Fuzzy logic control of a pneumatic muscle system using a linearing control scheme

A linearizing control scheme for a highly nonlinear pneumatic muscle (PM) system is presented in this paper. Linearizing controllers have been widely used in the control of robotic systems. Since PM is a highly nonlinear system, the concept of linearizing control can be extended to the control of these muscles. Pneumatic muscle has air pressure as its input and the output is a displacement of the muscle. The system is considered to be a mass-spring-damper system with a nonlinear damper and a spring. This nonlinearity makes the design of a mathematical controller more difficult. The scheme presented in this paper uses fuzzy logic to implement the controller. The controller has a model-based portion and a servo-based portion. The model-based portion cancels all the nonlinearities caused by the nonlinear damper and spring. Therefore, the system as seen by the servo-based portion is linear, which can then be controlled using a linear PID controller. The controller is conceptually simple but exhibited superior tracking capability.