Integrated Batch-to-Batch Control and within-Batch Online Control for Batch Processes Using Two-Step MPLS-Based Model Structures

Abstract

A feedback profile tracking scheme is proposed for batch-to-batch and within-batch control of the end-point quality in batch processes. This new method is based on two-step multiway partial least squares (MPLS) models. The first-step MPLS model, called the quality MPLS, is used to relate the final qualities with the online measurements; the second one, called the measurement MPLS, can relate the online measurements with both the manipulated variables and the prior measured variables. Because the standard MPLS model embeds all process variables into a single input data block, the input variables can be adjusted only on the basis of target qualities at the end point. With the proposed method, the desired online measured variables along the time axis can be computed using the quality MPLS; then the operating input variables can be appropriately adjusted using the measurement MPLS to match the desired online measured variables at each time point and finally get the target qualities at the end-time point. Under these two-step MPLS model structures, the integrated control strategy is sequentially developed by combining batch-to-batch control with within-batch control. Also, the conventional double exponentially weighted moving average control method can be separately and directly applied to each input−output variable in the reduced space of the latent variables. It can gradually reduce the model errors for the model-plant mismatches between batches. The applications are discussed through a typical batch reactor to demonstrate the advantages of the proposed method in comparison with the conventional methods.