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Submitted by Donnie on Mon, 03/24/2008 - 05:50

Ok, I've investigated the drift issue that I'm having but I'm still unable to come to a conclusion. I checked the voltage going to the motors from the amps and when the computer is in control its around 0V(no drift) but as soon as i turn the PID settings to 0 i start getting a 1.7 - 2.0 VDC and the motors begin to drift. I've tried adjusting the pots on the amp but it doesn't seem to have an effect on the drift or the voltage going to the motor. Everything I've read on tuning motors say that with PID set to 0 the motor should go limp. I don't know if I have a wiring issue or something else could be causing the drift. Any advice would be very helpful.

Comments 5

Galil_AndyH on 03/25/2008 - 08:08

Do you have an OF set (maybe to 1.7 or 2V)?

Start with a master reset of the controller. Set the PID's to 0 and disconnect the motor command signal and ground from the amplifier and measure the voltage of the motor command. Are you still seeing 1.7 - 2V? Connect the motor command signal and ground back up to the amplifier. Measure the motor command signal again, is it 0V? What is the TT command returning?

Reply to this post with what you find.

Galil_AndyH on 03/25/2008 - 08:09

A master reset will clear all parameters, settings and programs that you have stored on the controller. Make sure you have this information saved on your PC.

Donnie on 03/26/2008 - 05:31

When i did a master reset and turned the motors on they began to drift immediately. I set the PID values to 0. The OF command returned 0.000 and the TT command also returned 0.000,0.000,0.000 . I disconnected the command wires from the ICM and found that the Amp won't activate without the ground of the command signal being connected, but I still have the drift without the + command connected to the ICM. Also, I'm still reading 1.7V from the command from the Amp to the motor. For some reason the Amps are sending 1.7V to the motors when not under computer control.

Galil_AndyH on 03/26/2008 - 10:05

"For some reason the Amps are sending 1.7V to the motors when not under computer control."

This is the root of your problem. With the PID's activated and the motor command connected, the controller will compensate for this offset and hold the motor in place. If you issued a TT in this scenario, it would probably return ~-1.7 for that axis. Basically that means that the controller is outputting -1.7V to compensate for the offset on the amplifier.

Try contacting the amp manufacture to see why there is an offset on the amplifier.

Donnie on 03/28/2008 - 11:35

Well I've tried contacting the company that manufactured the amp and was told that short of paying a technician to come look at it they couldn't help me, and to contact the manufacturer of the lathe. Daihatsu CNC is the Manufacturer for the lathe and they are no longer in existence. So I suppose I'll look into it a little more and if I still can't get anywhere on it I may find a technician to come look at it. Thanks for the help.