Over the past several decades, a considerable interest has been devoted to problems involving signals and systems that depend
on more than one variable. 2-D signals and systems have been studied in relation to several modern engineering fields such
as process control, multi-dimensional (m-D) digital filtering, image enhancement, image deblurring, signal processing, etc.
Among the major results developed so far concerning the 2-D signals and systems, 2-D digital filters are investigated as a
description in frequency domain or as a convolution of the input and the unit impulse response. Its great potential for practical
applications in the 2-D image and signal processing has been shown [64][65]. On the other hand, a technically very important
range of 2-D problems exist which require feedback control [44]. 2-D control has previously been approached from a predominantly
systems theoretical point of view. This has two main branches, seen in [60][72], taking an input-output transfer function
approach and a state-space approach, respectively. 2-D state-space models, however, have attracted a lot of interest due to
its advantage of providing a simple and intuitive research method for 2-D signals and systems. Although it appears something
like the one-dimensional (1-D) state space model, there exist some essential differences between them. Therefore, 2-D state-space
representations have been extensively studied theoretically and practically.