lower speed control

[Yahoo1]

I am fine tune my motion control system right now and I encountered some issue which frustrated me.
I fine tune my system at 9,000psi (which is in 2 in" diameter area). At high speed, it worked fine; but at low speed, I always got overload error and current jump up and down untill reached the amplifier's peak current(15A).
Is it because the fine-tuning is not very good or because the amplifier's peak current is not high enough (my motor's peak current is 31A)? If it is because the peak current, how come it draw such big current at low speed?

Any opinion is very welcome.

Thanks,

Wendy

 

[Yahoo1]

There are a speed reducer(harmonic drive), a roller screw then the piston.

 

[EdDanzer]

Without knowing more I will guess that the inertia of the drive components is causing the problem. If the motor is driving the speed reducer and it driving the roller screw, the inertia of the roller screw is multiplied by the reducer and the motor has to over come this additional load at low speeds.
You will need to recalculate the load reflected to the motor including inertia of all components including the motor armature to determine actual starting torque for the motor at the programmed acceleration rate.
It may be possible to reduce the acceleration rate to make the existing motor work.

 

[jbartos]

Suggestion: The motor may be under-rated.

 

[EdDanzer]

Yahoo1,
Have you had any luck with your problem?

 

[Yahoo1]

Hi EdDaner,

One thing has been found which is mechanical wear in the harmonic drive. Some parts were worn and there are some trash in it.
I hope it would be ok after this problem is fixed.

Thank you very much for your kindly help.
Thanks everyone.

 

[Barry1961]

I have found that the baldor auto tune does not work if there is any "spring" in the mechanicals. I can't say for sure without knowing more about your system but i have had success for years using zero integral gain and keeping the proportional gain at tens times the derivative. This balance seems to work well over a very wide range of applications. I have heard that integral is used with success in very low speed metal cutting operations.

Barry1961

 

[jbartos]

Suggestion: The integral is good to smooth any abrupt fluctuations of variables dependent on time.