Clutch spring knee exoskeleton

This is an exoskeletal architecture for augmenting running leveraging a spring–clutch exoskeleton consisting of a custom interference clutch with an integrated planetary gearbox.

Specifications for the exoskeletal joint were derived from existing biomechanical data. The design also includes a control system to enable clutch locking and unlocking throughout a running gait cycle. 

The elastic element of the exoskeleton consists of thin strips of semirigid unidirectional “E” fiberglass laminate located proximal and distal to the lockable exoskeletal joint. The net system constitutes a compression spring, characterized by the geometry of these elastic elements. 

The exoskeletal joint consists of an interference clutch (chosen for its high ratio of holding torque to mass) in series with a planetary gearbox which decreases the load on the clutch plates and increases effective resolution, compensating for the discretized engagement of the interference clutch. 

Electronics are housed in a lateral subassembly with only a single pair of wires necessary to connect to the solenoid. A quadrature phase encoder for measuring the exoskeletal joint angle and a break beam for measuring solenoid position are both interfaced optically. The sensor suite is completed by a three-degrees of freedom sagittal plane inertial measurement unit.