Development Of Functional Electrical Stimulator And Research On Stimulus Artifact Filtering

According to electrodes position of the skin, functional electrical stimulation can be divided into three categories:percutaneous surface electrical stimulation, subcutaneous electric stimulation and fully implantable electric stimulation. The Obvious advantage for the percutaneous surface electrical stimulation is the non-invasive treatment with little negative side effects and also has a good clinical effect with this method in the rehabilitation training. Furthermore, the therapeutic method is easy and convenient to use in hospital or at home after the short-time training. Therefore, for the therapeutic method the acceptance has been quite high by great majority of patients.In this article the low frequency pulse functional electrical stimulator with the four channels and the adjustable stimulus parameter of each channel was developed and could be used in helping promote blood circulation and correcting the foot drop. This stimulator is the constant current source output. The design of this low frequency pulse functional electrical stimulator in my article was based on the C8051F121 single chip microcomputer. The start and stop of my stimulator could be controlled by both the keyboard and plantar pressure. The MPC1652 chip was employed to design the boosted circuit. Meanwhile, the boosted circuit combined the bidirectional voltage controlled constant current technique to create a kind of bipolar stimulation waveform with completely symmetrical positive and negative phase which had been widely used in the clinical application. The traditional keyboard and LCD (Liquid Crystal Display) pattern of human-computer interaction were used in the Stimulator. The stimulator channels could be selected and the stimulus parameters of each channel including the output stimulus signal intensity, frequency and pulse width also could be adjusted by the keyboard. Meanwhile, the information of output stimulus signals could be displayed in real time by LCD. Each channel of the stimulator was connected to the stimulating electrode by electrode wires and four channels could work together at the same time. Compared with past traditional single channel stimulators and other stimulators, my stimulator is more flexible to use. After seeking patients’ optimal stimulus parameters, the number of electrodes could be selected and the stimulus parameters of each channel also could be adjusted upon the optimal stimulus parameters. At last, the discrete wavelet transform was employed to filter the stimulus artifact from the contaminated electromyographic signals. This provided references to extract electromyographic signal feature as the amount of feedback for the closed-loop stimulator research in the future.My paper was divided into six parts. Firstly, the functional electrical stimulation in both the domestic and overseas development situations were analyzed and summarized. After that, the basic theory knowledge was introduced, and the stimulator output waveform and the range of parameters were determined. Then based on the C8051F121 single chip microcomputer, the hardware design of the stimulator was accomplished and a kind of bipolar stimulation waveform with completely symmetrical positive and negative phase was created. Next, the modular design method was adopted in the software design of the stimulator, and after the on-line debugging of software and hardware system, the experimental results had reached the requirement of the design. Lastly, the discrete wavelet transform was employed to filter the stimulus artifact from the contaminated electromyographic signals.