In: Proc. IEEE Int. Conf. on Systems, Man, and Cybernetics (SMC'98), 11-14 October 1998, San Diego, CA, pages 119-124. 1998.
Abstract: Timestamp Petri nets, introduced in this paper, offer a new method to deal with time critical problems in the field of automation of manufacturing systems. The each token in a timestamp net, a timestamp is assigned, which denotes the time when the token was put on its place. In those nets, intervals are assigned to the incoming arcs of transitions, which describe the permeability of the arc relative to the token on the adjacent place. In timestamp nets it is possible that synchronizing transitions are not able to fire although they are supplied with tokens sufficiently, because their incoming arcs are not permeable simultaneously. In this case the transition is said to be timewise stuck. This paper examines how transitions of a timestamp net are getting timewise stuck. Based on a symbolic analysis, these investigations can be reduced to solving systems of linear inequalities. The method can also be used to determine parameters for a timestamp net in order to prevent transitions from getting timewise stuck. The paper shows the method's applicability by the dynamic model of a small technical plant as an example. Forbidden states of the uncontrolled system are described by transitions which can get timewise stuck. The method is used to determine time parameters of a controller, which ensures that forbidden states in the controlled system are unreachable.
Keywords: manufacturing systems, time-critical systems, timestamp Petri nets.