An internal model control scheme is proposed to compensate both a long dead-time of a system and a harmonic disturbance. The controller is based on an inversion of the first-order model used to approximate the system dynamics together with an input delay. Two other components of the controller consists of a filter and an additional delay by which the harmonic modes are targeted via adjusting the control loop gain and phase shift. Design of the filter-delay pair is fully analytical and the implementation of the scheme is straightforward.
The main attention is paid to the complete compensation of a single harmonic disturbance. Besides, an extension of the scheme is proposed to target a double harmonic disturbance. Increased attention is paid to the robustness aspects of the schemes. Excellent performance in terms of harmonic disturbance compensation of the proposed schemes are demonstrated on a series of laboratory experiments.