[Iron-Man]

Could use some general servo tuning advice. This is my first AC servo experience. Years of DC servo.

We have a 5axis trunnion, on a machining center. I have the 4th axis tuned and running. The 4th drive is a yaskawa SGDC-05AJA. (0.4kw) This series of drives does NOT have autotuning. Old school.

We are having problems tuning the 5th axis motor. The 5th drive is a SGDC-15AJA, (So a bit large at 1.5kw for the small motors) And have to use a 0.9kw motor code.

Could use some tuning advice. Out of the table, the 5th motor jumps wildly and alarms. Or is stable, but jumps when touched by hand, or when jogged 0.01°. Increasing position gain just causes the motor to oscillate and OVERHEAT. It is a brand new motor. When using the same parameters as the 4th, the motor just jumps/alarms consistently when energized.

I have the following tuning parameters:
Position Gain. Kp.
Speed loop gain. Kv.
Speed loop time Ki.
Speed torsion filter.
Load inertia.

The encoder output looks good, and I am getting good encoder position data on the control when spinning the motor by hand.

What gain parameters would you modify in order of priority? Once I get past jumping, and to oscillating, how much incrementally would you decrease position gain? 1, 10, 100, 1000? (Position gain currently set to: 4000. Speed gain: 4500. Time: 550.

What causes the servo energize, and wild jump? Too high speed gain, or too low position gain? Or some other gain parameter?

You will need to do a few things; Each drive will need to have its internal parameters set to the correct motor. If you do not do this, any tuning external to the drive will be very difficult, a waste of time.
In addition you will be able to set some of the tuning parameters.

1. Download Sigma Win software or purchase the Digital Operator.
2. Each servo drive's parameters must be configure to its attached motor.
3. Are these step-dir or +- 10V.
4. What software / hardware is connected to the drives? The loop in this software will also have to be set / tuned.

In summary, the software loop and the {drive loop and proper motor configuration} will need to be set.

Bottom Line, you MUST configure each drive to the attached motor first!!!
Second Tune: the PID loop.

Hope this helps,

Iron-Man

[claya]

Iron-Man,

So far, you know more about these drives than anyone we have talked to. So that helps a lot.

The SGDC-15AJA drive does NOT have the PCB & connector for the Digital operator. The AJA drives are just simple amps. All the parameters come from the Machine control.
We do have an SGDC-05AJA that works like it should. The problem we are having is with the higher wattage -15AJA drive. The control uses motor codes to configure the drive/motor. And an Encoder code to configure the encoder. The drive (or control) does not recognize the correct motor code as valid for the -15 drive. So we have a work-around that according to one Yaskawa expert should be working.

So some VERY basic servo questions:

We are getting motor jumps, or oscillation at drive energize. Changing parameters one at a time on the control does NOT converge the symptoms, at least that we can tell.
What causes the Jumps? Gain Parameters, or servo configuration? The error is 3045, Encoder pulse following error.
What causes the oscillations? Gain parameters, encoder errors, or servo configuration. We get no error with the oscillations, but the motor heats up FAST, and is at 200% max current load.
On this era drive do we have to adjust the Kp/Kv/Ti gains together to get the rough motor tune? Or just the fine tuning? In other words, change two or all three parameters to stabilize the motor.

A Fanuc expert suggests it might be a commutation error. These motor/drive use the C-channel, but I don't really understand how. We have seen a commutation error on a different motor/encoder, but that was from taking the Encoder off the motor, and not getting it timed correctly. How do the Yaskawa AC motors manage commutation? Could the jumps/oscillation instability be a commutation error?

You will need to do a few things; Each drive will need to have its internal parameters set to the correct motor. If you do not do this, any tuning external to the drive will be very difficult, a waste of time.
In addition you will be able to set some of the tuning parameters.

1. Download Sigma Win software or purchase the Digital Operator.
2. Each servo drive's parameters must be configure to its attached motor.
3. Are these step-dir or +- 10V.
4. What software / hardware is connected to the drives? The loop in this software will also have to be set / tuned.

In summary, the software loop and the {drive loop and proper motor configuration} will need to be set.

Bottom Line, you MUST configure each drive to the attached motor first!!!
Second Tune: the PID loop.

Hope this helps,

Iron-Man