Source of Chatter of Robot’s Drivetrain

Our 2016 robot has had problems with chattering or “hesitation” when speed and direction is changed abruptly. When traveling forward at maximum speed the robot acts normally but this changes suddenly when it begins traveling backward. We have messed around with voltage ramp rate with little success. We believe that it is an issue caused by programming. Our programming team is relatively inexperienced and we are looking for potential solutions and/or a point in the direction. We’ve done a general check of our electronics for loose connections and are unable to find any errors of the mechanical side, but are definitely willing to triple check. We compared our competition robot with our practice robot, the latter of the two had more chatter. Now more than two months after the offseason we see that the condition has not improved one bit. Please help!

I definitely am not a mechanical or programming guy but that sounds like an issue with gears or the wheels, not something relating to programming.

Did you have a scoop or other ground interfacing something?

That was the source of our chatter.

Need more information to help you effectively. Electrically can you describe the drivetrain? (4 cim tank?)

You did not mention which language you use, if your code supports test mode, if you run each motor independently at the same power, do they all spin at about the same speed and in the expected direction?

Try putting the robot up on blocks. If you go backwards slowly from a stop does it still chatter? Is one side behaving differently than the other?

Can you post your code?

On Talon SRXs I’ve seen the wheels make a loud chattering sound because they were in brake mode. It might also apply to other motor controllers as well.

Every second or so the Talon would brake the motor for a short time so the gears would chatter due to a quick deceleration. Make sure to put the motor controller into coast mode. It’d also be a good idea to double check the code and make sure there’s no noise on the output to the Talon causing it to want to stop or change direction. Hope this helps.

Same thing occurred on the (admittedly very old) Victor 884 and 888 when near software dead zone. Whenever I did 4-motor drives with them, we had one in brake and one in coast on each side. Stopping was still firm, but the jitter was less noticeable.