How are Controls Handled at the End of the Match?

What happens at the end of a match? We are using an arm and if the robot is disabled, it will come crashing down. Does the robot stay enabled, with controller input removed? Or is it disabled?

Thanks!

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It is disabled. You’ll need to design with that in mind for any system. Higher gear ratios that are harder to backdrive can slow the fall with the motor in brake mode (which operates as long as the controller has power).

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Yes, the robot is disabled. Brake mode is about the only thing you can do in software to mitigate this problem. High gear ratio will make the brake mode more effective.
You should think about setting it on all your motors (with special handling for drive train).

Many teams add pneumatic brakes to elevators/arms, and I believe it is possible to set those up so they stay engaged when disabled.

Please watch your heads when turning off robot power on the field!

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Some things do run when the robot is disabled, like LEDs, NetworkTables, and sensors, but motors are off and pneumatics can no longer be controlled (but may still operate if commanded before the robot is disabled). Basically you want to end in a state that won’t change within 5ish seconds.

Thanks for the advice! Fortunately, with our gear reduction, brake mode seems to work well.

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Yes. Assuming you do not have a leak, you do not lose air pressure at the end of the match (it is maintained until you manually activate your release valve). So any pneumatic actuators should remain in the position they were end at match end.

Another option that is sometimes useful is a worm gear which if properly designed and setup are highly resistant to being back-driven.

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Its not super accurate, but you can use a rough estimate of match time to enable any braking devices (ie: pneumatics or brake mode (if default is coast)) before match ends.

I believe this only applies with double solenoids. A single solenoid would lose power and disengage if it were powered at the end of the match.

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As far as I am aware, our single solenoids do not lose power when disabled, they just lose the ability to change states. You should still be able to actuate the cylinder on disable and it will stay.

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Perhaps there are different kinds of them, but this is how the ones we have work.

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