Experimental Physics and
Industrial Control System

Folks,

 

I am having 2 serious issues with using “set” mode in the motor record to set the current motor position on a Galil controller.

 

• It works fine to set the position when the motor is not using an encoder and when not at a hard limit.  Setting the position sets both the drive values (VAL, DVAL, RVAL) and the readback values (RBV, DRBV, RRBV).
• When setting the position of a motor with an encoder the VAL, DVAL, and RVAL are set correctly.  However, the readbacks are not set.  This means that subsequent moves are not correct, because they act as if the motor is currently at the readback position, and move by the wrong amount.  I have attached a screenshot (Set_to_0_at_1.png) showing a motor that had been at DVAL=1, and then I set it to DVAL=0.  Note that the readbacks are still for DVAL=1.
• If the motor has an encoder and is at a hard limit when I set the position then the result is that RVAL gets set to -2^31.  The system is totally unusable, because it now thinks the motor is outside the soft limits.  This is shown in screen shot Set_to_0_at_-10_on_limit.jpg.  The motor was on a limit with a DVAL of about -10.7.  I set the position to 0, and now the DVAL is -107374. 

 

Note that driving to a limit and then setting the position is a common operation, because we know what the absolute position of the limit switch is.  But this does not work at all with the Galil.

 

Have others seen these problems?  Am I doing something wrong?

 

Thanks,

Mark