Hardware

Compliant Actuator

A compliant actuator is an actuator that intentionally incorporates elasticity or low mechanical impedance between the motor and load, in contrast to stiff, highly geared designs. The canonical example is the series elastic actuator (Pratt and Williamson, 1995), which places a spring in the drivetrain to enable force sensing and shock tolerance; quasi-direct-drive and variable stiffness actuators are related approaches. Compliance improves safety and contact robustness at some cost in position bandwidth.

Why it matters for physical AI

Actuator-level compliance and force transparency determine how safely robots can share space with people and how faithfully force-based demonstrations and learned contact skills execute on hardware.