Minimal PID controller in Python.

Optional features:

• Output limiting
• Anti-windup mechanism
• Lowpass filtering of derivative component
• Bumpless transfer between manual and automatic control
• Gain scheduling
• Feed forward component

• Output dithering
• No output change if we are near the setpoint, for, e.g. reducing motor noise
• Beyond gain scheduling also schedule, limits, and anti-windup
• Output rate limiting