“…The use of the positive invariance property in the control of constrained dynamical systems has been receiving much attention in the last years (Blanchini, 1990;Blanchini, 1994;De Santis, 1994;Georgiou and Krikelis, 1991;Gilbert and Tan, 1991;Hennet, 1989;Hennet and Béziat, 1991;Kolmanovski and Gilbert, 1995;Milani and Dórea, 1996;Tarbouriech and Gomes da Silva Jr., 1997;Tarbouriech and Castelan, 1993;Tarbouriech and Castelan, 1995). This property is used, for instance, to guarantee the maintenance of the state trajectories of a controlled system in the interior of some prescribed sets of admissible states determined from some sets of control or state constraints.…”