Hardware

Transmission (Mechanical)

A transmission is the mechanical stage between a motor and a robot joint that converts speed to torque and relocates or redirects motion, encompassing gearboxes such as planetary, harmonic, and cycloidal drives, as well as belts, ball screws, linkages, and tendons. Transmission choice trades torque density against efficiency, backlash, friction, reflected inertia, and backdrivability: harmonic drives offer zero backlash at high ratios, while low-ratio planetary stages preserve transparency for contact-rich work.

Why it matters for physical AI

Transmission properties like friction and reflected inertia are what learned controllers actually feel through the actuators, shaping both the sim-to-real gap and whether a robot can safely absorb impacts and sense contact through its motors.