Real Time Acquisition of Stump Angle as a Feedback Signal for Development of Low Cost Electronic Knee Prosthesis

Electronic knees provide a wide range of mobility for amputees but the high cost of these knees, due to the wide variety of sensors used and the ensuing complexity of the hardware and algorithms used there in, makes them inaccessible to most amputees in developing countries. The goal of this paper is to develop a low-cost sensor to measure the angular change of the ‘stump’ socket, and that of the thigh movement, with the aim of reducing the overall cost of the electronic knees. The proposed measurement system, named as Stump Angle Measurement (SAM) system, uses a low cost accelerometer, which provides a direct feedback of angular change of the thigh movement, and ultimately that of the hip joint. Preliminary results of SAM module show that the properties of feedback signal alone (amplitude and frequency) can be used to vary the speed of actuator (knee joint) resulting in a wider mobility for the amputee. The proposed system also reduces complexity of the hardware as well as algorithms used in modern electronic knee, thereby reducing the overall cost of knee prosthesis and making it more accessible to amputees in developing countries like India.