International Journal of Robust and Nonlinear Control最新文献

Measuring element is always accompanied by uncertainty disturbances and multiple faults during the long time operation of industrial system in complex environment such as blade and pitch system of floating wind turbines. Timely detection of the fault and fault-tolerant control (FTC) perform a significant part in ensuring the stable operation of the system and saving maintenance fees. Sliding mode control is extensively applied to FTC because of its good robustness. Therefore, a sliding mode controller is constructed to guarantee the stability of the industrial plant which suffers multiple faults and uncertain disturbances. At the same time, most existing literature does not take into account several faults and uncertain disturbances. Firstly, employing generalized sliding mode method, we devise a sliding mode observer for evaluating state vector, actuator fault and sensor fault of the system. Secondly, according to the state estimation, we construct a sliding mode controller and prove its validity by Lyapunov's theorem. Our controller achieves satisfactory performance, and it is easier to be implemented in practical engineering than other controllers. Finally, we establish a SIMULINK model of blade and pitch system and make simulation experiments. Simulation outcomes validate the availability and practicability of our controller, which also provides a general scheme for fault estimation and FTC of other industrial plants.

This article studies the almost output regulation (OR) issue for switched Takagi–Sugeno fuzzy systems (T-SFS) with the OR and the disturbance suppression properties simultaneously considered. A switched fuzzy dynamic output feedback controller (OFC) is firstly constructed for switched T-SFS with modeled and unmodeled disturbances. By considering the average dwell-time (ADT) constraint and introducing different coordinate transformations of subsystems, a solvability condition on the almost OR issue of switched T-SFS is then established with the multiple Lyapunov functions method. Furthermore, the controller gains are designed to drive the switched T-SFS to satisfy the OR and $��{�L�}_{�2�}�$-gain properties. Finally, a simulation case is provided to validate the feasibility of the offered control technique.

This article addresses the dynamic event-triggered output-feedback control problem for a class of large-scale feedforward nonlinear discrete-time impulsive systems. The investigated systems are allowed to contain impulse effects, discrete-time dynamics, and large-scale coupled characteristics, which brings substantial difficulties to the event-triggered control. It is worth noting that this scenario has not been considered in the existing works. For that, a novel dynamic event-triggered output-feedback control strategy is proposed in this article. Specifically, we apply a gain scaling approach to cope with system uncertainties and employ an average impulsive interval technique to suppress the undesirable impulse effects. Then, a novel low-gain discrete-time impulsive observer is constructed to estimate the unmeasurable system states. After that, a dynamic event-triggered output-feedback controller, which has a concise linear-like form, is delicately designed to ensure that all the signals of the resulting closed-loop system are globally bounded, and the system states converge to the origin. Moreover, by enhancing the gain scaling mechanism, we further develop an improved output-feedback control strategy to counteract stronger nonlinearities. Finally, the effectiveness of the proposed control strategy is demonstrated by a practical simulation example.

This paper investigates the resilient event-triggered control (ETC) for nonlinear multi-agent systems in the presence of communication delays and denial-of-service (DoS) attacks. The communication delays and asynchronous DoS attack are considered for each communication link. Based on sampling-receiving events and DoS attack events, flow and jump sets are formulated to describe the system's transmission time status. An independent event-triggering mechanism (ETM) is designed for each communication link. Furthermore, a resilient control scheme is constructed in which sufficient conditions for achieving system input-output stability are provided, including the constraints of frequency and DoS attack duration, the conditions of Lyapunov functions, and the maximally allowable transmission interval. Finally, the attitude cooperative control problem of multiple unmanned aerial vehicles (multi-UAVs) is adopted as a simulation example. The simulation results show the effectiveness of the proposed scheme.

In this paper, a Lyapunov-like sufficient condition for the fast fixed-time stability of autonomous systems is proposed. The proposed fast fixed-time stability theorem ensures a smaller upper bound on the convergence time than the existing fixed-time stability theorems. The fixed-time sliding mode controls require switching from the fixed-time sliding surface to the general sliding surface in the vicinity of the origin to avoid non-differentiability at that point. It is demonstrated that the switching method converges the system states either to a residual set around the equilibrium point or directly to the equilibrium point, depending on the tuning parameter settings. To address this issue, a new nonsingular sliding surface is proposed based on the fast fixed-time stability theorem. This approach ensures singularity-free convergence of the system states to the equilibrium point without additional switching logic for the sliding surfaces or any constraints on tuning parameters. Furthermore, a novel continuous adaptive fast fixed-time sliding mode control (AFFTSMC) law is proposed for attitude control of a satellite in the presence of the satellite inertia uncertainty and unknown upper-bounded external disturbance torques. The proposed AFFTSMC law ensures chattering-free and singularity-free satellite attitude control. Simulation results are presented for both rest-to-rest and tracking attitude maneuvers of a satellite, demonstrating the superiority of the proposed controller.

The paper proposes a novel model-free adaptive robust controller for load frequency control in multi-area interconnected power systems. The controller combines model-free control based on a nonlinear disturbance observer (NDOB) and adaptive integral sliding mode control. The main aim of the controller is to maintain the power system frequency close to the nominal value and achieve a balanced power exchange between tie-lines, considering the system's nonlinearities and disturbances. The proposed controller comprises four components. First, model-free intelligent PID control is implemented to overcome the complexity of the current controller, introduce the required dynamics, and reduce higher-order output derivatives. Second, a nonlinear disturbance observer is utilized to estimate the system dynamics considering uncertainties and load fluctuations. Third, fast convergence is achieved by employing an integral sliding surface. Finally, an adaptation gain dynamic is used to achieve high accuracy. The advantage of the proposed model-free adaptive robust controller lies in its simple structure and ease of regulation. The closed-loop system's stability and finite-time convergence are examined using Lyapunov stability theory. A comparison with recently published papers is conducted to validate the proposed controller's effectiveness. Additionally, robustness testing of the proposed method is performed in different scenarios.

The current contribution introduces a nonsingular fixed-time sliding mode control (SMC) scheme for position and velocity tracking of robot manipulators. The approach avoids singularities by introducing a new sliding surface with the special attribute that the exponent employed to achieve fixed time convergence depends on the tracking error and is smaller than one except when the error is exactly zero, whereas the exponent becomes one at zero, which makes the derivative at zero to be well defined. A new theoretical result has been introduced in the form of a lemma to prove this innovative property. Furthermore, model uncertainties are handled by means of a time-varying gain given by a polynomial of the powers of the norms of the tracking and velocity errors. The fixed-time convergence is proven employing Lyapunov theory, and the result holds globally. Simulation outcomes confirm the developed theory, and the advantages of the proposed scheme are shown qualitatively by comparing its performance with well-known equivalent control schemes.

In this article, the dynamic event-triggered output feedback control problem for a class of uncertain nonlinear systems is studied. Since system states are not available for controller design, a state observer is designed to estimate them. On the basis of the estimated states, a dynamic event-triggered control scheme is proposed. Compared with existing event-triggered schemes, a dynamic auxiliary variable is added in the event conditions. By properly designing the dynamics of the auxiliary variable, it is proved that the tracking/stabilization error is able to converge to zero without the presence of Zeno behavior. The effectiveness of the control scheme is verified by simulation results.

This work is absorbed in the neighboring mode-dependent event-triggered control scheme for Markov jump systems with unknown interconnections. To save communication resources and reduce cost, a dynamic event-triggered scheme relies on neighboring modes information is proposed. Then, the state feedback controllers are designed based on neighboring mode–dependent dynamic event-triggered approach to assure the stability of the system. Distinguished from existing results, the proposed method does not need to access the operation modes of all sub-systems. The cyclic-small-gain criterion is used to tackle the unknown interconnections, thereby a novel stability criteria are obtained for the closed-loop systems with $��H_{\infty }�$ performance. Finally, two simulation results are given to reveal the validity of the obtained results.