PID vs Bang-Bang for Shooter Consistency

[lori558]

The jumper is in the coast position. We made sure as we were wiring the robot that it was put there.
Before we modified the code we had tried changing the 10ms to 1ms and it was way better, but still not as consistent as it is with the modification. It could just be the way that our bot is designed and programmed, but it works for us.

[Ether]

Originally Posted by lori558

Before we modified the code we had tried changing the 10ms to 1ms and it was way better, but still not as consistent as it is with the modification.

Did you try it without the waveform chart ?

It could just be the way that our bot is designed and programmed, but it works for us.

Understood. But here's a chance for you to help those who helped you. We'd like to understand what's going on; to contribute to the community knowledge base.

[Kevin Sevcik]

So turn the robot on and leave it in disabled mode. Try turning your wheel by hand, then unplug one of the motor wires and try turning it by hand again. If it doesn't get easier to turn when you unplug a wire, then it's definitely in coast.

Also, if it's fairly hard to turn even with a wire unplugged, then you just have a lot of mechanical resistance in your system. That would also explain why you're seeing better stability with a -0.3 instead of 0. The extra mechanical resistance is slowing your wheel down more rapidly, so giving it a little push instead of letting it coast makes it ramp down slower. So you're having to bump it less often to keep it in tolerance, which I assume is what you're counting as better stability.

[billbo911]

Originally Posted by Kevin Sevcik

...

Also, if it's fairly hard to turn even with a wire unplugged, then you just have a lot of mechanical resistance in your system. That would also explain why you're seeing better stability with a -0.3 instead of 0. The extra mechanical resistance is slowing your wheel down more rapidly, so giving it a little push instead of letting it coast makes it ramp down slower. So you're having to bump it less often to keep it in tolerance, which I assume is what you're counting as better stability.

Excellent point!
An ideal system for Bang Bang have very little resistance to rotation and a considerable amont of rotational inertia.
Maybe Lori's solution is something to consider when using Bang Bang on a less than optimal system. This is deffinately something I would like to invetigate a bit more.