Multi-Attribute Dispatching Rules For Agv Systems With Many Vehicles

Internal transport systems using automated guided vehicles (AGVs) are widely used in many facilities such as warehouses, distribution centers and transshipment terminals. Most AGV systems use online dispatching rules to control vehicle movements. In literature, there are many types of dispatching rules such as single- and multi-attribute dispatching rules. However, a dispatching rule that is good for all cases does not exist. In this research, we study a specific type of AGV environments which has not received much attention from researchers - AGV systems with many vehicles as can be seen in airport baggage handling systems. We propose two new multi-attribute dispatching rules for this type of environment and compare their performance with that of two of the best dispatching rules in literature. Using simulation we show that the new multi-attribute dispatching rules are robust and perform very well

Online Dispatching Rules For Vehicle-Based Internal Transport Systems

On-line vehicles dispatching rules are widely used in many facilities such as warehouses to control vehicles' movements. Single-attribute dispatching rules, which dispatch vehicles based on only one parameter, are used commonly. However, multi-attribute dispatching rules prove to be better in general. In this study, we introduce new dispatching rules and evaluate their performance compared to several good dispatching rules in literature, using the experimental design of a real case study. The performance criteria are minimizing the average load waiting time while keeping the maximum load waiting time as small as possible and better utilize vehicles. The experiments show that newly introduced hybrid dispatching rule yields the best performance overall

Dynamic Scheduling of Handling Equipment at Automated Container Terminals

In this paper we consider the problem of integrated scheduling of various types of handling equipment at an automated container terminal in a dynamic environment. This means that the handling times are not known exactly beforehand and that the order in which the different pieces of equipment handle the containers need not be specified completely in advance. Instead, (partial) schedules may be updated when new information on realizations of handling times becomes available. We present an optimization based Beam Search heuristic and several dispatching rules. An extensive computational study is carried out to investigate the performance of these solution methods under different scenarios. The main conclusion is that, in our tests, the Beam Search heuristic performs best on average, but that some of the relatively simple dispatching rules perform almost as good. Furthermore, our study indicates that it is effective important to base a planning on a long horizon with inaccurate data, than to update the planning often in order to take newly available information into account.beam search;dynamic scheduling;container terminal;dispatching rules

A Simulation study of dispatching rules and rework strategies in semiconductor manufacturing

The semiconductor industry is fast paced and on the cutting edge of technology, resulting in very short life spans of semiconductor products. In order to stay competitive, manufacturers must be able to quickly adapt to produce new products, and they must achieve a high level of productivity. Two major operational components of semiconductor fabrication plants (fabs) that effect productivity are dispatching rules and rework strategies. Although prior research has been conducted independently on these two issues, the hypothesis is that the interrelationship between the dispatching rules and rework strategies has a significant effect on the productivity of the fab. Moreover, the goal is to determine which combination of widely-used dispatching rules and new and existing rework strategies results in the highest level of fab productivity. To test this hypothesis, the significance of rework is evalutated, and a four-factor experiment is conducted to determine the effect of dispatching rules, rework strategies, fab types, and rework levels on key fab performance measures. Five dispatching rules are combined with three previously studied rework strategies and the first bottleneck strategy which is developed in this study. The treatment combinations are compared based on fab performance measures including cycle time, percentage on time, work-in-process, and the XTheoretical value. Simulation models based on actual fab data are constructed to carry out the experiments. The detailed results of the experiment show that combinations of dispatching rules and rework strategies have a significant impact on fab performance measures at each rework level in both fab types. In general, two dispatching rules, rework priority and first-in-first-out, in combination with the first bottleneck rework strategy perform the best. Further analysis concludes that the rework priority dispatching rule and the first bottleneck rework strategy result in the highest level of fab performance and are most robust over alterative fab configurations

Learning dispatching rules via an association rule mining approach

This thesis proposes a new idea using association rule mining-based approach for discovering dispatching rules in production data. Decision trees have previously been used for the same purpose of finding dispatching rules. However, the nature of the decision tree as a classification method may cause incomplete discovery of dispatching rules, which can be complemented by association rule mining approach. Thus, the hidden dispatching rules can be detected in the use of association rule mining method. Numerical examples of scheduling problems are presented to illustrate all of our results. In those examples, the schedule data of single machine system is analyzed by decision tree and association rule mining, and findings of two learning methods are compared as well. Furthermore, association rule mining technique is applied to generate dispatching principles in a 6 x 6 job shop scheduling problem. This means our idea can be applicable to not only single machine systems, but also other ranges of scheduling problems with multiple machines. The insight gained provides the knowledge that can be used to make a scheduling decision in the future

PENJADWALAN 20 JOB 8 MESIN DENGAN METODE GENETIC ALGORITHM (GA)

Penelitian ini merupakan perluasan dari penelitian sebelumnya yang dilakukan oleh Iskandar (2013) dengan judul “IMPLEMENTASI PENJADWALAN MESIN JOB SHOP DENGAN METODE HEURISTIC DISPATCHING RULES DI CV BOEING TEKNIK MANDIRIâ€. Pada penelitian tersebut dilakukan penjadwalan mesin job shop dengan menggunakan metode Heuristic Dispatching Rules. Tujuan dari penelitian ini adalah untuk melakukan penjadwalan mesin job shop dengan menggunakan metode Genetic Algorithm dan membandingkan hasil yang didapat dengan hasil penjadwalan yang dilakukan Iskandar (2013) dengan metode Heuristic Dispatching Rules. Setelah dilakukan proses pengolahan data dengan menggunakan metode Genetic Algorithm selama 27 menit 33 detik, didapatkan hasil penjadwalan untuk kriteria Cmax (Completion Time Maximum) sebesar 2391,017 menit, kriteria Fmax (Flow Time Maximum) sebesar 2391,017 menit, kriteria Lmax (Lateness Maximum) sebesar -151,05 menit dan kriteria Tmax (Tardiness Maximum) sebesar 0 menit. Dibandingkan dengan hasil penjadwalan awal yang dilakukan oleh CV Boeing Teknik Mandiri, penjadwalan dengan menggunakan metode Genetic Algorithm dapat menghasilkan efisiensi sebesar 5,25% dalam kriteria Cmax serta Fmax. Untuk kriteria Lmax metode Genetic Algorithm menghasilkan efisiensi sebesar 106,2%. Kata Kunci: Penjadwalan mesin, Job Shop, Metode Heuristic Dispatching Rules, Genetic Algorithm

Solving two production scheduling problems with sequence-dependent set-up times

In today�s competitive markets, the importance of good scheduling strategies in manufacturing companies lead to the need of developing efficient methods to solve complex scheduling problems. In this paper, we studied two production scheduling problems with sequence-dependent setups times. The setup times are one of the most common complications in scheduling problems, and are usually associated with cleaning operations and changing tools and shapes in machines. The first problem considered is a single-machine scheduling with release dates, sequence-dependent setup times and delivery times. The performance measure is the maximum lateness. The second problem is a job-shop scheduling problem with sequence-dependent setup times where the objective is to minimize the makespan. We present several priority dispatching rules for both problems, followed by a study of their performance. Finally, conclusions and directions of future research are presented.Production-scheduling, set-up times, priority dispatching rules

A Simulation of composite dispatching rules, CONWIP and push lot release in semiconductor fabrication

This paper evaluates dispatching rules and order release policies in two fabs representing two wafer fabrication modes, namely, ASIC and low-mix high-volume production. Order release policies were fixed-interval (push) release, and constant work-in-process, CONWIP (pull) policy. Following rigorous fab modeling and statistical analysis, new composite dispatching rules were found to be robust for system cycle time and due-date adherence measures, in both production modes

An Analytical Review Of The Relationship Between Dispatching Rules And Performance For Dynamic Scheduling In An Identical Parallel Machine Environment

This report consist an analytical review of the relationship between dispatching rules and performance measure for dynamic scheduling problem. The review is focused on an identical parallel machine environment. The dynamic issues that considered are machine breakdown and operator absent. The main objective of the research work is to analyze the performance of dispatching rules against different performance measures. Five suitable dispatching rules that considering the priority of weighs which called weighted dispatching rules is used. Dispatching rule is used to specify which job should be selected for work next from among a queue of jobs. Simulation model is developed based on real world case study using WITNESS software. Than the experiment model is developed by adding disturbance parameter likes machine breakdown and operator absent. The experiment is done to determine the effects of the disturbance parameter to the performance of dispatching rules used. The experiment result is proved by analysis of variance (ANOVA). From the experiment analysis, the different dispatching rules provide the different result of performance measures. Dispatching rules can be used to determine the minimum throughput time, minimum lateness and earliness of the jobs. The performance of dispatching rules also depends on disturbance parameter that used in the experiment model and the quantity of jobs required