Fault Estimation And Prescribed Performance Control For A Class Of Nonlinear Systems

With the increasing complexity of modern control systems,the demand for system safety and reliability is also increasing.As the basis of fault-tolerant control,fault diagnosis technology has been widely applied to the actual system.Fault estimation has also become to a hot spot,as it have the capabilities of both fault detection and isolation.In addition,prescribed performance control plays a key role in some systems witch need to ensure a high performance.In practice,many control scheme have nonlinear characteristic,it is necessary to get a further study about the fault tolerant tracking control of nonlinear systems.The fault estimation and prescribed performance control for a class of nonlinear systems was solved in this thesis.The main tasks are as follows:Consider a fault estimation and prescribed performance control problem for a class of strict-feedback nonlinear systems with matched faults.Firstly,a nonlinear state observer is designed for nonlinear systems by using the differential mean value theorem,also,a fault estimator is designed based on the method of intermediate estimator.Secondly,a state feedback controller is developed by combining appropriate error transform function and smooth directional function.Based on the idea of proof by contradiction,it is proved that the state error converges to a preset compact set and all the closed-loop signals are bounded.Finally,an actual simulation example is used to verify the effectiveness of the proposed control strategy.Based on the second chapter,consider a fault estimation and prescribed performance control problem for a class of strict-feedback nonlinear systems with unmatched faults.Firstly,a fault estimator and state observer are designed based on the scheme mentioned in above.Secondly,a state feedback controller is developed by using the prescribed performance control.The stability analysis shows that the proposed control strategy guarantees a good tracking performance,and all the closed-loop signals are bounded.Finally,a simulation example is given to verify the effectiveness of the proposed control strategy.