Encoding a belted system on a jockey pulley

jjem

Hello, I have a large cartesian system with a belted linear axis which I want to encode. Instead of encoding the drive shaft of a motor, it would be useful to encode a toothed jockey pulley which engages with the belt, so that in addition to detecting motor stall, the system could also detect the belt skipping on the drive shaft, or coming loose from the belt clamp.

Should this be possible using the Duet system? I'm using the Duet 3 Main Board 6HC, with NEMA 34 motors and CUI Devices AMT102-V encoder connected to 1HCL expansion board.

Thanks in advance,
Josh

CNCModeller

@jjem I've done something similar in my large polar printer but it didn't work great.

You can see my rotary encoder mounted top right in this picture...

There is an experimental option w.r.t using a magnetic encoder on the motor and a quadrature on the axis. The magnetic encoder boards aren't available yet and I'm waiting to test one when they arrive.

I suggest you touch base with @T3P3Tony and @dc42 on the topic. See @dc42 response to my recent post here.

https://forum.duet3d.com/post/309464

Good luck with your build!

All the best
Barry M

jjem

@CNCModeller Thanks for sharing, in what way did this set-up not work for you?

CNCModeller

@jjem I worked with the dev team and struggled with poor closed loop behaviour, from memory axis jitters and choppy motion.

Based on the latest dev work I guess there were some issues with commutation and an on axis encoder that is "loosely coupled" with the motor hence the need for a motor shaft encoder as well as an axis feedback encoder.

I abandoned on axis closed loop, in favour of just motor closed loop and the team said they'd look into it some more. I guess the latest dev activity is the result of further thinking.

I've been out of the loop for quite a while so it's great to see the duet team have continued with development.

All the best
Barry M