Adaptive rejection of unmatched input disturbances for output tracking using a control separation LQ method

In this paper, an adaptive disturbance rejection scheme is developed for output tracking of multivariable nonminimum-phase systems in the presence of uncertain unmatched input disturbances. Using a new cost function, a control separation-based LQ control framework is established for desired disturbance rejection and output tracking. The finite-time and infinite-time control separation-based LQ solutions are derived in an explicit composite controller structure, which has enhanced disturbance compensation and output tracking properties, as compared with a traditional LQ solution. An adaptive parameter update algorithm is used for estimation of uncertain disturbances, based on which an adaptive control separation-based LQ control solution is developed for plants in the presence of uncertain disturbances. Simulation results are presented to verify the desired adaptive disturbance rejection control system performance.