Importance of series elasticity in a powered transtibial prosthesis with ankle and toe joints

The authors have previously developed a powered transtibial prosthesis with ankle and toe joints to help lower-limb amputees obtain more natural walking gaits. Inspired by the importance of series elasticity in increasing muscle work output and efficiency, series elasticity has been added into the actuators which are used to drive the ankle and toe joints. In this paper, we analyze the effects of series elasticity on the displacement, velocity, and energy consumption of the actuators. Dynamic models of the ankle and toe joints are built and simulations are performed. In these models, the imposed plantar pressures and objective joint angles are measured from locomotion experiments on healthy subjects. Simulation results show that series elasticity can reduce the displacement, maximal velocity, and energy consumption of the actuators. Walking experiments on an amputee subject wearing the prosthesis prototype are carried out. Experimental results validate the importance of series elasticity in reducing the energy consumption of the prosthesis.