A Humanoid Foot with Polypyrrole Conducting Polymer Artificial Muscles for Energy Dissipation and Storage

This paper describes the design and analysis of a humanoid foot constructed using polypyrrole (PPy) conducting polymer (CP) actuators. The compliance and damping of natural muscles plays an important role in natural human gait. Conducting polymers actuators and other smart structure actuators can store energy by means of inherent mechanical compliance that traditional DC motor actuators do not possess. This paper presents a method for optimizing the inherent compliance and damping of the actuators in order to minimize the active control effort required to generate a natural human gait. A simplified kinematic model of the design is evaluated using biomechanical joint angle and ground reaction force (GRF) data to yield the desired force versus displacement characteristics of the posterior and dorsal actuators. Numerical simulations illustrate the multifunctional nature of the PPy actuators and the overall power requirements of the system during the stance phase of walking gait.