Data-driven flatness intelligent representation method of cold rolled strip

A high-accuracy flatness prediction model is the basis for realizing flatness control. Real flatness is typically reflected as the strain distribution, which is a vector. However, it is difficult to obtain ideal results if the real flatness is directly used as the output value of the flatness intelligent prediction model. Thus, it is necessary to seek an abstract representation method of real flatness. For this reason, two new intelligent flatness representation models were proposed based on the autoencoder of unsupervised learning theory: the flatness autoencoder representation (FAR) model and the flatness stacked sparse autoencoder representation (FSSAR) model. Compared with the traditional Legendre fourth-order polynomial representation model, the representation accuracies of the FAR and FSSAR models are significantly improved, better representing the flatness defects, like the double tight edge. The optimal number of bottleneck layer neurons in the FAR and FSSAR models is 5, which means that five basic patterns can accurately represent real flatness. Compared with the FAR model, the FSSAR model has higher representation accuracy, although the flatness basic pattern is more abstract, and the physical meaning is not clear enough. Furthermore, the accuracy of the FAR model is slightly lower than that of the FSSAR model. However, it can automatically learn the flatness basic pattern with a very clear physical meaning for both the theoretical and real flatness, which is an optimal intelligent representation method for flatness.