1756-MO2AE MAM cmd does not reach position

[Darkzadow]

I have a 1756 MO2AE card controlling a AB 1395 sevro drive. When I use the MAM command it does not reach the position I command it to. When the MAM command is executed the drive will move until Command Position reaches the position in the MAM command and stop moving even though the Actual Position tag shows the drive has not yet reached the point. I am using slow speed .2 inches/sec with accel = 1, jerk=100% of the time. The drive does drift slightly when no commands are executed but it does not stop close enuf to the setpoint for drift to make up the distance. Any thoughts on why it stops well short of actual position = set point would be helpful. The command position ramps to my setpoint and when = set point drive stops. So I think I might have to get the drive to follow the command position faster.

 

[scalelar]

Check your Position Lock Tolerance. Does the MAM.PC bit come on?

 

[Peter Nachtwey]

It didn't happen until it is documented.
Make a trend showing the target and actual positions and the control output.
Displaying the target and actual velocities would be good too.
Status bits can be displayed as 0s or 1s too.
This way scalelar won't have to ask 20 question. I certainly won't.

 

[Darkzadow]

I will get trends of position, statuses, and velocities. All I can say without those is that the actual position changes at about half the speed as cmd position my position, lock tolerence is .1 units, and PC does come on when cmd position reaches SP.

 

[Darkzadow]

I found the issue, I think. When running the tuning I would get the tune values but they would not be applied even after the tuning told me it was successfully completed. So I was using tune values that were too low for my drive. The MAM command was completing the ramp to position. I still do not know why the PC bit came on possibly the feedback noise because everything is not wired neatly so I can swap control systems for testing. The symptoms of my tuning not completing correctly were that the tune window would flash twice before saying operation completed.

 

[kamenges]

I may be way off here, but it sounds to me like the motion command is being executed on a virtual axis and the axis command velocity command value is being routed to the drive. This would result in a system that produces a profiled motion but no position loop closure. I can't think of an axis or instruction set-up for a closed loop axis that would indicate a motion complete if the axis isn't inside the in position window.

Keith