Hardware

Hydraulic Actuator

A hydraulic actuator is an actuator that converts pressurized fluid flow into linear or rotary motion, offering exceptional force and power density along with inherent shock tolerance. Hydraulics powered the original Boston Dynamics Atlas and BigDog as well as most heavy construction machinery, but leaks, plumbing complexity, noise, and poor energy efficiency have driven most new humanoid and legged designs to electric actuation.

Why it matters for physical AI

The industry-wide shift from hydraulic to electric actuation traded peak force density for cleanliness, efficiency, and the precise torque control that learned controllers exploit, reshaping legged robot design.