Synthesized sliding mode and time-delay control for a class of matched and unmatched uncertain systems

Sliding mode control (SMC) is incorporated with time-delay control (TDC) during sliding phase to reduce the switching gain. TDC identifies the unknown system dynamics and disturbance directly every delay-time. For a system with a lumped perturbation which is relatively slow varying with respect to the sampling interval, a much lower switching gain can be used if a reasonably good estimate of the derivative of system state can be obtained using the past information, hence chattering can be reduced or eliminated while retaining the tracking accuracy. The paper considers unmatched uncertainties.