Atime-varying generalization of the classical deadbeat controller is derived directly from input-output data in the present paper. The natural extension of the time invariant deadbeat condition to the time-varying case is presented by using the key developments of the observer/Kalman filter time-varying system identification theory reported recently by the authors. In stark contrast to the time invariant deadbeat controller design, it is shown that the time-varying deadbeat controller parameters do not follow the recursive relationship that was developed in the past. In the special case of periodic systems, where repeated experimental data are available naturally, it seems that such a controller can be designed to set the output of the closed-loop system to rest after a few time steps. Numerical simulation example demonstrates the efficacy of the deadbeat controller design method proposed in this paper. A deadbeat controller, realized from the departure motion dynamics of a spacecraft, is then shown to enhance the performance of an attitude control system by minimizing the deviations from a reference trajectory.
