This work combines two well-known approaches to control: dual control and h
armonic control. The combination results in high speed of adaptation and th
e possibility of using feedback controllers in practical situations where t
raditionally feedforward controllers were preferred. The use of frequency-s
elective filters results in fast adaptation without substantial increase in
on-line computing effort. The approach proposed is more suitable for adapt
ive cancellation of periodic output disturbances. Dual controllers are comp
uted around each relevant frequency of the disturbance and the control inpu
t to the plant is synthesized from them. Simulations illustrate how the con
trol scheme works. Copyright (C) 2000 John Wiley & Sons, Ltd.