Abstract
This paper presents a robust adaptive fuzzy control scheme for a class of uncertain nonlinear systems containing an unknown dead-zone. Dead-zone characteristics are quite commonly encountered in actuators, such as hydraulic and pneumatic valves, electric servomotors, and electronic circuits, etc. Therefore, by using a description of a dead-zone and by exploring the properties of this dead-zone model intuitively and mathematically, a robust adaptive fuzzy control method is presented without constructing the dead-zone inverse. The unknown nonlinear functions of the controlled system are approximated by the fuzzy logic system according to some adaptive laws. By means of Lyapunov stability theorem, the proposed robust adaptive fuzzy control scheme can guarantee the robust stability of the whole closed-loop system with an unknown dead-zone in the actuator and obtain good tracking performance as well. Finally, an example and simulation results are illustrated to demonstrate the validity of the proposed method.
Highlights
Many practical control systems have the structure of a dynamical system preceded by some nonsmooth nonlinearities in the actuator, such as dead-zone, backlash, saturation, etc[1,2,3]
In the controller design of nonlinear systems, the feedback linearization methods have been widely studied and developed, and these methods can be utilized to transform a nonlinear dynamic system into a linear system by means of state feedback approach[7,8]. These methods can only be applied to nonlinear systems whose dynamics must be exactly known
D v (t ) : R → R is the model intuitively and mathematically, a robust adaptive fuzzy control method is presented without constructing the dead-zone inverse
Summary
Many practical control systems have the structure of a dynamical system preceded by some nonsmooth nonlinearities in the actuator, such as dead-zone, backlash, saturation, etc[1,2,3]. Due to the nonlinearity of dead zone and uncertainties, the indirect adaptive fuzzy control scheme is adopted to tackle the control problem of these nonlinear systems. In order to eliminate the effects arising from the dead-zone input nonlinearity, a robust adaptive fuzzy control scheme is proposed to overcome the stabilization problem of a class of uncertain nonlinear systems preceded measurement, v ∈ R and y ∈ R are the input and output of the system, respectively, f and g are unknown nonlinear functions and ∆f is the unknown uncertainty. Based on the Lyapunov stability theorem and the theory of variable structure control, the proposed robust adaptive fuzzy control scheme can guarantee the robust stability of the whole closed-loop system with an unknown dead-zone in the actuator and obtain good tracking performance as well.
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