A robustness approach for prefiltering the GPC

Robustness of closed loop systems, subjected to unmodeled dynamics, using the Generalized Predictive Controller (GPC) is analysed. A stability bound equation for the GPC controller is derived using the small gain theorem and, from the analysis of this equation, guidelines for selecting the order of the observer polynomial T in the GPC are developed. The choice of the polynomial T order is based on the stability bound equation tendency in high frequencies and is a function of the GPC tuning knobs. Different strategies for choosing the polynomial T roots are also included. The aim is to improve robustness. Key words: GPC, robustness, unmodeled dynamics, closed loop stability.