Adaptive Fault-Tolerant Tracking Control For A Class Of Nonlinear Systems

In actual engineering,many controlled systems can be modeled as non-strict feedback nonlinear systems,such as mass-spring-damping systems,electrical systems,mechanical systems,and helicopter systems.Therefore,the research on control methods of non-strict feedback nonlinear systems not only has considerable theoretical value but also has practical application needs.For a controlled system,its nonlinear input characteristics such as dead zone,quantization,and saturation often occur in the industrial production process,making the system unstable and seriously causing abnormal operation of the system.Therefore,the non-strict feedback nonlinear system with nonlinear input also needs more in-depth and extensive research.On the other hand,during the operation of the system,the actuators and sensors may suffer sudden faults,which may cause the input and output of the controlled system to fluctuate,which may lead to serious accidents.For the system to have strong robustness and production can be carried out safely,an effective fault-tolerant control method needs to be designed,which not only enables the controlled system to achieve the desired performance but also needs to ensure that the system has a certain tolerance for possible faults.Up to now,although many valuable research results have been proposed for nonlinear systems with non-strict feedback structures,there are still many control problems that need to be solved.Based on the development status at domestic and foreign,combined with adaptive control methods and fuzzy fault-tolerant control methods,this paper conducts the following research on non-strict feedback nonlinear systems:Firstly,the problem of adaptive finite-time tracking control for non-strict feedback nonlinear systems with unmeasured states and actuator faults is studied.To reach fast transient performance,the stability of finite-time is achieved by exploiting the backstepping method.By benefiting the approximation property of fuzzy logic systems,a fuzzy observer is introduced to tackle the difficulties of the unmeasurable states involving non-strict feedback nonlinear systems.A damping term in the intermediate control law is utilized to compensate for the possibly unlimited number of faults.The investigated strategy ensures that all the responses of the systems are semi-global practical finite-time stable.Meanwhile,the tracking error converges to a small neighborhood of the origin within finite-time.Secondly,the problem of adaptive finite-time fault-tolerant fuzzy tracking control for non-strict feedback nonlinear systems with input quantization and full-state constraints is studied.By utilizing the fuzzy logic systems and less adjustable parameters method,the unknown nonlinear functions are addressed in each step process.In addition,a dynamic surface control technique combined with fuzzy control is introduced to tackle the variable separation problem.The problem for the effect of quantization and unlimited number of actuator faults is tackled by a damping term with smooth function in the intermediate control law.Finite-time stability is achieved by combining barrier Lyapunov functions and the backstepping method.The finite-time controller is designed such that all the responses of the systems are semi-global practical finite-time stable and ensured to remain in the predefined compact sets while tracking error converges to a small neighborhood of the origin in finite time.Finally,simulation examples are utilized to verify the validity of the investigated strategy.