Need some help with motor jittering issues rendering my sim unusable

My sim used to run absolutely fine, I could race in it for a long period of time without really any issues, the occasional glitch.

After a pc upgrade it's pretty much unusable. After about a minute either one of the motors starts jittering. I can see it's still trying to do the motion but osculating.

Heres a video



Anyone have any idea what could be causing this or had a similar issue? Would love to here some suggestions for a fix.

I am using a 24v 1000w PSU and a sabertooth 2x32. Motors are 24v 400w. Ardunio with latest smc3 code. Issue happens with simtools v2.5.1 and V3 alpha

Reduce the p number and try again

Sorry, can you elaborate on what the p number is? Do you mean KP? It's set at 150, if I go any lower the motor struggles to keep up with the output in smc3

Ok

Now set pwm rev to a much smaller number

Appreciate your help, but can you explain why this will solve the issue? I had all the smc3 settings dialed in, the rig was working perfectly for months so reluctant to make changes when I'm not sure why I'm making them?

Its very difficult to diagnose a problem remotely

We need to keep trying things till the problem goes away.

Another solution is to swap parts from left to right.

My guess is you have electrical noise, probably usb related. Or your usb/serial port is struggling to process the data becoming a bottleneck

Do you usb3 ports ?

I also think this is emi related, just odd that it wasn't occuring that much and now it is. I've turned all other electronic devices around it off, and the ardunio is connected directly to the pc via usb3.

I'm going to try some ferrite cores on the power, usb and motor cables. Pot cables are already shielded.

If that fails it's all going in the bin

SOLVED

To recap, my sim (2 DOF, Arduino Uno clone, sabertooth) would work fine for up to 5 mins, but then my motors would behave erratically. It would also run perfectly fine for any length of time using the outputs from smc3 utilities.

Resetting the Ard or going into smc3 utilities is required to reset the motors, but the problem would always return after a very short period.

After racking my brains and pulling my hair out for weeks, trying all manor of things both hardware and software related (moving components, adding ferrite cores, trying a different Ard (only clones), rewiring everything, changing smc3 settings, etc) I stumbled on some posts of users having the exact same issue.

The problem was down to the simtools 'bitspersec' setting (baud rate) being 500000 and the Arduino Uno being overloaded, possibly due to it being non genuine.

The fix for this was to ground pin 8 on the Uno (connect a cable from pin 8 to the ground pin) which changes the baud rate in the code to 115200 and also changing the 'bitspersec' in simtools to 115200.

After this change, everything works great and I have had my sim running perfectly for long periods of time without any issues.

One thing to note is that you will not be able to access smc3utilites with this setting. You will need to remove the wire connecting pin 8 to ground on the Uno, reset it, and then you can enter smc3 utilities to change settings. Once done, ground pin 8 again.

This info can actually be found in the faq but took me some time to find it, so I hope this post will help someone save a bit of time