Effective Transfer Function Models by Input, Output Variables Reduction

Transfer function models used for early stages of design are large dimension, contain all possible physical inputs, outputs, may be badly conditioned and possibly degenerate. The problem considered here is the selection of maximal cardinality subsets of the physical input, output sets, such as the resulting model is nondegenerate and satisfies additional properties such as controllability and observability and avoids the existence of high order infinite zeros. Conditions for characterisation of such properties are given. A selection procedure for natural subsets of inputs and outputs, which guarantee well conditioning in the above sense, may be based on these criteria.