This proportional-integral-derivative (PID) controller, implemented wholly within [helm.h], features:
- low pass filtering of the process derivative,
- windup protection,
- automatic reset on actuator saturation,
- anti-kick on setpoint change using "derivative on measurement",
- incremental output for bumpless manual-to-automatic transitions,
- a unified controller gain parameter,
- exposure of all independent physical time scales, and
- the ability to accommodate varying sample rate.
-- Astrom, Karl J. and Richard M. Murray. Feedback systems: an introduction for scientists and engineers. Princeton University Press, April 2008. Available online.
-- Wescott, Tim. Applied control theory for embedded systems. Newnes, 2006.