Abstract: To cope with the unmeasurable external disturbance having known waveform but unknown magnitudes, a disturbance compensator is designed for a class of nonlinear systems with multiple state and input time-variant delays.When the unbounded disturbance enters the time-delay systems, the systems state variables will go out of control.Thus it is necessary to design a reduction controller to compensate or minimize the effects of the disturbance.In order to obtain the estimation of state and disturbance, an augmented system is constructed by the nonlinear system and the disturbance system, and a time-delay composite state observer is designed to give the estimation of state and disturbance.Hence, the disturbance reduction controller is derived and the systems state variables are kept in control.An illustrative example shows the effectiveness of the proposed methods.

Key words: multiple time-variant time-delays, disturbance waveform, observer, disturbance reduction controller, nonlinear system