On eigenstructure assignment for robust fault diagnosis

This paper presents a theoretical and tutorial treatment of the eigenstructure assignment approach for robust fault detection. The principles, existence conditions and design procedures are presented. The main contribution of the paper is the development of the assignment of right observer eigenvectors for robust residual generation. When some of the observer right eigenvectors are assigned parallel to the disturbance distribution directions, the diagnostic residual generated by the observer is insensitive to disturbances. Robust fault-detection design can be achieved by either left or right eigenvector assignment method. For left eigenvector assignment method, the sufficient conditions are presented. For right eigenvector assignment method, both necessary and sufficient conditions are proposed. Finally, two numerical examples are used to illustrate the eigenstructure assignment methods studied in the paper.