Siphon-based control suffers from the problem that the number of problematic siphons grows quickly with the size of the system. To reduce the number of monitors, Li and Zhou proposed to divide problematic siphons into elementary and dependent ones. Monitors are added only for elementary siphons; the number of which grows linearly. They adjust the control depth variable for a dependent siphon, if the siphon does not satisfy the controllability and can become unmarked. The control policy for weakly dependent siphons is rather conservative because of some negative terms in the controllability. This study proposes a better estimate of the negative terms and the policy needs no longer be that conservative.
IET Control Theory & Applications, 4(7), 1298-1302