Flywheel Subsystems
Although a flywheel is often used to describe a system that spins a heavy disk, in this context we are referring to any motor driven subsystem that spins a wheel, drum or set of wheels. The speed of the spinning objects is the primary concern of these subsystems, unlike a drive subsystem which is really concerned with the linear movement caused by the wheels. These types of subsystems are typically used to pull in or push out game pieces.
A flywheel motor may be run open loop at a defined voltage or it could be commanded though a feedback controller to maintain a constant speed as the load changes, for example when a launcher grabs and accelerates a disk through the mechanism. This can be done with a PID Controller and a Feedforward can be used along with the PID controller to provide a better response. In this case the Feedforward does not need to account for gravity, so a simple motor feedforward can be used.
References:
WPILIB Motor Feedforward
https://docs.wpilib.org/en/stable/docs/software/advanced-controls/introduction/introduction-to-feedforward.html
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