Feedback Practical-Stabilization of nD Systems

In many practical situations, the independent variables i1,...,in of an nD signal x(i1,...,in) are bounded spatial variables, except that perhaps one is the unbounded temporal variable. Taking this feature into account, Agathoklis and Bruton developed the concept of practical-BIBO stability for nD discrete systems, and showed that the conventional-BIBO stability conditions are too restrictive for many applications. This paper deals with the problem of feedback practical-stabilization of nD discrete systems whose input and output signals are unbounded in, at most, one dimension. A constructive algorithm is first presented for solving Bezout equation over the ring of practically-stable rational functions. Then, a necessary and sufficient condition for an nD system to be practically-stabilizable is derived and the parametrization of all nD practically-stabilizing compensators is given. These results make it clear that the nD practical-stabilization problem can be essentially solved by using 1D approaches.