Feasibility of PI control for a double-acting cylinder actuated by McKibben muscles

Abstract

Pneumatic actuators are fast becoming a key instrument where cost, safety or pollution is a concern. They can be of linear or rotary type, depending on the motion they produce. Linear pneumatic actuator is also commonly known as pneumatic cylinder because it usually consists of a piston housed in a hollow cylinder. In this study, the feasibility of PID control for a double-acting cylinder actuated by McKibben muscles (DACAM) had been investigated. Due to the nonlinearity and hysteresis properties of the muscle, separate controllers for forward actuation and reverse actuation had been used. Result shows that when given a staircase input, the feedback system gave an average response of 4.28 s rise time, 6.06 s settling time, 0.01% overshoot and 0.01% steady-state error for forward actuation and 8.25 s fall time, 9.28 s settling time, 2.86% overshoot and 2.86% steady-state error for reverse actuation. The evidence from this study suggests that position control of a DACAM using PI control is possible. An implication of this is the possibility of developing a small, lightweight and simple pneumatic cylinder using McKibben muscles.