A Semi-Active Control Method for Pneumatic Actuators with Evolutionary Algorithm

Abstract

Pneumatic actuators have been investigated for assistive technologies such as exoskeletons. Compliant and energy efficient devices are desirable to use in daily activities. This paper introduces a novel control method to make an air cylinder function as a passive nonlinear spring with controllable stiffness. The controller computes the desired pressures based on a given stiffness. The air pressures in the cylinder are tuned accordingly, and the air cylinder starts to perform as a passive spring by closing the valves. Performance of the proposed method is validated through two experiments. The proposed method satisfies the desired stiffness response of less than 20 milliseconds and within $\\pm5\\%$ of the desired pressures.