Control of Air Cylinder Actuator with Common Bias Pressure

In this study, we propose a control algorithm for a pneumatic actuator that has dynamics and features similar to those of the human muscle, mainly with the aim of helping elderly persons communicate. The algorithm in this study can estimate gains by using a simple method with a double-acting air cylinder and can realize accurate speed control and position control. Specifically, we aimed to achieve quick response and less overshoot by providing a PD controller for common bias pressure control, that can generate passive stiffness, in addition to a PID controller capable of controlling disturbance and target tracking without any complicated control system. We performed gain estimation by first theoretically estimating the PID gain and then determining the optimum PD gain by actually moving an air cylinder. We tried controlling a system consisting of one air cylinder and a solenoid valve and found that the overshoot, which was nearly 30% with only the PID controller, was controlled to 4%, while the rise time was less than 200 ms of that when only the PID controller was used.