A Compliance Controller for a Pneumatic Actuator With Observer-Based Friction Compensation

This paper proposes a compliance controller for a pneumatic actuator, the controller composed of a pressure controller and a positioning controller whose performance is improved by the introduction of a friction observer. The pressure controller incorporated into the compliance controller compensates for the actuator´s response delay. The friction observer performs an on-line estimation of the friction force at the seals between the sliding parts in the actuator and cancels the adverse influence of the friction force on positioning. Its estimation performance is also enhanced by modifying it for a pneumatic actuator. It is experimentally confirmed that the proposed controller realizes highly accurate positioning when unrestrained by an obstacle and appropriate compliance under contact with an obstacle