Physiological control of prostheses and orthoses using magneto-transducers

The objective of prostheses and of dynamic orthoses is to provide restorative function to anatomical joints of the upper or lower limb that are either absent or physiologically compromised. This study considers the volitional demands of upper limb function and the periodicrequirements of the lower limb during gait. Control strategies using discrete magneto-transducers to measure normal residual physiological activities which predict intended joint positions of dysfunctional or absent joints in the lower or upper limb, have been investigated andtested by experiment.The restoration of ankle dorsiflexion in hemiplegics with drop foot using functional electrical stimulation (FES) has been investigated. FES is traditionally controlled using a pressure switch in the heel of the shoe switching the stimulation on only when the foot is not weight bearing.However functional and cosmetic constraints of this method of control do not make it universally acceptable. A novel FES controller using a magneto-transducer to measure the cyclic variation of angular velocity of the leg through the knee has been developed. Experimentation with this controller showed that reliable switching of FES during successive gait cycles was possible in some patients with a hemiplegic drop foot.Most powered prosthetic prehensors and wrist units are controlled using the myoelectric activity of muscles. Such prostheses however have no intrinsic relationship between the position of the prosthetic prehensor and wrist unit and hence a degree of conscious effort in their control is required. A powered prosthetic prehensor and wrist unit has been developed using magneto-transducers which sense the myokinemetric activity of muscles dedicated to grasping and which measure forearm rotation. Reliable volitional control of the position of prosthetic prehension and wrist rotator has been demonstrated over several cycles of grasping and wrist rotation