Ankle Prosthesis with an Active Control of the Pitch and the Release of the Energy

This paper describes a model of a prosthesis of ankle able to control the pitch and the release of energy recovered during the gait; moreover, the model is able to provide to the user more power than the one recovered during the gait, in order to ensure a natural gait. The development of the model has been articulated in 3 steps: the study of the gait of able body people; the design of a mechanical system able to adjust the pitch of the ankle and at the same time able to store the mechanical energy; the development of an active control of the foot and of the energy recovery system. The conceived model is made of a four-bar linkage with a further fifth element. Two of those elements can modify the length: one is an active shock absorber for damping and for the energy recovery; the other is a linear actuator for the pitch adjusting. The first is equipped with two control flow valves; the second is made of a screw nut mechanism. The control system is based on a central control unit that detects signals from three sensors to determine the gait phase, to control the shock absorber and to adapt the actuator to the correct position.