Re: Tuning Results Confusion
Hi EvanR,
Measured Velocity is normally noisy due to quantization error of the encoder. KFLOP samples the encoder every 90us and computes the velocity based on dx/dt where dx is the encoder change and dt is 90us. So the resolution of measurement is 1/90us = 11,111 counts/sec. However your noise seems to be ~ +/-40,000 counts/sec which would correspond to a few encoder counts of noise not just 1 count of quantization. Let me guess that you are using the CUI/AMT capacitive encoders instead of a true optical encoder?
Saving and attaching the raw data would allow us to zoom in and see things more clearly.
Re: Tuning Results Confusion
Hey Tom,
The mill came with Dynamics Research Corp encoders PN#: 152-021-500-18UJ
I cant find much on them online anymore but the closest i can come are these:
https://ecatalog.dynapar.com/ecatalo...769.1602014459
I also purchased these just because I was not sure if my encoders were any good (during my trial and error):
https://www.amazon.com/gp/product/B0...0?ie=UTF8&th=1
As far as the step response file, it appears to be too large to post it here. can I email it to you?
Thanks again
Re: Tuning Results Confusion
Hi EvanR,
Strange they would have that much noise. Do they ever lose/gain countsr? Are they differential? Where/how are they connected? What is the resolution?
Regarding the file: if you zip it (then add a .txt extension) and/or capture less time it should be under the 1MB cnczone limit.
1 Attachment(s)
Re: Tuning Results Confusion
Tom,
I agree with you completely on the noise, I was really surprised also. I thought it was from being in the same liquitite as the motor power & tach but if the shield was properly grounded I would think that would drain any incoming noise. Regardless, I changed the signal cable and just temporarily ran it outside of that liquitite, only to have the same result. I do have a VFD for the spindle in the same cabinet, however, it is only a 2HP drive and it was not even powered at the time (just in case that was your next question)..
The encoders are a 500ppr differential line driver, but they do not loose counts. When I was determining the resolution I set my scale at zero, completed 1 full rev and my count was 2000. i then reversed 1 full rev and i was back at zero.
I have them connected 5vdc and 0vdc connected to the KAnalog board on JP8 via a 2 conductor shielded cable, then I have a+, a-, b+, b- on JP1 of the KAnalog. I tried to isolate the a & b channels with separate (shielded) cables but nothing changed so I returned to the 4 conductor cable.
Hopefully the step response file gives you a bit more of an idea what's going on.
-Evan Rice
1 Attachment(s)
Re: Tuning Results Confusion
Hi Evan,
It seems strange. Its seems like where it should be simply moving slowly +1 instead it does -1, -1, -1, +5
Attachment 449990
Maybe something out of alignment with the optical mask to to the optical disk?
Re: Tuning Results Confusion
That is really interesting. I am going to try to change that encoder to a brand new one then review the same plot and see if the issue (-1, -1, -1, +5) clears up. If it winds up being the encoders are the problem, what brand do you recommend for the best results?
Re: Tuning Results Confusion
Hi Evan,
USDigital makes good encoders.