High gain observer-based higher order sliding mode controllers

It is well known that standard sliding mode controller, usually, gives rise to a dangerous chattering effect. This problem can be overcome using a higher-order sliding mode controller which preserves the main properties of the standard sliding mode and deliberately increases the control smoothness. In this paper, we propose a new sliding variable of a recently proposed higher order sliding mode controller. In the original algorithm, the sliding variable is a function of the output error. Here, we propose to add to such variable another component defined by the error between the system model and an established model reference. As the proposed sliding variable depends on the whole system state, a high gain observer is incorporated into the controller to estimate the missing states. The effectiveness of the proposed approach is showed throw numerical simulations.