Incomplete knowledge of plant or disturbance dynamics complicates the design of a feedback control system. Uncertainty in plant dynamics can cause feedback instabilities, and uncertainty in disturbance dynamics may deteriorate feedback performance. In this monograph, we develop and analyze methods that can be used tune feedback controllers to overcome these two difficulties. Several algorithms are presented that deal with uncertainty in the disturbance model alone. Time- varying internal models are used to reject time- varying disturbances, and the stability and performance of the...