Robot starts and stops rapidly. Makes a meshing sound.

Hey, our robot is having some problems. I finally got it to be able to drive, and I’m messing with making the driving smoother with an Xbox controller. Right now, we’re having a problem where the robot stops and starts while it’s enabled, and it makes a strange sound. It’s similar to what the FLL robots do when they have an issue, so I think they may be similar. I’m not even sure if it’s the programming, because it might be the electronics or mechanical issues. Can someone help me out?

Any chance you could post a video of what is happening? There are a multitude of things it could be.

I am also not familiar with that FLL sound.

Does the diagnostics tab of the DS show errors? What is the battery voltage before driving, and while driving?

Greg McKaskle

We had similar issues caused by small connection loses between the driver station and the radio (the robot even one time starting driving randomly). The problem was an insecure power connection to the radio. A simple wire tie around the radio and power cord to hold it in fixed it.

We had a similar problem today. Turned out to be sign error in our drive code logic that caused a good setting to be followed by a zero. The resulting “dither” sounded exactly as you described.

Are you sure your code is not trying to write weird numbers to the motors? Perhaps a 100% followed by a 0% in rapid succession?

If you go back to the “non smoother” code, does this problem still exist?

This ^^. Make sure you aren’t commanding the speed controllers a specific direction and then immediately reversing that direction somewhere in code.

What language are you using for programming? Can you maybe post the code that you changed to do the “smoothing”?

If command based pay attention to your isFinished and end methods. If your command is returning true from isFinished immediately and your end method stops the motors you could have this behavior.