ESCON or EPOS: What controller should I select?

Topic:

• I need a controller for my motor but I do not know how to select the right one.

Solution:

maxon offers mainly two different controller product lines:

1.) ESCON

2.) EPOS4

Selection criteria of the controller product line: ESCON or EPOS4?

There are two 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 correct choice then.

Remark:

• 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 any kind of EPOS4 control!
• ESCON can just be operated as a Velocity or Current/Torque controller.
  
  

2.) Command interface?
Commanding by bus => EPOS4 mandatory!

If your system demands for commanding of the motor controller by a bus interface, the EPOS4 is mandatory too (independent what operating mode is required).

Remark:

• The EPOS4 can be commanded and exchange data (e.g. in case of IoT applications) by its USB, RS232, CANopen® or optional EtherCAT® interface. There are also software libraries available for commanding the EPOS4 by a Windows or Linux system (e.g. PC, Raspberry Pi) via USB, RS232, or CAN. There is some comprehensive documentation present for integration of the EPOS4 into the system manager tools of typical PLCs (like Beckhoff's TwinCAT by EtherCAT).
• The ESCON demands mandatory for analog or digital I/O signals for commanding. Its USB interface can just be used by maxon's "ESCON Studio" software for configuration, tuning of parameters, and test during initial commissioning. There is no(!) protocol specification and no(!) software library available for ESCON's data exchange by USB. ESCON's USB cannot be used by 3rd party tools and also not by application software developed by your own.
  
  

3.) Sensor feedback interface

The ESCON can be operated with the following motor / feedback sensor combinations:

• DC motor with incremental encoder or DC tacho.
• EC motor with Hall sensors plus incremental encoder.
• EC motor with Hall sensors (without encoder).
  Restriction:
  An encoder is recommended for precise low speed control (< 1000 rpm).
• DC motor without a feedback sensor.
  Restriction:
  In this case just current control and open loop speed control (based on an IxR compensation) is possible. 

The ESCON cannot(!) be operated with an absolute encoder.
If there is an absolute encoder (SSI) in use, the EPOS4 is the only possible choice!

The EPOS4 can be operated with the following motor / feedback sensor combinations:

• DC motor with incremental encoder.
• EC motor with Hall sensors and incremental encoder or SSI absolute encoder. 
• EC motor without Hall sensors but a SSI absolute encoder.
• EC motor with Hall sensors (without encoder).
  Restriction:
  Operation without encoder is not recommended for position control and not for low speed control (e.g. less than 1000 rpm).

The EPOS4 cannot(!) be operated without any feedback sensor and not with a DC tacho.
In this case the ESCON is the only possible choice!

General remark:
In case of an encoder it is always recommended to choose an encoder type with differential signal types (sometimes also called RS422 or "with Line Driver").

Additional criteria to select the concrete controller's product type:

As soon as the controller product line (ESCON or EPOS) has been clarified the concrete controller can be selected based on the details of your motor combination in use and specific system or installation demands, e.g.

• Required supply voltage to fulfill the application's motor speed demands
  (see also 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 and ESCON product line:

• ESCON
  • Velocity and current/torque control only.
  • Commanding by analog (e.g. +/-10V) or digital I/O signals.
  • Different predefined functions can be linked to I/O signal states.
  • No(!) data exchange or commanding by USB interface possible.
    (USB can just be accessed for initial commissioning, parameter tuning, parameter up-/download, controller monitoring, or data recording with maxon's "ESCON Studio" software.)
  • No(!) software libraries or protocol specification available.
  • No(!) documentation of internal control structures and control algorithms available.
  • Overview of available ESCON product types:
    http://escon.maxongroup.com 
    
    
• EPOS4
  • Position, Velocity, and Current-/Torque control.
    
  • Sinusoidal / FOC motor communication in case of EC motors with an encoder.
  • Different bus interfaces: USB, RS232, CANopen®, EtherCAT®
  • Master controller (e.g. PLC, PC, Raspberry Pi) mandatory to command the EPOS4 by bus.
  • 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 just possible for velocity and current control.
    (Position control can just be commanded by bus commands by a master.)
  • Comprehensive documentation about the EPOS4's object dictionary and control structures / algorithms.
  • Software libraries for Windows and Linux systems (e.g. PC, Raspberry Pi)
  • IMPORTANT:
    It is mandatory that there is a feedback sensor present for any kind of 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.
    Following motor and motor combinations types are supported: 
    
    • DC motor with an incremental or SSI absolute encoder
    • EC motor with Hall sensors and incremental or SSI absolute encoder
    • EC motor with SSI encoders (even without hall sensors)
    • EC motor with Hall sensors
      The use of an EC motor with Hall sensors only is possible but not(!) recommended, since the resolution of Hall sensors is not sufficient for precise speed and position control. Based on Hall sensors only, poor low speed accuracy and consistency as well as some oscillation of the motor shaft around the target position must be expected. 
      More information about the question and relevance of the resolution of the feedback device can also be found in the following Support Center document:
      -> Which encoder resolution should be chosen? 
  • Overview of available EPOS4 product types:
    http://epos.maxongroup.com 

If need more guidance concerning product selection, please contact one of maxon's local worldwide sales offices or submit a Support Center ticket. 

Please also note the training and selection videos available here:
Support Center / Tutorials