Extended Linearisation Control Approaches for a High-Speed Linear Axis with Pneumatic Muscles

Abstract

This paper presents nonlinear control approaches based on extended linearisation techniques for a high-speed linear axis driven by pneumatic muscles. Its guided carriage is actuated by a nonlinear drive system consisting of two pulley tackles with pneumatic muscle actuators mounted at both sides. This innovative drive concept allows for an increased workspace as well as higher carriage velocities as compared to a direct actuation. The proposed control scheme has a cascaded structure, where two alternative design methods in the framework of extended linearisation are discussed and investigated: eigenvalue placement (EVP) and an optimal design based on the state-dependent Riccati equation (SDRE). Unmodelled hysteresis in the force characteristic of the pneumatic muscles is counteracted by an additional control loop with proportional-integral (PI) behaviour. Implementations of both control approaches on a test rig are compared to each other and show excellent closed-loop performance.