Discrete time minimax tracking control with disturbance estimation

The paper proposes an alternative way to solve robust reference tracking problem. Instead of rejecting the effect of the disturbance directly, an intermediate step is built into the state estimation problem. The advantage of the methodology is to elaborate a modified optimal state estimation problem taking the unbiased estimate of the disturbance into account. Henceforward, the solution of the discrete time, optimal LQ minimax tracking problem is modified and subjected to attenuate the disturbance residual. The paper addresses the nominal case for constant reference and disturbance signal showing the asymptotical stability and the tracking performance of the discrete time, optimal min-max control. Suboptimal solution is given for time varying reference and disturbance signal. A linearized hovering quadrotor example demonstrates the importance of the suggested technique.