A Petri-Net-Based Scheduling Strategy for Dual-Arm Cluster Tools With Wafer Revisiting

International audienceThere are wafer fabrication processes in cluster tools that require wafer revisiting. The adoption of a swap strategy for such tools forms a 3-wafer cyclic (3-WC) period with three wafers completed in each period. It has been shown that, by such a scheduling strategy, the minimal cycle time cannot be reached for some cases. This raises a question of whether there is a scheduling method such that the performance can be improved. To answer this question, a dual-arm cluster tool with wafer revisiting is modeled by a Petri net. Based on the model, the dynamical behavior of the process is analyzed. Then, a 2-wafer cyclic (2-WC) scheduling strategy is revealed for the first time. Cycle time analysis is conducted for the proposed strategy to evaluate its performance. It shows that, for some cases, the performance obtained by a 2-WC schedule is better than that obtained by any existing 3-WC ones. Thus, they can be used to complement each other in scheduling dual-arm cluster tools with wafer revisiting. Illustrative examples are given

Modeling of quad-station module cluster tools using petri nets

The semiconductor industry is highly competitive, and with the recent chip shortage, the throughput of wafers has become more important than ever. One of the tools that the industry has deployed is to use of quad-station modules instead of the traditional single-station modules that allow for higher throughput and better wafer consistency by processing multiple wafers at the same time and distributing work. The industry trend is to use multiple transfer chamber robots to stack the quad-station modules in a series, particularly for etch products. In this work, the quad-station cluster tool wafer movement is modeled by using Petri net as a process-bounded system. The system analysis and simulations are performed by using timed and colored Petri nets. The results are useful to deepen our understanding of the discrete-event dynamics of quad-station module cluster tools and offer the highly needed insight into their efficient and deadlock-free operation

Cluster tools with chamber revisiting-modeling and analysis using timed Petri nets

Timed Petri nets are formal models of discrete concurrent systems. Since the durations of all activities are included in the model descriptions, many performance characteristics can be derived from such models. In the case of cluster tools, net models represent the flow of wafers through the chambers of the tool as well as consecutive actions performed by the robotic transporter. Steady-state performance of cluster tools with chamber revisiting is investigated in this paper. A systematic development of detailed tool schedules, based on a general behavioral description of the tool, is proposed and is used to derive the corresponding Petri net models. Symbolic performance characteristics of the modeled tools are obtained by using place invariants, without exhaustive reachability analysis. Simple examples presented in the paper can be easily extended in many ways

Maximal good step graph methods for reducing the generation of the state space

This paper proposes an effective method based on the two main partial order techniques which are persistent sets and covering step graph techniques, to deal with the state explosion problem. First, we introduce a new definition of sound steps, the firing of which enables to extremely reduce the state space. Then, we propose a weaker sufficient condition about how to find the set of sound steps at each current marking. Next, we illustrate the relation between maximal sound steps and persistent sets, and propose a concept of good steps. Based on the maximal sound steps and good steps, a construction algorithm for generating a maximal good step graph (MGSG) of a Petri net (PN) is established. This algorithm first computes the maximal good step at each marking if there exists one, otherwise maximal sound steps are fired at the marking. Furthermore, we have proven that an MGSG can effectively preserve deadlocks of a Petri net. Finally, the change performance evaluation is made to demonstrate the superiority of our proposed method, compared with other related partial order techniques

Modeling and formal verification of probabilistic reconfigurable systems

In this thesis, we propose a new approach for formal modeling and verification of adaptive probabilistic systems. Dynamic reconfigurable systems are the trend of all future technological systems, such as flight control systems, vehicle electronic systems, and manufacturing systems. In order to meet user and environmental requirements, such a dynamic reconfigurable system has to actively adjust its configuration at run-time by modifying its components and connections, while changes are detected in the internal/external execution environment. On the other hand, these changes may violate the memory usage, the required energy and the concerned real-time constraints since the behavior of the system is unpredictable. It might also make the system's functions unavailable for some time and make potential harm to human life or large financial investments. Thus, updating a system with any new configuration requires that the post reconfigurable system fully satisfies the related constraints. We introduce GR-TNCES formalism for the optimal functional and temporal specification of probabilistic reconfigurable systems under resource constraints. It enables the optimal specification of a probabilistic, energetic and memory constraints of such a system. To formally verify the correctness and the safety of such a probabilistic system specification, and the non-violation of its properties, an automatic transformation from GR-TNCES models into PRISM models is introduced. Moreover, a new approach XCTL is also proposed to formally verify reconfigurable systems. It enables the formal certification of uncompleted and reconfigurable systems. A new version of the software ZIZO is also proposed to model, simulate and verify such GR-TNCES model. To prove its relevance, the latter was applied to case studies; it was used to model and simulate the behavior of an IPV4 protocol to prevent the energy and memory resources violation. It was also used to optimize energy consumption of an automotive skid conveyor.In dieser Arbeit wird ein neuer Ansatz zur formalen Modellierung und Verifikation dynamisch rekonfigurierbarer Systeme vorgestellt. Dynamische rekonfigurierbare Systeme sind in vielen aktuellen und zukünftigen Anwendungen, wie beispielsweise Flugsteuerungssystemen, Fahrzeugelektronik und Fertigungssysteme zu finden. Diese Systeme weisen ein probabilistisches, adaptives Verhalten auf. Um die Benutzer- und Umgebungsbedingungen kontinuierlich zu erfüllen, muss ein solches System seine Konfiguration zur Laufzeit aktiv anpassen, indem es seine Komponenten, Verbindungen zwischen Komponenten und seine Daten modifiziert (adaptiv), sobald Änderungen in der internen oder externen Ausführungsumgebung erkannt werden (probabilistisch). Diese Anpassungen dürfen Beschränkungen bei der Speichernutzung, der erforderlichen Energie und bestehende Echtzeitbedingungen nicht verletzen. Eine nicht geprüfte Rekonfiguration könnte dazu führen, dass die Funktionen des Systems für einige Zeit nicht verfügbar wären und potenziell menschliches Leben gefährdet würde oder großer finanzieller Schaden entstünde. Somit erfordert das Aktualisieren eines Systems mit einer neuen Konfiguration, dass das rekonfigurierte System die zugehörigen Beschränkungen vollständig einhält. Um dies zu überprüfen, wird in dieser Arbeit der GR-TNCES-Formalismus, eine Erweiterung von Petrinetzen, für die optimale funktionale und zeitliche Spezifikation probabilistischer rekonfigurierbarer Systeme unter Ressourcenbeschränkungen vorgeschlagen. Die entstehenden Modelle sollen über probabilistische model checking verifiziert werden. Dazu eignet sich die etablierte Software PRISM. Um die Verifikation zu ermöglichen wird in dieser Arbeit ein Verfahren zur Transformation von GR-TNCES-Modellen in PRISM-Modelle beschrieben. Eine neu eingeführte Logik (XCTL) erlaubt zudem die einfache Beschreibung der zu prüfenden Eigenschaften. Die genannten Schritte wurden in einer Softwareumgebung für den automatisierten Entwurf, die Simulation und die formale Verifikation (durch eine automatische Transformation nach PRISM) umgesetzt. Eine Fallstudie zeigt die Anwendung des Verfahren

Bilişim paylaşımı ile gerçek zamanlı üretim planlama ve kontrol sistemi tasarımı

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Dijital teknolojilerin yaygınlaşması ve hayatın her alanına girmesi ihtiyaçların bireysel kapsamda ele alınmasını sağlamış, rekabeti kişiye özgü çözüm ve ürün üretme boyutuna taşımıştır. Buna bağlı olarak, üretim sistemlerinin gelişimi de çeşitliliği artırmaya ve yönetmeye yönelik olarak devam etmektedir. Bu gelişim ve dönüşüm süreci temel taşlarından birisi kitlesel özelleştime (mass - customization) olan dördüncü sanayi devrimi (Endüstri 4.0) olarak adlandırılmıştır. Dünyanın Endüstri 4.0'a ayak uydurabilmesi için üretim ortamında çeşitliliği ve çeşitliliğe bağlı olarak meydana gelecek değişkenliği yönetebilmesi gerekmektedir. Üretim ortamında, değişkenliğin yönetilebilmesi için geliştirilen yöntemler değişkenlikleri stok tutarak veya zaman toleransları ile çalışarak yönetmektedirler. Bu durum verimliliğin azalmasına ve birim başına düşen sabit maliyetin artmasına neden olmaktadır. Çalışmada, klasik yaklaşımların olumsuz yönlerinen arındırılmış bir üretim planlama yaklaşımı ve modeli önerilmiştir. Önerilen modelin değişkenliklerden etkilenmemesi için model değişken olan miktar parametresi yerine, değişkenliklerden daha az etkilenecek olan zaman parametresi üzerine kurulmuştur. Modelde stok seviyesi yerine stoğun tükenmesine kalan süreye dikkat edilmekte, çizelgeleme sürecinde de üretimin tamamlanmasına kalan süreye ve termin tarihine göre önceliklendirme yapılmaktadır. Model zaman hedeflerine bağlı çalığtığından gerçek zamanlı bir modeldir. Üretim modeli nin gerçek zamanlı olması değişkenliklerden, miktar tabanlı yaklaşıma göre, çok az etkilenmesini sağlamıştır. Yapılan kıyaslama çalışmalarıyla gerçek zamanlı planlama sisteminin üretim ortamındaki değişkenliklerden etkilenmediği ve emniyet stoksuz ortamda, gecikmeleri azaltarak üretimin tamamlanmasını sağladığı ortaya konmuştur. Üstelik bu çıktılar O(n) zaman karmaşıklığına sahip, kısa sürede, sonlanan algoritmalarla elde edilmiştir. Modelin uygulanması algoritmik olarak kolay olsa da, gerçek zamanlı olduğundan, gerçek zamanlı olarak belirlenen işlem döngüsü içerisinde güncel stok ve üretim verisine ihtiyaç duyulmaktadır. Bu veriler Endüstri 4.0 teknolojileriyle elde edilebilen veriler olduğundan, gerçek zamanlı üretim modeli modern üretim sistemlerinde uygulanabilir bir modeldir. Modelin üretim sistemine katkısı, sistemi aynı anda hem itme hem de çekme sistemi gibi çalıştırabilmesidir. Bu sayede üretim sistemi iki biçimde de çalışabilmektedir. Verimli olan stretejiye dinamik olarak geçmek de stok maliyetinin %90'dan fazla azalmasını sağlamıştır.Spread of digital technology in every slice of life provides that the needs have been addressed within the individual scope and also it increases competition to the level of both individual solution and personal production. Accordingly, the development of production systems continues to enhance for managing the diversity. One of the milestones of this development and transformation process is mass customization called the fourth industrial revolution, Industry4.0. Enterprises should be able to overcome with the diversity and variability due to diversity in the production environment in order to keep pace with Industry 4.0. The methods improved in attempt to cope with variability in the production, are keeping inventory or working with time tolerances. In this case, efficiency decreases and overhead cost per unit increases in. A novel production planning approach and a model which is eliminated from negative aspect of conventional methods has been proposed, in this study. The proposed model is based on a time parameter less affected by the variances rather than the quantity in order to avoid being influenced by the changes. The remaining time to stock-out instead of inventory level is taken into account in this model, and prioritization is proceed according to the time remaining to complete the production and due date in the scheduling process. Thus, the model based on a time parameter is a real-time model. Being real-time provides, the model, to be affected from variances less than quantity based methods. It is presented that the real-time model is not affected by the variances in the manufacturing environment, and provides completing manufacturing process with less delays by using no safety stock. Besides, an algorithm having O(n) time complexity provides this result. Though the application of model is easy as algorithmically, the model, being real-time, requires the live inventory and production data within the determined time cycle. Because the data can be gained by the cyber-physical technologies of Industry 4.0, real-time model can be applied to modern production systems. The contribution of this model to production systems is that the model assimilates manufacturing systems as pull or push system at the same time. Selecting the productive strategy dynamically enables the decrease of more than 90% inventory cost

Contemporary Robotics

This book book is a collection of 18 chapters written by internationally recognized experts and well-known professionals of the field. Chapters contribute to diverse facets of contemporary robotics and autonomous systems. The volume is organized in four thematic parts according to the main subjects, regarding the recent advances in the contemporary robotics. The first thematic topics of the book are devoted to the theoretical issues. This includes development of algorithms for automatic trajectory generation using redudancy resolution scheme, intelligent algorithms for robotic grasping, modelling approach for reactive mode handling of flexible manufacturing and design of an advanced controller for robot manipulators. The second part of the book deals with different aspects of robot calibration and sensing. This includes a geometric and treshold calibration of a multiple robotic line-vision system, robot-based inline 2D/3D quality monitoring using picture-giving and laser triangulation, and a study on prospective polymer composite materials for flexible tactile sensors. The third part addresses issues of mobile robots and multi-agent systems, including SLAM of mobile robots based on fusion of odometry and visual data, configuration of a localization system by a team of mobile robots, development of generic real-time motion controller for differential mobile robots, control of fuel cells of mobile robots, modelling of omni-directional wheeled-based robots, building of hunter- hybrid tracking environment, as well as design of a cooperative control in distributed population-based multi-agent approach. The fourth part presents recent approaches and results in humanoid and bioinspirative robotics. It deals with design of adaptive control of anthropomorphic biped gait, building of dynamic-based simulation for humanoid robot walking, building controller for perceptual motor control dynamics of humans and biomimetic approach to control mechatronic structure using smart materials

K-State graduate catalog, 1997-1999

Course catalogs were published under the following titles: Catalogue of the officers and students of the Kansas State Agricultural College, with a brief history of the institution, 1st (1863/4); Annual catalogue of the officers and students of the Kansas State Agricultural College for, 2nd (1864/5)-4th (1868/9); Catalogue of the officers and students of the Kansas State Agricultural College for the year, 1869-1871/2; Hand-book of the Kansas State Agricultural College, Manhattan, Kansas, 1873/4; Biennial catalogue of the Kansas State Agricultural College, Manhattan, Kansas, calendar years, 1875/77; Catalogue of the State Agricultural College of Kansas, 1877/80-1896/97; Annual catalogue of the officers, students and graduates of the Kansas State Agricultural College, Manhattan, 35th (1897/98)-46th (1908/09); Catalogue, 47th (1909/10)-67th (1929/30); Complete catalogue number, 68th (1930/31)-81st (1943/1944); Catalogue, 1945/1946-1948/1949?; General catalogue, 1949/1950?-1958/1960; General catalog, 1960/1962-1990/1992. Course catalogs then split into undergraduate and graduate catalogs respectively: K-State undergraduate catalog, 1992/1994- ; K-State graduate catalog, 1993/1995-Citation: Kansas State University. (1997). K-State graduate catalog, 1997-1999. Manhattan, KS: Kansas State University.Call number: LD2668.A11711 K78

Efficient buffer design algorithms for production line profit maximization

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 447-465).A production line is a manufacturing system where machines are connected in series and separated by buffers. The inclusion of buffers increases the average production rate of the line by limiting the propagation of disruptions, but at the cost of additional capital investment, floor space of the line, and inventory. Production lines are also a special case of assembly/disassembly systems as well as closed-loop systems. This thesis makes contributions to production system profit maximization. The profit of a production line is the revenue associated with the production rate minus the buffer space cost and average inventory holding cost. We assume that machines have already been chosen and therefore our only decision variables are the buffer sizes and the loop population. The difficulties of the research come from evaluation and optimization. We improve evaluation of loop systems. The optimization problem is hard since both the objective function and the constraints are nonlinear. Our optimization problem, where we consider the nonlinear production rate constraint and average inventory cost, is new. We present an accurate, fast, and reliable algorithm for maximizing profits through buffer space optimization for production lines, and extend the algorithm to closed-loop systems and production lines with an additional maximum part waiting time constraint. A nonlinear programming approach is adopted to solve the optimization problem. Two necessary modifications are proposed to improve the accuracy of the existing loop evaluation method before optimization of loops is studied. An analytical formulation of the part waiting time distribution is developed for two-machine one-buffer lines. It is used in the profit maximization for production lines with both the production rate constraint and the maximum part waiting time constraint. Numerical experiments are provided to show the accuracy and efficiency of the proposed algorithms. Finally, a segmentation method and an additive property of production line optimization are studied. They enable us to optimize very long lines rapidly and accurately.by Chuan Shi.Ph.D