Pitching Machine Control - PID Needed?

[Joe Ross]

In 2006, we used a relatively light shooting wheel (two skyway wheels). We designed it so that our "normal" shooting speed was 80% of full speed. When we ran it open loop at 80%, it would take about 1.5 seconds to get back to speed after shooting a ball. With PID control, it took 0.7 seconds. A shooting wheel with more inertia would have made both of these better.

I would recommend starting with open loop control, and if the students aren't happy with the result, then you can start teaching PID.

[AdamHeard]

Originally Posted by Joe Ross

In 2006, we used a relatively light shooting wheel (two skyway wheels). We designed it so that our "normal" shooting speed was 80% of full speed. When we ran it open loop at 80%, it would take about 1.5 seconds to get back to speed after shooting a ball. With PID control, it took 0.7 seconds. A shooting wheel with more inertia would have made both of these better.

I would recommend starting with open loop control, and if the students aren't happy with the result, then you can start teaching PID.

This a key point. Teams need to realize it is not the surface speed of the wheel that directly matters, but rather the energy stored in this flywheel. One could make the trade off of longer initial spinup time for a much decreased energy loss per shot.

[SuperBK]

No need to port another PID library to the cRIO, WPLib already has a PID class. We used it last year to control our arm.

[mikegrundvig]

Thanks for all the useful discussion everyone.

Originally Posted by SuperBK

No need to port another PID library to the cRIO, WPLib already has a PID class. We used it last year to control our arm.

Thanks for bringing this up. I'd not seen this yet in the big PDF file. If it's already built into the system this seems to be an easy choice to me. The concern was adding more code on the students but a quick look in the PDF shows they've made this as easy as possible. Even the sensor and controller we'd be using has already been set up for us.

Any advice on using this in practice? Is it a good implementation or any gotchas we need to know? Thanks!

-Mike