Robust control of a parallel robot

This work presents the implementation of two model based control schemes in parallel mechanisms; the H∞ robust control designed by the mixed sensitivity approach and the Computed Torque Control (CTC). Simulations results are illustrated for the 3DOF parallel robot namely the “Delta robot”. Performances of the CTC and the H∞ controllers are compared for a semi elliptic pick and place trajectory and with a parabolic position profile. The movement dynamic is increased up to the acceleration of 12 G and a velocity of 1m/s. For robustness tests, parametric disturbances are introduced by additional loads on the travelling plate of the Delta robot. The simulation results performed on a SimMechanics model of the Delta robot show that the H∞ controller presents better performances and robustness compared to the CTC controller. It is implemented in the control scheme without the incorporation of the inverse dynamic model (IDM) of the system which reduces significantly the computation time of the control law.