Designing Fuzzy Controller For Automatic Carrier Landing Of Aircraft

Due to the difficulty of landing task, we put forward aircraft automatic carrier landing system (ACLS). The PID controller is the core of longitudinal guide control law of F/A-18A automatic carrier landing system in US navy. However the PID controller with fixed parameters lacks flexibility and accuracy in the face of ship air wake and deck motion and affects the error and satisfaction of landing. So this paper puts forward fuzzy logic automatic carrier landing system (FACLS) for the aircraft. Fuzzy controller which in the landing different stages, according to experience of senior pilot made corresponding fuzzy rule can take place of the traditional ACLS. The main work is focused on the following sections.Firstly, on the base of defined the coordinate system, build the mathematic model of aircraft and the model of engine, analyzes the geometry environment of carrier, and sets up the model of deck motion and ship air wake. In order to compare with FACLS, we simultaneously build up H-dot ACLS. With the brief structure, ACLS is designed from inner loop to outer loop. Control augmentation system, automatic flight control system, approach power compensator system, guide control law and deck motion compensator are successively researched and designed respectively. Moreover ACLS is established in the MATLAB/SIMULINK. The results of simulation show that the obtained structure of ACLS is correct.Secondly, introduce the theory of fuzzy. It consists of the method of escertaining membership functions, the method of fuzzy discursion and solution, and the process of designing fuzzy controller. On the base of the fuzzy control theory, we design fuzzy controller.According to the model of the F/A-18A, to begin with we determine the architecture of FACLS. Then we establish inputs and outputs of each rule base in the architecture and membership function. And then we design fuzzy rule bases. Finally, we make up FACLS. The FACLS is designed so that at carrier process, the aircraft has the proper position, sink rate,angular attitudes, and speed. The FACLS has six sensor inputs, two outputs, and several hundred fuzzy rules. The fuzzy rules are distributed among four rule bases. The use of fuzzy controller was different from many applications since fuzzy logic is used not only to model a set of human rules, but to combine the best features of human and automatic control approaches. This cannot be easily in conventional control systems.Finally,we build FACLS with FIS (Fuzzy Inference System) in MATLAB. The FACLS is tested in simulation and compared with the conventional F/A-18 Automatic Carrier Landing System. Results suggest that the FACLS increases excellent landings and acceptable landings over the conventional F/A-18A ACLS. Especially poor environment, the FACLS achieves a significant reduction in hard landing, ramp strikes, and wave-offs, also achieves these improvements in maximum overshoot and settling time and these improvements are better control in turbulence, reduces glide slope errors due to turbulence, and in a slightly high position with slightly slow sink rate, the FACLS allows the settling effect of the air wake to return the aircraft to glideslope and proper sink rate, and makes the FACLS incorporate some pilot heuristics. Simultaneously in the poor landings, the number of bolters is slightly increased for the FACLS. This shows that as some as the pliot, the FACLS is more concerning with low errors than high errors.