Abstract
We introduce a new prosthetic leg design adapted to elderly trans-femoral amputees. The technical progresses in prosthesis design mainly concern active individuals. An important number of ederly amputees are not very mobile, present high fatigability, reduced muscle strength and have difficulties to manage their balance. Therefore, the needs and characteristics of this specific population are very different from younger ones and prosthetics solutions are not adapted. Our artificial knee has been designed to fulfill specific requirements of this population in terms of capabilities, transfer assistance, security, intuitiveness and simplicity of use and type of physical activities to be performed. We particularly focused our efforts in ensuring safe and secured transfers from stand to sit postures. We developed an approach to control the different states of the prosthetic joint (blocked, free, resistant), associated to different physical activities. Amputee posture and motion are observed through one multi-axis force sensor embedded in the prosthesis. The patient behaves naturally while the controller analyses his movements in order to detect his intention to sit down. The detection algorithm is based on a reference pattern, calibrated individually, to which the sensor data are compared and submitted to a set of tests allowing discriminating intention to sit down from other activities. Preliminary validation of the system has been performed in order to validate the prosthesis in different tasks: walking, standing, sitting down, standing up, picking up an object from a chair, slope and stair climbing.