  In this paper, a novel data-driven approach named Augmented Imagefication for
Fault detection (FD) of aircraft air data sensors (ADS) is proposed.
Exemplifying the FD problem of aircraft air data sensors, an online FD scheme
on edge device based on deep neural network (DNN) is developed. First, the
aircraft inertial reference unit measurements is adopted as equivalent inputs,
which is scalable to different aircraft/flight cases. Data associated with 6
different aircraft/flight conditions are collected to provide diversity
(scalability) in the training/testing database. Then Augmented Imagefication is
proposed for the DNN-based prediction of flying conditions. The raw data are
reshaped as a grayscale image for convolutional operation, and the necessity of
augmentation is analyzed and pointed out. Different kinds of augmented method,
i.e. Flip, Repeat, Tile and their combinations are discussed, the result shows
that the All Repeat operation in both axes of image matrix leads to the best
performance of DNN. The interpretability of DNN is studied based on Grad-CAM,
which provide a better understanding and further solidifies the robustness of
DNN. Next the DNN model, VGG-16 with augmented imagefication data is optimized
for mobile hardware deployment. After pruning of DNN, a lightweight model
(98.79% smaller than original VGG-16) with high accuracy (slightly up by 0.27%)
and fast speed (time delay is reduced by 87.54%) is obtained. And the
hyperparameters optimization of DNN based on TPE is implemented and the best
combination of hyperparameters is determined (learning rate 0.001, iterative
epochs 600, and batch size 100 yields the highest accuracy at 0.987). Finally,
a online FD deployment based on edge device, Jetson Nano, is developed and the
real time monitoring of aircraft is achieved. We believe that this method is
instructive for addressing the FD problems in other similar fields.
