Hardware

Capstan Drive

A capstan drive is a friction-based cable transmission in which a cable wraps around a driven drum and a larger output pulley, transmitting torque with effectively zero backlash and low friction. Because there are no meshing teeth, capstan drives offer smooth motion, high backdrivability, and quiet operation, at the cost of limited torque capacity and cable maintenance. They are used in haptic devices, some low-cost robot arms, and teleoperation interfaces where transparency matters.

Why it matters for physical AI

Backdrivable, zero-backlash transmissions produce cleaner demonstration data during kinesthetic teaching and teleoperation, and make force-sensitive learned skills easier to execute than high-friction geared alternatives.