Prototype Development of a 3-DOF Pantographic Exoskeleton Joint with Embedded Motion Sensing System

A wearable joint sensing system for motion-measurement and misalignment-compensation is particularly important for stroke patients who lack force perception. Built upon the principle of a pantographic exoskeleton (PGE) that traces motion of a natural joint in the sagittal plane with minimum reaction, this paper presents a PGE with an embedded magnetic sensing system for real-time 3-DOF motion measurements of an ankle joint. The sensing system has been developed and experimentally evaluated on a prototype PGE measuring ankle-joint motion during sit-to-stand. The effectiveness of the PGE ankle-joint motion sensing system has been experimentally demonstrated by comparing measurements with that obtained using commercial VICON. While both systems agree closely on the joint rotation measurements, the PGE can track the instantaneous displacements of the joint center as the foot flexes during STS, which cannot be captured by an imaging system that relies on skin-attached markers.