How to stop a moving piece of a robot

My team has been working with a lot of electro mechanical components to our robot but one problem we are running into is when we stop running the motors gravity pulls down our system. we know about motor braking but that is not enough. Is there a different solution that we are missing?

Depends on what type of subsystem you are using, but this is a popular solution.

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There’s a few options.

One is to use a higher gear reduction, which is harder to backdrive, but that may not work.
There’s always the good ol’ worm gear trick, but that will really slow down whatever you’re running.
Or you could apply a disc brake to whatever is rotating (or a similar solution to whatever is sliding).

Also, depending on what you are doing: Use PID to hold position. Won’t work while the robot is disabled, but while you’re operating it should work well.


You could also use a spring to counteract some of the forces-which will also make it easier to speed things up


Spring counterbalancing is good solution if your system is on some sort of pivot, team 846 made a really good video explaining how it works and how to implement it. Monkey Box #3 - Gravity Arm Counterbalancing - YouTube


could using a PID loop flame out a motor?

I’ve seen ‘bots that use bicycle disc brakes to stop a rotating mechanism. I think a pneumatic cylinder was used to actuate the brake.

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Unlikely. Unless you severely underpower the motor.

We’re in a similar situation. Our robot uses a virtual four-bar mechanism and one idea we had was using a vex through bore encoder paired with motor braking. We run a 165:1 gear ratio so it should be sufficient, but in your situation, you may be able to underpower a motor to keep enough tension.