Motion Profiling

[Paul Copioli]

That profile actually gives you a predictable and repeatable motion path almost regardless of battery voltage (I say almost because a dead battery is a dead battery). The PID should only be used for disturbance correction. All high end industrial robots that need ridiculously good repeatability use the motion planning method. FANUC uses trapezoidal Acceleration profile and triangular acceleration profile (for really short motions) to control motion. The biggest issue fighting repeatability is Jerk (the derivative of Acceleration) and the trapezoidal acceleration profile helps fight this.

Most wafer robots used in the silicon industry use triangular aceeleration, but the loads are a bit higher with a tradeoff of shorter time to target.

In general, it is good practice to do some sort of motion planning to increase reliability. Most of us FRC people are just too lazy to actually do it and use PID to control everything.