A new less conservative design for nonlinear robust tracking predictive controller

Abstract

Abstract This paper develops a less-conservative robust tracking predictive controller (LCRTMPC) for nonlinear affine systems capable to deal with changing setpoints and non-additive unknown disturbance. The existence of disturbance and/or sudden changes in a setpoint may lead to feasibility and stability issues in the stabilizing terminal constraint-based MPC. The robust tracking MPCs (RTMPC) usually consider all probable realizations of disturbance or its upper bound in optimization problem which leads to a conservative (poor) tracking performance. The less-conservative method presented here extends the RTMPC to have a large robust positively invariant set (RPI) and appropriate tracking performance. The key idea is tightening control input using estimated disturbance observation error. In this method, the set of tightened control input is calculated using time response characteristics of disturbance observation error. The simulation results of the satellite attitude control system are provided to demonstrate the efficiency of the proposed predictive controller.