Pulsing motors
 

I'm hoping someone can give me an idea of where to start on troubleshooting a problem with our robot. It has just been in the last week that we've had the opportunity to test our code on the robot and after several failed attempts we finally have limited driving capability. Unfortunately the motors seem to be pulsing when the joystick is pushed to full. To isolate electrical problems we've pulled all the circuit breakers but 1 at a time and it occurs for each motor. To isolate programming issues we deployed a generic arcade drive program with no modifications and it still pulses. Any suggestions on where we could look next?

Thanks

Re: Pulsing motors
 

I am more of a mechanical guy, but this sounds like a PWM problem. I will ask my programming friend what he thinks.

Re: Pulsing motors
 

Check the Driver Station log to see if that sheds some light. Run the robot with the problem a few minutes, then look at the Driver Station Charts tab and in the lower right you'll see "Launch Viewer". You'll get a popup viewer with a list of logs by date to click on.
Driver Station Log File Viewer

Are the Driver Station Diagnostics or status lights showing any error messages?

I'd try the generic arcade drive, but with a different computer running the Driver Station. In case the computer is causing the pulsing action.

Re: Pulsing motors
 

Is the motor only pulsing when you push the stick to 100%, or is it just the most noticeable at that point?

Usually the first thing I think of when I see pulsing motors is that the code may be writing to the motor in multiple places. If every scan the motor is set to 0% in one place, and then 100% in another it will rapidly toggle between the two.

When things are going not as expected I always recommend to our programmers to put some print statements in the code to show what the program is doing. (In this case, I'd probably want to print out the joystick input and the output to the motor controllers) That way you can narrow down which section of code might be causing the issue. If the output of the code is acting as expected, then you know it is likely an electrical problem.

Hope this provides some insight. Good luck.

Re: Pulsing motors
 

What motor controllers are you using?

Re: Pulsing motors
 

What language are you programming in? Can you post your basic arcade code?

Re: Pulsing motors
 

Our team had a problem that sounded like this, what we found is that the talons that the motors were hooked up to were not properly calibrated.
To fix this we calibrated them which is a super simple 60 second process that can be found here
This stopped the pulsing/creep we found in our motors.
Hope this helps.

Re: Pulsing motors
 

Thank you all for the suggestions. I decided to do two things - I started with fresh code and I unplugged all of the pwm's and re-added them 1 at a time. My 4 drive motors are now operating properly without pulsing. I wasn't able to isolate the exact cause of the problem, but I have a functioning, drivable robot and can now begin working in additional functionality (compressor, launcher, grippers, etc.).

Thanks again.