Experimental Physics and
Industrial Control System

Hello,

 

At Diamond we often implement a software PLC on the motor controllers to disable the amplifier of in-vacuum motors (sending a kill command) when they have completed a move.  This is to avoid the motors overheating in vacuum. 

 

However, recently we had an overheating problem on an in-vacuum motor because a motor amplifier was constantly being re-energised after this PLC had de-energised it.  This was due to the motor’s flickering encoder causing it to regularly register a soft limit condition.  Whenever the motor record went into a soft limit state it issued a Stop command to the motor re-energising its amplifier.  The PLC and the motor record would then ‘fight’ each other, one disabling the motor, the other enabling it.

 

We were using motor record version 6-7-1 when we encountered this issue.  After upgrading to 6-9 the problem appears to have gone away.  This is good news but I would like to understand what may have changed to avoid this situation?  I see a lot of limit related changes have happened between these two release numbers.  Can anyone point me to a change which may explain the fix we see?

 

The change must be to do with not sending a Stop command if the motor is already stopped?

 

Thanks for any guidance,

 

James