Manufacturing flow control using fluid event graphs

Flow control of manufacturing systems subject random events is considered in this paper using a fluid stochastic event graph model that is a decision-free Petri net. In this model, tokens are considered as continuous flows. A transition can be in operating state or in failure state. A transition in operating state can fire at its maximal speed and a transition in failure state cannot fire. Transitions between failure and operating states arc independent of the firing conditions and the sojourn time in each state is a random variable of general distribution. For the purpose of performance evaluation, a set of evolution equations that determines continuous state variables at epochs of discrete events is established. Gradient estimators of the cumulative firings with respect to the system parameters are derived. Finally, an optimisation problem of the initial marking that maximises a concave function of throughput rate and the initial marking is addressed. Copyright (C) 2000 IFAC.