Modele dayalı öngörülü ağ baglantılı kontrol sistemi

Ağ bağlantılı kontrol sistemlerinin endüstriyel alandaki ihtiyaçları karşılayan çeşitli avantajları vardır. Uygulamalar karmaşıklaştıkça ağ bağlantılı kontrol sistemlerinin kullanımının kaçınılmaz hale gelmesi beklenmektedir. Ancak haberleşme ağının neden olduğu belirsiz gecikmeler ve veri kayıpları, çevrim dinamiklerini olumsuz etkilemekte ve kararsızlıklara sebep olabilmektedir. Bu çalışmada veri gecikmesi ve kaybı ile algılayıcı gürültüsü gibi ideal olmayan durumlarda da çalışabilen bir ağ bağlantılı kontrol sistem mimarisi tanıtılacaktır. Yapı olarak, kontrol edilen sistemin bir modelinin, kontrolörün de içinde bulundurulması sayesinde haberleşme ağının neden olduğu kayıplar ve gecikmelerin kompanze edilmesi sağlanmaktadır. Model sayesinde, öngörülmüş kontrol çıktıları hesaplanıp haberleşme gerçekleşemediği durumlarda sistemin bunlarla kontrolü sayesinde yüksek derecede veri kayıplarında bile kararsızlıg˘ın önlenmesi amaçlanmaktadır. Önerilen yöntemde kontrol edilen sistemin durumu ile kontrolör içindeki modelin durumunun eşleştirilmesi önemli bir problem haline gelmektedir. Bu yapı bilgisayar, kontrol ve haberleşme dallarının özelliklerini kullanarak her birinin eksiğini tamamlamaya yönelik olup, çeşitli kontrol metotlarıyla kullanılmaya açıktır. Önerilen Modele Dayalı Öngörülü¨ Ağ Bağlantılı Kontrol Sistemi (MODOAKOS) benzetim yolu ile bir doğru akım motorunun kontrolüne uygulanmıştır. Normal ağ bağlantılı kontrol sistemin kararlılığını bozucu gecikme ve kayıplar varken bile önerilen sistem altında kontrol uygulandığında kararlı çalışma bozulmamış ancak referans girişine olan cevabın geciktiği gözlenmiştir

Exploring the Evolution of Node Neighborhoods in Dynamic Networks

Dynamic Networks are a popular way of modeling and studying the behavior of evolving systems. However, their analysis constitutes a relatively recent subfield of Network Science, and the number of available tools is consequently much smaller than for static networks. In this work, we propose a method specifically designed to take advantage of the longitudinal nature of dynamic networks. It characterizes each individual node by studying the evolution of its direct neighborhood, based on the assumption that the way this neighborhood changes reflects the role and position of the node in the whole network. For this purpose, we define the concept of \textit{neighborhood event}, which corresponds to the various transformations such groups of nodes can undergo, and describe an algorithm for detecting such events. We demonstrate the interest of our method on three real-world networks: DBLP, LastFM and Enron. We apply frequent pattern mining to extract meaningful information from temporal sequences of neighborhood events. This results in the identification of behavioral trends emerging in the whole network, as well as the individual characterization of specific nodes. We also perform a cluster analysis, which reveals that, in all three networks, one can distinguish two types of nodes exhibiting different behaviors: a very small group of active nodes, whose neighborhood undergo diverse and frequent events, and a very large group of stable nodes

Model based predictive networked control systems /

Advantages of networked control systems (NCS) are very diverse and NCS’s address many of the demands of industrial development. As more and more sophisticated problems arise, networked control systems will not only become a convenience or an advantage but they will become an indispensable necessity. However usage of networked control systems introduces different forms of timedelay uncertainty in closed-loop system dynamics. These time delays are caused by the time sharing of the communication medium as well as computation time necessary for control algorithms and digital to analog conversions and have a destabilizing effect on system performance. Computational power of computers has increased dramatically; networks speed has also increased. Although both the network and computer architectures have tended to improve throughput over time, their real-time characteristics have not evolved to match the requirements from a control point of view. New control methodologies that cope with these factors and even take advantage of them are emerging. This work first examines some current methods in design and implementation of networked control systems that try to improve existing methods. Then a novel networked control system architecture that runs under non ideal network conditions with packet loss and noise is introduced. The proposed network control system architecture uses a model to predict the plant states into the future and generate corresponding control signals, then an array of the predicted control signals is sent to the actuator node side of the NCS rather than a single control signal like in basic networked control systems. This array of signals can control the plant if they are applied consecutively with sampling time intervals. However this is not the case under ideal conditions, where the network is lossless. Only the first control signal in each array is applied to the plant as a newer packet arrives every sampling period. The remainder of the array of predicted control signals is only used when packet loss occurs. This approach enables the system to be controlled in a pre-simulated manner and stability can be maintained even with high packet loss probabilities. Synchronization of the network elements becomes a major problem in this approach since models are involved. Synchronizing the actuator and controller nodes is done by an algorithm that can identify control signal arrays that have trustable information. Also the controller has a distributed architecture; some parts of the controller are implemented in the sensor node. This is to ensure that sensor to controller synchronization is not broken. The proposed model based predictive networked control system architecture was tested on a DC motor. The effects of packet loss were examined to reveal that the packet loss does not cause destabilization of the system, when packet loss occurs and the control packet cannot be sent to the actuator node, which prevents the changes in reference from being applied to the plant. The overall effect is the retardation of the response of the plant to the reference. Effects of noise are also examined. Under low packet loss conditions noise does not have an unusual effect on the system but when packet loss increases noise cannot be tolerated because the feedback loop is interrupted due to packet loss. Finally a method for determining the number of predictions to be made at the controller node (the prediction horizon) is suggested. The systems settling time is examined and the settling time is taken as the basis for the prediction horizon. The transmission of a single array of control signals from the controller node to the actuator node will enable the system to reach the desired reference. However this approach is only valid for open loop stable systems

Software framework for high precision motion control applications

Developing a motion control system requires much effort in different domains. Namely control, electronics and software engineering. In addition to these, there are the system requirements which may be completely different to these spanning from biomedical engineering to psychology. Collaboration between these fields is vital, however these fields should be involved only as much as they are needed to be in the fields of expertise of the others. Several software frameworks exist for the creation of robotics applications. But currently there is no standard for the creation of mechatronics systems nor is there a complete software package that can deal with all aspects in the programming of such systems. Existing frameworks each have their advantages and disadvantages, however they generally have limited or no dedicated structure for the development of the motion control aspect of the problem and deal extensively with the robotenvironment interactions and inter mechanism communications. Dealing with the higher levels of the problem, they are usually not well suited for hard realtime; since the interactions can run on soft realtime constraints. The software framework proposed in this study aims to achieve a level of abstraction between the different domains utilized within a system. The aim in using the framework is to achieve a sustainable software structure for the system. Sustainability is an important part of systems, as it permits a system to evolve with changing requirements and variable hardware, with the ultimate goal of having robust software that can be utilized on different platforms and with other systems using an abstraction layer between the hardware and the software. This ensures that the system can be migrated from a processing platform to any other platform and also from one set of hardware to another. The framework was tested on several systems that have precision motion control requirements such as a 10 degree of freedom micro assembly workstation, a modular micro factory and a haptic system with time delay. Each of the systems works in di erent processing platforms and have different motion control requirements. The achieved results from the implementations show that the software framework is an important tool for the development of motion control software

On fraction order modeling and control of dynamical systems

This paper demonstrates the feasibility of modeling any dynamical system using a set of fractional order di®erential equations, including distributed and lumped systems. Fractional order differentiators and integrators are the basic elements of these equations representing the real model of the dynamical system, which in turn implies the necessity of using fractional order controllers instead of controllers with integer order. This paper proves that fractional order differential equations can be used to model any dynamical system whether it is continuous or lumped

Miniaturized modular manipulator design for high precision assembly and manipulation tasks

In this paper, design and control issues for the development of miniaturized manipulators which are aimed to be used in high precision assembly and manipulation tasks are presented. The developed manipulators are size adapted devices, miniaturized versions of conventional robots based on well-known kinematic structures. 3 degrees of freedom (DOF) delta robot and a 2 DOF pantograph mechanism enhanced with a rotational axis at the tip and a Z axis actuating the whole mechanism are given as examples of study. These parallel mechanisms are designed and developed to be used in modular assembly systems for the realization of high precision assembly and manipulation tasks. In that sense, modularity is addressed as an important design consideration. The design procedures are given in details in order to provide solutions for miniaturization and experimental results are given to show the achieved performances

A versatile and reconfigurable microassembly workstation

In this paper, a versatile and reconfigurable microassembly workstation designed and realized as a research tool for investigation of the problems in microassembly and micromanipulation processes and recent developments on mechanical and control structure of the system with respect to the previous workstation are presented. These developments include: (i) addition of a manipulator system to realize more complicated assembly and manipulation tasks, (ii) addition of extra DOF for the vision system and sample holder stages in order to make the system more versatile (iii) a new optical microscope as the vision system in order to visualize the microworld and determine the position and orientation of micro components to be assembled or manipulated, (iv) a modular control system hardware which allows handling more DOF. In addition several experiments using the workstation are presented in different modes of operation like tele-operated, semiautomated and fully automated by means of visual based schemes

Mikro montaj İş İstasyonu

Bu makalede, mikro boyuttaki komponentlerin verimli ve güvenilir montajı için açık-mimarili, tekrar yapılandırılabilir bir mikromontaj iş istasyonu sunulmaktadır. Bu iş istasyonu mikro dünyadaki problemlerin çözümlendirilmesine yardımcı olmak amacıyla bir araştırma aracı olarak tasarlanmıştır. Böyle bir iş istasyonunun geliştirilmesi aşağıdaki alt sistemlerin tasarımını içermektedir: (i) montaj görevlerininin gerçekleştirilebilmesi için yeterli hareket menzilini ve hassasiyeti sağlayabilecek hareket platformlarından oluşan bir manipülatör sistemi, (ii) mikro dünyanın görselleştirilmesini ve montajı yapılacak olan mikro parçaların konum ve yönelimlerini belirleyebilmek için bir görü sistemi, (iii) dayanıklı bir denetleme sistemi ve bunlara ek olarak manipülasyon araçlarının kolayca değişmesine olanak sağlayan ve sistemin önceden belirlenmiş göreve hazır hale getirilmesine yardımcı olacak uç takımlar için gerekli fikstürler. Ayrıca sistemde kumandalı ve yarı otomatik montaj uygulamaları da gerçekleştirilmiştir. Tasarım mikro parça manipülasyonu içeren çeşitli uygulamalar yapılarak test edilmiştir. İş istasyonunun çok yönlülüğü ve yüksek doğrulukta konumlama yeteneği yapılan deneylerle gösterilmiştir

Development of system supervision and control software for a micromanipulation system

This paper presents the realization of a modular software architecture that is capable of handling the complex supervision structure of a multi degree of freedom open architecture and reconfigurable micro assembly workstation. This software architecture initially developed for a micro assembly workstation is later structured to form a framework and design guidelines for precise motion control and system supervision tasks explained subsequently through an application on a micro assembly workstation. The software is separated by design into two different layers, one for real-time and the other for non-realtime. These two layers are composed of functional modules that form the building blocks for the precise motion control and the system supervision of complex mechatronics systems

A field programmable gate array based modular motion control platform

The expectations from motion control systems have been rising day by day. As the systems become more complex, conventional motion control systems can not achieve to meet all the specifications with optimized results. This creates the necessity of fundamental changes in the infrastructure of the system. Field programmable gate array (FPGA) technology enables the reconfiguration of the digital hardware, thus dissolving the necessity of infrastructural changes for minor manipulations in the hardware even if the system is deployed. An FPGA based hardware system shrinks the size of the hardware hence the cost. FPGAs also provide better power ratings for the systems as well as a more reliable system with improved performance. As a trade off, the development is rather more difficult than software based systems, which also affects the research and development time of the overall system. In this paper a level of abstraction is introduced in order to diminish the requirement of advanced hardware description language (HDL) knowledge for implementing motion control systems thoroughly on an FPGA. The intellectual property library consists of synthesizable hardware modules specifically implemented for motion control purposes. Other parts of a motion control system, like user interface and trajectory generation, are implemented as software functions in order to protect the modularity of the system. There are also several external hardware designs for interfacing and driving various types of actuators