An improved control strategy based sliding mode approach for high-order systems with mismatched disturbances

This paper develops an improved design of sliding mode control for high-order systems subjected to matched and mismatched disturbances. Unlike most of the literature implementations, that consider the mismatched disturbances as time vanishing disturbances with a known upper bound; the proposed approach works under time non-vanishing of both, the mismatched disturbances and their time derivatives. Furthermore, these disturbances and their time derivatives are bounded by an unknown constant. In contrast to the classical approaches that search for an approximation to the disturbance and then incorporates it into the controller to stabilise the system, the proposed scheme conducts the system output to achieve asymptotic convergence and this is without the need of any exact estimation of the disturbance. Two simulation examples are provided to illustrate the effectiveness of the proposed approach.