A simplified derivation of the Zeheb-Walach 2-D stability test with applications to time-delay systems

Zeheb and Walach gave a stability test for
N-D
systems. For 2-D systems, a simpler derivation is presented here using the results of DeCarlo et al. It is then shown how the method may also be used to test for stability (independent of delay) of retarded time-delay systems.