The minimum gap and the robust stability under graph uncertainty

This work defines and studies the nullity, the deficiency and the minimum gap between the graph of the plant and the inverse graph of the compensator. The stability criterion is given based on two closed graphs associated with the feedback control system. The minimum gap is introduced to analysis the robust stability under graph uncertainty. The perturbation bound is given based on the relationship between the gap and the minimum gap without destroying the stability of the closed-loop system.