Petri nets (PNs) are useful tools for the modeling and analysis of discrete
event systems, This work deals with the estimation of firing and enabling
sequences for timed transition PNs with unknown time delays. The marking an
d the reserved marking of the places are measured on line. The estimation p
roblem has exact and approximated solutions that are described, Sufficient
conditions are given on the measurement accuracy of the marking and reserve
d marking vectors, so that the estimation of firing and enabling sequences
is an exact one. If the estimation provides several solutions, the PN is ex
tended in order to give a unique solution, Numerical aspects of the estimat
ion are also investigated. As a consequence of this, the proposed method pr
ovides interesting tools for the modeling, the performance analysis, and ab
ove all the monitoring of manufacturing systems and roadway traffic network
s.