Abdellah El Moudni

Control of an electroplating line in the max and min algebras

The paper develops the state equation model of an electroplating line in the max algebra. The state equation includes a control vector designed to ensure the control of movements of the transporting system, to respect constraints and to optimize the production. An industrial application and some results are given for the dynamic modelling of minimum-maximum P-time event graphs in dioids, namely in the max and min algebras.

Resolution of the two-part cyclic hoist scheduling problem with bounded processing times in complex lines’ configuration

The performance of an enterprise largely depends on the schedule of its resources. A good schedule may increase the output rate and reduce the production costs. Therefore, in this paper, we consider the cyclic schedule of hoist activities in automated electroplating lines which is commonly known as cyclic hoist scheduling problem (CHSP). The CHSPs appear in the manufacturing facilities to achieve a mass production and to search a repetitive sequence of moves for the hoist. In such kind of lines, hoist is used for moving electroplates through a line of tanks containing chemical baths. In this paper, we first study the impact of non-fixed processing time in cycle duration and then we extend our elaborated two-degree cyclic model to a more complex configuration of the production lines. [Received 26 June 2010; Revised 14 November 2010; Accepted 15 February 2011]

On the control of manufacturing lines modelled by controlled continuous Petri nets

We present a new methodology to study the control of a class of discrete event dynamic systems, opened manufacturing lines and closed manufacturing lines. Our contribution is based on the controlled variable speed continuous Petri net model. The computation of the control variables is made using a classic constrained optimization method. The resulting control solution is used to guide the real system behaviour. Some properties linked to the accessibility problem of the reference input are given. Through illustrative examples, the practical application of this approach issue will be made prominent

Some subclasses of Petri nets and the analysis of their structural properties: a new approach

The purpose of the paper is to consider some special types of Petri nets, introduced by Lien (1976), and to propose a complete and unified approach for the study of their structural properties by using techniques of linear algebra of matrices. We distinguish four subclasses: forward-conflict-free, backward-conflict-free, forward-concurrent-free, and backward-concurrent-free Petri nets. A modification of the classical incidence matrix results in a square matrix, called a modified incidence matrix, with nonpositive (nonnegative) off-diagonal elements when backward-(forward-) conflict-free or concurrent-free Petri nets are considered. The modified incidence matrix eigenvalues are computed and theorems on matrices of this type are used to prove several sufficient and/or necessary conditions for structural boundedness, liveness, repetitiveness, conservativeness, and consistency of these four subclasses of Petri nets.

Integrated scheduling of production and distribution operations: a review

There are many practical production systems with distribution operations where finished jobs are transferred from supplier to the customer by transporters. In these systems, the coordination of production and logistics operations can help to improve overall system performance and reduce the total operation cost. This paper focuses on two categories of integrated scheduling problems. One is Integrated Scheduling of Production-Distribution Problems (ISPDP) and the other is Integrated Scheduling of Production-Inventory-Distribution Problems (ISPIDP). This paper presents a review of the state-of-the-art articles and suggests the corresponding further research directions for the above two categories of integrated scheduling problems.

Production scheduling problem with delivery considerations in a mono-product supply chain environment to minimise the total joint cost

This paper chooses a supply chain which involves multiple supply links as the studied object. In each supply link, we consider an integrated scheduling problem in which a set of identical jobs are first processed on a single machine, and then batch delivered to a customer by a transporter. Each job has a due date specified by the customer in each supply link. It is supposed that a job which is finished before its departure date or delivered to the customer before its due date will incur a corresponding inventory cost. The objective is to find a joint schedule for each supply link such that the total cost of the supply chain is minimised. We show that this problem is NP-hard in the maximum capacity of the transporters, and then propose a dominance-related greedy algorithm and a genetic algorithm. Computational results illustrate the efficiency of the proposed heuristics. [Received 7 January 2010; Revised 18 February 2011; Revised 21 June 2011; Accepted 13 February 2012]

A branch and bound algorithm for one supplier and multiple heterogeneous customers to solve a coordinated scheduling problem.

Considerable attention had previously been given to the single-vendor single-customer integrated inventory problem, but there had been very little work on the integrated single-vendor multi-customer and multi-product consideration. Here, we develop a generalized single-vendor multi-customer with multi-product consideration supply chain model with one transporter available to deliver the products from the supplier to the customers.The objective is to solve the proposed model and to find the minimized total cost, while guaranteeing a certain customer service level. A mathematical formulation of the problem is given in a general way. Then, we propose a branch and bound algorithm as an exact method and an efficient heuristic greedy algorithm. Both procedures are then compared through computational experiments which show that the heuristic algorithm is capable of generating near-optimal solutions within a short amount of CPU time.

On the determination of numerical control for two time scale continuous system

The multi-time-scale systems are subject of a great number of research works concerning their reduction and simplification, in order to elaborate the control. The singular perturbations theory is perfectly adapted to systems presenting multi-time-scale. The multi-time-scale property is due to the presence of slow and fast dynamic phenomena. The use of singular perturbations permits the decomposition of the global system in two sub-systems giving prominence to slow and fast parts. So, the determination of the control from these systems is faster than its calculation from the global one.<<ETX>>