This article addresses the decentralized tracking control problem for a class of strong interconnected nonlinear systems with actuator faults. The considered interconnections are allowed to be ...dominated by some bounding functions, which are linear growth in the status of all subsystems. First, an adaptive high-gain technique is introduced to deal with the unknown strong interconnections. Then, a group of fault-tolerant controllers is designed to adaptively compensate for the effects of the actuator failures, in which the controller gain parameters are adjusted online only according to local available information. Furthermore, with the aid of an algebraic graph theory result, it is proved that all signals of the closed-loop system are globally uniformly bounded, and the tracking errors of all subsystems converge to zero asymptotically. The effectiveness of the proposed control algorithm is demonstrated by a numerical simulation.
This article studies the robust trajectory tracking control problem of a quadrotor unmanned aerial vehicle (UAV). In order to guarantee the desired trajectory tracking performance in the presence of ...external disturbances and model uncertainties, the design process of the quadrotor UAV controller is divided into two steps. First, by decomposing the attitude dynamic system into two serial-connected subsystems, a cascade active disturbance rejection control scheme is applied to the attitude subsystem. Second, by introducing an additional high-gain design parameter, a novel backstepping sliding-mode control scheme for position subsystem is constructed. Moreover, the Lyapunov stability analysis is provided to show that the trajectory tracking error can converge to an arbitrarily small residual set. Numerical results illustrate the effectiveness of the designed control method and its robustness to the external disturbances and model uncertainties. Finally, the proposed method is implemented on a quadrotor UAV to demonstrate its feasibility in practical application.
•An event-triggering mechanism with dynamic threshold parameters is developed to reduce the transmission frequency of sampled data. Compared with the fixed threshold event-triggering mechanism, the ...proposed scheme can provide a better tradeoff between the data transmission frequency and the system control performance.•The proposed quadrotor trajectory tracking control scheme can suppress the influences of unknown disturbances and model uncertainties. In addition, the control deviation caused by the event-triggering mechanism is treated as an additional disturbance whose effects can be successfully suppressed by the proposed control scheme.•Unlike the previous ADRC methods in 10-19, an adaptive parameter adjustment mechanism is introduced in the controller design.
This paper considers the problem of trajectory tracking control for a quadrotor unmanned aerial vehicle. In order to suppress the influences of unknown disturbances and model uncertainties, an event-triggered cascade active disturbance rejection trajectory tracking control scheme is developed for the quadrotor position system. The proposed control scheme can reduce the transmission frequency of sampled data, and suppress the influence of additional disturbance caused by the event-triggering mechanism. With the proposed control scheme, the trajectory tracking control of the quadrotor system can be achieved and Zeno behavior can be excluded. Moreover, a parameter adaptive adjustment mechanism is introduced to ensure the trajectory tracking performance of the system. Finally, the proposed control scheme is applied to a quadrotor system to verify its effectiveness, and its ability to suppress the influences of unknown disturbances is also verified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this article, the problem of decentralized adaptive tracking control for a class of interconnected nonlinear systems is investigated, in which the interconnection term in each subsystem is related ...to the states of all subsystems. By utilizing the backstepping controller design method and dynamic high‐gain technique, two kinds of decentralized adaptive control schemes are developed. Some dynamic parameters are introduced into the controllers to counteract the effects of interactions among subsystems. Moreover, with the aid of graph theory, it is shown that all signals of the closed‐loop system are bounded. The novelty of the proposed method lies in that the tracking accuracy of each subsystem can be preset without adjusting the controller parameters. Finally, two illustrative examples are presented to demonstrate the efficiency of the proposed schemes.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this article, the problem of decentralized event-triggered fault-tolerant control (FTC) for a class of interconnected nonlinear systems with unknown strong coupling and actuator failures is ...considered. In order to enable each subsystem output to track the desired trajectory, a new decentralized adaptive control scheme is given. First, an event-triggering mechanism is introduced to reduce the signal transmission frequency between the controller and the actuator. Second, a fuzzy high-gain observer is designed for each subsystem to estimate unknown nonlinear functions and actuator efficiency factor. Third, a decentralized FTC strategy is proposed to compensate for the effects of actuator failures and achieve the desirable system tracking performance. With the aid of graph theory, it is shown that all the closed-loop signals are semiglobally uniformly ultimately bounded, and the tracking error of each subsystem can converge to an arbitrarily small residual set by adjusting a design parameter. The effectiveness of the proposed scheme is demonstrated by a practical interconnected system.
This paper studies the fault-tolerant control (FTC) problem for unknown affine nonlinear systems with actuators faults. The considered types of faults are stuck (lock-in-place), loss-in-effectiveness ...(LIE), and bias, under which a part of the actuators is disabled. The objective is to find the remaining (not fully LIE) actuators, and manipulate them to obtain the best achievable performance in real time. First, considering that the best achievable performance is determined by the remaining actuators, a set of basic policies is predesigned with multiple levels of performances for different groups of activated actuators. Second, an identifier is designed based on history data to find the remaining actuators and, thus, the suitable predesigned basic policy. Third, to further accommodate the partial LIEs and biases, a compensator works together with the selected basic policy, to build the predesigned performance. In addressing the FTC problem, several techniques are developed: adjustable mechanisms are novelly integrated to deal with the state-dependent nonlinearities in neural network (NN) approximation, disturbances, and mismatch errors; history data are newly applied to estimate the faulty parameters; and a compensator is specially designed to deal with LIEs and biases in different input channels. Also in theory, the convergences of algorithms and the stability of closed-loop systems are proved, by formally giving the invariant sets of the initial state and the NN weights. Unlike the existing FTC methods dealing with LIE and bias based on model information to optimize the tracking error, this result can handle stuck faults without knowing system dynamics and satisfy different levels of performances described by Hamilton-Jacobi-Bellman equations. Finally, a simulation example of quadrotor unmanned aerial vehicle is given to verify the effectiveness of the proposed FTC scheme.
In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in ...graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.
Summary In this paper, a distributed adaptive output feedback consensus tracking control scheme is developed for heterogeneous nonlinear multi‐agent systems (MASs) with actuator failures. Unlike most ...existing results, the parameters in the considered MAS are unknown, and the system's nonlinear functions are not required to satisfy the Lipschitz condition. A kind of K‐filters with an additional design parameter is designed to suppress the effects of unknown actuator failures. In addition, an event‐triggering mechanism with a switching threshold method is designed to reduce the communication burden. With the proposed control scheme, the tracking error of each subsystem converges exponentially to an adjustable bound. Finally, a nonlinear MAS consisting of multiple single‐link robot manipulators is given to verify its effectiveness.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The practical leader-follower issue is addressed for multi-agent systems via adaptive event-triggered observer-based distributed control. Besides the network transmission delay is considered when the ...data is transferred from sensor to controller in a shared network communication. Furthermore, in order to avoid unnecessary information transmissions among agents and achieve better resource utilization, we introduce the developed event-triggered condition with dynamically adjustable threshold parameter. And as a expansion, based on the proposed controller and event-triggered scheme, we study the chaotic system. Finally, simulations which contain a linear system and a Chua's circuit system are performed to demonstrate the availability of the proposed theoretical results.
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