On the use of FES to attenuate tremor by modulating joint impedance

In this paper, we describe a closed-loop pathological tremor attenuation system using Functional Electrical Stimulation (FES). The proposed strategy, which is based on the modulation of joint impedance using FES, was developed after experimental evidence was obtained on open-loop trials with tremor patients. The method relies firstly on an online tremor estimation algorithm, which also filters the voluntary motion performed by the patient. Based on this information, the impedance of the trembling joint may be increased accordingly by applying the appropriate stimulation parameters on a pair of antagonist muscles that act on the joint, thus attenuating the effects of tremor. An experimental evaluation of the system, which involved 4 healthy subjects and 1 tremor patient, is also presented.