A METHODOLOGY FOR THE DEVELOPMENT OF ACTIVE ANKLE PROSTHESIS

In the present work a methodology for the functional design of ankle prostheses is presented. This methodology is applied to the functional design of an innovative active prosthesis for the lower limb able to guarantee the physiologically correct movement of the ankle. This new prosthesis, described in this paper, is based on a mechanism with two links: one replaces the tibia and the other, coupled together with a hinge at the ankle level, replaces the foot. For the functionality of the device, an active shock absorber is placed between the two links and acts for damping and for accumulating potential elastic energy; furthermore, the anchoring point of the shock absorber on the tibia is adjustable by means of a motor that acts on a rocker arm. The methodology for the functional design of ankle prosthesis is based on 4 steps: 1) the analysis of the gait of able-bodied men with the definition of a dimensionless model of the lower limb in a numerical computing environment; 2) the analysis of the force exchanged with a sensorized treadmill in a virtual ambient; 3) the functional design of the prosthesis able to adjust the pitch of the ankle and at the same time able to store and provide the mechanical energy; 4) the preliminary draft of the control system of the actuators able to define the law of motion to reproduce the physiological gait.