Nonstationary robust control for time-varying system

This paper presents a synthesis method of non-stationary robust controller for a time-varying system considering various uncertainties. For the uncertainties, a scaled structured uncertainty is regarded as weightings for variations of parameters and a design function in the time domain. Meanwhile, an unstructured uncertainty is counted by a filter enveloping model errors of a control object in the frequency domain. A wire changing its length is adopted as the controlled object and then its vibration control is discussed as a practical problem for solution. The performances of controllers are demonstrated in the time and the frequency domains through the numerical calculations for the case that the object is subjected to disturbance and variation of parameters. The proposed controller designed by considering both uncertainties shows the advantages for the robustness.