Research On Longitudinal Control Strategy Of The Automatic Carrier Landing System

The automatic carrier landing system(ACLS)is a powerful support to ensure the combat of aircraft carrier,and the design of its control strategy has always been the most important research of landing guidance technology.Due to the influence of carrier air-wake and carrier deck motion,the requirements of ACLS for track control and attitude keeping are improved.At the same time,the landing accident may be caused by the change of landing performance when the carrier-based aircraft fails.The following three problems need to be considered in the design of ACLS control strategy: First,it is necessary to improve the tracking ability of the ACLS to the ideal glide path in the final-approach;Second,it is necessary to consider the carrier-based aircraft failure to design the control strategy of ACLS;Third,it is necessary to consider changing the current indirect lift control method to improve the track correction ability and realize the direct lift control in the final-approach.Aiming at the three problems,this paper has studied the control strategy of the ACLS.First,in order to ensure that the control strategy can be effectively verified and analyzed the shortcomings of the existing ACLS,the model of approach landing is established by analyzing the influence of external environment factors,and the longitudinal guidance law and control strategy of ACLS are studied.In the approach landing model,the frequency spectrum model and the engineering model are used to build the aircraft carrier deck motion model and the carrier air-wake model,through the selection of coordinate system and aircraft force analysis,the total nonlinear dynamic model is simplified to obtain the longitudinal dynamic nonlinear model.In the research of longitudinal guidance law and control strategy,PID control strategy is designed based on the H-dot ACLS.By analyzing the relationship between aerodynamic resistance and approach speed in the final-approach,it is proved that the speed of carrier-based aircraft in final-approach is instability,and the APCS is designed to keep the angle of attack constant.The PID control strategy is simulated to verify the effectiveness of the control strategy,and the research direction of the control strategy is determined through the analysis of the simulation results.Secondly,a backstepping control strategy of ACLS is proposed to solve the problem of track control in final-approach.The backstepping control is used in the control augmentation system(CAS)design,the backstepping method is used to reduce the order and simplify the complex pitching attitude and horizontal tail deflection function.In the design of longitudinal guidance law and approach power compensation system(APCS),sliding mode control is usedto improve the robustness of the system,continuous sliding mode is used to reduce chattering.Compared with PID control strategy in the final-approach,the simulation results show that the control strategy can realize the precise track control and improve the attitude keeping ability.The design provides a solution for improving the track control ability of the ACLS.Thirdly,the fault-tolerant control strategy of the ACLS is designed to solve the problem of landing safely in the fault state.Based on the analysis of the ACLS,the fault model of the the carrier-based aircraft is established.The fuzzy radial basis function neural network(FRBFNN)is used to approximate the unknown fault function,and an adaptive fuzzy RBF neural network controller is designed.The fault-tolerant control strategy is designed on the basis of the backstepping control strategy.The FRBFNN is used to deal with the actuator fault of CAS and APCS,and the design of adaptive law is used to adjust the network weight and ensure the system stability.By comparing with PID control strategy under actuator failure,it is proved that the fault-tolerant control strategy can effectively guide the carrier-based aircraft to complete the landing task under actuator failure,and the ACLS has strong fault tolerance.This design provides a feasible scheme for the fault-tolerant control strategy design of the ACLS.Finally,through the research of recovery precision enabling technology and direct lift control,the control strategy of ACLS based on the direct lift control is designed based on the analysis of lift characteristics of carrier-based aircraft in final-approach.In the direct lift control system,the lift is realized by flap deflection,and the fight angle rate feedback and fight angle increment feedback are used to improve the track correction ability.In the attitude control system,the flight attitude is stabilized by controlling horizontal tail deflection,and the angle of attack feedback is used to keep the angle of attack constant.Because the direct lift control has the ability to keep the angle of attack constant,the APCS is designed to keep the speed constant.Compared with the PID control strategy based on the H-dot and the backstepping control strategy of the ACLS,the simulation results show that the direct lift control has strong track correction ability and the ability of keeping the angle of attack constant.This design provides a reasonable technical route for the design and research of ACLS.