Development of Robust Fuzzy Sliding Mode Control Technique for Nonlinear Drive Systems M A. A. Morsy Electronics Research Institute Cairo Egypt M Said A. Moteleb Electronics Research Institute Cairo Egypt motelebgeri.sci.eg H. T Dorrah Cairo University Cairo Egypt Abstract: This paper presents a fuzzy sliding mode controller (FSMC) used for switched reluctance motor (SRM) speed regulation. The combination between fuzzy logic control (FLC) theory and variable structure control (VSC) technique based on sliding mode is achieved to include their merties and eleminate their disadvantages. The proposed approach is used to implement fuzzy sliding mode controller by using Lyapunove function. The results that have been simulated through the matlab - simulink toolbox show that the proposed controller, in the speed loop, gives best and robust responses. 1. INTRODUCTION Switched Reluctance motors are fast becoming a popular attractive to induction motors in the variable speed drives market due to their advantages. SRM is simple and rugged in structure, has high energy density, and low rotor inertia. References [1, and 2] show the implementations of controllers used with SRM speed drive are complex and too difficult to implement. Since the 1960's, with the advent of power electronics and high power semiconductor switches, control of the SRM become much easier and there has been a renewed interest in SRM drives. In recent years sliding mode control, based on the theory of variable structure systems has attracted a lot of research on robust control of nonlinear systems for the last two decades. The main important advantages of sliding mode control, especially for application in the power electronics area, are high accuracy, fast dynamic response, good stability, simplicity of design implementation, and beside to its robustness or low sensitive to variation of system parameters and external disturbances. [3, and 4]. VSC with sliding mode is a high speed switching control law driving the system states from any initial state onto a user specified surface in state space called switching or sliding surface, and maintained the states on the surface for all subsequent time. As a result, the system dynamics, governed by the parameters, is described by that sliding surface which is always stable [5]. The switching action in VSC methodology causes a severe chattering in steady state which is undesirable in some dynamic systems. Several chattering reduction methods based on using a boundary layer in the sliding mode have been reported [3, 6, and 7]. Fuzzy logic control (FLC) is recently finding wide popularity in various applications that include managements, economics, medicines, and process control systems. The theory was introduced by Zadeh [8]. FLC have generated a good deal of interest in certain applications due to its advantages over the conventional controller like: not need accurate mathematical model, works with imprecise inputs, handles nonlinearty, and is more robust than conventional nonlinear controller. The application of fuzzy theory in power electronics is almost entirely new [9 and 10]. Although there has been some research on the stability analysis of fuzzy control systems, fundamental problems, however, still exits in the control of complex systems using fuzzy logic controller like the huge amount of fuzzy rules for a high order system makes the analysis complex, and no general stability analysis tools applied to FLC [ 1]. Recentely, the synthis algorithems of modern control and arifitial intellegent (Al) have been studied to upgrade the performance of SMC. Fuzzy sliding mode control, which takes the features of both SMC and FLC to overcome the disadvantages of chattering and enhnce the robustness of the controllers [6-7]. It is proposed in this paper a description of robust fuzzy sliding mode controller (FSMC) for speed regulation of 6/4 poles SRM. The introduced controller applied to control the reference current of the hysteresis controller to improve the electromechanical torque to ensure a robust speed regulator. The proposed controller structure gives a better performance, global stability, and also the robustness is assured. 2. SWITCHED RELUCTANCE MOTOR 2.1. Basic of Operation The 6/4 SRM is an electrical motor as shown in fig. (1), which the stator windings on diametrically opposite pole are connected in series to form one phase since there are no windings or magnets on the rotor. D2 Vdc Q2\ X t t D 01 Fig. (1) 6/4 poles switched reluctance motor 1