Disturbance rejection for multivariable processes with time delays based on partial inverted decoupling control

Motivated by the thought of using couplings to reject disturbances, the authors propose a novel partial inverted decoupling control for improving the disturbance rejection of multivariable processes with time delays. With the relative disturbance gain (RDG) for n x n processes, whether the couplings among loops are favorable is evaluated. The inverted decoupling usually used in full decoupling control is then extended to partial decoupling control to retain the favorable couplings and remove the unfavorable ones. The elements of the partial inverted decoupler are derived and the implementation structure is provided. Based on the partially decoupled processes, the decentralized controllers for both the decoupled and non-decoupled loops are designed. An analytical design method for the decentralized controllers is proposed to improve disturbance rejection. Controller parameters are determined in terms of both performance and robustness. Two simulation examples show that the presented partial inverted control strategy can provide superior disturbance rejection to several other classical multivariable control strategies.