Structural invariants of linear multivariable systems

The class {∑} of all linear multivariable systems is partitioned into equivalence classes by the group consisting of all basis, all state feedback and all output injection transformations. This paper provides a new derivation of a set, of complete invariants and a corresponding canonical form first given by Morse. Strong reachability and strong observability concepts are the key tools. The method yields relatively simple proofs and economical matrix algorithms.