Analysis of Job Shop problem through an expert system

[ENG] In the present work it is defined a new methodology, based on Experts Systems, for sequencing in Job Shop Environments. This work is developed in two phases. In the first one, the different techniques used are defined. In the second one, the necessary statistical tests are executed. The results show that the new technique don’t produce an optimal result every single time; but in few seconds, this technique can find sub-optimal solutions with an approximation of 92.95 % and 73.88%, to the optimal solution, in the variables of total process time (makespan) and total idle time, respectively. Finally, the new technique is compared with other similar techniques

Algorítmo de búsqueda de entorno variable para minimizar la tardanza total ponderada en una máquina de procesamiento por lotes

En este artículo se presentan los resultados de una investigación desarrollada para resolver el problema de programación de producción, en un sistema en el cual el objetivo principal es cumplir con las fechas de entrega. Cada trabajo está descrito por su tiempo de proceso, su fecha de liberación, su fecha de entrega, su importancia relativa con respecto a los otros trabajos y su peso. La máquina de procesamiento por lotes (MPL) puede procesar múltiples trabajos simultáneamente, siempre y cuando el peso total de éstos no exceda la capacidad máxima de la máquina. El tiempo de proceso del lote es el tiempo máximo de proceso de los trabajos que lo componen. De la misma forma, el tiempo de liberación de un lote es el tiempo máximo de liberación de los trabajos que lo componen. Teniendo en cuenta que el problema es NP–Completo, en este artículo se propone un heurístico de búsqueda de entorno variable para minimizar la tardanza total ponderada en una MPL. Los experimentos computacionales realizados para establecer la calidad de las soluciones encontradas demostraron que, en un tiempo de cómputo restringido a un máximo de 30 minutos, el heurístico propuesto encuentra soluciones considerablemente mejores que las encontradas mediante la implementación de un modelo de programación entera mixta, disponible en la literatura e implementado en un software comercial de optimización.This paper presents the results of a research project conducted to solve a production sche-duling problem observed in a system in which meeting customer due dates is the primary objective. Each job to be scheduled is defined by its processing time, ready time, due date, weight and size. The Batch Processing Machine (BPM) can process several jobs simulta-neously as a batch as long as its capacity is not violated. The processing time of a batch is the largest processing time among the jobs in the batch, and the batch ready time is the largest ready time among the jobs in the batch. Given that the problem is NP-hard we propose a Variable Neighborhood Search (VNS) heuristic to minimize the total weighted tardiness on a single BPM. The computational experiments conducted to assess the quality of the solutions found show that in a computational time restricted to a maximum of 30 minutes, the proposed heuristic finds solutions considerably better than the solutions obtained after implementing a mixed integer programming model available in the literature in a commercial solver

Metodología integral soportada en simulación para el mejoramiento de sistemas de producción job shop. aplicaciones en pymes metalmecánicas

En el municipio de Caldas (Colombia), uno de los sectores estratégicos para la economía regional es el de las pymes metalmecánicas; de hecho, este sector, según estadísticas del DANE a 2005, participa aproximadamente con el 31% de los establecimientos industriales del departamento y con un 29% del empleo industrial, además tiene vocación exportadora hacia países andinos. Sin embargo, estudios preliminares realizados al 57% del universo empresarial de este sector (no incluye microempresas ni famiempresas), demuestran serias falencias de tipo estructural (tecnologías, procesos, instalaciones) e infraestructural (programación de la producción, sistemas de calidad, etc.) en los sistemas de producción de estas organizaciones. Mediante este artículo se espera divulgar entre la comunidad académica los resultados obtenidos al aplicar una metodología integral de mejoramiento del sistema de producción en una empresa piloto del sector. A partir de la definición y ponderación de las prioridades competitivas que la empresa debe alcanzar, y siguiendo la metodología universalmente aceptada en estudios de simulación discreta, se propone un marco de experimentación para mejorar los niveles alcanzados por el sistema en dichas prioridades empleando técnicas de bifurcación secuencial, diseño factorial en experimentación y superficies de respuesta. Al final se presentan las mejoras alcanzadas en las prioridades competitivas en términos de un índice de efectividad (IE) del sistema de producción de una empresa piloto estudiada al pasar éste de 1,84 a 2,46.Metalworking companies represent one of the strategic sectors in the regional economy of the Caldas department in Colombia; in fact, this sector is involved in 31% of the department’s industrial establishments and 29% of industrial employment according to DANE (Colombian State Statistical Department) statistical data from 2005. The sector also exports to Andean countries. However, preliminary studies conducted with 57% of the entrepreneurs from this sector (excluding micro companies and family businesses) have revealed serious structural (technology, processing, installations) and infrastructure weaknesses (production planning, quality systems) in these organisations’ production systems. It is hoped that this paper will lead to disseminating the results amongst the academic community of implementing a comprehensive methodology for improving the production system of a pilot company from this particular sector. An experimental framework for improving the levels reached by the system regarding such priorities is proposed following universally accepted methodology in discrete simulation studies; it proposes using sequential bifurcation, factorial design and response surface experimentation based on defining and weighting the competing priorities which the company should achieve. The improvements in the pilot company’s production system priorities are presented in terms of an effectiveness index (EI) which rose from 1.84 to 2.46 by the end of the study

Variable Neighborhood Search for Parallel Machines Scheduling Problem with Step Deteriorating Jobs

In many real scheduling environments, a job processed later needs longer time than the same job when it starts earlier. This phenomenon is known as scheduling with deteriorating jobs to many industrial applications. In this paper, we study a scheduling problem of minimizing the total completion time on identical parallel machines where the processing time of a job is a step function of its starting time and a deteriorating date that is individual to all jobs. Firstly, a mixed integer programming model is presented for the problem. And then, a modified weight-combination search algorithm and a variable neighborhood search are employed to yield optimal or near-optimal schedule. To evaluate the performance of the proposed algorithms, computational experiments are performed on randomly generated test instances. Finally, computational results show that the proposed approaches obtain near-optimal solutions in a reasonable computational time even for large-sized problems

Aproximações heurísticas para um problema de escalonamento do tipo flexible job-shop

Mestrado em Engenharia e Gestão IndustrialEste trabalho aborda um novo tipo de problema de escalonamento que pode ser encontrado em várias aplicações do mundo-real, principalmente na indústria transformadora. Em relação à configuração do shop floor, o problema pode ser classificado como flexible job-shop, onde os trabalhos podem ter diferentes rotas ao longo dos recursos e as suas operações têm um conjunto de recursos onde podem ser realizadas. Outras características de processamento abordadas são: datas possíveis de início, restrições de precedência (entre operações de um mesmo trabalho ou entre diferentes trabalhos), capacidade dos recursos (incluindo paragens, alterações na capacidade e capacidade infinita) e tempos de setup (que podem ser dependentes ou independentes da sequência). O objetivo é minimizar o número total de trabalhos atrasados. Para resolver o novo problema de escalonamento proposto um modelo de programação linear inteira mista é apresentado e novas abordagens heurísticas são propostas. Duas heurísticas construtivas, cinco heurísticas de melhoramento e duas metaheurísticas são propostas. As heurísticas construtivas são baseadas em regras de ordenação simples, onde as principais diferenças entre elas dizem respeito às regras de ordenação utilizadas e à forma de atribuir os recursos às operações. Os métodos são designados de job-by-job (JBJ), operation-by-operation (OBO) e resource-by-resource (RBR). Dentro das heurísticas de melhoramento, a reassign e a external exchange visam alterar a atribuição dos recursos, a internal exchange e a swap pretendem alterar a sequência de operações e a reinsert-reassign é focada em mudar, simultaneamente, ambas as partes. Algumas das heurísticas propostas são usadas em metaheurísticas, nomeadamente a greedy randomized adaptive search procedure (GRASP) e a iterated local search (ILS). Para avaliar estas abordagens, é proposto um novo conjunto de instâncias adaptadas de problemas de escalonamento gerais do tipo flexible job-shop. De todos os métodos, o que apresenta os melhores resultados é o ILS-OBO obtendo melhores valores médios de gaps em tempos médios inferiores a 3 minutos.This work addresses a new type of scheduling problem which can be found in several real-world applications, mostly in manufacturing. Regarding shop floor configuration, the problem can be classified as flexible job-shop, where jobs can have different routes passing through resources and their operations have a set of eligible resources in which they can be performed. The processing characteristics addressed are release dates, precedence constraints (either between operations of the same job or between different jobs), resources capacity (including downtimes, changes in capacity, and infinite capacity), and setup times, which can be sequence-dependent or sequence-independent. The objective is to minimise the total number of tardy jobs. To tackle the newly proposed flexible job-shop scheduling problem (FJSP), a mixed integer linear programming model (MILP) is presented and new heuristic approaches are put forward. Three constructive heuristics, five improvement heuristics, and two metaheuristics are proposed. The constructive heuristics are based on simple dispatching rules, where the main differences among them concern the used dispatching rules and the way resources are assigned. The methods are named job-by-job (JBJ), operation-by-operation (OBO) and resource-by-resource (RBR). Within improvement heuristics, reassign and external exchange aim to change the resources assignment, internal exchange and swap intend changing the operations sequence, and reinsert-reassign is focused in simultaneously changing both parts. Some of the proposed heuristics are used within metaheuristic frameworks, namely greedy randomized adaptive search procedure (GRASP) and iterative local search (ILS). In order to evaluate these approaches, a new set of benchmark instances adapted from the general FJSP is proposed. Out of all methods, the one which shows the best average results is ILS-OBO obtaining the best average gap values in average times lower than 3 minutes

A study on flexible flow shop and job shop scheduling using meta-heuristic approaches

Scheduling aims at allocation of resources to perform a group of tasks over a period of time in such a manner that some performance goals such as flow time, tardiness, lateness, and makespan can be minimized. Today, manufacturers face the challenges in terms of shorter product life cycles, customized products and changing demand pattern of customers. Due to intense competition in the market place, effective scheduling has now become an important issue for the growth and survival of manufacturing firms. To sustain in the current competitive environment, it is essential for the manufacturing firms to improve the schedule based on simultaneous optimization of performance measures such as makespan, flow time and tardiness. Since all the scheduling criteria are important from business operation point of view, it is vital to optimize all the objectives simultaneously instead of a single objective. It is also essentially important for the manufacturing firms to improve the performance of production scheduling systems that can address internal uncertainties such as machine breakdown, tool failure and change in processing times. The schedules must meet the deadline committed to customers because failure to do so may result in a significant loss of goodwill. Often, it is necessary to reschedule an existing plan due to uncertainty event like machine breakdowns. The problem of finding robust schedules (schedule performance does not deteriorate in disruption situation) or flexible schedules (schedules expected to perform well after some degree of modification when uncertain condition is encountered) is of utmost importance for real world applications as they operate in dynamic environments

Scheduling and Resource Efficiency Balancing. Discrete Species Conserving Cuckoo Search for Scheduling in an Uncertain Execution Environment

The main goal of a scheduling process is to decide when and how to execute each of the project’s activities. Despite large variety of researched scheduling problems, the majority of them can be described as generalisations of the resource-constrained project scheduling problem (RCPSP). Because of wide applicability and challenging difficulty, RCPSP has attracted vast amount of attention in the research community and great variety of heuristics have been adapted for solving it. Even though these heuristics are structurally different and operate according to diverse principles, they are designed to obtain only one solution at a time. In the recent researches on RCPSPs, it was proven that these kind of problems have complex multimodal fitness landscapes, which are characterised by a wide solution search spaces and presence of multiple local and global optima. The main goal of this thesis is twofold. Firstly, it presents a variation of the RCPSP that considers optimisation of projects in an uncertain environment where resources are modelled to adapt to their environment and, as the result of this, improve their efficiency. Secondly, modification of a novel evolutionary computation method Cuckoo Search (CS) is proposed, which has been adapted for solving combinatorial optimisation problems and modified to obtain multiple solutions. To test the proposed methodology, two sets of experiments are carried out. Firstly, the developed algorithm is applied to a real-life software development project. Secondly, the performance of the algorithm is tested on universal benchmark instances for scheduling problems which were modified to take into account specifics of the proposed optimisation model. The results of both experiments demonstrate that the proposed methodology achieves competitive level of performance and is capable of finding multiple global solutions, as well as prove its applicability in real-life projects

Metodología multiobjetivo basada en un comportamiento evolutivo para programar sistemas de producción flexible job shop. Aplicaciones en la industria metalmecánica

El objeto de estudio de la presente tesis es el taller de trabajo flexible en el sector metalmecánico. El problema de investigación se derivó a partir de la búsqueda sistemática de metodologías y algoritmos para programar sistemas productivos; se identificaron configuraciones de variables de proceso no abordadas en la literatura, lo que se considera un vacío en el conocimiento. Consecuente con lo anterior, se diseñó una metodología basada en un algoritmo evolutivo para programar los pedidos en un taller de trabajo flexible, con restricciones de tiempo, secuencia, mantenimiento, liberación de pedidos, disponibilidad, consumo y costo de recurso que varía en el tiempo, con el fin de minimizar tiempo de proceso y costo de producción; incluyó un proceso de ponderación para escoger la mejor secuencia de programación. Como aporte principal se propone una metodología novedosa que al compararla con otras metodologías encontradas en la bibliografía, demostró mejoras mayores al 10% en makespan y costo total del recurso consumidoAbstract: The study object of the present thesis is the flexible job shop in the metal mechanic sector. The research problem was derived from the systematic search of methodologies and algorithms to schedule production systems; configurations of process variables not addressed in the literature were identified, which is considered an empty in knowledge. Consequent with previous, a methodology was designed based on an evolutionary algorithm to schedule orders in a flexible job shop, with time restrictions, sequence, maintenance, liberation of orders, availability, consumption and cost of resource that varies in time, in order to minimize processing time and cost of production; it includes a weighting process to choose the best programming sequence. As main contribution a novel methodology was proposed which, compared with other methodologies found in the literature, it demonstrated greater improvements to 10% in Makespan and total cost of consumed resourceDoctorad

Support for operational production planning and resource management in small and medium-sized enterprises

У оквиру ове докторске дисертације истражена је подршка процесу оперативног планирања производње и управљања ресурсима у малим и средњим предузећима. Посебан фокус стављен је на активности распоређивања и терминирања, који чине најкомплексније планерске проблеме на оперативном нивоу. Мала и средња предузећа (МСП) представљају доминантну категорију предузећа у Републици Србији, а и шире у земљама Европске уније (ЕУ-28). МСП представљају најучесталију категорију и у производном сектору Републике Србије и ЕУ. Производња према поруџбини и жељама купаца и процесна организација производње представљају најзаступљенији облик производње у МСП, а Job Shop проблем распоређивања је саставни део процеса оперативног тј. краткорочног планирања производње у овој врсти предузећа. Имајући у виду да оперативно планирање непосредно претходи активностима трансформације предмета рада и стварању додатне вредности, посебан нагласак дат је на управљању производним ресурсима у процесу производње (сировине, материјали и други предмети рада, машине, алати и остала средства за рад, људски ресурси, време према коме се активности планирања реализују, новац тј. капитал, информације, тржиште). У дисертацији се даје преглед основних теоријских појмова: мала и средња предузећа, подршка МСП, процес управљања у МСП, планирање производње и управљање ресурсима. Поред тога, посебно је дефинисан процес оперативног планирања производње, са аспекта активности из којих се састоји. Распоређивање и терминирање у производњи су препознати као једни од најчешћих проблема из домена оперативног планирања производње. Они подразумевају распоређивање производа на машине, тј. проналажење редоследа радних задатака или послова који треба да се изврше на свакој од више машина. Поред тога обухватају и дефинисање временских термина за почетак и завршетак појединих производних активности. Циљ прављења адекватног распореда, тј. редоследа операција, произилази из ограничења капацитета производних ресурса (радници, машине и друга производна опрема).This dissertation proposal explores the support for operational production planning in small and medium-sized enterprises (SME). Special emphasis is put on scheduling activities that represent the most complex planning problem at the operational level. SMEs are the predominant category of enterprises both in Serbia and in the European Union (EU-28). SMEs also present the most frequent type of enterprises in the manufacturing sector in Serbia and the EU-28 countries. Make-to- Order (MTO) production and production organization according to the process are the most common forms of production in small and medium-sized manufacturing enterprises, and the Job Shop scheduling problem is an integral part of operational, i.e. short-term production planning in this group of enterprises. Bearing in mind that operational production planning is directly and closely related to the transformation of raw materials and semi-manufactured goods, which creates and adds value, we emphasize the need to manage manufacturing resources adequately in the production process (materials, machines, tools, labour force, time, money - i.e. capital, information, market). The dissertation proposal presents the overview of basic theoretical concepts: small and medium-sized enterprises, support for SMEs, the process of management in SMEs, production planning, and resource management. Additionally, the process of operational production planning is defined from the aspect of activities it encompasses. Production scheduling problems are observed as one of the most frequent issues in the field of operational production planning. They include scheduling products to machines, i.e. finding the sequence of tasks and activities that need to be performed on each of available machines. Also, it includes determination of time slots for the beginning and completion of certain manufacturing activities. The aim of an adequate schedule, i.e. sequence of operations, arises from the capacity constraints of production resources (workers, machines and other production equipment). Therefore, special attention is dedicated to the improvement of scheduling activities, to make adequate operational planning process which is harmonised with the needs of a particular enterprise