Modelling and condition-based control of a flexible and hybrid disassembly system with manual and autonomous workstations using reinforcement learning

Remanufacturing includes disassembly and reassembly of used products to save natural resources and reduce emissions. While assembly is widely understood in the field of operations management, disassembly is a rather new problem in production planning and control. The latter faces the challenge of high uncertainty of type, quantity and quality conditions of returned products, leading to high volatility in remanufacturing production systems. Traditionally, disassembly is a manual labor-intensive production step that, thanks to advances in robotics and artificial intelligence, starts to be automated with autonomous workstations. Due to the diverging material flow, the application of production systems with loosely linked stations is particularly suitable and, owing to the risk of condition induced operational failures, the rise of hybrid disassembly systems that combine manual and autonomous workstations can be expected. In contrast to traditional workstations, autonomous workstations can expand their capabilities but suffer from unknown failure rates. For such adverse conditions a condition-based control for hybrid disassembly systems, based on reinforcement learning, alongside a comprehensive modeling approach is presented in this work. The method is applied to a real-world production system. By comparison with a heuristic control approach, the potential of the RL approach can be proven simulatively using two different test cases

Analysis and improvement of a bottling line using a simulation modelling approach

This project thesis is focused on the study of a bottling production line using a modelling simulation method, through which we analyse the inefficiencies and then improve their performance. Moreover, the line is also analysed thorugh an analytic approach applying a formula to optimize the buffer sizing. The two approachs are compared to highlight the differences

The Project Scheduling Problem with Non-Deterministic Activities Duration: A Literature Review

Purpose: The goal of this article is to provide an extensive literature review of the models and solution procedures proposed by many researchers interested on the Project Scheduling Problem with nondeterministic activities duration. Design/methodology/approach: This paper presents an exhaustive literature review, identifying the existing models where the activities duration were taken as uncertain or random parameters. In order to get published articles since 1996, was employed the Scopus database. The articles were selected on the basis of reviews of abstracts, methodologies, and conclusions. The results were classified according to following characteristics: year of publication, mathematical representation of the activities duration, solution techniques applied, and type of problem solved. Findings: Genetic Algorithms (GA) was pointed out as the main solution technique employed by researchers, and the Resource-Constrained Project Scheduling Problem (RCPSP) as the most studied type of problem. On the other hand, the application of new solution techniques, and the possibility of incorporating traditional methods into new PSP variants was presented as research trends. Originality/value: This literature review contents not only a descriptive analysis of the published articles but also a statistical information section in order to examine the state of the research activity carried out in relation to the Project Scheduling Problem with non-deterministic activities duration.Peer Reviewe

Matrix-structured manufacturing systems : Simulation performance analysis as a successor to dedicated production lines

ABSTRACT: Growing demand for product variations has led to mass personalized production in the manufacturing industry. Many manufacturers still use traditional product line configurations based on a dedicated manufacturing system (DMS). This system is not considered compatible with ongoing manufacturing trend. The challenge is finding a manufacturing system that would combine high productivity with the flexibility to produce multiple types of products. To this end, a matrix-structured manufacturing system (MMS) was developed. In addition, a reconfigurable manufacturing system (RMS) has been researched as a replacement for the DMS. The problem is that these two systems are not compared performance-wise. Moreover, it has not been investigated in which cases MMS or RMS would provide better compatibility to replace the product line. This Master’s thesis aims to answer how MMS and RMS perform compared to DMS regarding productivity and flexibility. Furthermore, it is evaluated in which manufacturing scenarios MMS provide better performance than RMS and DMS. Finally, thesis seeks to answer what are the benefits and disadvantages of MMS compared to RMS and DMS. To fill this research gap in knowledge, thesis presents a discrete-event simulation experiment. Thesis follows principles of experimental research with deductive approach and collects quantitative data from manufacturing simulation. Theoretical review is conducted focusing on characteristics and background of manufacturing systems. This information is utilized when designing and constructing simulation experiment. Simulation results are evaluated from the following performance perspectives: efficiency, effectiveness, delivery, and operational flexibility. These are based on com mon manufacturing competitive priorities. It was discovered that MMS provides highest workstation utilization and overall production effectiveness. RMS performed best in efficiency, delivery, and flexibility perspective. Flexibility was measured with production scenarios which involved simulated production disturbances and changes in number of products in system. It was found that production flow in MMS is declined significantly when number of products in system increases to high level. DMS resulted lowest in every scenario and performance view. The problem is the inflexibility to alternative production routes making it sensitive to production disruptions. Both MMS and RMS provided notably better productivity and flexibility performance than DMS. Based on the results, MMS is recommended for production scenarios where product variety extends over product family with importance in production customization and high station utilization. RMS is suitable for scenarios where delivery performance with flexibility is crucial.TIIVISTELMÄ: Kasvava määrä tuotevarianttien kysynnälle johtanut massapersonointiin massatuotannossa. Monet teollisuuden yritykset käyttävät yhä perinteisiä tuotelinjakonfiguraatioita, jotka kuuluvat kiinteisiin työasemiin perustuviin tuotantojärjestelmiin (DMS). Kuitenkaan näiden ei nähdä soveltuvan käynnissä olevaan tuotantotrendiin. Haasteena on löytää valmistusjärjestelmä, jossa korkea tuottavuus yhdistyisi joustavuuteen tuottaa monenlaisia tuotteita. Tätä varten kehitettiin matriisirakenteinen valmistusjärjestelmä (MMS). Lisäksi uudelleen konfiguroitavaa valmistusjärjestelmää (RMS) tutkitaan korvaajaksi perinteiselle tuotantolinjalle. Ongelmana on, että näitä kahta järjestelmää ei ole vertailtu suorituskyvyllisesti. Lisäksi ei ole tutkittu, missä tapauksissa MMS tai RMS olisi parempi vaihtoehto perinteisen tuotelinjan korvaajaksi. Tämän Pro gradu -tutkielman tavoitteena on vastata kysymykseen, miten MMS ja RMS suoriutuvat verrattuna perinteiseen tuotelinjaan tarkasteltaessa järjestelmän tuottavuutta ja joustavuutta. Lisäksi arvioidaan, missä valmistusskenaarioissa MMS tarjoaa parempaa suorituskykyä kuin RMS ja DMS. Viimeisenä tutkielmassa pyritään vastaamaan mitkä ovat MMS:n edut ja haitat verrattuna RMS:ään ja DMS:ään. Tutkimusaukon täyttämiseksi opinnäytetyö esittää diskreetti tapahtumapohjaisen simulaation. Tutkielma noudattaa kokeellisen tutkimuksen periaatteita deduktiivisella lähestymistavalla, jossa kerätään kvantitatiivista dataa tuotantosimulaatiosta. Teoreettinen katsaus keskittyy valmistusjärjestelmien ominaispiirteisiin sekä taustaan. Tätä tietoa hyödynnetään suunniteltaessa ja rakentaessa simulaatiokoetta. Simuloinnin tuloksia arvioidaan seuraavista suorituskyvyn näkökulmista: hyötysuhde, tehokkuus, toimituskyky ja järjestelmän joustavuus. Nämä perustuvat yleisiin tuotannon kilpailuprioriteetteihin. Tutkielmassa havaittiin, että MMS tarjoaa korkeimman työaseman käyttöasteen ja tuotantojärjestelmän tehokkuuden. RMS suoriutui parhaiten hyötysuhteen, toimituskyvyn ja joustavuuden näkökulmista. Joustavuutta mitattiin tuotantoskenaarioilla, joissa simuloitiin tuotantohäiriöitä ja muutoksia yhtäaikaisesti valmistettavien tuotteiden määrässä tuotannossa. Tutkielmassa todettiin, että MMS:n tuotantovirta hidastuu merkittävästi, kun valmistettavien tuotteiden määrä järjestelmässä kasvaa korkealle tasolle. DMS suoriutui huonoiten kaikissa skenaarioissa ja suorituskykynäkökulmista. Tämä johtuu joustamattomuudesta vaihtoehtoisille tuotereiteille tekien siitä herkän häiriöille. Molemmat sekä MMS että RMS tarjosivat huomattavasti paremman tuottavuus- ja joustavuuskyvyn kuin DMS. Tutkimuksen tuloksiin perustuen MMS:ää suositellaan tuotantoskenaarioihin, joissa tuotevalikoima ulottuu myös yli tuoteperheen, ja jossa tuotannon kustomointikyky ja korkea työasemien käyttöaste on tärkeää. RMS sopii skenaarioihin, joissa tuotannon toimituskyky ja joustavuus on ratkaisevan tärkeää

Strict Minimal Siphon-Based Colored Petri Net Supervisor Synthesis for Automated Manufacturing Systems With Unreliable Resources

Various deadlock control policies for automated manufacturing systems with reliable and shared resources have been developed, based on Petri nets. In practical applications, a resource may be unreliable. Thus, the deadlock control policies proposed in previous studies are not applicable to such applications. This paper proposes a two-step robust deadlock control strategy for systems with unreliable and shared resources. In the first step, a live (deadlock-free) controlled system that does not consider the failure of resources is derived by using strict minimal siphon control. The second step deals with deadlock control issues caused by the failures of the resources. Considering all resource failures, a common recovery subnet based on colored Petri nets is proposed for all resource failures in the Petri net model. The recovery subnet is added to the derived system at the first step to make the system reliable. The proposed method has been tested using an automated manufacturing system deployed at King Saud University.publishedVersio

Financing and Deploying Automated Freight Systems

New technologies are bringing Automated Freight Systems (AFS), which aim to reduce congestion, mitigate environmental impacts and enhance public safety, to fruition. The financing and deployment issues of AFS differ from other Intelligent Transport System applications. This chapter briefly introduces major concepts of AFS. The financing strategies for these concepts are discussed, in which the government subsidies play an important role through the use of public-private partnership. Economies of scale and externalities of the current and new systems are discussed. In the discussion of the deployment of AFS, it is suggested that deployment schemes are highly correlated with financing strategies.Automated Freight, Pipeline, Trucks, Rail

A simulation modelling approach to improve the OEE of a bottling line

This dissertation presents a simulation approach to improve the efficiency performance, in terms of OEE, of an automated bottling line. A simulation model of the system is created by means of the software AnyLogic; it is used to solve the case. The problems faced are a sequencing problem related to the order the formats of bottles are processed and the buffer sizing problem. Either theoretical aspects on OEE, job sequencing and simulation and practical aspects are presented

Deep Space Network information system architecture study

The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control