, which is usually not relevant for stepper motor drives and is suppressed within the drive by
low-pass filtering. The resonance frequency between the motor and the load is frequently in the range
between 20 and 500 Hz. It is therefore often in the operating range of the drive control. Design measures to
reduce the influence of the load resonance include a small load ratio kJ and a rigid coupling of the motor
shaft to the connected load.
• Resonance
At certain speeds, stepper motors run less smoothly. This phenomenon is particularly pronounced when the
motor runs without coupled load, in which case it may even stop (in standard mode). This is caused by
resonance. A distinction can roughly be made between
• resonances in the lower frequency range up to approx. 250Hz; and
• resonances in the medium to upper frequency range.
Resonances in the medium to upper frequency range essentially result from electrical parameters such as
inductance of the motor winding and supply line capacity. They can be controlled relatively easily through
high pulsing of the control system.
Resonances in the lower range essentially result from the mechanical motor parameters. Apart from their
impact on smooth running, such resonances can lead to significant loss of torque, or even loss of step of the
motor, and are therefore particularly undesirable.
In principle, the stepper motor represents an oscillatory system (comparable to a mass/spring system),
consisting of the moving rotor with a moment of inertia and a magnetic field that creates a restoring force that
acts on the rotor. Moving and releasing the rotor creates a damped oscillation. If the control frequency
corresponds to the resonance frequency, the oscillation is amplified, so that in the worst case the rotor will
no longer follow the steps, but oscillate between two positions.
EP7047-1032 prevents this effect thanks to the field-oriented control (Extended Operation Modes) for all
Beckhoff stepper motors.
EP7047-103220 Version: 1.0
Product overview
•Torque constant
In the Extended Operation Modes the torque constant kT is used as an additional parameter for the
mechanical controlled system. It indicates the ratio between the torque-forming motor current and the active
torque at the shaft. However, since the field-oriented operating mode is not common for stepper motors, the
torque constant is usually not listed in the motor data sheet.
Electrical system
• Nominal voltage, supply voltage and winding resistance
Under steady-state conditions, the rated current at the rated voltage depends on the winding resistance. This
voltage should not be confused with the supply voltage of the power output stage. EP7047-1032 applies a
controlled current to the motor winding. If the supply voltage falls below the nominal voltage, the power
output stage can no longer apply the full current, resulting in a loss of torque. It is desirable to aim for
systems with small winding resistance and high supply voltage in order to limit warming and achieve high
torque at high speeds.
• Induced countervoltage
Like servomotors, hybrid stepper motors induce a voltage ui [Vs/rad] in the stator winding of the motor, which
is proportional to the speed. It is also referred to as Back Electromotive Force (BEMF). In conjunction with
the DC link voltage (motor voltage), the induced countervoltage determines the physically achievable
maximum speed of the motor.
The ratio of the magnitude of the induced countervoltage and the motor speed varies depending on the
design and is described via the voltage constant ke.
ui = ke·ω
m
The motor parameter ke [mV/(rad/s)] is required for step loss recognition without encoder.
For stepper motors where the voltage constant is not specified in the data sheet, it can be relatively easily
determined using a digital multimeter. To this end the motor to be measured must be operated (within the
rated speed range) by an auxiliary motor via a coupling with constant speed. The motor phases of the motor
to be measured must be open (not connected or shorted). The multimeter can then be used to determine the
RMS value of the induced countervoltage, and therefore the voltage constant, at one of the two open motor
phases (A or B).
• Step angle
The step angle indicates the angle travelled during each step. Typical values are 3.6°, 1.8° and 0.9°. This
corresponds to 100, 200 and 400 steps per motor revolution. Together with the downstream transmission
ratio, this value is a measure for the positioning accuracy. For technical reasons, the step angle cannot be
reduced below a certain value. Positioning accuracy can only be improved further by mechanical means
(transmission). An elegant solution for increasing the positioning accuracy is the microstepping function. It
enables up to 64 intermediate steps. The smaller "artificial" step angle has a further positive effect: The drive
can be operated at higher speed, yet with the same precision. The maximum speed is unchanged, despite
the fact that the drive operates at the limit of mechanical resolution.
• Winding resistance, winding inductance
The winding inductance and winding resistance of the stepper motor stator determine the electrical motor
time constant Te = L / R, which is a key parameter for current controller configuration.
EP7047-1032 21Version: 1.0
Product overview
2.5.2 Selecting a stepper motor
Specifying the stepper motor
1. Determine the required positioning accuracy and hence the step resolution. The first task is to determine the maximum resolution that can be achieved. The resolution can be increased via mechanical
gear reduction devices such as spindles, gearing or toothed racks. The 64-fold microstepping also has
to be taken into account.
2. Determine mass m and moment of inertia (J) of all parts to be moved
3. Calculate the acceleration resulting from the temporal requirements of the moved mass.
4. Calculate the forces from mass, moment of inertia, and the respective accelerations.
5. Convert the forces and velocities to the rotor axis, taking account of efficiencies, moments of friction
and mechanical parameters such as gear ratio. It is often best to start the calculation from the last
component, usually the load. Each further element transfers a force and velocity and leads to further
forces or torques due to friction. During positioning, the sum of all forces and torques acts on the motor shaft. The result is a velocity/torque curve that the motor has to provide.
6. Using the characteristic torque curve, select a motor that meets these minimum requirements. The
moment of inertia of the motor has to be added to the complete drive. Verify your selection. In order to
provide an adequate safety margin, the torque should be oversized by 20% to 30%. The optimisation
is different if the acceleration is mainly required for the rotor inertia. In this case, the motor should be
as small as possible.
7. Test the motor under actual application conditions: Monitor the housing temperatures during continuous operation. If the test results do not confirm the calculations, check the assumed parameters and
boundary conditions. It is important to also check side effects such as resonance, mechanical play,
settings for the maximum operation frequency and the ramp slope.
8. Different measures are available for optimising the performance of the drive: using lighter materials or
hollow instead of solid body, reducing mechanical mass. The control system can also have significant
influence on the behaviour of the drive. EP7047-1032 enables operation with different supply voltages.
The characteristic torque curve can be extended by increasing the voltage. In this case, a current increase factor can supply a higher torque at the crucial moment, while a general reduction of the current can significantly reduce the motor temperature. For specific applications, it may be advisable to
use a specially adapted motor winding.
EP7047-103222 Version: 1.0
Product overview
2.5.3 Standard mode
Stepper motors were originally operated with very simple output stages, which were only able to switch the
voltage of the motor phases separately (nowadays current control takes place via PWM with pulse-width
modulation as standard). Initially the motor phases there were controlled individually in turn. A switching
sequence in the positive direction of rotation corresponds to the switching sequence (+A, +B, -A, -B).
Sequential switching results in rather irregular operation in this mode. In order to make the operation
smoother, so-called microstepping was introduced later, in which the four set voltages were extended by
intermediate values (e.g. from a stored sine table). These days, microstepping based on 64 steps is
commonly used.
Fig.2: Control structure of a standard stepper motor drive
Neglecting the sampling resulting from the microstepping, the motor current I as function of the electrical
angle φe and of the magnitude of the motor current I
(when using a current controller) can be described as
ABS
follows:
I(φe) = IA+ jIB= I
cos(φe) + jI
ABS
ABS
sin(φe)
Represented by magnitude and angle:
I(φe ) = I
ABS
· e
jφe
It follows that a rotation of the electrical angle φe is equivalent to four full steps. (A stepper motor with 200
full steps therefore has 50 pole pairs).
The shaft aligns itself if a constant current is set with no load at the motor shaft. Within a pole pairs the shaft
points in the direction of the active stator field.
If an external load is applied to the motor shaft, the shaft is turned out of the field direction, resulting in a load
angle (also referred to as angular displacement) (relative to an electric rotation of the angle φe). The load
angle depends on the design of the stepper motor itself, the motor current and the torque acting on the shaft.
The relationship is non-linear!
If the load angle exceeds a motor-dependent maximum value (i.e. if the maximum machine torque under
these boundary conditions is exceeded), the load torque can no longer be maintained by the motor. If the
shaft is turned further out of the rotary field, it "tips", resulting in one or more step losses. The "tip angle" may
vary between motor types. Often, it lies between around 45° and 65°.
EP7047-1032 23Version: 1.0
Product overview
Fig.3: Behaviour of the rotor under load
The load angle is of interest for the user, because it allows conclusions about the load on the shaft. It is
measured by evaluating the induced countervoltage* and can be used to optimise the drive system.
EP7047-103224 Version: 1.0
Product overview
2.5.4 Field-oriented control
In the Extended Operation Modes the stepper motor is operated like a servomotor, based on the principle of
field-oriented control.
Function
The operating behaviour of the motor corresponds to that of a traditional DC motor, with commutation via a
mechanical commutator. With a constant exciter field, the torque of the DC machine is directly proportional to
the stator current and can be directly influenced by it. The exciter field is generated, depending on the
machine type, by permanent magnets or, with a separately excited DC machine, for example, via a separate
excitation winding.
Fig.4: Coordinate transformation of field-oriented control
For servomotors and also hybrid stepper motors, initially there is no direct link between the phase currents
and the torque. Field and torque are decoupled mathematically via Park's transformation. Two current
components, "d" for "direct" in field direction and "q" for "quadrature" in torque-forming direction, are
calculated from the phase currents. Via the torque-forming current component iq, the torque of the machine
can now be regulated directly, like for a DC machine.
A prerequisite is that the rotor position is available with sufficiently high accuracy. For a stepper motor the
encoder resolution should be at least 4000 increments per mechanical revolution, in order to achieve
adequate positioning accuracy. The minimum encoder resolution also depends on the number of full steps
and can be calculated approximately as follows.
Fig.5: Calculation of the resolution
Commutation determination for Extended Operation Modes
Because the absolute actual position is not available for incremental encoders, on system start-up there is
no direct reference to the rotor position, which is required for field-oriented operation. Therefore, the
reference between the actual position and the rotor position must be generated at start-up via a commutation
determination process. During this process the rotor is moved forward and back several times up to two full
steps.
Commutation determination
• The maximum current should be set just below the rated motor current.
• During commutation determination the rotor shaft should not be subject to an external torque. If
this condition is not met, the Extended Operation Modes cannot be used.
Control structure
The drive control structure is a cascade control structure with a position control loop and a lower-level speed
and current control loop. If a speed setpoint is specified, the external position control loop can be omitted.
EP7047-1032 25Version: 1.0
Product overview
Fig.6: Cascade control structure with field-oriented control (Extended Operating modes)
Motor dependency
Due to the fact that the control is strongly dependent on the motor parameters, the controller parameters and
motor behaviour itself, field-oriented control is limited to Beckhoff motors. This mode is not supported for
motors from other manufacturers.
Main advantages compared with standard mode
• Low current consumption (almost full load-dependence)
• High efficiency
• Consistent dynamics compared with standard mode
• Step losses are inherently avoided
Requirement
• Encoder with sufficiently high resolution required (minimum 4000 [INC/360°])
• Slightly higher parametrisation effort required (speed controller)
• Commutation determination at startup (due to incremental encoder)
• Only possible with stepper motors from Beckhoff Automation (AS10xx)
EP7047-103226 Version: 1.0
3 Mounting and connections
150
60
141
Ø 4.5
3.1 Mounting
3.1.1 Dimensions
Mounting and connections
Fig.7: Dimensions
All dimensions are given in millimeters.
Housing features
Housing material PA6 (polyamide)
Sealing compound polyurethane
Mounting two fastening holes Ø 4.5 mm for M4
Metal parts brass, nickel-plated
Contacts CuZn, gold-plated
Power feed through max. 16 A at 40°C (according to IEC 60512-3)
Installation position variable
Protection class IP65, IP66, IP67 (conforms to EN 60529) when screwed together
Dimensions (H x W x D) approx. 150 x 60 x 26.5mm (without connectors)
EP7047-1032 27Version: 1.0
Mounting and connections
FE
FE
3.1.2 Fixing
NOTE
Dirt during assembly
Dirty connectors can lead to malfunctions. Protection class IP67 can only be guaranteed if all cables and
connectors are connected.
• Protect the plug connectors against dirt during the assembly.
Mount the module with two M4 screws in the centrally located fastening holes.
3.1.3 Functional earth (FE)
The fastening holes [}28] also serve as connections for the functional earth (FE).
Make sure that the box is earthed with low impedance via both fastening screws. You can achieve this, for
example, by mounting the box on a grounded machine bed.
Fig.8: Functional earth via the fastening holes
EP7047-103228 Version: 1.0
Mounting and connections
X60 X61
X01
X40 X41
X02
X05
X06
X03
X04
X07
X08
3.2 Connections
NOTE
Risk of confusion with M12 sockets
The M12 sockets X01 to X08 are assigned very different functions. Connecting a plug connector to the
wrong socket can result in damage.
3.2.1 Connector overview
Fig.9: Connector overview
Name Function Connector
type
Tightening
torque
X01 - M12 socket 0.6Nm
X02 - M12 socket 0.6Nm
X03
X04
X05
X06
X07
X08
X40
X41
X60
X61
1)
Mount plugs on these connectors using a torque wrench, e.g. ZB8801 from Beckhoff.
Protective caps
Incremental encoder [}34] with 5 V supply
Incremental encoder [}34] with 24 V supply
Digital inputs for limit switches [}35]
Latch input [}36]
Digital output for the motor brake [}37]
Stepper motor connection [}38]
EtherCAT input [}30]
EtherCAT-Weiterleitung [}30]
Supply voltage input [}32]
Supply voltage downstream connection [}32]
M12 socket 0.6Nm
M12 socket 0.6Nm
M12 socket 0.6Nm
M12 socket 0.6Nm
M12 socket 0.6Nm
M12 socket 0.6Nm
M8 socket 0.4Nm
M8 socket 0.4Nm
7/8“ plug connector 1.5Nm
7/8“ socket 1.5Nm
• Seal unused connectors with protective caps.
• Ensure the correct seating of pre-assembled protective caps.
Protective caps are pre-assembled at the factory to protect connectors during transport. They may not
be tight enough to ensure IP67 protection.
1)
1)
1)
1)
1)
1)
1)
1)
1)
1)
EP7047-1032 29Version: 1.0
Mounting and connections
3 1
24
3.2.2 EtherCAT: X40 and X41
3.2.2.1 Connectors
EtherCAT Box Modules have two green M8 sockets for the incoming and downstream EtherCAT
connections.
Fig.10: EtherCAT connectors
Connection
Fig.11: M8 socket
EtherCAT M8
Signal Contact ZB9010, ZB9020, ZB9030, ZB9032,
Tx + 1 yellow
Tx - 4 orange
Rx + 2 white
Rx - 3 blue
Shield Housing Shield Shield Shield
1)
Core colors according to EN61918
connector
Core colors
ZK1090-6292,
ZK1090-3xxx-xxxx
1)
1)
1)
1)
ZB9031 and old versions of
ZB9030, ZB9032, ZK1090-3xxxxxxx
orange/white white/orange
orange orange
blue/white white/green
blue green
TIA-568B
Adaptation of core colors for cables ZB9030, ZB9032 and ZK1090-3xxxx-xxxx
For standardization, the core colors of the ZB9030, ZB9032 and ZK1090-3xxx-xxxx cables have
been changed to the EN61918 core colors: yellow, orange, white, blue. So there are different color
codes in circulation. The electrical properties of the cables have been retained when the core colors
were changed.
EP7047-103230 Version: 1.0
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