Design, Simulation and Kinematic Verification of a Multi-Loop Ankle-Foot Prosthetic Mechanism

Inspired by the bionic characteristics of ankle and calf skeletal muscles, a novel ankle-foot prosthesis (AFP) with variable stiffness mechanisms (VSMs) is proposed to assist transtibial amputees to restore ankle plantarflexion-dorsiflexion. The prosthesis is designed in the form of a spring-loaded three-loop linkage for function of continuous energy absorption-release in gait stance phase, which can facilitate ankle plantarflexion- dorsiflexion and keep human body move forward steadily. A compliant crank slider mechanism is also developed to power-assist AFP mechanism to improve the adaptive compliant contact between prosthesis and ground. In this letter, mechanics models of the ATP are developed to reveal the variable moment of the ankle joint, which is verified by human-machine simulation. An AFP prototype is built to validate the design experimentally. The results demonstrate that the AFP mechanism has the advantages of low power consumption, human-like joint moment profile. In particular, it is shown that the AFP mechanism with 54 W power provided in toe-off phase can reduce the peak power of the motor by 24%.