Decoupling filtered Smith predictor design for multivariable systems with multiple time delays

This paper aims to show a methodology to design multivariable filtered Smith predictor for n × n processes with multiple time delays based on the centralized direct decoupling structure. A decoupler is introduced in this control scheme for achieving a better performance. In some cases it is necessary to introduce additional delays into the plant model transfer functions for the shortest time delay of each row of the matrix of transfer functions to appear on the main diagonal. If this condition is met, it is possible to obtain the prediction of the process output. This structure improves both the setpoint tracking and disturbance rejection responses with respect to the conventional extensions of the Smith Predictor to MIMO systems. The realizability conditions for the decoupler are provided and it is demonstrated that dead-time compensation must be enclosed in the decoupling controller matrix for simplifying the problem to multiple single-loops. The effectiveness of the method is illustrated through different simulation examples.