Hybrid Soft Pneumatic and Tendon Actuated Finger with Selective Locking Chain Link Joints

Rigid robots excel in structured conditions but struggle in more unpredictable or populated environments. Soft robots address these difficulties, but the compliance which gives them their inherent safety also limits their ability to apply desired forces. Jamming/locking reduces this back-drivability but does not allow for directional application of force. We present a hybrid system including pneumatic and tendon actuation as well as a system of cable-driven locking modules, able lock individual joints. Combining these mechanisms yields a device, which can behave as: a soft finger, a fully-rigid finger, and a locally-locking finger which mimics a traditional rigid-link robot. This finger is able to switch between these behaviors on-the-fly, allowing it to adapt to unexpected scenarios, critical for social robots. Using these modes and the ability to adapt real-time, our finger is able to complete common household tasks, difficult for current robots. We characterize the finger's ability to resist force in three actuation modes (Pneumatic, Cable, and Locked), its ability to apply force, and its ability to actuate in 31 different configurations (plus a static all-locked configuration). We also present a demonstration in which the finger conforms to the shape of a computer mouse then clicks a mouse button, and of the finger conforms to the shape of a heavy door handle, then pulling it open. We present the design, fabrication, and characterization of this finger as a demonstration of the underlying concept, which can be broadly applied to social robotics.