A linear time-varying (LTV) discrete-time controller for the rejection of harmonic disturbances with timevarying frequencies on linear time-invariant (LTI) systems is proposed and validated in real-time experiments. The controller is an observer-based state feedback controller with a time-varying observer system matrix and a time-invariant state feedback gain. For the controller design, the combination of plant and disturbance is modeled as a polytopic linear parameter-varying (pLPV) system and linear matrix inequalities (LMIs) derived from quadratic stability theory and LMIs for an upper bound on the H 2 performance are used. The design guarantees closed-loop stability even for arbitrarily fast changes of the varying parameters. The controller is tested on an active noise control headset for a disturbance signal consisting of four harmonics.

A design method for a discrete-time ∞ H -optimal gain-scheduling controller that rejects harmonic disturbances with time-varying, known frequencies is presented. This is motivated by active vibration control and the controller is experimentally validated on an active vibration control test bench. The harmonic disturbances are modeled as outputs of a linear parameter varying system (LPV) where the frequencies are the varying parameters. The design method and the controller synthesis are discussed and experimental results for constant and time-varying frequencies are shown. The design method leads to a controller that stabilizes the closed-loop system even for arbitrarily fast changes in the disturbance frequencies. In the real-time experiment, the controller suppresses a disturbance consisting of six independent harmonics with frequencies that vary over ranges of 20 Hz.

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