Servo Oscillation Issue at ±6.6V 5i25 + 7i77, Analog Control

Hello everyone,I’m running LinuxCNC 2.9.3 with a Mesa 5i25 and 7i77 setup, controlling servo motors via analog signals. The 7i77 is powered directly from the computer.I’ve encountered an issue where the servos start oscillating when the analog command voltage reaches approximately ±6.6V. This corresponds to around 5 m/min of movement speed.Interestingly, when I change the max RPM in the servo drive from 3000 RPM to 5000 RPM, I can reach about 8.3 m/min without oscillation. However, when I control the servo directly from the servo drive, it moves smoothly at any speed without any oscillations.Has anyone experienced this kind of issue before? What could be the cause?
 

Could be tuning or marginal 5V at the 7I77 (check when running)
Does lowering the P term make the oscillation go away?
 

Lowering P does nothing further, at this point oscillation occurs and F error is displayed. Pastes my configuration files for reference. I tried to power the 7i77 from a separate power supply, it didn't change anything.

 
 

How low did you adjust P?
 What is the oscillation frequency?

P I went down to 10 and it was still the same, I don't know if it can be called oscillation, maybe I called it wrong, the axis accelerates and when it reaches a speed above 8.3 m/min there is a loud sound as if the servo lost its position and was trying to make up for it. Should I record a video or halscope? What pins should halscope show when moving? I will add that I made a mistake with 3.3V, it happens at 6.6 V because I have a 2:1 screw servo ratio

Sounds like you have exceeded the maximum encoder count rate
with the (15 clock) digital filter.

You might try:

setp hm2_5i25.0.encoder.00.filter 0

Which sets the digital filter count to 3 so allows  5X the filter=1 count rates

I'm not at the machine right now, but I'll check it in the evening. I will add that changing the number of pulses at the encoder output to smaller ones in the servopack did not change anything.

I checked:
setp hm2_5i25.0.encoder.00.filter 0
It doesn't change anything.
In the evening I will try to take halscop photos of what they look like.

Note that

setp hm2_5i25.0.encoder.00.filter 0

only changes the X axis.

Plotting the velocity, commanded and feedback position
should give the information needed to diagnose the issue.
 

I'm posting screenshots from halscope. I think the encoder had some noise.