Design optimization of a knee joint for an active transfemoral prosthesis for weight reduction

This paper describes the optimized design of a knee joint for an active transfemoral prosthesis with a fully active knee joint. The active transfemoral prosthesis which can help amputees to walk naturally with a powered motor has been actively developed around the world with advances in battery technology and others. However, most of them are designed for level walking, especially in South Korea, research about active prosthesis is insufficiently carried out, also depends on foreign technology. Therefore, this study focuses on the development of prosthetic knee joint that can overcome complex walking environment including stair walking. The developed prosthesis has one degree of freedom at the knee joint and can mimic the human walking mechanism. The prosthetic knee joint has a simple high-torque mechanism comprising a flat BLDC motor, harmonic drive, and pulley to generate the torque required for walking on stairs, which requires the largest torque. As one of the most important factors for comfort and fatigue, the total weight of the prosthesis should be minimized. Topology optimization was carried out to reduce the weight, and an advanced knee joint design was developed based on the optimization. The structural safety was validated via finite element analysis and a strain experiment under working conditions.