Sliding Mode Control Case Study

1.1 Introduction
In recent years, the sliding mode control system has been widely used for robust control of nonlinear systems (the author Slotine and Li, 1991). The sliding mode control, based on the theory of variable structure systems, has attracted a lot of investigate on control systems for the last two decades. A comprehensive survey on variable structure control was given in Hung and other. (1993). The salient advantage of sliding mode control is robustness against structured and unstructured uncertainties. However, the system invariance properties are observed only during the sliding phase. In the reaching phase, tracking may be hindered by disturbances or parameter variations. The straightforward way to reduce the tracking error and reaching time is
This is applied in the presence of modeling inaccuracies, parameter variation and disturbances, in the provided upper bounds of their absolute values are known. Modeling inaccuracies may come from certain uncertainty about the plant, or from the choice of a simplified representation of the system dynamic. The sliding mode controller design provides a systematic approach to the problem of maintaining stability and satisfactory performance in presence of modeling imperfections. Sliding mode control is especially appropriate for the tracking control of motors, and robot manipulators whose mechanical load change over a wide range. Induction motors are used as actuators which have to follow complex trajectory specified for manipulator movements. Advantages of sliding mode controllers are that it is computationally simple compared adaptive controllers system with parameter estimation and also robust to parameter variations. Disadvantage of sliding mode control is sudden and large change of control variables during the process in which leads to high stress for the scheme to be controlled. It also leads to chattering of the system