Tendon-driven mechanisms use flexible cables, wires, or synthetic tendons to transmit force from motors to the points where motion is needed. This design mirrors the human musculoskeletal system, where muscles in the forearm pull tendons that flex and extend the fingers. By placing heavy motors away from the moving joints, tendon-driven designs can create lightweight, compact limbs and hands with high dexterity.
This approach is especially popular in robotic hand design. Shadow Robot's Dexterous Hand uses tendon-driven actuation to achieve 24 degrees of freedom with motors housed in the forearm, keeping the hand itself slim enough to fit a human-sized glove. Similarly, several research platforms and startups have adopted tendon routing to build anthropomorphic hands capable of fine manipulation tasks that would be impossible with bulkier direct-drive joints.
The trade-offs are significant, however. Tendon routing is mechanically complex, prone to friction and cable stretch, and difficult to maintain. Tendons can wear, slip, or break, requiring careful engineering of routing paths and tensioning systems. Control is also more challenging because the relationship between motor input and joint output is nonlinear. Despite these difficulties, tendon-driven designs remain a leading approach for high-dexterity applications where compactness and biomimetic performance outweigh maintainability concerns. For deeper coverage, see HumanoidIntel.