1995 Volume 31 Issue 8 Pages 1136-1143
If influences of such uncertainties as perturbations and disturbances on controllers possess nonstationary characteristics, it is important to develop a nonstationary robust control method. This paper presents a nonstationary robust control method taking account of the nonstationary uncertainty influences by using a time-varying criterion function. In order to improve the robustness of the control, in this method, an integrated design of both H2 control used under the condition of little influences of uncertainties and H∞ control used under the condition of large influences are realized by applying a smooth change of the two kinds of controllers and solving time-varying Riccati equations in stead of time-invariant Riccati equations.
In this paper, as an example in which influences of uncertainties possess nonstationary characteristics, a positioning and vibration control problem of flexible structures is adopted. In this problem, influences of such uncertainties as Coulomb friction and parameter variations are generally severer in the period after positioning than in the period during positioning. In comparison with the former methods proposed by authors, the usefulness of the method is verified by numerical calculations and experiments by its application to a positioning problem of the two-degree-of-freedom flexible structure.
