A new representation of siso systems for studying approximated models

Abstract A nonlinear matrix equation is introduced and it is shown that a particular solution of the considered equation contains for SISO systems the same type of information carried in closed-loop characteristic values. In addition, it contains equivalent information on the so-defined closed-loop system “signature” where its importance in model reduction problems is outlined. An illustrative example is presented, and results are compared to those of other methods by using the proposed approximated model in a closed-loop scheme.