Continuous input-output robust tracking control of SISO continuous-time systems with fast time-varying parameters: a model reference approach

The output tracking problem of time-varying systems is investigated. The system under consideration contains time-varying parameters which may change arbitrarily fast and is subject to nonlinear disturbances. A robust controller requiring only input-output measurement is proposed. The control guarantees exponential stability or stability of uniform ultimate boundedness which can be made through choosing a design constant to be arbitrarily close to asymptotic stability. The resulting control is continuous, and uniformly bounded, and designed by a recursive mapping procedure. The only information of unknown systems required by the robust control approach is the bounding function of nonlinear disturbances and the bounds on the parameters and their derivatives. Time-varying parameters are not restricted to be either slow time-varying or of known structure