Control of a flexible manipulator with artificial muscle-type pneumatic actuators, using μ-synthesis

In this work, position and vibration control of a flexible one-link manipulator, with an unknown but bounded payload mass and a pair of artificial muscle-type pneumatic actuators, are investigated both analytically and experimentally. A robot with flexible links originally drew attention for its capability to generate fast motion with small-powered actuators. A flexible-link robot also has advantages over a rigid-link robot in the sense that it is much safer when it comes into contact with its environment, including humans. Furthermore, for the sake of safety, it would be more desirable if an actuator could deliver required force while maintaining proper compliance. An artificial muscle-type pneumatic actuator is adequate for such cases. However, it is difficult to make an effective control scheme for this type of robot due to the nonlinearity and uncertainties on the dynamics of the actuator and the vibration of the flexible link. In this study, a controller based on μ-synthesis is developed. Robust performances on the accurate positioning of the arm and vibration suppression of the flexible link are achieved against various model uncertainties on these actuators, the flexible link, the payload, and sensor noise. The effectiveness of the proposed control scheme is confirmed through simulations and experiments.