Configuring a Spindle motor

[Raghav]

Dear All,

We have a spindle motor with it's own amplifier unit and encoder gets closed in their own amplifier. Initially we enable the spindle motor from PMAC by "O" command and the spindle is able to respond. Now we have a provision to tap the encoder signal from the amplifier to the PMAC. Once we connect it in this fashion, when we provide the JOG STOP command to put the motor in closed-loop, the motor starts to rotate continuously. Since this is the first time I'm working on a rotary motor with feedback, I'm not able to understand the issue. Kindly let me know how to go about with the initial configuration of the spindle and setting a closed-loop control of the motor using the motion program (M03,M04) etc. I need to do this since, I need to assign the motor to an axis.

 

Thanks in advance.

[Richard Naddaf]

You need to do the following:

- Make sure you are outputting DAC.

- Make sure you have feedback.

- Set Ixx69 properly.

- Perform an open loop test to make sure that the encoder is counting in the same direction as the output. Meaning when you issue a positive O command, the encoder counts positive. And vice versa

- Tune the motor. Set up PID tuning gains.

 

These steps and procedures are usually covered the beginner's PMAC traigning.

[Raghav]

You need to do the following:

- Make sure you are outputting DAC.

- Make sure you have feedback.

- Set Ixx69 properly.

- Perform an open loop test to make sure that the encoder is counting in the same direction as the output. Meaning when you issue a positive O command, the encoder counts positive. And vice versa

- Tune the motor. Set up PID tuning gains.

 

These steps and procedures are usually covered the beginner's PMAC traigning.

 

Thank you Richard. Solved the issue. The encode/decode control was opposite to the actual encoder feedback. But at times, after I run the motor for sometime and issue a J/ command, the motor tries to rotate back and forth. Is it a tuning issue?

[Richard Naddaf]

Yes, it sounds like it is.

Also, it could be that your deceleration rate (Ixx19) is too fast for the inertia/amplifier capacity.

[tahoe brian]

Based on what I am reading, it sounds like your motor-encoder-amplifier system that you bought closes a velocity loop around the spindle, i.e. by giving it a command, for example an O command, you get a speed. Is this true? If so:

 

1. Make sure that this loop is well tuned, i.e. the speed follows the commanded speed well. Step inputs to the velocity is a good way to test this.

2. Close the position loop in PMAC using largely P and I gains, and feedforward as required. You probably won't need a lot of D. It sounds like your P gain is way too low and/or your I gain is way to high.