A ΔC Detection Circuit for Capacitive Sensing Based Prosthetic Control Applications

Limb amputation impairs the physical functioning and mobility of people. For many patients, an artificial limb can improve their mobility and ability to manage everyday activities and provide the means to remain independent. The conventional human-machine interfaces using EMG are not very user friendly which is the primary reason for the rejection of active prosthetics. In this paper, we demonstrate the idea of capacitive sensor technology for the human-machine interface and present a robust capacitive interface circuit with offset cancellation and auto-nulling capabilities for upper limb prosthetic control. The proposed analog front-end circuit measures only incremental capacitance change due to the movement of the amputated hand and nullifies the effect of offset capacitance present in the sensor. A prototype was built and the initial results were presented in this paper. Experiments show that the circuit can detect a variation in capacitance in the range of 100 pF with an offset capacitance as high as 1nF.