Tendon-Driven Actuation

Placing the motor far from a joint and pulling it with a cable, like a tendon.

Tendon-driven actuation imitates the tendons in a human hand: the motor sits in the forearm or palm, and a thin, high-strength cable (commonly ultra-high-molecular-weight polyethylene, UHMWPE, fiber) runs through pulleys or a sheath to pull a finger joint. The upside is that the fingers themselves stay light and slim, letting the hand approach human size with many degrees of freedom; the downside is that the cable stretches over time and has friction and changing pre-tension, making modeling and control harder and requiring regular calibration and maintenance. Because a cable can only pull, not push, a joint typically needs two cables, or one cable plus a return spring, giving rise to wiring schemes described as N-type, N+1-type, or 2N-type. The Shadow Dexterous Hand is a classic tendon-driven hand, and Tesla's Optimus hand is reported to use a similar approach.

ExampleThe Shadow Dexterous Hand keeps its motors in the forearm and pulls more than 20 finger joints via tendons, giving it a shape and size close to a human hand.

Also called

Tendon Drive, Cable-Driven Actuation

Related

Dexterous Hand · Shadow Dexterous Hand · Bowden Cable · Tendon Routing Configurations (N / N+1 / 2N) · Tendon Material (UHMWPE) · Linkage Transmission

Sources

Shadow Dexterous Hand - Shadow Robot Company