Selection of nonlinear function in integral sliding mode-based composite nonlinear feedback method for transient improvement of uncertain linear systems

The objective of this paper is to combine the composite nonlinear feedback and integral sliding mode strategies for fast and accurate robust tracking of a class of linear systems subject to uncertainties. In fact, the theory of integral sliding mode-based composite nonlinear feedback method is presented such that the resulting controlled output would track a target reference as fast as possible with small overshoot and without any steady state bias. The proposed control method retains the actual structure of composite nonlinear feedback controller in following the reference trajectory within a given accuracy and the invariance property of integral sliding mode method in rejecting disturbances and at the same time preserves the stability of the whole system. Also, a collection of nonlinear functions in different forms are studied to improve the reference tracking performance of the system. Simulation results show that the control law designed by this approach yields excellent performance.