Abstract
Disturbance observer-based controllers have been widely used in various control applications to compensate for plant uncertainties and external disturbances. This paper considers mismatched disturbances that do not satisfy the matching condition, which implies a disturbance enters the system in the same channels as the control input. The disturbance is supposed to be a biased sinusoidal signal with a known frequency. Since it is difficult to completely reject the effects of mismatched disturbances on the system, this paper proposes a controller to reduce the effect of mismatched disturbances on the output of the controlled system. The proposed controller consists of an observer-based state feedback controller and a compensation term using the estimated disturbance. By using the original system model, the proposed method estimates the system states, as well as a disturbance with unknown amplitude and phase but a known frequency. The estimated disturbance is used for the disturbance compensation input by multiplying the proposed disturbance compensation gain. To test the performance of the proposed method, comparative computer simulations have been performed for a fourth-order numerical example and a dc-motor system.
Published Version
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