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228 CHAPTER 11. H 2 MODEL-ORDER REDUCTION FROM ORDER N TO N-3
11.5.2 Comparing the co-order three technique with the co-order one
and two technique
Finally, the performance of the co-order one, co-order two and co-order three techniques
is compared with each other. The same system H(s) as in Subsection 11.5.1
of order four is reduced to order one by applying the co-order three reduction once,
by applying a co-order one and co-order two reduction consecutively and by applying
the co-order one technique three times.
Table 11.3 shows the outcomes of these computations ordered by an increasing
H 2 -criterion value V H = ||H(s) − G(s)|| 2 H 2
. The co-order 3 technique performs the
best, whereas the other techniques show only a slightly worse performance in terms
of the H 2 -criterion value V H .
Table 11.3: Reducing the model-order of a system of order 4
Method G(s) of order 1 Pole of G(s) V H
−3.1894
Co-order 3
−0.174884 6.16803
0.17488+s
Co-order 2, co-order 1
Co-order 1, co-order 1, co-order 1
Co-order 1, co-order 2
−3.1584
0.17266+s
−0.172657 6.16826
−3.1523
0.17287+s
−0.172869 6.16828
−3.1716
0.16854+s
−0.168542 6.17014