Research Of Functional Electrical Stimulation System With Surface Array Electrode

Through the stimulation current imposed on the muscle tissue of the patients, thisFunctional Electrical Stimulation(FES) could bring about the muscle contraction whichresults in body movements; and help to the rehabilitation and reconstruction of theparalyzed or deteriorative muscles to facilitate the medical treatment and the restoration ofthe muscle’s functioning. The surface electrical stimulation is woundless and convenientto carry out; however, there are deficiencies lying in the accuracy and selectivity of thestimulation. This thesis aims to develop a multi-channel FES stimulator based on surfacearray electrodes, which would be applied in the optimization study of accuracy andselectivity of surface electrical stimulation.Firstly, the electrophysiological principles of FES are described in this thesis. Then,based on the previous theories, the author of this paper has designed a portablemulti-channel FES system which is assembled with the C8051F020microcontroller unit(MCU) as its main control chip and four stimulation channels under respectivelyindependent control. In addition, the parameters of each stimulation channel can beadjusted independently and five bipolar stimulation waveforms can be output. Meanwhile,with good human-computer interface, the system is reliable and easy to operate. Thehardware part of this system consists of five basic modules including the control module,DA converter module, human-computer interaction module and the power supply module.The design and debugging of the system’s software is being carried out in thedevelopment environment of integrated Silicon Labs IDE; five distinct stimulationwaveforms are gained through the waveform generation module of the software. Theauthor of this thesis has made functioning test through human experiment after theimplementation of the system. The result shows that the system can be applied intoelectrical stimulation on human safely; and the target muscle can have contractioninvoluntarily after appropriate parameters of stimulation signals have been set.In the following part, the finite element method (FEM) is used to simulate theextracellular potential of the motor nerve in the forearm with the cathodic direct currentstimulation. Moreover, the activation function of the nerve fiber is used to evaluate theeffect of external excitation on the activity of the nerve axon. The array electrodes with different element size and pattern are investigated, while both the peak value and halfwidth of the activation function are used to assess the stimulation performance. Finally,surface array electrodes are to be designed on the basis of previous research.