Diane Riopel

Integrated production and material handling scheduling using mathematical programming and constraint programming

In this article, we propose an integrated formulation of the combined production and material handling scheduling problems. Traditionally, scheduling problems consider the production machines as the only constraining resource. This is however no longer true as material handling vehicles are becoming more and more valuable resources requiring important investments. Their operations should be optimized and above all synchronized with machine operations. In the problem addressed in this paper, a job shop context is considered. Machines and vehicles are both considered as constraining resources. The integrated scheduling problem is formulated as a mathematical programming model and as a constraint programming model which are compared for optimally solving a series of test problems. A commercial software (ILOG OPLStudio) was used for modeling and testing both models.

Dispatching, routing, and scheduling of two automated guided vehicles in a flexible manufacturing system

This article presents a new approach for planning the dispatching, conflict-free routing, and scheduling of automated guided vehicles in a flexible manufacturing system. The problem is solved optimally in an integrated manner, contrary to the traditional approach in which the problem is decomposed in three steps that are solved sequentially. The algorithm is based on dynamic programming and is solved on a rolling time horizon. Three dominance criteria are used to limit the size of the state space. The method finds the transportation plan minimizing the makespan (the completion time for all the tasks). Various results are discussed. A heuristic version of the algorithm is also proposed for an extension of the method to many vehicles.

Spine layout design

Abstract We present a method for designing spine layouts. A spine layout is a layout in which a main aisle is used for the movements between the work cells located on both side and for the temporary storage of work in process. Our objective is to find a layout that minimizes both the handling costs and the investment costs. Also, a rectangular layout shape is searched for. With the proposed method, a design skeleton is first constructed with a heuristic. This design skeleton is then optimally transposed into a net layout via an integer linear program. Numerical results for layouts of 12 and 22 cells are presented.

Value Analysis and Optimization of Reusable Containers at Canada Post

We analyzed the use and sharing of a logistics package, a returnable container, often out of stock, between Canada Post and its large mailing customers. Standardizing and sharing logistical packaging should bring members of a supply chain tangible benefits from productivity and efficiency gains. We determined that inventory imbalance between supply locations and demand locations caused the problem. We found that different accounting methods gave very different results in calculating the benefits. We concluded that there is always a benefit for the mailer. For Canada Post to benefit, however, the container must be returned quickly. We used a minimum-cost-flow model to confirm that the company has enough containers to satisfy demand. With better planning and control of the inventory, Canada Post can prevent disequilibrium between supply and demand.

Review: A survey of models and algorithms for emergency response logistics in electric distribution systems. Part II: Contingency planning level

This is the second part of a two-part survey of optimization models and solution algorithms for emergency response planning in electric distribution systems. The first part of the survey addresses reliability planning problems with fault considerations related to electric distribution operations. The aim of this second part is to provide a comprehensive survey of optimization models and solution methodologies for contingency planning problems related to electric distribution operations. These problems include the restoration of service, the sequencing of switching operations, the routing of repair vehicles, the scheduling of repair crews, and the assignment of crews to repair sites.

The storage location assignment and interleaving problem in an automated storage/retrieval system with shared storage

Storage location assignment and interleaving policy are two closely related problems in warehousing management. This paper addresses the location assignment and interleaving problem at the same time in an automated storage/retrieval system with duration-of-stay based shared storage policy. Based on the heuristics for single command operation, a two-step procedure is developed to solve the problem. A tabu search algorithm is proposed to improve the solution for medium and large sized problems. The computational results indicate that the tabu search algorithm is effective in finding high quality solutions, and efficient in solving large sized problems.

Review: A survey of models and algorithms for emergency response logistics in electric distribution systems. Part I: Reliability planning with fault considerations

Emergency response operations in electric distribution systems involve a host of decision-making problems at the reliability and contingency planning levels. Those operations include fault diagnosis, fault location, fault isolation, restoration, and repair. As the first of a two-part survey, this paper reviews optimization models and solution methodologies for reliability planning problems with fault considerations related to electric distribution operations. Contingency planning problems of emergency distribution response are discussed in the second part. The present paper surveys research on determining a distribution substation single-fault capacity, reallocating excess load, configuring distribution systems, partitioning a geographical area into service territories, and locating material stores and depots.

Minimizing the peak load: An alternate objective for dedicated storage policies

This paper deals with the problem of minimizing, over a fixed horizon, the peak load in single-command cycle dedicated storage policies. The daily load is the expected total time of the command cycles and the peak load is an approximation of the maximum daily processing capacity requirement. Mixed integer programming models are presented and their solutions are compared to turnover-based solutions, which are known to minimize the average load per day. It is shown that turnover-based solutions may not be suitable for the peak load criterion.

The Network of Logistics Decisions

This chapter provides a framework for business logistics decision-making by classifying logistics decisions and highlighting the relevant linkages among them. We focus on the precedence relationships among logistics decisions and on how each decision influences and is influenced by other decisions. We also identify the key information required for making various logistics decisions. The core of our framework is a three-part decision hierarchy consisting of a strategic planning level, a network level and an operations level for 48 fundamental logistics decisions. The intricacy of the linkages between the various decisions demonstrates how thoroughly the decisions are interrelated and highlights the complexity of managing logistics activities.

Decision modelling of reverse logistics systems: selection of recovery operations for end-of-life products

Many studies have shown that Reverse Logistics (RL) practices can result in substantial cost savings for companies. Since product returns are the most common aspects of RL, this research is focused on recovery operations for end-of-life products. We develop a decision model that assists the decision makers in determining the best reprocessing option of any given return. This model is based on a classification scheme of the returned products and takes into consideration various technical, economical and environmental factors. Two industrial cases demonstrate the applicability of the proposed model.