Adaptive asymptotic tracking of repetitive signals-a frequency domain approach

The problem of designing an adaptive tracking controller for repetitive signals is considered. It is assumed that the controlled plant is linear time-invariant (LTI) and that its steady-state behavior can be described by its frequency response. The proposed controller, being able to identify the gain and phase of a plant at selected frequencies, adjusts the input/output (I/O) map at frequencies contained in the reference signal so as to achieve zero steady-state errors. Hence, no structural knowledge of the plant is needed. However, the proposed controller does not alter the transient property of the plant, e.g., locations of poles. The transient property can be improved by adding feedback control action. A combination of the adaptive controller and a feedback LTI controller is studied