Control

PID Controller

A PID controller is a feedback controller that computes its output from three terms on the tracking error: a proportional term for present error, an integral term that eliminates steady-state offset, and a derivative term that damps the response. It is the most widely deployed controller in industry and closes the joint-level servo loops of virtually every robot, typically running at kilohertz rates beneath higher-level planners and policies.

Why it matters for physical AI

Learned policies almost never command motor currents directly; they output setpoints tracked by PID-style loops, so the bandwidth and tuning of these inner loops bound what any higher-level controller can achieve.