Study On Sensory Feedback System Based On Electrotactile Stimulation

At present, commercial myoelectric prostheses mainly depend on open-loop control paradigm and tactile feedback is absent in general, which results in low participation and high mental load of users. In order to address such problems, researchers have investigated some methods of sensory substitution including invasive and noninvasive stimulation.In this work, noninvasive electrotactile stimulation is adopted for providing sensory feedback through human skin. Experiments are conducted on seven amputees and some healthy subjects. Three scientific topics are investigated and corresponding conclusions are achieved. Firstly, this thesis investigates the different influences between somatotopical feedback and non- somatotopical feedback on discriminating electrotactile sensation of multi-type, multi-strength and multi-position. The results indicate that somatotopical feedback is more effective than nonsomatotopical feedback in general, especially for the discrimination of position. A balance between rich information(channels) and high performance(accuracy and response time) is found and potential solutions are provided for different situations of amputees. Secondly, this thesis investigates the quantitative performance of discriminating two key grasping-related properties(object’s stiffness and economical grasping force) based on pressure feedback and slipping feedback generated by electrotactile stimulation. The results show that the subjects can successfully discriminate different stiffness or economical grasping force of objects. It means that electrotactile stimulation is effective to provide artificial tactile feedback for myoelectric prostheses. Thirdly, this thesis investigates the influence of different kinds of electrotactile sensation on controlling grasping force. The study compares different contribution of different feedbacks. It indicates slipping feedback is more important than pressure feedback towards a better control of grasping force. Slipping feedback plus pressure feedback has a very good performance, which is even comparable to visual feedback.In order to accomplish the above three scientific studies, a multichannel electrical stimulator with multi-electrode array is designed according to the equivalent circuit of human skin. A full experimental system and platform including hardware and software is developed for electrotactile feedback towards closed-loop control of myoelectric prostheses.