Design and evaluation of automated guided vehicle systems for flexible manufacturing systems: an extended timed Petri net-based approach K. RAVI RAJUt and O. V. KRISHNAIAH CHETTYtThe design and evaluation of automated guided vehiclesystems(AGVSs)for flexible manufacturing systems (FMSs) is complex because of the randomness and number of variables involved. A Petri net-based methodology is proposed in this paper for modelling and simulating AGVSs for FMSs. To this end, the capabilities of time Petri nets are expanded. The proposed methodology is elucidated with an example. Several design and operational and control issues,including the number of vehicles required, buffer sizes,siding sizes and vehicledispatching, are addressed. The effect of machine and AGV scheduling rules on system performance is also investigated. I. IntroductionAutomated guided vehicles (AGVs) are driverless vehicles which carry workpieces rapidly among workstations by following guide paths. They are usually controlled by off-board computers, communication with which is established with dedicated wiring in the floor. AGV systems (AGVSs) are widely used in flexible manufacturing systems (FMSs) on account of their flexibility and adaptability. However, they are highly complex and expensive. To realize the full potential of these systems, careful design and operational planning are essential. Computer simulation is usually employed to design and verify the operation of complex automated handling systems.This paper proposes a faster and more flexible approach for modelling and simulating AGVSs by expanding the power oftimed Petri nets. It also addresses some of the design and operational control issues of AGV-based FMSs. The paper is

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The increasing worldwide competition requires economical manufacture, high quality and short delivery time. The Just-In-Time (JIT) philosophy of manufacturing is increasingly being considered by manufacturing organizations, as a response to the increased pressure to supply high quality products with short delivery times and at low cost. A very simple shop floor control system that was developed by Toyota in the 1970s specifically for their Just-In-Time assembly plant, has received considerable attention in the Western World, and is known as the 'kanban' system (literally translated as 'card' system). Japan's success has prompted many scholars and practitioners, to turn their attention to Japanese management practices. This article is to address the modelling, simulation and implementation issues of Just-In-Time in flexible manufacturing environments. Priority nets are used for modelling and analysis of the kanban system. A large number of simulation runs are conducted/presented to probe the behaviour of the system, with respect to different parameter changes.

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Manufacturing Engineering Section D e p a r t m e n t of Mechanical Engineering Indian Institute of Technology, Madras-36, INDIA Dynamic iicheduling of Flexible Manufacturing Systems is highly complex due to a number of variables and feasible alternatives. In this conten Priority Nets are developed for flexiile and realistic modeling and simulation of FMSs. A dynamic scheduling algorithm is described which employs Priority net aided simulation in conjunction with Orthognal experimentation a:nd Neural networks to determine the operating policies under varying contlitionsof FMS operation. The efficacy of the algorithm is demonstrated with a case study.