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This paper investigates the fault-tolerant prescribed performance control problem for a class of multiple-input single-output unknown nonlinear systems subject to process faults and actuator failures. In contrast to the related works, we consider a general class of nonlinear systems with both multiplicative nonlinearities and additive nonlinearities corrupted by the process faults; only the boundedness of the process faults and the continuity of the nonlinear functions are required, without the explicit or fixed structures of the fault functions. To conquer this problem, a less-demanding and low-complexity fault-tolerant prescribed performance control approach is proposed. The controller is independent of the specific information of faults or the system model and does not invoke fault diagnosis or neural/fuzzy approximation to acquire such knowledge. It achieves the reference tracking with the predefined rate and accuracy. A comparative simulation on a single-link robot is conducted to illustrate the effectiveness and superiority of the proposed approach. • Both process faults and actuator failures are considered. • The virtual control coefficients are time-varying nonlinear functions. • We consider a general class of systems with multiplicative and additive nonlinearities. • Both multiplicative and additive nonlinearities are impacted by process faults. • The reference tracking with predefined rate and accuracy is achieved. [ABSTRACT FROM AUTHOR]

In this paper, an interval type-2 fuzzy model is presented to describe the nonlinear singular fractional order systems (SFOSs) with 0 < α < 2. The problem of actuator and sensor fault estimation is addressed by designing a non-fragile sliding mode observer (SMO). Firstly, a new criterion is provided to analyse the admissibility of SFOSs, which does not need to divide the fractional order interval (0 , 2) into interval (0 , 1) and interval [ 1 , 2) to study them separately. Then, by expanding the dimension of the SFOS, the non-fragile SMO and the sliding surface are constructed and the accurate estimations of faults and the SFOS state simultaneously are achieved. A new reaching law is designed, which can divide the process of the system moving to the sliding surface into three stages. Further the control law is constructed to guarantee the observation error reaches the sliding surface in finite time. Finally, three examples show the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article is concerned with the fault-tolerant tracking control problem for pneumatic continuum manipulator (PCM) systems with actuator faults. Conventional control strategies applied to PCMs have difficulty addressing the tracking control issue for systems subject to actuator faults. In this article, we provide a robust fault-tolerant control strategy for solving this issue. We first present an error transformation approach that possesses potential robustness against model uncertainties and unknown actuator faults. To relax certain restrictions in the error transformation approach, we then adopt a tuning function to adjust the error variables. By doing so, global stability of the closed-loop system is ensured. Finally, the effectiveness of this control strategy is validated through experiments on a PCM. [ABSTRACT FROM AUTHOR]

This article is concerned with the tracking control problem for a sort of networked system with unknown nonlinear functions, unmatched disturbances, and event-triggered input. A novel prescribed performance control strategy together with an actuator update protocol is developed to form a solution. Different from the existing results, only a binary signal (either 0 or 1) needs to be sent to the actuator. In this way, the number and the bit of data transmission are both curtailed, leading to the economy of the communication cost. On the other hand, output tracking with guaranteed transient and steady-state performance is achieved regardless of unknown nonlinearities, disturbances, and measurement errors. Finally, simulation results are given to illustrate the established theoretical findings. [ABSTRACT FROM AUTHOR]

This article investigates the trajectory tracking control problem for a family of underactuated autonomous surface vessels under the condition of model uncertainties, actuator faults, and environmental disturbances. The emphasis or difficulty is how to ensure the trajectory tracking with specified accuracy in the fixed-time settings. A new-type fault-tolerant tracking control strategy is developed based on the marriage of a novel bounding function and a method of handling constraints. Compared with the existing results it can be noted that: first, the position error enters into a preassigned residual set in a priori designate time and remains there; second, no adaptive mechanisms, disturbance observers, or command filters are involved, leading to a simplicity control attribute. Results from a comparative simulation on the CyberShip II further illustrate the above theoretical findings. [ABSTRACT FROM AUTHOR]

Summary: This article studies the fault‐tolerant control problem for unknown nonlinear strict‐feedback systems subject to actuator failures yet with dynamic redundancies. The prescribed performance control methodology is newly combined with a modification‐based supervisory switching strategy to solve the problem. To implement failure detection, the performance function is properly modified to synthesize a monitoring function to supervise the behavior of an error variable. Once a failure is detected, the current actuator is shut down and the backup actuator is switched in to execute the reconfigured control command. Compared with the existing results, (1) the postfailure and postswitching tracking performance is improved, other than uniform ultimate boundedness and (2) the dependence on extra robust control schemes (eg, adaptive or approximating structures) to deal with model uncertainties or the need to compute analytic derivatives of virtual control signals in the backstepping design is eliminated. [ABSTRACT FROM AUTHOR]

This paper explores the fault-tolerant control problem for a family of nonlinear systems in Brunovsky form. The presence of process and actuator faults leads to an unknown and time-varying system structure, such that neural networks or fuzzy logic systems cannot be utilized for approximation directly. To solve this problem, a new-type control strategy is proposed. A zero-overshoot error constraint technique is first introduced to keep the sign of a certain variable invariant, while ensuring the premise on a compact set. Then, a fuzzy logic system is adopted to approximate the bound of the unknown and time-varying nonlinear dynamics. Further a group of adaptive mechanisms are employed to compensate for the approximation error as well as actuator faults. It is proved that by applying the presented method, both the tracking performance and the boundedness of closed-loop signals can be guaranteed. Finally, simulation results are given to illustrate the established theoretical findings intuitively. [ABSTRACT FROM AUTHOR]

Summary: This paper concentrates on the leader‐follower formation control problem for marine surface vessels with unknown nonlinear dynamics and actuator faults. The unknown inertia matrix and multiplicative fault render the existing methods infeasible. To solve this problem, a low‐complexity prescribed performance controller is first proposed without the help of auxiliary neural/fuzzy systems or adaptive mechanisms. A modification technique is further adopted to relax the initial condition, such that global closed‐loop stability is guaranteed. Finally, simulation results illustrate the above theoretical results. [ABSTRACT FROM AUTHOR]

This paper studies the fault-tolerant tracking control problem for a class of strict-feedback nonlinear systems subjected to actuator faults and external disturbances. The prior knowledge for actuator fault, nonlinearity, and external disturbance is totally unknown, besides the control directions. Based on a backstepping approach, an adaptive fault-tolerant control scheme is developed, without utilizing neural networks. In the control design, a group of new feedback mechanisms are proposed to compensate for the unknown system dynamics and actuator faults. Furthermore, to relax a requirement of the initial system states, a modification technique is designed to adjust the reference signal and virtual control laws for a short time. It is shown that the global closed-loop stability is guaranteed and the tracking performance is achieved. The above result is illustrated via simulations on a one-link manipulator and a ship autopilot. [ABSTRACT FROM PUBLISHER]

This paper explores the output-constrained tracking control problem for unknown Euler–Lagrange systems subject to actuator faults, in the case where the reference trajectory is unknown in advance. The presence of actuator faults may lead to the loss of strong controllability of the system assumed in the existing literature on robust control of multi-input multi-output nonlinear systems. The lack of a priori knowledge on the reference trajectory renders the current constraint-handling techniques to achieve prescribed tracking accuracy infeasible. To conquer the above obstacles, a novel fault compensation scheme is designed in this paper, and a new-type error boundary is introduced to the control design. It is proved that the proposed approach guarantees output tracking with prescribed accuracy and constraint satisfactions simultaneously, even if actuator faults occur. A comparative simulation on a robot manipulator is conducted to further illustrate the established theoretical findings. [ABSTRACT FROM AUTHOR]