On the history of system zeros and the work of Kronecker

The structure of linear, multivariable control systems has now been studied rather intensively for three decades, yet it still gives room for further work. The author concentrates on the engineering motivation for investigation system zeros, emphasizing the significance of Kronecker´s work in its later states. The problems encountered in applying state space methods are outlined. The discussion also encompasses the system matrix, minimal indices, hierarchical theory, and nonproper systems