NONLINEAR MODEL PREDICTIVE CONTROL OF A FAST PARALLEL ROBOT ACTUATED BY PNEUMATIC MUSCLES

This paper presents a nonlinear predictive control scheme for a fast two-degree-of-freedom parallel robot driven by two pairs of pneumatic muscle actuators. Modelling leads to a system of nonlinear differential equations including polynomial approximations of the volume characteristic as well as the force characteristic of the pneumatic muscles. The robot consists of a light-weight closed-chain structure with four moving links connected by revolute joints. The two base joints are active and driven by pairs of pneumatic muscles by means of toothed belt and pulley. For the control of the end-effector position and the mean pressures a nonlinear model predictive trajectory control is designed. The main idea of the used method consists in a minimization of the tracking error at the end of the prediction horizon. That way the computation load can be kept relatively small. Simulation results demonstrate a good control performance.