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Traditional Control Engineer Tools
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Generations of control engineers have used root-locus and frequency-domain plots for analysis and design. *Control System Professional* implements these familiar tools, with the same object-oriented approach.

Consider, for example, a poorly balanced, controllable realization of a system (from [Moore 1981]).

The system can be brought to the internally balanced form using the function InternallyBalancedForm. The function DominantSubsystem selects the subsystem that provides the dominant modes (and balances the system, if necessary).

Using the option RejectionLevel, we can adjust the relative value of modes that are to be considered "weak," if the default value of 10% does not give satisfactory results. In our case, raising the value of RejectionLevel to 20% results in the second-order system.

We can display the Bode plots for the original and reduced-order systems with the function BodePlot.

The curves for the original system are drawn with solid lines; the dashed and dashed-dotted lines represent the two reduced-order systems. The plot shows that in the reduced models, the lowfrequency behavior is preserved while the highfrequency states are eliminated.