PID

Hello Engineers,
I have a cnc machine when I just enable a servo (without giving motion commands) this appears to me on the Halscope

ibb.co/XWj9Th3

and the value of the last two decimal digits i.e. y=0.0xx fluctuates.
The servo moves more properly in low jogging speeds, while it vibrates hard and then gives position error
Is it just a noise problem?can it be fixed by EMI filter?, or something else causing the problem?

@Bahaa
no double posting.
thank you.

Without further diagnosis we can't say if the noise you recorded there is due to noise on the encoder lines, or if it is actual motion in the servo. With the drive enabled and the servo not properly tuned, movement like that could be possible. With the drive disabled so we can be sure there is zero motion, if there is still noise on the encoder lines, then you can be sure there is a noise problem, that you will need to remedy.

No movement, change in axis values, or halscope vibrations take place when drive is disabled...., I already tried a lot of values for pid..

Did you follow one of the servo tuning tutorials, to tune your PID settings?
Such as this one:
gnipsel.com/linuxcnc/tuning/servo.html

You also need to view your f-error with a bit of perspective, the movement you are seeing there in that photo is only +/- a few encoder counts, with the largest peak only -7 counts. What is your encoder scale? Do you have a value for the dead band setting? Sometimes setting that to 1.5-2x the encoder scale can help to quiet a nervous joint at rest.

Bahaa_Asem wrote:

No movement, change in axis values, or halscope vibrations take place when drive is disabled...., I already tried a lot of values for pid..

 

Did you try the open loop test in pncconf?
It is used to confirm the analog setting actually moves the motors and that the encoders count in the right direction.