| The automatic guide and control system has attracted much attention because of its great importance in modern carrier/carrier-based airplane system. Automatic Carrier Landing System (ACLS) can totally embody carrier-based airplane automatic approach and landing technology, and also guide and control carrier-based aircraft to land on the moving deck of aircraft carrier safely. In this dissertation, theory and simulataion on the key technology of designing longitudinal ACLS is studyed. The main work is focused on the following sections.1. Deck movement and carrier airwake are the main causes of the carrier-based airplane landing error among all the environment factors of carrier-based airplane approach and landing. Power spectral density model is built to reflect the real motion of carrier taking into accounting that carrier motion has the characteristics of stationary random process. The ideal glide trajectory carrier-based airplane approach and landing is analyzed in this part. The characteristics and causes of carrier airwake are analyzed and the model of airwake is simulated by an industrial method referring to US Navy criteria.2. Based on the flight dynamics, the motion and mechanics of carrier-based airplane during approach and landing process is studied and corresponding mathematical model of longitudinal motion movement with and without wind are established. The model is linearized to get small disturbance equations and transformed to the linear state space model using coefficient freezing method. The general impact of the carrier airwake is simplified. Taking F/A-18A airplane for a typical example, the approach and landing airframe characteristics is analyzed and the responses show the instability of air speed.3. In this section, H-dot ACLS is designed using classic control theory of frequency domain analysis, while the time domain analysis is adopted for parameter selection. With the brief structure, ACLS is designed from inner loop to outer loop. Automatic flight control system, approach power compensator system, guide control law and deck motion compensator are successively researched and designed respectively. The results of Matlab/Simulink simulation show that the obtained structure of ACLS is correct. 4. Fuzzy PID controller is designed to improve the longitudinal guide control law of the H-dot ACLS. According to the characteristics of ACLS, fuzzy control system is designed to regulate the parameters of controller online, using the control rule derived from experience of engineering experts. With the simulation in Matlab, this method is proved to reduce the landing error and improve the airplane's landing quality.5. A longitudinal ACLS based on H-infinity techniques is designed. The structure of the augmented control model is determined and the principle of selecting the right weighting functions is provided according to the frequency domain requirement. The H-infinity controller is solved using linear matrix inequalitie (LMI) method via Matlab robust control toolbox. Simulation results show that the designed H-infinity longitunal automatic landing controller can effectively restrain the effect of carrier airwake and meet the landing requirements.In summary, this work investigates the longitudinal control of the carrier-based airplane systematically. With the existence of the carrier airwake and deck motion, Fuzzy PID control and H-infinity control technology are used to improve the control law. Simulation results show that the designed control system can restrain the impact of carrier airwake and track moving deck, which basically meet the landing requirements and can provide numerical reference basis for the actual design of ACLS. |
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