ABSTRACT:
It is shown that the stability of composite feedback control systems with delays both in the state and the input can be checked from the stabilities of the individual isolated subsystems, if the composite system matrix has a certain new structure called the GKK-structure; and if the numerators and denominators of the determinants of the overall system transfer matrix and of the isolated system transfer matrices contain some term of a certain expansion called the principal term. The GKK-structure includes diagonal dominance, the Hadamard (M-matrix) structure, and normality as special cases.
Systems & Control Letters 04/1983; 2(6-2):363-368. DOI:10.1016/0167-6911(83)90046-4