Brother TC-225 / TC-229 adventure!

ah, right. although it would do the same think just offset from the desired speed.

basically, im thinking that i can start with smooth, then slowly up p til it goes bad. maybe then we will notice some clues.

or not.

ok, so no plots cause I forgot my phone.

buuuuut.

with P at 1, ff1 at .67 (or whatever, it never would center at this level P) I get a very smooth analogue output in the scope.

encoder velocity is still all over the place.

so, it must be noise. either noise on the analogue out, or noise on the encoder in, or a combination of both. based on the motion "feeling" and sounding smoother, I'm going to guess it might be more encoder noise.

my cables are 24 inch long patched in extensions onto the originals. they are twisted in pairs on the encoder and on the analogue speed/ground. there are not however shielded. maybe the analogue should not be twisted?

sadly I don't have a real scope, so I cant check that way.

any specific thoughts on how to figure this out? I was thinking of getting an Ethernet cable and running the encoder and analogue speed/ground through that. it would easily tell me if it helps in any way. I could even do encoder, then analogue separately.

thanks

To check for encoder noise issues you can enable encoder quadrature error detection
and then check if you ever get an error, that is:

setp hm2_5i25.0.encoder.00.quad-error-enable true
and then watch or halmeter hm2_5i25.0.encoder.00.quad-error

Do the drives have differential analog inputs?

drive has analogue speed and analogue ground. in my head they would have been paired, but maybe thats wrong.

anyhow, how does error detection work? what is it detecting? incomplete pulses?
ill try that tomorrow.

thanks

I see that we can also just scope the raw a/b encoder channels. I can manually spin the screw and see if its smooth too.

I think encoder error makes a lot of sense. adding or subtracting a pulse every few moments would give a 'slightly" bad velocity feedback and then our perpetual compensation loop.

I went back. Ha. So there's basically what looj like missed pulses. And they correspond to f error.


But....

If I push the axis by hand its clean. But it may be just appearing that way.

Quad error seems to stay at 0.