**4. Feature-level fusion for bearing fault diagnosis**

This section will propose a new multiple sources feature-level fusion model for bearing fault diagnosis using GEP. At present, the research of fault diagnosis based on feature-level fusion is still less, far from decision-level fusion attention. This is mainly because feature-level fusion is more difficult. But feature-level fusion application for fault diagnosis can be more effective to extract fault feature information. It is a way to improve the performance and robustness of bearing fault diagnosis system.
