Deep learning is an important and effective tool for process soft sensor modeling in industrial artificial intelligence. Traditional deep learning methods like stacked autoencoder (SAE) usually learn high-level features from their low-level ones progressively by minimizing the reconstruction error for the inputs at each layer. However, the reconstruction cannot be exactly accurate. There is loss cumulation of raw data information from the lowest to the highest levels in SAE. To deal with this problem, a novel deep stacked isomorphic autoencoder (SIAE) is proposed to obtain better feature representation for raw input data in this paper. Different from the original SAE, SIAE aims to extract abstract features at each layer from its previous one by stacking hierarchical isomorphic autoencoders (IAE), in which each IAE reconstructs the same raw input data as well as possible. Thus, SIAE can better describe the complex data patterns and obtain good features for the raw data. Then, SIAE is used to construct soft sensor model for quality prediction. The application on an industrial sulfur recovery unit shows that SIAE can improve the prediction performance for the quality variable.
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