The automatic flight control system has complex structure with many relevant components, resulting in long time fault diagnosis, which affects the efficiency of aircraft operation. Aiming at the problems, a remote real-time fault diagnosis scheme based on Aircraft Communication Addressing & Reporting System (ACARS) was proposed. Firstly, the fault characteristics of the automatic flight control system were analyzed, and the detection filter was designed and built. Then, the key information of the automatic flight control system transmitted in real time by ACARS data-link was used to realize the residual calculation of the relevant components, and the fault diagnosis and location were carried out according to the residual decision algorithm. Finally, because of the large difference between residual errors of different fault components and inconsistent decision-making threshold, an improved residual decision-making algorithm based on quadratic difference was proposed. This algorithm reduced the overall change trend of the detection object, reduced the influence of random noise and interference, and avoided a transient fault being considered as a system fault. The simulation results show that the proposed algorithm avoids the complexity of multiple decision-making thresholds. Its fault detection time is about 2 seconds with 0.1 second sampling time, which shortens the fault detection time greatly, and the effective fault detection rate is more than 90%.

Aiming at the problem that common nonlinear Stochastic Resonance (SR) system is subject to the restriction of small parameter and is failure to detect the high frequency weak signal, a new detection method of parameter-tuning SR for weak signal with high frequency was proposed. Firstly, the relationship between the damping coefficient and the signal frequency was derived in a bistable system, and by using Kramers rate for analysis, the influence of changing damping coefficient on the SR of the system was verified. Then, the influence of SR phenomenon produced by system shape parameters was deduced, the SR of high frequency weak signal was realized through adjusting the damping coefficient and the system shape parameters, and the effect of output spectrum characteristics of the system and different sampling frequency was discussed, the stability of the algorithm was verified by the results. Finally, using the received actual signals with noise as experimental research data, the experimental results show that ultrahigh frequency weak signal under strong noise background can be extracted effectively and steadily using the strategy even when the signal frequency reaches MHz and GHz. The proposed method extends the application field of SR principle of weak signal detection.