Robust Tube Based MPC for PVTOL Trajectory Tracking using Systems Flatness Property

The paper presents a tube based Model Predictive Control (MPC) strategy for robust tracking control of PVTOL aircraft. PVTOL system is considered as a benchmark for investigating dynamics and control related issues for unmanned aerial vehicles (UAVs). Due to non-linear dynamics and under actuated nature of this system, the task of building control algorithm for such systems becomes challenging. Here, the systems flatness property is used to obtain the dynamics in terms of flat outputs. The linear form of the obtained dynamics facilitates the computation of error invariant set using LMI's. Also, by an LMI based optimisation approach the problem of maximisation of terminal region of MPC is solved. This Quasi-infinite horizon strategy for MPC guarantees the stability of system. The complete process reduces the computation cost for MPC and makes the system robust against large additive disturbances. The effectiveness of the proposed control strategy is shown via simulations by tracking a given trajectory while rejecting the effects of disturbances.