The Design of a Powered Ankle Prosthesis With Electrohydrostatic Actuation

This paper presents the design and modelling of a new powered ankle prosthesis which combines electrohydrostatic actuation with a controllable passive damper. The new powered ankle prosthesis can switch quickly between passive mode and powered assistance mode, and is intended to just give assistance at certain points within the gait cycles, such as during toe push-off. The design concept and a prototype built to demonstrate the concept are presented. A simulation model was developed to help analyse the performance characteristics. The structure and parameterisation of the simulation model are described. A comparison between simulation results and experiment results is undertaken in order to validate the model and assist in the optimisation of the design. Some results from an initial trial with amputees are included in the paper. According to subjective feedback from the amputees, the new powered ankle prosthesis provides sufficient force at push-off to assist with walking. Future investigations will be focusing on the compactness, weight reduction and control of the powered ankle prosthesis.