AC Servo tuning - Joint 0 following error at high velocities

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28 Apr 2025 13:05 #327215 by abi9624
Hi,
I am a newbie to Servo tuning. I made a linear guide (Travel length: 500 mm) and attached servo motor to it.

Servo Motor: Inovance MS1H2-10C30CB-A331Z-INT with 23 bit encoderServo
Drive: Inovance SV670P
Mesa card:7i97T

Servo drive is configured in speed mode and controlled through analog voltage - 10V. Followed the Servo tuning guide from this forum and tuned the P, FF1, FF2 values. Tuned with a displacement of 5mm.

This setup works upto 3000 mm/min for both continuous jogging and fixed length. Above 3000 mm/min, i am getting Joint-0 following error during continuous jogging and less error for small lengths and frequent errors for larger lengths.

I doubt whether the tuning is correct or not. Help me to solve this issue.

I have attached servo drive manual, INI file, HAL file and Hal Scope screenshots at 2880 mm/min and 6000 mm/min for both 5mm and 50 mm jogging.

Thanks in advance.  

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28 Apr 2025 15:06 - 28 Apr 2025 15:07 #327219 by PCW
It looks to me like the FF1 term is different (too low) in the plots where the following
error tracks the velocity (higher velocity plots) Did you change some drive parameter
in these plots?

Also note that the velocity is not higher in the 6000 mm/m plots as it only gets to ~50 mm/s
(3000 mm/m) because of the acceleration bound
Last edit: 28 Apr 2025 15:07 by PCW.

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30 Apr 2025 07:54 #327330 by abi9624
Thanks for your quick reply.

I haven't changed any drive parameters.

Since i am new to Servo tuning, its quite confusing to conclude, whatever i am doing is correct or not. Now i have a fundamental question,

With the above setup is it possible to achieve 15,000 mm/min feedrate within 20 micron positional accuracy and +- 20 micron repeatability? I doubt whether the control loop is fast enough to reach this speed and accuracy ?

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30 Apr 2025 14:11 #327343 by tommylight
In your ini file, you have limited max_output to 8, should usually be 10.
Here is a detailed tuning guide:
forum.linuxcnc.org/10-advanced-configura...ning-detailed-how-to
Do read it fully first so you know what parts to pay more attention, no skipping steps.
And do let me know if something there can be explained better.

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30 Apr 2025 14:49 #327351 by PCW
With the above setup is it possible to achieve 15,000 mm/min feedrate within 20 micron positional accuracy and +- 20 micron repeatability? I doubt whether the control loop is fast enough to reach this speed and accuracy ?

The main control loop in this case is in the drive, its velocity feedback loop.
The position control loop in LinuxCNC can run more slowly and maintain
high accuracy and repeatability. Note that at 15000 mm/m you move only 250
microns per ms, so it takes only relatively crude velocity commands to keep
within 20 microns. Note that as you increase acceleration, tuning becomes more
difficult as you run into various physical limits.

 
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