The predefined-time fuzzy adaptive output feedback decentralised control problem is considered for fractional-order nonlinear large-scale (FONLS) systems. Firstly, by using fuzzy logic systems (FLSs) to model unknown nonlinear dynamics, a fuzzy decentralised state observer is designed to solve the immeasurable state problem. Secondly, the predefined-time stability criterion of fractional-order nonlinear systems is proposed, and then, based on the established predefined-time stability criterion of the fractional-order nonlinear systems, a predefined-time fuzzy adaptive output feedback decentralised control method is developed by combining the backstepping design technique with the cyclic-small-gain approach, and the semi-global practically predefined-time stable (SGPPTS) of the control system is proved. Finally, the numerical simulation is given and shows the effectiveness of the presented predefined-time control method.

The predefined-time fuzzy adaptive output feedback decentralized fault-tolerant control (FTC) problem is considered for fractional-order nonlinear large-scale systems with intermittent actuator faults. First, the predefined-time stability criterion of fractional-order nonlinear systems is proposed, and then by using fuzzy logic systems to model unknown nonlinear dynamics, a fuzzy decentralized state observer is designed to solve the immeasurable state problem. Second, based on the established predefined-time stability criterion of the fractional-order systems, a predefined-time fuzzy adaptive output feedback decentralized FTC method is developed and the semiglobal practically predefined-time stable of the controlled system is proved. Finally, we apply the developed predefined-time FTC method to fractional-order smooth-air-gap permanent magnet synchronous motor system, the simulation results verify the effectiveness of the proposed predefined-time FTC methodology.

The fuzzy adaptive exact-optimal consensus output-feedback control problem is investigated for uncertain nonlinear high-order multiagent systems (MASs) with unmeasurable states and unknown nonlinear dynamics. Fuzzy logic systems are utilized to model unknown agents; a fuzzy state observer with asymptotical property is established. Since the optimal point is unknown, optimal signal generator is formulated to obtain the optimal point. Based on the designed fuzzy state observer and optimal signal generator, a fuzzy adaptive exact-optimal consensus output-feedback control scheme is proposed by using backstepping control technology. It is proved that the presented control method can guarantee the controlled nonlinear MASs are asymptotically stable and the outputs of all agents asymptotically converge to the optimal point. Finally, we apply the proposed fuzzy adaptive exact-optimal consensus output-feedback control approach to multiple unmanned surface vehicles, the simulation results and comparison results verify its effectiveness.

The predefined-time fuzzy adaptive output feedback control problem is considered for non-strict feedback stochastic nonlinear systems with state constraints. Since the controlled plant contains unknown nonlinear dynamics and unmeasured states, the unknown nonlinear dynamics are handled by using fuzzy approximation technique, and a fuzzy state observer is established to estimate unmeasured states. Then, under the frameworks of a predefined-time stability theory and backstepping control design technique, a new fuzzy adaptive output feedback control method is proposed. It is proved that the controlled system is semi-global practically predefined-time stable in probability by constructing suitable barrier Lyapunov functions. Finally, the spring–mass–damper system is given to confirm the effectiveness of the presented control method.

The event-triggered predefined-time output feedback control problem is considered for fractional-order nonlinear systems (FONSs) with input saturation. The controlled plant contains unknown nonlinear dynamics and unmeasured states. The unknown nonlinear dynamics are handled by using fuzzy approximation technique; a fuzzy state observer is established to estimate unmeasured states and an event-triggered mechanism is given to improve the efficiency of communication resource utilization. The predefined-time stable criterion of FONSs is first developed. Then, an event-triggered predefined-time output feedback control is proposed by using the dynamic surface control technique. Based on the proposed predefined-time stable criterion and Lyapunov function, it is proved that the controlled system is semiglobal practically predefined-time stable and all the signals are bounded in predefined-time interval. Finally, the simulation results are given to confirm the effectiveness of the presented predefined-time control method.