Abstract
In a networked control system (NCS), time delays, uncertainties, packet losses, and exogenous disturbances seriously affect the control performance. To solve these problems, a modified disturbance suppression configuration of NCS was built. In the configuration, a proportional–integral observer (PIO) reproduces the state of a plant and reduces the observation error; an equivalent input disturbance (EID) estimator estimates and compensates for the disturbance in the control input channel. The stability conditions of the NCS are given by using a linear matrix inequality, and the gains of the PIO and state feedback controller are obtained. Numerical simulation results and an application of a magnetic levitation ball system verifies the effectiveness of the presented method. Comparison with the conventional PIO and EID methods shows that the presented method reduced the tracking error to about one-fifth and two-thirds of their original values, respectively. This demonstrates the validity and superiority of the presented method.
Highlights
This study considered the effect of packet losses and exogenous disturbances on an uncertain system output as the result caused by an equivalent artificial disturbance on the input
The proportional–integral observer (PIO) reproduced the state of the controlled object with uncertainties
equivalent input disturbance (EID) estimator compensated for both packet losses and exogenous disturbances
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is important to consider the effects of time delay [3], packet losses, exogenous disturbance [4], and uncertainty on system performance in an NCS [5]. We consider the input and output measurement delays of a networked control system and take packet losses and disturbance as the exogenous disturbances of the system; we analyze the stability criteria of the system considering the time delays and parameter uncertainties. The uncertainties, time delay, packet losses, and exogenous disturbance which simultaneously exist in NCS are compensated for effectively.
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