Muscle-like Pneumatic Actuators for Below-knee Prostheses

This paper reports on the design of a biorobotic actuator intended for use in a powered, below-knee prosthesis. Design requirements for the artificial muscle and tendon are based on the properties of the natural limb. As biological properties often exhibit significant variability, data from a variety of vertebrate species are extracted from published reports in the biological literature and used to specify model parameters of both muscle and tendon. To achieve the required relationships between force, length, velocity, and activation, an artificial myo-tendinous actuator is proposed whose components include a flexible, pneumatic actuator, a hydraulic damper, and die compression springs. To verify performance, a series of tests were conducted that enveloped the conditions expected from a muscletendon unit used as an actuator for a below-knee prosthesis. The experimental results show the force-length-velocity properties of the artificial myo-tendinous actuator to be similar to its biological counterpart.