| dc.description.abstract | This work presents an adaptive fuzzy sliding-mode controller for a class of uncertain nonlinear systems. The controller design deals with handles the problems of the dimensionality of fuzzy input variables in fuzzy logic control, and effectively frees it from the chattering phenomena in sliding-mode control. The designed adaptive fuzzy controller based on sliding-mode has these features. The main results are as follows.
1. An adaptive fuzzy sliding-mode control strategy for a class of chaotic oscillators is presented. This class of chaotic systems includes both externally and parametrically excited systems. The controller can track the states and disturbances of at nonlinear system and construct an adaptive law, even when the exact model of the system is not known. This distance-based adaptive fuzzy sliding-mode control method makes three main contributions to this proposed model-free fuzzy sliding-mode control. First, it removes the trial-and-error process for finding suitable fuzzy rules, thus significantly decreasing the computational effort. Second, the fuzzy adaptation mechanism reduces the effects of parameter variations and disturbances. Considering the existing approaches of handling external disturbances, the proposed approach does not need a bound to be known; only requiring that it exists, and can guarantee that the state trajectory be zero. Finally, this on-line modification rule with dead-zone also improves the stability property, and increasing the speed at which the sliding surface can be reached.
2. A decoupled adaptive fuzzy sliding-mode control design scheme is described, along with a consequence adaptation, for a class of fourth-order nonlinear systems. Every subsystem, which is decoupled into two second-order systems, is said to have a main and a sub-control purpose. Two sliding surfaces are built from the state variables of the decoupled subsystem. The main and sub-target conditions for these sliding surfaces, and an intermediate variable obtained from the sub-sliding surface condition is then introduced. The proposed adaptation law, which results from the direct adaptive approach, is adopted to determine the appropriate center of the unknown system variables. The membership functions in the THEN-part vary according to the width of the adaptation of consequence. If the bound of the estimated error chosen is too large, then the control effort causes significant chattering. If the estimate error bound chosen is too small, the stability of the control system cannot be ensured. The proposed method is robust in the presence of uncertainties and bounded external disturbances. Besides, with the effects on system dynamic performance, both the slope of sliding-mode surface, are automatically tuned by real-time fuzzy inference, respectively.
3. A robust indirect adaptive fuzzy sliding-mode controller for a robotic manipulators is designed. This controller is adopted for a class of multiple-input multiple-output systems with unknown non-linear dynamics. Indeed, it is suggested that an on-line fuzzy adaptation methods can approximate unknown non-linear functions to design the sliding-mode control. An indirect adaptive fuzzy sliding-mode control technique is adopted to attain tracking for a robot manipulator in cases with external disturbances. The proposed methodology combines the attenuation technique, fuzzy logic approximation method, and adaptive control algorithm to generate a robust tracking control design for a robotic manipulator. The adaptive fuzzy approximation technique is adopted as rough tuning while the disturbance attenuation technique is adopted for fine-tuning. With this adaptive fuzzy control algorithm not only assures the stability of the closed-loop, but also maintains the need tracking performance. | en_US |