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Motor change with absolute encoder | 07 Sep 2015 | |

Motor change with absolute encoder


my customer has Servostar S300 with Bobry motor that uses SKM36 encoder. Now they ordered AKM motors, also with SKM36 encoder. But changing the motor was not successful, they were not able to operate the drive with new motor - they got a position error when they moved their linear unit to a position. They have position table in the drive and 2 positions only. They did try to set reference point but when they moved the unit to the end position motor missed it by 5mm. Can somebody tell me what is the proper procedure when you want to replace one motor with absolute encoder with a new one?

Thank you.


Comments & Answers

kenny.hampton@… said ...

kenny.hampton@… |

If you are using the absolute position of the Hiperface feedback without homing the S300 system, the parameter to adjust is ROFFSADS.

The ROFFSABS parameter is used with an absolute encoder (multi-turn, homing to reference point is also possible)
The ROFFSABS sets an offset to the absolute encoder position. This procedure is executed by drive power on. The parameter must be saved in the EEPROM (using the SAVE command) after every alteration of the ROFFSABS variable, and the amplifier must then be switched off and on again (COLDSTART command).

If a position 10000 (PFB) is shown when the amplifier is switched on with ROFFSABS = 0, ROFFSABS = –10000 will shift the position to the value 0.


It sounds like the velocity loop and position loop gains in the drive may also require some adjustment due to the differences in the motors to make sure you can get to position. 

Use this link to get to the Interactive Tuning Guide for the S300:


Dear Kenny, Thanks for your answer. I will check this with my customer and post back the results. Have a nice day. Borut

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