Hardware

Direct Drive Actuator

Direct Drive Actuator is an actuator that couples the motor to the load without a gearbox, or in quasi-direct-drive form through a low single-digit reduction. Eliminating high gear ratios removes backlash and reflected inertia, yielding high backdrivability and accurate torque estimation from motor current, at the cost of requiring large-diameter, high-torque motors. The MIT Mini Cheetah popularized quasi-direct-drive actuation for dynamic legged robots.

Why it matters for physical AI

Transparent, backdrivable actuation enables proprioceptive contact detection and safe physical interaction without dedicated force sensors, properties that dynamic locomotion and contact-rich manipulation policies increasingly rely on.