Modeling and simulation of a self-tuning rapid-releasing shock absorber for above-knee prosthesis

The shock absorber inside the above-knee amputation prosthesis is a feasible solution to absorb impact forces from the ground during patent's walking and running. A conventional shock absorber consists of a spring and a damper with constant coefficients, producing too rigid reactions when encountering impact forces, whereas extremely weak reactions for gentle loadings. This study proposes a novel shock absorber design for an above-knee prosthesis, which provides automatic smooth tuning of the damping coefficient and rapid rebounds after impact loads. This design achieves the automatic tuning by a pressure-sensitive plunger valve system and check valves without any electronic devices. Theoretical modelling of the shock absorber is established in this study. Parameters of the valve system under certain absorbing performance requirements are determined in this paper.