Continuous I/O robust control of SISO time-varying systems

Abstract In this paper output tracking problem of timevarying systems is investigated. A system under consideration contains time-varying parameters which may change very fast and may be subjected to high-order nonlinear disturbances. A robust controller requiring only input-output measurement is proposed. The control guarantees at least stability of uniform ultimate boundedness which can be made arbitrarily close to asymptotic stability through choosing a design constant. The resulting control is continuous, uniformly bounded, and designed by a recursive mapping procedure. The only information of unknown systems required by the robust control approach are the bounding function on the magnitude of nonlinear disturbances and the bounds on the parameters and their derivatives, which represent the distinct feature of the proposed result. That is, time-varying parameters are not restricted to be either slow time-varying or of known structure.