Multi loop robust H-infinity control design based on the dynamic PLS approach to chemical processes

摘要

In this paper, a multiloop robust control strategy is proposed based on H-infinity control and a partial least squares (PLS) model (H infinity-PLS) for multivariable chemical processes. It is developed especially for multivariable systems in ill-conditioned plants and non-square systems. The advantage of PLS is to extract the strongest relationship between the input and the output variables in the reduced space of the latent variable model rather than in the original space of the highly dimensional variables. Without conventional decouplers, the dynamic PLS framework automatically decomposes the MIMO process into multiple single-loop systems in the PLS subspace so that the controller design can be simplified. Since plant/model mismatch is almost inevitable in practical applications, to enhance the robustness Of this control system, the controllers based on the H-infinity mixed sensitivity problem are designed in the PLS latent subspace. The feasibility and the effectiveness of the proposed approach are illustrated by the simulation results of a distillation column and a mixing tank process. Comparisons between H infinity-PLS control and conventional individual control (either H-infinity control or PLS control only) are also made. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.