On the selection of the reduced order via balanced state representations

It is shown that a conjecture concerning actual and internal dominance advanced in a previous publication is not in general true. Thus, use of the second-order modes only to select the order of a given SISO high-order system's
H
reduced approximant may lead to unsatisfactory results. It is then proposed to use instead certain formulas giving the impulse response energy and the steady-state step response of
H
.