Topic:
- I need a controller for my motor but I do not know how to select the right one.
Solution:
maxon offers mainly three different controller product lines:
-
EPOS4
Position, Speed, and Current / Torque control
commanded by bus (CANopen®, EtherCAT®, USB, RS232)
-
ESCON2
Speed and Current / Torque control
commanded by I/O signals or bus (CANopen®, USB, SCI)
- ESCON
Speed and Current / Torque control
commanded by I/O signals only
Selection criteria of the controller product line: EPOS4, ESCON2, or ESCON?
There are some main questions which have to be answered initially to clarify which controller product line is the right choice for an application:
1.) Operating mode?
Position control => EPOS4 mandatory!
If the motor's or gear's output shaft respectively its attached load has to be moved to a defined position and keep this position stable, there is a position controller required. The EPOS4 product line is the only correct choice then.
- EPOS4 can be operated as a Position, Velocity, or Current/Torque controller.
- It is mandatory that there is a feedback sensor (e.g. Hall sensors, encoder) mounted on the motor shaft for "Position" and "Velocity" control mode!
Remarks:- Just "Current / Torque control" is possible without any sensor in case of a brush DC motor.
- In case of a BLDC (= brushless) motor, there is always the need for a feedback sensor independent of the operating mode. The sensor is required for rotor position detection and commutation of the windings.
- ESCON and ESCON2 only offer "Velocity control" and "Current/Torque control" but no(!) "Position control" and no(!) position feedback.
2.) BLDC motor winding commutation
"Block commutation" results in a torque ripple of 14% within each commutation cycle. FOC (= sinusoidal commutation) has no such torque ripple in theory (and a quite low one in practice). In case of an application demanding for smooth motor operation with less torque ripple, it is recommended to select a controller and feedback sensor which enables FOC (= sinusoidal commutation). Additionally, it is recommended to select an iron-less motor (i.e. no EC-i or EC-flat) to get rid of any motor's cogging torque too.
-
EPOS4:
-
Block commutation
in case of a BLDC motor with Hall sensors only. -
FOC (= sinusoidal commutation)
in case of a BLDC motor with Hall sensors + incremental encoder or SSI absolute encoder
-
Block commutation
-
ESCON2:
-
Always FOC (= sinusoidal commutation)
independent of feedback sensor type. FOC is even active if there are only Hall sensors present.
-
Always FOC (= sinusoidal commutation)
-
ESCON:
-
Always Block commutation
independent of feedback sensor type.
-
Always Block commutation
3.) Command interface?
Commanding by bus => EPOS4 or ESCON2 mandatory!
If your system demands for commanding of the motor controller by a bus interface, the EPOS4 or ESCON2 can be used depending on the required bus interface and operating mode (as explained in above in point 1.).
Remarks:
-
EPOS4 and ESCON2:
- The data exchange of EPOS4 and ESCON2 is based on the standardized protocols CiA301® "Application layer and communication profile" and CiA402® "CANopen device profile for drives and motion control".
- The data exchange of EPOS4 and ESCON2 is based on the standardized protocols CiA301® "Application layer and communication profile" and CiA402® "CANopen device profile for drives and motion control".
-
EPOS4:
- The EPOS4 can be commanded and exchange data by its USB, RS232, CANopen® or optional EtherCAT® interface.
- Just in case of "Velocity control" or "Current / Torque control" an analog set value and enable / disable input can be used alternatively to commanding by bus. too. There are no functions available to map feedback data (e.g. speed, current, status, ...) to analog outputs. All feedback data has to be exchanged via the bus system.
- Configuration, regulation tuning, initial commissioning and testing can be done with maxon's free of charge "EPOS Studio" PC software.
- There are software libraries available for commanding the EPOS4 via Windows or Linux systems (e.g. PC, Raspberry Pi) using USB, RS232, or CAN.
- There is some comprehensive documentation present for integration of the EPOS4 into the EtherCAT system manager tools of typical PLCs (like Beckhoff's TwinCAT + NC Library).
-
ESCON2:
- The ESCON2 can be fully commanded via analog and digital input / output signals and selected mapped functions or it can be commanded and exchange data by its CANopen®, USB, or SCI interface.
- Configuration, regulation tuning, initial commissioning and testing can be done with maxon's free of charge "Motion Studio" PC software.
-
ESCON:
- The ESCON must(!) be fully commanded via analog or digital I/O signals and selected mapped functions.
- ESCON's USB interface can only be used by maxon's "ESCON Studio" or "Motion Studio" software for configuration, tuning of parameters, and test during initial commissioning.
- There is no(!) protocol specification and no(!) software library or possibility to exchange data with an ESCON by USB. ESCON's USB cannot be used by 3rd party tools and also not by any application software developed of top-level controllers.
4.) Sensor feedback interface
Operating mode and controller type aspects impacting sensor requirements:
-
"Velocity control" (of EPOS4, ESCON2) or "Position control" (-> EPOS4) mandatory demands for feedback sensors.
- In case of "Speed control" of just some 100 rpm or "Position control" it is recommended to use an encoder with at least 500 cpt.
-> "Which encoder resolution should be chosen? - In case of an encoder and esp. "Position control" it is strongly recommended to choose an encoder type with differential signal types (sometimes also called RS422 or "with Line Driver").
- In case of "Speed control" of just some 100 rpm or "Position control" it is recommended to use an encoder with at least 500 cpt.
-
"Current / Torque control" of a brush(!) DC motor is possible without a sensor in case of an EPOS4, ESCON2, or ESCON.
- Just the "ESCON Module 50/4 EC-S" (P/N: 446925) can operate BLDC motors without any sensors at all but its applicability still depends on the motor and required working points.
-> "ESCON EC-S: Applications and restrictions of sensorless control"
- Just the "ESCON Module 50/4 EC-S" (P/N: 446925) can operate BLDC motors without any sensors at all but its applicability still depends on the motor and required working points.
Overview of required sensors depending on the selected controller type:
-
EPOS4: Required (alternative) sensors
- Hall sensors
- Incremental encoder
In case of a BLDC (= EC) motor there are Hall sensors required in addition. - SSI absolute encoder
In case of a maxon motor combination with an SSI encoder there is no need for Hall sensors because the encoder is mounted in a defined rotor position ex-factory. - Exception:
No sensors required in case of "Current / Torque control" of a brush DC motor.
-
ESCON2: Required (alternative) sensors
- Hall sensors
- Incremental encoder
In case of a BLDC (= EC) motor there are Hall sensors required in addition. - Exception:
No sensors required in case of "Current / Torque control" of a brush DC motor.
-
ESCON: Required (alternative) sensors
- Hall sensors
- Incremental encoder
In case of a BLDC (= EC) motor there are Hall sensors required in addition. - DC-tacho
- Exceptions:
No sensors required in case of open loop control of a brush DC motor.
No sensors required in case of "ESCON Module 50/4 EC-S" (for BLDC motors).
5.) Additional criterias to select the concrete controller's product type:
As soon as the controller product line (EPOS4, ESCON2, ESCON) has been clarified, the concrete controller can be selected based on the details of your motor combination in use, motor's required working points (i.e. speed / torque range), and specific system or installation demands, e.g. ...
-
Required supply voltage to fulfill the application's motor speed demands
see here: "What supply voltage is required by a controller?" - Required motor current (resp. controller's output current rating) demands to fulfill the application's torque demands.
-
Encoder type in use
Check that the encoder type of your motor combination is compatible with the controller's encoder or sensor interface. - Preferred type of electronics design, i.e. Module, Compact, Enclosure
Summary
Main distinguishing marks of the EPOS4, ESCON2, and ESCON controller product lines:
-
EPOS4
- Different bus interfaces: USB, RS232, CANopen®, optional EtherCAT®
- Position, Velocity, and Current-/Torque control
- FOC (= sinusoidal commutation) in case of EC motors with an encoder
-
maxon's software "EPOS Studio" for initial commissioning
e.g. motor, sensor, I/O configuration and automatic regulation tuning, testing, data recording - A Master controller (e.g. PLC, PC, Raspberry Pi) mandatory to command the EPOS4 by bus.
- EPOS4 is a so-called Motion control slave based on CiA402® (= "CANopen device profile for drives and motion control").
Supported operating modes: PPM, PVM, HM, CSP, CSV, CST -
Commanding by analog input only possible for velocity and current control:
-> EPOS4 / IDX: Analog set value commanding
Restriction: Position control can just be commanded by bus. - Comprehensive documentation about the EPOS4's "Object dictionary" and control structures.
- Software libraries for Windows and Linux systems (e.g. PC, Raspberry Pi)
- Additional notes:
It is mandatory that there is a feedback sensor present for Velocity and Position control.
The usage of an encoder (with at least 500 cpt.) stiffly mounted on the motor shaft (e.g. as a maxon motor combination) is highly recommended for "Speed control" below some 100 rpm and "Position control".
-
ESCON2
- Different bus interfaces: CANopen®, USB, SCI
-
Velocity and current/torque control only
No position control and no position feedback -
Always(!) FOC (= sinusoidal commutation) of BLDC motors
independent if there is an encoder or just Hall sensors present -
maxon's software "Motion Studio" for initial commissioning
e.g. motor, sensor, I/O configuration and automatic regulation tuning, testing, data recording -
Commanding by analog (e.g. +/-10V) and / or digital I/O signals
Different predefined functions can be linked to I/O signal states. -
Commanding by bus (CANopen®, USB, SCI)
Motion control slave based on CiA402® (= "CANopen device profile for drives and motion control").
Supported operating modes: PVM, CSV, CST, IOVM, IOCM - Comprehensive documentation about the ESCON2's object dictionary and control structures / algorithms.
-
ESCON
- Velocity and current/torque control only
- Block commutation only (i.e. no FOC of BLDC motors)
-
maxon's software "ESCON Studio" or "Motion Studio" for initial commissioning
e.g. motor, sensor, I/O configuration and automatic regulation tuning, testing, data recording -
Commanding by analog (e.g. +/-10V) or digital I/O signals only.
Different predefined functions can be linked to I/O signal states. -
Restrictions:
No(!) commanding via USB, no software libraries, no USB protocol specification
No(!) documentation of internal control structures and control algorithms.
General notes / cross references:
- Find a more detailed overview of controller's specified data, please check section "Motor & motion control" of maxon's catalog:
-> http://epaper.maxongroup.com - Check for the website link of each product type and the feature chart of the product line here:
-> http://escon.maxongroup.com (covers ESCON2 and ESCON)
-> http://epos.maxongroup.com
Points of contact for some personal guidance by maxon engineers:
- If you would like personal advice on product selection and application options, either by phone or in person, please contact one of maxon's local offices (-> click on "Global" in "A global network" section).
- Feel also free to submit a Support Center ticket to discuss your application's technical demands and recommended controller selection.
Please also note the training and selection videos available here:
Support Center / Tutorials
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