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Summary: This study developed a new strategy for adaptive fixed‐time output feedback control of multi‐input multi‐output (MIMO) nonlinear systems involving unmeasurable external disturbances and actuator faults. Two actuator faults, loss of effectiveness and lock‐in‐place were simultaneously considered. Furthermore, a composite observer was used in MIMO systems to estimate unmeasurable states and external disturbances simultaneously, and radial basis function neural networks were employed to identify unknown internal nonlinearities. Additionally, the command‐filtered backstepping approach was applied to avoid tedious analytic calculations of the backstepping framework, and a compensation item was constructed to attenuate the filter error. A fault‐tolerant controller was developed to ensure that the overall states of the controlled system were practically fixed‐time bounded while the tracking error was regulated to the equilibrium region having a fixed‐time convergence ratio. Illustrative studies showed the validity and practicability of the proposed theory. [ABSTRACT FROM AUTHOR]

In this article, an event-triggered control problem for partial differential equation systems with pointwise measurements is investigated via relaxed Lyapunov–Krasovskii functionals. First, the Takagi–Sugeno fuzzy model is introduced to describe the nonlinear systems and a fuzzy event-triggered pointwise controller is proposed with pointwise measurements, which can make a tradeoff between the system’s performance and implementation complexity subject to limited transmission bandwidth. Second, some relaxed conditions are established to ensure the closed-loop system’s stability by using the Lyapunov method and inequality techniques. Finally, two simulation examples are provided to demonstrate the effectiveness and practicability of the designed controller. [ABSTRACT FROM AUTHOR]

This article presents a novel reliable fuzzy output feedback controller for a class of semilinear parabolic partial differential equation systems with Markov jump actuator failures. First, the control strategy’s novelties include the following aspects: 1) the considered system is represented by using a fuzzy modeling approach, based on which a new asynchronous fuzzy observer is constructed via utilizing a series of discrete output signals that are induced by samplers and quantizers; 2) a novel Markov jump input model, which is more fit for real applications, is introduced to depict various stochastically occurring actuator faults; and 3) inspired by the above discussion, a reliable mode-dependent fuzzy piecewise control strategy, which only needs limited actuators, is developed. Then, some new conditions, which can ensure that the closed-loop system is finite-time bounded, are established. Furthermore, some slave matrices are introduced to relax the strict constraints caused by asynchronous membership functions. Finally, two simulation examples are provided to support the validity of the proposed method. [ABSTRACT FROM AUTHOR]

This article presents a new sampled-data-based event-triggered pointwise security controller by pointwise measurements for partial differential equation (PDE) systems under stochastic cyberattacks. First, according to the Takagi–Sugeno fuzzy model, the considered nonlinear system is reconstructed and an event-triggered pointwise fuzzy controller is proposed with pointwise measurements. Moreover, networked control systems are introduced to improve the transmission convenience; however, two deception cyberattacks with different characteristics are brought into PDE systems for the first time. In addition, based on novel Lyapunov–Krasovskii functionals, some relaxed conditions to assure system’s exponential stability are established. Finally, the effectiveness and practicability of the designed controller are demonstrated by numerical and application examples. [ABSTRACT FROM AUTHOR]

This article investigates a spatial- $\mathcal {L}^{\infty }$ -norm-based reliable bounded control problem for a class of nonlinear partial differential equation systems in a finite-time interval. The main novelties are reflected in the following aspects: 1) inspired by the sector-nonlinearity approach, the considered nonlinear system is reconstructed by a Takagi–Sugeno fuzzy model, which provides an effective method for control design. Besides, several actuator failures, such as stuck faulty, outage faulty, and bias faulty, are taken into account and modeled by a novel Markov process; 2) partial areas’ states are sampled and transmitted based on a new distributed event-triggered communication strategy, which reduces the cost of the system design and saves the limited network resources to some extent; and 3) on the basis of the first two works, a new piecewise fuzzy controller, which requires fewer actuators compared with the distributed control method, is constructed. Then, some sufficient conditions to guarantee the finite-time boundedness (in the sense of spatial $\mathcal {L}^{\infty }$ norm) and mixed $\mathcal {L}_{2}-\mathcal {L}_{\infty }/\mathcal {H}_{\infty }$ disturbance attenuation performance are established, and a new linear matrix inequality relax technique is introduced to deal with the strict constraint that is caused by the asynchronous phenomenon between plant and controller. Finally, two simulation studies are given to illustrate the effectiveness and advantages of the developed controller. [ABSTRACT FROM AUTHOR]

This article investigates the adaptive output feedback resilient control problem for a class of incommensurate fractional-order (FO) nonlinear systems in the presence of time-varying delays and actuator faults by combining with an adaptive backstepping technique and a modified FO dynamic surface control (FODSC) method. Considering that the information of system states is not fully available, a hybrid fuzzy observer is designed to estimate the unmeasurable system states, where the neuro-fuzzy network system is introduced to handle the unknown nonlinear functions existing in the system. Furthermore, in order to overcome the problem of the explosion of complexity caused by traditional backstepping design procedure, an FO filter is constructed to pass the virtual control signal based on the FODSC scheme. Moreover, according to an indirect Lyapunov stability method, an adaptive hybrid fuzzy output feedback controller is designed to guarantee that all the signals of the closed-loop systems are bounded. Finally, three examples are given to verify the validity and superiority of the presented control scheme. [ABSTRACT FROM AUTHOR]

• This work considers a networked control strategy based on pointwise measurements for fuzzy parabolic PDE systems with a novel AET communication mechanism. Unlike the distributed controllers, the controller designed in this paper only requires finite sensors and actuators. By defining a time-varying threshold that can be adjusted adaptively as needed, the AET control scheme introduced in our work can further reduce the communication frequency without destroying the dynamic performance, which will be demonstrated in the simulation part. • A novel two-sided looped-functional improved form the existing results is constructed in this paper. Unlike the traditional looped-functional or discontinuous LKF, the two-sided looped-functional (TSLF) proposed in this paper not only considers the information in [t p , t), but also takes full advantages from [t, t p + 1). With the help of the proposed TSLF and some advanced inequalities, a less conservative result is obtained in this paper, and the examples show a comparison between our result and some existing results. • To better fit the engineering practice, stochastic actuator failures are considered in our work. In comparison with the Markov jump failures, the proposed semi-Markov jump model allows sojourn-time to be non-exponential distributed, which includes the normal Markov jump failures model as a special case. In the simulation part, a Weibull distributed actuator failures model is introduced, which makes our research more practical. This paper investigates the fault-tolerant control problem for fuzzy semi-linear parabolic PDE systems with stochastic actuator failures. First, a pointwise measurement-based adaptive-event-triggered control scheme is newly proposed for semi-linear PDE systems to reduce the waste of communication resources. Second, by introducing a more practical semi-Markov jump model describing the random occurring actuator failures, the closed-loop system is exactly represented by a T–S fuzzy PDE model with semi-Markovian switching parameters. Moreover, by constructing a suitable LKF including an improved looped-functional and using some advanced inequalities, sufficient stability conditions with less conservatism are established. Finally, two simulation examples including comparative studies are employed to demonstrate the superiority and effectiveness of the developed method. [ABSTRACT FROM AUTHOR]

This paper investigates the fixed-time prescribed performance trajectory tracking control for the unmanned surface vehicle with unknown dynamics and disturbances. At first, an improved prescribed performance function was introduced to transformation of coordinate for achieving a user-defined performance including the transient and steady-state performance of the USV. Then, an adaptive fixed-time trajectory tracking controller is designed by integrating the fixed-time stability and the event-triggered control (ETC) mechanism. Stability results prove that the proposed controller not only guaranteed that all the signals in the closed-loop system are the semi-global uniform ultimate bounded (SGUUB), but also ensured the tracking errors can converge to a preassigned area in a fixed-time. Moreover, by proposing a co-design of the ETC and 1-bit signal encoding–decoding mechanisms between controller and actuator, the trade-off between tracking performance and communication cost is achieved. Finally, the effectiveness of the developed control approach is verified through simulation results. [ABSTRACT FROM AUTHOR]