CONTROL OF PROSTHETIC ARM ROTATION BY SENSING ROTATION OF RESIDUAL ARM BONE

Abstract

Arm rotation is very useful for unilateral amputees and essential for bilateral amputees to perform tasks of daily living. We propose a new approach for improving the control of prosthetic arm rotation in amputees. This new approach involves inserting a small permanent magnet into the distal end of the residual bone of subjects with upper limb amputations. When a subject rotates the residual arm, the magnet will rotate with the residual bone, causing a change in magnetic field distribution. This field change can be detected by magnetic sensors in the prosthetic socket, from which information on the residual bone rotation is derived and used as an input signal to control a powered prosthetic rotator. Proprioception remains intact for residual limb skeletal structures, thus this control approach should be natural and easy to use. Studies have been conducted in both simulation and physical experimental models to assess the feasibility and performance of sensing the voluntary rotation of the residual bone with an implanted magnet. The results from the studies are encouraging, suggesting potential clinical applications to improve the control of powered prostheses with preservation of physiological proprioceptive feedback.