Optimal Design On Longitudinal Control Law For Automatic Carrier Landing

The aircraft carrier system is the core strength on modern naval battles, while the carrier landing safety severely restricts the power of the strength. In this paper, the flight control system design with respect to automatic guide and control of carrier-based airplane approach and landing was investigated. An example carrier-based aircraft was regarded as the controlled plant by the automatic carrier landing system (ACLS). The inner and outer loop,the automatic approach power compensation system (APCS), and the deck motion compensation system in ACLS were synthesized, and the corresponding simulated verifications were performed.First, an approaching motion model of the aircraft and the deck motion model were built.A full carrier air wake simulation model was constructed according to the specifications made by a U.S. military standard. On the basis,the ACLS component employed by F/A-18A"Hornet" was consulted to model a longitudinal ACLS for the example aircraft, and the controller parameters were adjusted preliminarily.Second, combined the classical control theory with the fuzzy control theory,a longitudinal automatic carrier landing under fuzzy control (Fuzzy-ACLS) was designed. The fuzzy controller was specific to two parts of the ACLS, autopilot and APCS. This needed to designate the inputs as well as the outputs of the controller, besides made a practical set of fuzzy rules and membership functions. The numerical simulation was performed to compare the traditional ACLS with the fuzzy one in responding to the command, in order to examine the performance of the Fuzzy-ACLS.Using genetic algorithm techniques, the longitudinal ACLS was optimized to improve the rejection capability of the air turbulence around the glide slope. For three kinds of random components in the carrier air wake model, an offline optimization of the controller parameters was carried out by the properly designed fitness function (system performance evaluation function). In the optimizing procedure, the property indices in time and frequency domain were taken into account with a comprehensive optimization method proposed. Then, the optimized parameters were fixed, and a compensation command was added to the ACLS inner loop to suppress another burble component, the steady one. Finally, the combination of parameters optimization and instruction compensation permitted a benign rejection effects for full carrier air wake disturbance, and the integrated response ability of the improved controller was verified by simulations.Finally, a compensator and a predictor for the deck motion were designed, respectively,and both of them were integrated into the existing longitudinal ACLS to keep the aircraft’s pace with the motion of the desired touchdown point, so that the landing accuracy at heavy sea could be guaranteed. After the aircraft’s tail hook model and the touchdown point detection model were established, the final carrier approach simulations, with both of deckmotion and carrier air wake field involved, were performed. Statistics on the touchdown dispersion were made to evaluate the performance of the whole longitudinal ACLS designed.