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Minimal state-space realization for a class of linear, discrete, \(n\)D, SISO systems. (English) Zbl 1035.93015

The problem of minimal realizations for \(n\)D linear systems is considered. Since general solutions do not exist in the general case, the aim of this paper is to emphasize a new class of systems for which this problem is solvable; this class consists of SISO \(n\)D linear systems represented by transfer functions of the form \[ f(s_{1},s_{2},\dots,s_{n})= \frac{a(s_{1},s_{2},\dots,s_{n})} {b(s_{1},s_{2},\dots,s_{n})} \] where \(a(s_{1},s_{2},\dots,s_{n})\) and \(b(s_{1},s_{2},\dots,s_{n})\) are multi-linear polynomials, i.e. they are of degree one in each indeterminate. In this case, the method proposed by the author in a previous paper (based on the construction of the companion matrix for the associated polynomial \(a_{f}(s_{1},s_{2},\dots,s_{n},s_{n+1})= s_{n+1}b(s_{1},s_{2},\dots,s_{n})-a(s_{1},s_{2},\dots,s_{n})\)) provides a set of equations which can be solved by isolating the independent ones. The existence and construction of minimal realizations are analyzed and a suitable procedure is given. If a minimal realization does not exist (i.e. the existence conditions do not hold), the so-called elementary operation algorithm developed by the author in a previous article is adapted to obtain a non-minimal realization, possibly of the least order. System equivalence is studied by employing variable transforms such as a generalized multivariable bilinear transform and variable inversion. Some examples illustrate the main ideas and the proposed procedures.

MSC:

93B20 Minimal systems representations
93C35 Multivariable systems, multidimensional control systems
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