Comments on "Stability Tests of -Dimensional Discrete Time Systems Using Polynomial Arrays"

In this brief, we wish to point out that the author of the above paper overlooked a mistake in the stability test procedure for -dimen- sional ( -D, systems proposed in the above paper, which made the polynomial array approach not general. It is shown that Hu's test proce- dure applies only to a very restricted class of -D stability test problems, and for a general case, instead of necessary and sufficient conditions it pro- vides only sufficient conditions. A counterexample is also given. Index Terms—Multidimensional systems, polynomial array, stability test.