Tendon-Driven Robot Hands Explained

Borrowing the same basic trick human hands use: move the muscle, pull the tendon, bend the finger.

In a tendon-driven hand, motors located in the palm, wrist, or even the forearm pull cables routed through the fingers, flexing joints without needing a motor at each individual joint — closely mirroring how human hand tendons connect to forearm muscles.

Why this design is popular for humanoid hands

It keeps the fingers themselves light and slim, since the heavier motors sit further up the arm, which matters both for how natural the hand looks and for keeping the hand's own inertia low (a heavy hand makes every arm motion harder and slower).

The engineering challenges

Tendons stretch slightly under load and wear over repeated cycles, requiring either periodic retensioning or software that compensates for the resulting position error. Routing multiple independent tendons through a small finger without them binding or fraying against each other is also a genuinely difficult mechanical design problem.