Non-diagonal multivariable fractional prefilter in motion control

Abstract

A novel approach for robust Commande Robuste d'Ordre Non Entier (CRONE) control of multi input multi output (MIMO) systems using quantitative feedback theory (QFT) design is discussed through fractional prefilters with off-diagonal elements. More design flexibility is guaranteed when using the non-diagonal prefilter. For a given system, the CRONE control approach is combined with QFT design to get the controller matrix. After that, the classic diagonal fractional prefilter expression is extended to a fully populated prefilter matrix. The Davidson-Cole fractional prefilter optimisation is used to determine the diagonal terms of prefilter. The role of the off-diagonal elements of prefilter is to eliminate loop interactions in the case of reference tracking. So a sequential design procedure is proposed in order to get the fully populated prefilter matrix elements. The performance of the novel methodology is finally verified by adopting the designed prefilter and controller to govern the MIMO SCARA robot model.