Disturbance observer-based control with partially coupled inverse model for stable TITO processes with time delays

This paper presents a modified multivariable disturbance observer-based (MDOB) control method for stable two-input-two-output (TITO) processes with multiple time delays. Different from the existing MDOB control strategies with diagonal or full elements inverse model, a partially coupled inverse model is used here to provide better disturbance rejection performance. First, an interaction measure, relative input disturbance gain (RIDG), is defined to quantify the disturbance rejection capabilities of the two common types of MDOB techniques. Based on RIDG, the partially coupled inverse model is derived. Then, to deal with the cross terms of the filter elements in the outputs, a single iteration strategy is presented to derive them one by one. Meanwhile, analytical forms of the filter elements are obtained by minimizing the 2-norm of the outputs. Finally, filter parameters are tuned taking into account criteria of performance and robustness. And application of the proposed strategy on simulation examples verifies its effectiveness and superiority.