A beam search-based algorithm and evaluation of scheduling approaches for flexible manufacturing systems

This paper presents a new algorithm for the flexible manufacturing system (FMS) scheduling problem. The proposed algorithm is a heuristic based on filtered beam search. It considers finite buffer capacity, routing and sequence flexibilities and generates machine and automated guided vehicle (AGV) schedules for a given scheduling period. A new deadlock resolution mechanism is also developed as an integral part of the proposed algorithm. The performance of the algorithm is compared with several machine and AGV dispatching rules using mean flow time, mean tardiness and makespan criteria. It is also used to examine the effects of scheduling factors (i.e., machine and AGV load levels, routing and sequence flexibilities, etc.) on the system performance. The results indicate thai the proposed scheduling algorithm yields considerable improvements in system performance over dispatching rules under a wide variety of experimental conditions. © 1998 "IIE"

Implementation of Shape – Based Matching Vision System in Flexible Manufacturing System

This research is regarding the application of a vision algorithm to monitor the operations of a system in order to control the decision making concerning jobs and work pieces recognition that are to be made during system operation in real time. This paper stress on the vision algorithm used which mainly focus on the shape matching properties of the product. The main focus of this paper is on the development of an adaptive training phase of the vision system, which is the creation of a flexible Region of Interest capability that is able to adapt to various type of applications and purposes depending on the users’ requirements. Additionally, an independent stand-alone control scheme was used to enable this system to be used in various types of manufacturing configurations. The system was tested on a number of different images with various characteristics and properties to determine the reliability and accuracy of the system in respect to different conditions and combination of different training traits

Implementation of Shape – Based Matching Vision System in Flexible Manufacturing System

This research is regarding the application of a vision algorithm to monitor the operations of a system in order to control the decision making concerning jobs and work pieces recognition that are to be made during system operation in real time. This paper stress on the vision algorithm used which mainly focus on the shape matching properties of the product. The main focus of this paper is on the development of an adaptive training phase of the vision system, which is the creation of a flex- ible Region of Interest capability that is able to adapt to various type of applications and purposes depending on the users’ requirements. Additionally, an independent stand-alone control scheme was used to enable this system to be used in various types of manufacturing configurations. The system was tested on a number of different images with various characteristics and properties to determine the reliability and accuracy of the system in respect to different conditions and combination of different training traits

Cost based rescheduling approach to handle disruptions in flexible manufacturing systems

Rescheduling is an essential operating task to efficiently tackle uncertainties and unexpected events frequently encountered in today's complex and flexible manufacturing systems. The main purpose of this thesis is to develop a real time reactive scheduling methodology in order to respond to such disturbances and uncertainties in a cost efficient manner. In order to assess the impact of schedule changes, a compound rescheduling cost function is developed based on machine, job, and material related rescheduling activities. A Total Rescheduling (TR) approach based on the Filtered-Beam-Search-heuristic algorithm (FBS) is proposed to generate a prespecified number of cost efficient suboptimal schedules by using the proposed cost function in case of each disruption. Thereafter, the current schedule is replaced by the alternative schedule which causes the minimum rescheduling cost. Responding to each single disruption with TR may cause system nervousness and increase the operational cost. Hence, a partial rescheduling approach is developed by a Modified Filtered-Beam-Search-heuristic algorithm (MFBSR) in order to generate a prespecified number of sub optimal cost-efficient schedules with a lower rescheduling cost and fewer deviations than TR. In order to validate the performance of the proposed methodologies, TR and MFBSR, different case studies and experimental designs have been performed considering various disruption scenarios. The performance of the suggested methods in terms of rescheduling cost, makespan efficiency and stability have been compared with similar rescheduling and repair methods in the literature. The results reveal that the proposed methodologies could be considered as competitive methods in responding to disruptions in flexible manufacturing system

Rescheduling frequency in an FMS with uncertain processing times and unreliable machines

Cataloged from PDF version of article.This paper studies the scheduling/rescheduling problem in a multi-resource FMS environment. Several reactive scheduling policies are proposed to address the effects of machine breakdowns and processing time variations. Both off-line and on-line scheduling methods are tested under a variety of experimental conditions. The performance of the system is measured for mean tardiness and makespan criteria. The relationships between scheduling frequency and other scheduling factors are investigated. The results indicated that a periodic response with an appropriate period length would be sufficient to cope with interruptions. It was also observed that machine breakdowns have more significant impact on the system performance than processing time variations. In addition, dispatching rules were found to be more robust to interruptions than the optimum-seeking off-line scheduling algorithm. A comprehensive bibliography is also included in the paper

An analysis of FMS scheduling problem: a beam search based algorithm and comparison of scheduling schemes

Ankara : Department of Industrial Engineering and Institute of Engineering and Sciences, Bilkent Univ., 1994.Thesis (Master's) -- Bilkent University, 1994.Includes bibliographical references leaves 77-80FMS scheduling procedures in the literature can be classified into on-line and off-line schemes according to the number of scheduling decisions made at a point in time. Online scheduling attempts to schedule operations one at a time when it is needed and off-line scheduling refers to scheduling operations of available jobs for the entire scheduling period. In the literature there is no unified argument for or against either of these scheduling schemes. This research has two main objectives: development of a new scheduling scheme called quasi on-line that makes a trade-off between on-line and off-line schemes and comparison of the proposed scheme with others under various experimental conditions. A new algorithm is proposed on which the quasi online scheme is based. The proposed algorithm is a heuristic and utilizes a beam search technique. It considers finite buffer capacity, routing and sequence flexibilities and generates machine and AGV schedules for a given scheduling period. A simulation model is also developed to implement and test scheduling schemes.Karabük, SüleymanM.S

Job shop scheduling with beam search

Cataloged from PDF version of article.Beam Search is a heuristic method for solving optimization problems. It is an adaptation of the branch and bound method in which only some nodes are evaluated in the search tree. At any level, only the promising nodes are kept for further branching and remaining nodes are pruned o permanently. In this paper, we develop a beam search based scheduling algorithm for the job shop problem. Both the makespan and mean tardiness are used as the performance measures. The proposed algorithm is also compared with other well known search methods and dispatching rules for a wide variety of problems. The results indicate that the beam search technique is a very competitive and promising tool which deserves further research in the scheduling literature. Ó 1999 Elsevier Science B.V. All rights reserved

Analysis of scheduling problems in dynamic and stochastic FMS environment : comparison of rescheduling polices

Cataloged from PDF version of article.In this thesis, we study the reactive scheduling problems in a dynamic and stochastic flexible manufacturing environment. Specifically, we test different scheduling policies (how-to-schedule and when-to-schedule policies) under process time variations and machine breakdowns in a flexible manufacturing system. These policies are then compared with on-line scheduling schemes. The performance of the system is measured for the mean flowtime criterion. In this study, a beam search based algorithm is used. The algorithm allows us to generate partial or full schedules. The results indicate that on-line scheduling schemes are more robust than the off-line algorithm in dynamic and stochastic environments.Kızılışık, Ö BatuhanM.S

Multi-agent based beam search for intelligent production planning and scheduling

Production planning and scheduling is a long standing research area of great practical value, while industrial demand for production planning and scheduling systems is acute. Regretfully, most research results are seldom applied in industry because existing planning and scheduling methods can barely meet the requirements for practical applications. This paper identifies four major requirements, namely generality, solution quality, computation efficiency, and implementation difficulty, for practical production planning and scheduling methods. Based on these requirements, method, a multi-agent based beam search (MABBS), is developed. It seamlessly integrates the multi-agent system (MAS) method and beam search (BS) method into a generic multi-stage multi-level decision making (MSMLDM) model to systematically address all the four requirements within a unified framework. A script language, called EXASL, and an open software platform are developed to simplify the implementation of the MABBS method. For solving complex real-world problems, an MABBS-based prototype production planning, scheduling and execution system is developed. The feasibility and effectiveness of this study is demonstrated with the prototype system and computation experiments. © 2010 Taylor & Francis.postprin