Adaptive Decoupling Switching Control On A Dual-tank Water System

Dual-tank water system is a typical multivariable nonlinear coupled plant. Many applied systems in industry can be abstracted into a dual-tank water system in whole or as a part. Thus, the study of level control on such system bares great research value and wide application background. However, most commonly used classical control methods neglect the coupling influence within controlled system while working with independent controlled loops. Consequently, it becomes a critical issue to design an effective controller against the strong nonlinear and coupling features which can achieve satisfactory results on the dual-tank water system.With the support of State Key Laboratory of Synthetical Automation for Process Industries (Northeastern University), this paper is focus on the research of nonlinear adaptive decoupling switching control on a dual-tank water system. The main work is as following:1. Establish the mechanism model of the dual-tank water system under dynamic mass balance condition and acquire the controller design model by linearization at a specific operating point. Then determine the unknown parameters within controlled system through experimental parameter identification;2. Reform the mathematical model as the combination of a low-level linear model and a high order nonlinear term, and design a nonlinear adaptive decoupling switching controller according to the nonlinear and coupling characteristics of the dual-tank water system around the operating point, which is comprised of a linear adaptive decoupling controller, a neural network based nonlinear adaptive decoupling controller and switching mechanism;3. Perform level control simulation with one designed nonlinear adaptive decoupling switching controller on the MATLAB\Simulink platform, and verify the effectiveness of such controller by comparing the simulation results with those acquired by regular a PI controller, a linear adaptive decoupling controller, a neural network based nonlinear adaptive decoupling controller and a nonlinear adaptive decoupling controller with nonlinear term compensation of last moment;4. Adopt nonlinear adaptive decoupling switching control on a real dual-tank water experiment system and testify that it can obtain satisfactory performance for level control around the preset operating point. Then compare with the results of a regular PI controller and a linear adaptive decoupling controller, and analyze achieved results. The experiment results on the dual-tank water system indicate that the nonlinear adaptive decoupling switching controller can greatly improve the level control performance using classical control methods, and thus is of significant value in application.