**5. CNN Method for Fault Diagnosis of HMCVT Shift Hydraulic System**

*5.1. Convolutional Neural Network Overview*

The convolutional neural network (CNN) is a hierarchical neural network. Its advantage is that the network model is simple, and the image can be directly used as the input of the network, which reduces the workload. These characteristics make the convolutional neural network have obvious advantages in identifying two-dimensional graphics [29].
