This article presents novel robust adaptive fault tolerant control strategies for the class of nonlinear Lipschitz systems in the presence of bounded matched or unmatched disturbances and actuator faults (failure, loss of effectiveness, and stuck). Two constructive algorithms, based on linear matrix inequalities with creatively using Lyapunov stability theory, are developed for online tuning of adaptive and fixed state feedback gains to stabilize the closed-loop control system asymptotically, to compensate actuator faults, and to attenuate disturbance effects. The resultant control schemes have simpler and constructive structures as compared with most existing methods. The merits of the proposed schemes have been verified by the simulation on an unstable nonlinear process subjected to actuator faults.
In this paper, two novel adaptive control strategies are presented based on the linear matrix inequality for nonlinear Lipschitz systems. The proposed approaches are developed by creatively using Krasovskii stability theory to compensate parametric uncertainty, unknown time-varying internal delay, and bounded matched or mismatched disturbance effects in closed-loop system of nonlinear systems. The online adaptive tuning controllers are designed such that reference input tracking and asymptotic stability of the closed-loop system are guaranteed. A novel structural algorithm is developed based on linear matrix inequality (LMI) and boundaries of the system delay or uncertainty. The capabilities of the proposed tracking and regulation methods are verified by simulation of three physical uncertain nonlinear system with real practical parameters subject to internal or state time delay and disturbance.
In this article, a novel sliding mode control (SMC) strategy for nonlinear Lipschitz systems with multiple and dissimilar time delays in the states and inputs is proposed. Using linear matrix inequality, a modified integral sliding surface scientifically based on which the innovative SMC approach is developed. Lyapunov–Krasovskii's theory is employed to guarantee asymptotic stability of the closed‐loop system, such that states starting from any arbitrary initial conditions reach the sliding surface in a finite time and stay on it for all subsequent time. It is also proved that the practical effects of the actuator's faults are simultaneously attenuated. An online adaptive tuning law is used to estimate and isolate actuators' possible faults reliably. From the implementation point of view, the controller structure is more straightforward than the most existing recent fault‐tolerant control methods. Simulation results performed on practical nonlinear systems (quadruple tank and industrial continuous stirred tank reactor) verified the outstanding merits of the proposed approach. The operational capabilities of the proposed scheme in the presence of actuators' faults and multiple delays in the states and inputs were also demonstrated.
This paper presents 2-novel linear matrix inequality (LMI)-based adaptive output feedback fault-tolerant control strategies for the class of nonlinear Lipschitz systems in the presence of bounded matched or mismatched disturbances and simultaneous occurrence of actuator faults, including failure, loss of effectiveness, and stuck. The constructive algorithms based on LMI with creatively using Lyapunov stability theory and without the need for an explicit information about mode of actuator faults or fault detection and isolation mechanism are developed for online tuning of adaptive and fixed output-feedback gains to stabilize the closed-loop control system asymptotically. The proposed controllers guarantee to compensate actuator faults effects and to attenuate disturbance effects. The resulting control methods have simpler structure, as compared with most existing recent methods and more suitable for practical systems. The merits of the proposed fault-tolerant control scheme have been verified by the simulation on nonlinear Boeing 747 lateral motion dynamic model subjected to actuator faults. KEYWORDS actuator fault, fault-tolerant control (FTC), linear matrix inequality (LMI), Lipschitz nonlinear systems, output feedback, robust adaptive control
INTRODUCTIONA permanent increase in the complexity, efficiency, and reliability of nonlinear systems from both the theoretical and practical aspects necessitates a continuous development in fault-tolerant control (FTC) theory and practice. In this way, the considerable interest in FTC system design has received great attention over the past decades. Fault-tolerant control is a control technique that provides the ability to maintain overall linear and nonlinear system stability besides the acceptable performance in the event of component (including sensors, actuators, and even the plant itself) faults. The faults may occur in each of the system components at an uncertain time, and the size of the faults is also unknown. 1 This means that for the design of the controller for each system, the probability of fault occurrences in system components should be considered, and then, the controller design must provide a way to compensate them.The latest results and published papers confirm that there are still some challenging areas within the FTC for nonlinear systems on methodologies and computational complexities. For instance, most FTC methods only considered some of the component faults or the design methods are dependent on the states of systems, 2-5 and then, implementation of these methods for a large domain of real applications will be hardly possible.
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