Design and Analysis of the Active-Passive Hybrid Ankle Prosthesis Based on Electro-Hydraulic Actuation

Wearing ankle prosthesis is an important means for patients with below-knee amputations to restore walking ability. The lower limb prostheses are divided into passive prostheses and power prostheses according to whether it can actively output torque. Power prostheses are further divided into active prostheses and active-passive hybrid prostheses. Passive ankle prostheses cannot provide active torque and have limited application scenarios. Powered ankle prostheses can output active torque, but it has the problem of incompatibility between low passive friction and high active transmission ratio. To improve the performance and adaptability of ankle prosthesis, this research proposed a new configuration of active-passive hybrid ankle prosthesis based on the principle of electro-hydraulic actuation from the perspective of practical application. Firstly, based on the analysis of the angle and torque of the human ankle joint, it designed the driving system of the ankle prosthesis and proposed the overall design scheme of the active-passive hybrid ankle prosthesis. Then, the mathematical model of the prosthesis system was established, the rationality of the prosthesis system was verified by the simulation analysis of the hydraulic system of the prosthesis, and the principle prototype of the prosthesis was developed. Finally, the performance of the prosthesis was verified by bench test and human walking experiment. The test results show that the maximum active output torque of the prosthetic ankle joint is 28 N·m when the walking speed is 1.0 m/s (close to the average walking speed of adults). The research results show that the active-passive hybrid ankle prosthesis proposed in this research can realize the active assist function in the human walking process, and can better fit the human ankle movement posture, enhance the wearing adaptability, and further reduce the volume and mass of the prosthetic. The work in this research provides a design idea and reference for the research of dynamic lower limb prosthesis.