Design, Development and Evaluation of Novel Force Myography Based 2-Degree of Freedom Transradial Prosthesis

Limb loss is a traumatic event as it has physical and psychological effects on an amputee. Recent advancements in mechatronics and biomedical engineering have resulted in development of dexterous myoelectric prostheses for rehabilitation of amputees. In addition, evolution in manufacturing and sensing technology presents ample room for improvement in mechanical design and control system of prostheses to enhance amputee experience while using prosthetic devices. The present study is focused on design of a novel and cost-effective externally powered two-degree-of freedom prosthesis for assisting amputees to switch from body-powered devices to externally powered prosthesis. The control system of the developed prosthesis is based on the muscles signals acquired through force myography (FMG) technique. For precise integration of force-sensitive resistor (FSR) inside the socket to measure muscle activity, a stand-alone housing for FSR was designed with the feature of mechanical adjustment to control sensitivity of FSR and auto-calibrate its threshold to meet the requirements of individual amputees. The housing was designed to handle the fabrication inconsistencies during socket shaping process and thus ensure that sensor is in-firm contact with the muscle to sense volumetric changes. The developed mechanical design and FMG based muscle acquisition technique was successfully tested on a transradial amputee and extensive experimentation was performed for characterization of the prosthesis. FMG signal for various gestures was successfully extracted from muscles of the amputee to control the prosthesis according to the developed control technique. The results suggested that integration of FSR in the socket has significantly reduced the effect of sweat and volumetric changes on the performance of the sensor. Due to its novel design, embedded features, and cost-effectiveness the developed prototype holds the promise to be successfully commercialized to assist transradial amputees in becoming active citizens for contributing towards socio-economic growth of their country.