Seminario Doble: Property preservation when fluidization of PN and control metods for continuous PN

Thu, 27/09/2012 - 12:00 - 13:00

Title: Marking homothetic monotonicity and fluidization of untimed Petri nets
Authors: Estíbaliz Fraca, Jorge Júlvez, Manuel Silva.

Abstract: Continuous net systems (technically hybrid systems) are the result of removing
the integrality constraint in the firing of transitions. This relaxation may highly reduce the
complexity of analysis techniques but may not preserve important properties of the original
system. This work deals with the basic operation of fluidization. More precisely, it aims at
establishing conditions that a discrete system must satisfy so that a given property is preserved
by the continuous system. These conditions will be mainly based on the here introduced marking
homothetic behaviours of the system. The focus will be on logical properties as boundedness,
deadlock-freeness, liveness and reversibility. Furthermore, testing homothetic monotonicity of
some properties in the discrete systems will be considered.

Title: Control of continuous Petri nets using ON/OFF based method
Authors: Liewei Wang, Cristian Mahulea, Jorge Júlvez, Manuel Silva.

Abstract: Continuous Petri Nets (CPN) can be used to approximate classical discrete Petri
nets which suffer from the state explosion problem. In this paper we focus on the control of
timed CPN (TCPN), aiming to drive the system from an initial state to a desired final one.
This problem is similar to the set-point control problem in a general continuous-state system.
In a previous work, a simple and efficient ON/OFF controller was proposed for structurally
persistent nets, and it is proved to be minimum-time. In this work the ON/OFF controller is
extended to general TCPN, but in this case, the minimum-time evolution is not guaranteed. Two
extensions are proposed, both of them are based on the ON/OFF strategy. Some comparisons
of different control methods are given in terms of their applications to an assembly system.

Seminario 23