Sophie Hennequin

Continuous Petri Nets with Delays for Performance Evaluation of Transfer lines

Thanks to their simplicity and efficiency, continuous flow models are frequently used for performance evaluation and optimization of manufacturing systems. Although resource capacity constraints can be explicitly taken into account in existing continuous flow models, delays are rarely explicitly taken into account. The purpose of this paper is to introduce continuous Petri nets with delay for explicit modeling of delays for more realistic performance evaluation of failure prone transfer lines. One salient feature of this model is the explicit modeling of delays without destroying the nature of pure continuous flow model. This feature preserves the analyticity of pure continuous flow models for performance evaluation and optimization.

Perturbation analysis and optimisation of continuous flow transfer lines with delay

This paper addresses the optimisation of failure-prone transfer lines with delays for material transfer and with a constant demand. A continuous flow model with delays is proposed. Compared with traditional continuous flow models in which materials flow from one station to another instantaneously, material flowing out a machine waits a period of time called a delay before arriving at its downstream buffer. Machines are subject to time-dependent failures. Times between failure and times to repair are random variables with a general distribution. The production of each machine is controlled by a base stock policy. We propose a simulation-based optimisation method for determining optimal base stock levels in order to minimise the long-run average cost incurred by inventory holding and demand backlogging. It is based on an infinitesimal perturbation analysis for the estimation of gradients along the simulation. The unbiasedness of the gradient estimators is established.

Assembly Line Balancing Problems Solved by Estimation of Distribution

In this paper, we propose an new algorithm based on an estimation of distribution (ED) to solve the type II assembly line balancing problem (ALBP-II). This problem aims to assign a set of assembly operations subject to precedence constraints to a given number of workstations of an assembly line in order to minimize the cycle time. We prove that the optimal solution for determinist ALBP-II problem can maximize the reliability of the least reliable station in the line if the operation times are random and normally distributed with constant variance-to-mean ratio. The ED algorithm is a population-based algorithm. The simulation results show that ED algorithm outperforms the simulated annealing algorithm especially for large-scaled problems.

A fuzzy hedging point policy for sustainable manufacturing system

This paper addresses a sustainable manufacturing system, i.e. a manufacturing system on which we try to minimize all economical costs while minimizing environmental impacts and improving workforce welfare. Indeed, on one hand, this system emits pollutants and greenhouse gases during its manufacturing process. On the other hand, the social dimension i.e. the human workforce and its working conditions are also discussed and considered because of the direct and indirect costs associated. A hedging point policy is then applied and adapted to this manufacturing system by using fuzzy logic to ensure sustainability. So, a fuzzy hedging point is defined to take into account pollutant emissions and human factors in order to minimize global costs.

Regular session production - 1

In this regular session many aspects of production problems are developed with regards to the following topics: Some topics developed in this session: • Inventory model; • Manufacturing environments; • Maintenance optimization; • Fuzzy Hierarchical; • Quality Management System; • Dynamic lot-sizing; • Optimization. Presented papers: • Buffer allocation, machine selection and preventive maintenance optimization in unreliable production lines • Comparative Study of Fuzzy Hierarchical Hybrid Approaches for Control of Quality Management System • A Fuzzy Hedging Point Policy for Sustainable Manufacturing System • Dynamic lot-sizing-based working capital requirement minimization model with infinite capacity • Local and global optimization in raw material processing