HI, back again with another thught and more problems...

As I said in my last post (above) things seemed OK, but I used it in my jog application (it's a motion platform, so we need to send position commands and am using the jog command as a position command, using the last part of your joystick app note).

The system is VERY unstable. I noted above that my encoder is 4096...is that simply too much resolution and likely causing a very unstable and unpredictable system?? I hope, because nothing else seems to work...??

I have not tried the TM command... I am sure the encoder is connected correctly.

-Gary

Gary,

You need to make sure your drive can accept a +/-10V analog input as a torque, or most likely a speed reference. Many VFD drives only accept a 0-10V signal, and this will make tuning the system very difficult.

Also, your tuning parameters will almost certainly produce an extremely unstable system.

You need to have a non-zero KP, and your KI setting is way too high - I would expect this to be in the 0-1 range. PL 1.8 is an invalid setting, set PL 0 and start tuning with just KP, KD and KI.

Andy:

Thanks for the reply. I am converting the Galil +/- 10 to the o- +10 using a Nord setpoint converter, all of this is no problem. The Nord is set to have +5 be zero, etc...this works perfectly.

I cannot use any value of KP without everything becoming unstable.

This is why i need another solution, and was asking about the 4096 line encoder I am using: is the system sample rate, which is whatever default is, too low, or?? Do I need to somehow tell it how many lines of encoder resolution I have?

It just feels like too much loop gain...as far as i can tell, I have the VFD set up very linear, no gain, just a one to one voltage to frequency conversion (speed).

Can I reduce feedback gain somehow?

Pulling my hair out!!

Andy:

Thanks for the reply. I am converting the Galil +/- 10 to the o- +10 using a Nord setpoint converter, all of this is no problem. The Nord is set to have +5 be zero, etc...this works perfectly.

I cannot use any value of KP without everything becoming unstable.

This is why i need another solution, and was asking about the 4096 line encoder I am using: is the system sample rate, which is whatever default is, too low, or?? Do I need to somehow tell it how many lines of encoder resolution I have?

It just feels like too much loop gain...as far as i can tell, I have the VFD set up very linear, no gain, just a one to one voltage to frequency conversion (speed).

Can I reduce feedback gain somehow?

Pulling my hair out!!

The fact that you can't get any KP into the system without it going unstable means that you likely have a fundamental problem with your system. E-mail support@galilmc.com and reference this post. Send those screen captures you tried to attach in the original post.

Andy:

I sent an e-mail...this is urgent for me, a call would be great...

-Gary