The deep learning model has gradually matured in the detection of mechanical faults. However, due to the changes in the mechanical operating environment and the application of new sensors in real work, the effect of the training model is not ideal in field applications. The key of this problem is the deviation of feature space mapping between training source domain and application target domain. This paper proposes an unsupervised adversarial domain adaptive fault diagnosis transfer learning model based on the minimum domain spacing to reduce the deviation. In adversarial network training, by training the weight parameters of the classifier, some features extracted by the composed classifier are added to the feature distribution of the target domain through weight changes, which reduces the feature distribution difference between the source domain and the target domain. It is reflected on the reduction of the maximum mean difference distance (MMD) between the two domains, and the fitting features of the data distribution are improved. Finally, through two experimental platforms of rolling bearing and planetary gearbox dataset, the results of six diagnostic tasks show that the new model reduces the amount of parameters by 33.66% and keeps accuracy more than 99% compared with the DANN model under the condition.

Over the past few years, cross-domain fault detection methods based on unsupervised domain adaptation (UDA) have gradually matured. However, existing methods usually assume that the source and target domains have the same label domain space, but ignore the problem of label expansion in the target domain. The source domain of such problems lacks transferable knowledge of newly added health categories, so the domain invariant features extracted by the UDA model only have a large correlation with the source domain health categories, but lack the key features to distinguish the newly added health categories. We found that most of the diagnostic results of this type of samples are distributed at the decision boundary of the source domain health category, and this special distribution means that the newly added health category samples have a high amount of information. Therefore, this paper considers using active learning to select samples of newly added health categories in the target domain to assist model training, and proposes an active domain adaptation intelligent fault detection framework LDE-ADA to deal with the label expansion problem. Finally, on the rotating machinery dataset, the analysis and comparison are carried out through six transfer tasks. The results show that when there is one new health category, the accuracy of LDE-ADA will increase by about 9.39% in the case of labeling three samples per round and training for 20 rounds. Experiments show that this method is an effective method to deal with the label expansion problem.