Research On Fault Tolerant Control Strategy Of Landing With Aircraft Faults

Since the birth of carrier-based aircraft,the technology of landing control has been an important research topic.Due to the complexity of the landing environment,the aircraft system has the characteristics of nonlinear coupling,multi-interference,uncertainty and so on.In order to ensure the aircraft landing in a small security area,adjusting the performance of aircraft in limited time and space is put forward in a very high demand of the aircraft control system.Normally,the automatic carrier landing system(ACLS)can ensure the aircraft landing safely.However,the control performance of aircraft is affected by the unpredictable impacts,even some serious accidents when engine faults and stabilizer faults happen.Therefore it is long-term significance for improving the reliability of aircraft control system with actuator faults.In this paper,the fault-tolerant controllers based on the advanced nonlinear control theory are designed to solve the landing problem with aircraft faults.Firstly,analysis on force and moment of aircraft during flight,the six degrees of freedom nonlinear model of aircraft and the landing environment model are established.It possesses representative meaning that can reflect the movement essence and flight characteristics of aircraft during landing.All possible fault types of flight control system,including the actuator fault,the sensor fault and the system fault,are presented and analyzed,while the characteristics of faulty models are provided in the form of parameterized model.On this basis,a model of landing with aircraft faults can be established.This paper presents the structure of ACLS which includes three control loops and the safe landing indicators of the U.S.Navy.From the above,it provides a reference and a research platform for carrier landing with aircraft faults.Secondly,the radial basis function neural networks(RBFNN)has an universal ability to approximate to any nonlinear function.So this paper present a new fault-tolerant control combining RBFNN and SMC based on NDI.Adaptive algorithm is adopted to adjust the network weights in RBFNN to realize the effective learning of RBFNN.What's more,the method can approximate to the systematic unknown nonlinear faults caused by different types of actuator faults.The best advantage of this method is the ability to handle system fault effectively and quickly.It can make the aircraft maintain acceptable landing conditions to ensure a successful landing.In addition,the Lyapunov method is used to analyze the existence of sliding mode and design the adaptive law of RBFNN weights.It ensures the features of system global asymptotic stability and good robustness.The simulation results are presentedto demonstrate the better control performance and fault-tolerant ability by the proposed approach.This scheme provides a solution for automatic landing with aircraft faults.Thirdly,this paper uses the advantage of the adaptive control which can automatically adapt to the characteristics of controlled object's changes.It can effectively solve the problem of system robustness and uncertainty.Considering the actuator faults and the engineering feasibility,a fault-tolerant control scheme based on adaptive sliding mode is proposed.This scheme applies the sliding mode controller to realize the complex control problem about global stabilization and trajectory tracking,and use the adaptive technique to estimate system fault online,avoiding huge change of system performance.At last,the Lyapunov method proves that the system is stable.The simulation results demonstrate that the designed method has strong robustness and fault-tolerant ability for different types of actuator faults in safe landing.Finally,the landing problem of fault-tolerant control with longitudinal flight path deviation is another significant research direction of landing with aircraft fault.It is studied for the sake of a more comprehensive view on the reliability of landing.A fault-tolerant control approach based on extended state observer(ESO)and sliding mode control is designed to deal with the problem of landing with actuator loss fault and the precision tracking control during aircraft landing.The sliding mode controller based on ESO is used to give the nonlinear dynamic compensation for actuator faults and eliminate the influence of landing environment.Then,the anti-windup compensation scheme is exploited,which can maintain the control inputs in the limited bound of saturation and heighten stability of system.The simulation results show that the proposed control scheme takes advantage of the SMC and ESO to reduce the accuracy requirements of system model.It can satisfy the robustness and fastness of the system,decrease the trajectory error and provide a reasonable and effective technical means for safe landing with aircraft faults.