A new positive real characterization and robust positive real control of descriptor systems

This paper investigates the positiv e re al c ontrol problem for uncertain descriptor systems.The parametric uncertainty i s as sumed to be norm bounded.Firstly,for the nominal system,a new positive real char acterization is given,which is expressed by a strict linear matrix inequality(LM I) without equality constraints.Secondly,for the uncertain system,necessary and suff icient conditions for the solvability of the positive real control problem a re d erived.Based on these conditioos a state feedback law is obtained,which rend ers the resultant closed-loop system robustly positive real.