Robust sliding mode control for nonlinear uncertain time-delay systems based on disturbance observer

The disturbance-observer-based sliding mode controller is designed for a class of nonlinear uncertain time-delay systems. A disturbance observer, unbiased in terms of the weighted mean, is designed to estimate the lumped disturbances with time-varying delay by the current system states, and the corresponding estimation error is analyzed. By incorporating H_infin control technique into sliding mode control approach, integral sliding mode controllers are designed to guarantee the H_infin performance of sliding mode dynamics and satisfy the reaching condition. The proposed scheme does not require uncertainties to satisfy matching condition and linear boundary condition, and chattering is efficiently restrained as well. A simulation example illustrates the obtained results.