Robust tracking of nonlinear MIMO uncertain flat systems

This work investigates the problem of robust trajectory tracking of a class of uncertain multi-input/multi-output (MIMO) nonlinear systems. A robust tracking control methodology for such systems using flatness theory is suggested. First, it is shown how feasible desired state-space and the associated nominal control input trajectory are generated by an exosystem subject to reference signal. This signal corresponds to the flat outputs. Next, nonlinear error model due to exogenous disturbance and parametric uncertainties is characterized; using flatness property. A first order linearization is performed along the nominal trajectory to obtain a linear parameter varying (LPV) model. Furthermore, LPV techniques are applied to design a gain-scheduled control system based on user defined performance specifications. Finally, simulation results are presented to demonstrate the effectiveness of the proposed techniques.