A Dual-Rate Model Predictive Controller for Fieldbus Based Distributed Control Systems

In modern Distributed Control Systems (DCS), an industrial computer network protocol known as fieldbus is used in chemical, petro-chemical and other process industries for real-time communication between digital controllers, sensors, actuators and other smart devices. In a closed-loop digital control system, data is transferred from sensor to controller and controller to actuator cyclically in a timely but discontinuous fashion at a specific rate known as sampling-rate or macrocycle through fieldbus. According to the current trend of fieldbus technology, in most industrial control systems, the sampling-rate or macrocycle is fixed at the time of system configuration. This fixed sampling-rate makes it impossible to use a multi-rate controller that can automatically switch between multiple sampling-rates at run time to gain some advantages, such as network bandwidth conservation, energy conservation and reduction of mechanical wear in actuators. This thesis is concerned about design and implementation of a dual-rate controller which automatically switches between the two sampling-rates depending on system’s dynamic state. To be more precise, the controller uses faster sampling-rate when the process goes through transient states and slower sampling-rate when the process is at steady-state operation. The controller is based on a Model Predictive Control (MPC) algorithm and a Kalman filter based observer. This thesis starts with theoretical development of the dual-rate controller design. Subsequently, the developed controller is implemented on a Siemens PCS 7 system for controlling a physical process. The investigation has concluded that this control strategy can indeed lead to conservation of network bandwidth, energy savings in field devices and reduction of wear in mechanical actuators in fieldbus based distributed control systems

FIELDBUS INTEROPERABILITY TESTING AND SYSTEM CONFIGURATION

This report is to discuss the research and Basic Interoperability testing for Foundation Fieldbus system, as well as the development of a control loop. Devices that use Foundation Fieldbus system cannot intemperate with devices from different manufacturers. PE1RONAS as the established company will apply Fieldbus technology in its plants. The objectives of the testing are to get a PETRONAS Technical standard on the Foundation Fieldbus system and come out with a report on the results from interoperability testing that will be the reference for system in PE1RONAS. The other objective is to test the controller performance using the three control modes, P, PI and PID. In order to achieve the objectives, first three tests should be done, basic interoperability test, Stress test and Diagnostic capability, and then a test on the controller performance will be held. Due to time constraint, UTP team was able to complete the Basic interoperability test and the control loop development. The author will only focus on testing HONEYWELL system and segment 2, provided by MTL. The Basic interoperability test was successfully done and the controller performance was successfully tested. The research about the Foundation Fieldbus should be performed continuously, to improve the system from time to time, and the analysis of results and reports will be used for future researches

IMPLEMENTATION OF CONTROL STRATEGIES ON CONTROL LOOPS FIELDBUS FOUNDATION PROTOCOL

The first process control systems used mechanical and pneumatic controllers. Ever since then, the process control sector has seen numerous developments; amongst them is the foundation fieldbus technology. Fieldbus has been around for sometime, but not until recently has it caught the attention of users and manufacturers alike. Fieldbus claims to require less hardware, have easy installation and commissioning, provide good data both in quality and quantity, need easy and simple maintenance and be interoperable with other devices. This project aims to prove those claims. A foundation fieldbus test platformwill be designed and built. This test platform will include a simple control loop with fieldbus transmitters, gauges and control valves. A control strategy of cascade control and PID control will be used. Influenced by the safety system of a plant, the test platform is designed to emulate part of the fire water pump system. When there is a leak in the fire water pipes, the drop in pressure inside the pipes will trigger the system to pump in more water. The first part of this project will cover the research and design stages. Thorough research on the fieldbus technology, different control strategies and installation and commissioning is needed for the success ofthe second part of the project. Once the design has been finalized, and deemed feasible, the test platform will be built. Tests, troubleshooting and maintenance will follow. In the light of further improving this project, state-space mode can be used as an alternative control strategy. It should provide greater performance, increased stability and controllability. Fieldbus has the potential of being the best, with its extra features, such as diagnostics and predictive maintenance. Digital control is the thing ofthe future

IMPLEMENTATION OF CONTROL STRATEGIES ON CONTROL LOOPS FIELDBUS FOUNDATION PROTOCOL

The first process control systems used mechanical and pneumatic controllers. Ever since then, the process control sector has seen numerous developments; amongst them is the foundation fieldbus technology. Fieldbus has been around for sometime, but not until recently has it caught the attention of users and manufacturers alike. Fieldbus claims to require less hardware, have easy installation and commissioning, provide good data both in quality and quantity, need easy and simple maintenance and be interoperable with other devices. This project aims to prove those claims. A foundation fieldbus test platformwill be designed and built. This test platform will include a simple control loop with fieldbus transmitters, gauges and control valves. A control strategy of cascade control and PID control will be used. Influenced by the safety system of a plant, the test platform is designed to emulate part of the fire water pump system. When there is a leak in the fire water pipes, the drop in pressure inside the pipes will trigger the system to pump in more water. The first part of this project will cover the research and design stages. Thorough research on the fieldbus technology, different control strategies and installation and commissioning is needed for the success ofthe second part of the project. Once the design has been finalized, and deemed feasible, the test platform will be built. Tests, troubleshooting and maintenance will follow. In the light of further improving this project, state-space mode can be used as an alternative control strategy. It should provide greater performance, increased stability and controllability. Fieldbus has the potential of being the best, with its extra features, such as diagnostics and predictive maintenance. Digital control is the thing ofthe future

Automação de uma unidade de experimentação de escoamento multifásico utilizando tecnologia Foundation Fieldbus

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2015.O Laboratório Experimental de Escoamento Multifásico (LEEM) do Departamento de Automação e Sistemas tem por objetivos: (i) o estudo dos escoamentos multifásicos aplicados à indústria do petróleo; (ii) o desenvolvimento de medidores de vazão multifásicos para a indústria do petróleo; (iii) o desenvolvimento de novas técnicas de controle de escoamentos multifásicos (supressão de golfadas, estabilização de regimes de escoamento, etc.); (iv) o desenvolvimento de novas técnicas de separação em linha de fluidos multifásicos. O LEEM conta com uma Unidade de Experimentação de Escoamentos Multifásicos (UEEM) e com uma sala de medição para testes de protótipos de medição e controle.A UEEM permite basicamente misturar vazões controladas de água, óleo inerte e ar comprimido previamente medidas com precisão. O fluído misturado é conduzido para uma área de ensaios onde podem ser testados diferentes protótipos, assim como medidores comerciais, de vazão monofásica, bifásica ou multifásica. A mistura multifásica passa pela área de testes e retorna ao separador que opera a pressão atmosférica. A planta conta com um sistema de aquisição de dados que permite adquirir dados dos instrumentos de medida de cada fração bem como aqueles do sensor sendo investigado. O objetivo principal deste trabalho consiste na automação da operação de uma unidade de experimentação de laboratório (UEEM). Em particular, (i) desenvolver sistemas de controle via rede; (ii) de instrumentação e de segurança; (iii) de automação da operação de ensaios e testes desta unidade. Para a automação da unidade aplicou-se a tecnologia de redes FOUNDATION Fieldbus (FF), uma rede interoperável com controle distribuído em campo e manutenção simples. Este trabalho mostra na prática e de forma detalhada a execução de todas as camadas da pirâmide da tecnologia FOUNDATION Fieldbus, enfatizando as suas funcionalidades, vantagens e desvantagens. Abstract : The Experimental Laboratory of Multiphase Flow (LEEM) of the Department of Automation and Systems aims to: (i) the study of multiphase flow applied to the petroleum industry; (ii) the development of multiphase flow meters for the oil industry; (iii) development of new multiphase flow control techniques (slugs, stabilizing flow regimes, etc.); (iv) the development of new techniques for separation of multiphase fluid line. The LEEM has an Experimentation Unit of Multiphase Flows (UEEM) and a measuring room for measurement and control prototype testing.The UEEM basically allows controlled mixing of water flows, inert oil and compressed air previously measured accurately. The mixed fluid is conducted to an area where testing different prototypes can be tested, as well as commercial meters, the flow monophasic, biphasic or multiphasic. The multiphase mixture passes through the testing area and returns to the separator which operates at atmospheric pressure. The plant comprises a data acquisition system that enables acquiring data of the measuring instruments of each fraction as well as those of the sensor being investigated. The aim of this work is the automation of the operation of a laboratory experiment unit (UEEM). In particular, (i) develop networked control systems; (ii) of instrumentation and safety; (iii) automation of the testing operation and testing of the unit.The FOUNDATION Fieldbus technology (FF), an interoperable network with distributed control in the field and simple maintenance, has been applied to the experimental unit. This work shows in practice and in detail the implementation of all the pyramid layers of FOUNDATION Fieldbus technology, emphasizing their features, advantages and disadvantages

Selection of a new hardware and software platform for railway interlocking

The interlocking system is one of the main actors for safe railway transportation. In most cases, the whole system is supplied by a single vendor. The recent regulations from the European Union direct for an “open” architecture to invite new game changers and reduce life-cycle costs. The objective of the thesis is to propose an alternative platform that could replace a legacy interlocking system. In the thesis, various commercial off-the-shelf hardware and software products are studied which could be assembled to compose an alternative interlocking platform. The platform must be open enough to adapt to any changes in the constituent elements and abide by the proposed baselines of new standardization initiatives, such as ERTMS, EULYNX, and RCA. In this thesis, a comparative study is performed between these products based on hardware capacity, architecture, communication protocols, programming tools, security, railway certifications, life-cycle issues, etc

On line control and monitoring applied in a bromelain precipitation process using digital fieldbus communication

Orientador: Flavio Vasconcelos da SilvaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia QuimicaResumo: Com o advento do sistema digital em rede (fieldbus) e a ampla divulgação das vantagens da utilização desta nova tecnologia aliada ao uso de instrumentos inteligentes, tornou-se inquestionável a melhora no desempenho e confiabilidade dos dados obtidos através deste sistema para o controle em novas plantas industriais ou em sistemas destinados à pesquisa tecnológica. Estratégias de controle clássicas, tais como o controle PID (proporcional ¿ integral ¿ derivativo), são largamente utilizadas no setor industrial devido à sua robustez e facilidade de implementação, embora limitações possam ser observadas quanto à adequação destes controladores às não-linearidades presentes nos sistemas reais. A utilização dos controladores adaptativos (baseados em parâmetros variáveis) permite tais adequações respeitando a dinâmica dos sistemas. Nas últimas décadas tem-se notado um significante aumento na aplicação da teoria de controladores avançados, entretanto, a sua utilização no setor produtivo ainda é incipiente. Apresenta-se, neste trabalho, uma automação híbrida alternativa para monitoramento, em tempo real, das variáveis de processo de um sistema para precipitação da enzima bromelina com supervisão, em tempo real, das condições do processo sob diferentes perturbações na carga, usando estratégia SISO em arquitetura de rede Fieldbus. Além disso, por se tratar de um bioprocesso, em batelada, as não linearidades e o aspecto essencialmente transiente da operação evidenciam a inevitável prioridade na aplicação dos controladores avançados, uma vez que os controladores convencionais possuem ação limitada neste tipo de sistema, garantindo a qualidade final da enzima obtida. Através dos resultados obtidos pôde-se comprovar a que ambos os controladores PID convencional e adaptativo tiveram um bom desempenho na manutenção da temperatura, porém houve um melhor desempenho com o PID adaptativo como foi observado pelos parâmetros de desempenho ITAE, overshoot e tempo de subidaAbstract: Fieldbus technology and intelligent sensors/actuators are increasingly being used in automated systems, opening up new possibilities for distributed control structures, mainly in new plants and research applications where is very important to have a flexible automation structure to different plant conditions with huge flow of information. Significant improvements have been seen in advanced controllers over the last years. However, linear PID controller is still applied extensively in industrial practice. The reason lies in its robustness and well-Known control design and implementation, although assumptions, simplifications, or lumping parameters are often made to build a mathematical model that may be far from the real situation. The behavior of most physical systems, especially bath systems, is nonlinear. Linear control may be effective for local operation, but is inadequate for controlling operations over a broad range. Adaptive controllers are nonlinear systems, which are commonly based on linear control theory. Despite many publications in the last decades illustrating advantages of adaptive controllers, this Kind of control is still not so common in industrial practice. One of reasons for the low incidence of application is relative difficulty to implement this controller. In this study, a comparative experimental design and tuning of conventional PID and adaptive PID controllers was developed for a pilot plant batch to precipitate of enzyme bromelain, using SISO strategy in fieldbus network architecture. The system was applied to the on line control of temperature of the extraction tank, involving a performance control analysis, under different load disturbances. From the results of this work, both controllers were considered suitable to control the temperature of the fedbatch tank. Nevertheless, the closed loop performance was improved under adaptive PID controller: the performance index ITAE, the overshoot and the rise time decreased.MestradoSistemas de Processos Quimicos e InformaticaMestre em Engenharia Químic

Virtuaalinen kenttäväylä -Sovellettavuus, teknologiat ja arviointi

In the present-day software and automation development, different methods of virtualization have become popular, as the final hardware is then not required for software development. This allows earlier and faster software process, reduced time to market and more fluent workflow. As distributed automation systems generally rely on fieldbuses of various types, implementing a virtual and fully operational fieldbus is a necessity for efficient utilization of the virtualized system. In this thesis, we take a comprehensive approach to virtual fieldbuses, from concept definition to experimental performance characteristics. We discuss the common behavior of different fieldbuses, list applications for virtual buses and compare possible implementation technologies such as TCP/IP and shared memory. Virtualization tools VirtualBox and QEMU are closely studied, as they bring additional challenges to data transfer. From the practical point of view, the study presents our experiences on implementing a virtual CAN bus for embedded development. With an extensive set of features and platform support in our design, it demonstrates the utilization of multiple technologies. Using the virtual CAN implementation, we then show the measured performance characteristics and evaluate the solution against actual hardware. Potential of virtual bus technology was proven by the performance measurements. Shared memory implementation provided extremely good performance, sufficient for implementing any virtual fieldbus system. It was also found to be efficient in respect to CPU load. Unfortunately, shared memory usually cannot cross virtualization boundaries. TCP was found as the best option for the rest of the use cases. In restricted local Ethernet or between VirtualBox and host OS, it is able to provide latencies under 700µs, similar to hardware performance. Observed bottlenecks were the use of the QEMU emulation tool without optimizations, and slow USB fieldbus adapters. We recommend using virtual fieldbuses in virtualized development and debugging of distributed systems and for automatic system level testing, if timing requirements are not extremely strict. Remote virtual connection to a hardware fieldbus is also seen as a valid application. The technologies and adapters must still be carefully selected for best results

Soluções de comunicação para controlo e monitorização de motores

O homem na sua busca incessante pela inovação criou um dispositivo, designado por motor elétrico, cuja principal função compreende a conversão de energia elétrica em energia mecânica. O motor elétrico é sem dúvida uma das maiores invenções da história, visto que impulsionou o processo de industrialização e alterou radicalmente o modo de vida das pessoas. De entre os diversos tipos de motores elétricos existentes, o motor de indução trifásico de rotor em gaiola de esquilo é indiscutivelmente o mais utilizado a nível mundial em aplicações industrias. A popularidade deste motor em particular advém da sua robustez, simplicidade, reduzido custo e excelente rendimento. O motor de indução apresenta contudo algumas desvantagens que se prendem com o decréscimo de rendimento em cargas de baixo valor. Para colmatar as limitações enunciadas surgiram algumas soluções tecnológicas, designadamente os contatores, os soft-starters e o InSwitch. O InSwitch pretende ser uma alternativa aos demais dispositivos de controlo de motores já existentes no mercado. Para além de controlar o motor de indução, este dispositivo pode disponibilizar informação pertinente relativa ao seu funcionamento. Assim sendo, utilizaramse as capacidades do InSwitch para desenvolver uma ferramenta intuitiva e de fácil acesso de forma a permitir aos técnicos de manutenção a visualização de toda a informação relevante relativa ao seu estado atual de funcionamento. Nesta dissertação são apresentadas duas soluções tecnológicas distintas, as quais foram desenvolvidas com o objetivo mencionado. Uma das soluções oferece ao utilizador a possibilidade de controlar e analisar os dados em tempo real do motor que pretende monitorizar, sem que para isso necessite de equipamento de medida de motores de indução, o qual é muito dispendioso. Através de qualquer dispositivo móvel equipado com o Sistema Operativo Android e Bluetooth o utilizador pode aceder a toda a informação do motor sem necessidade de parar todo o sistema de produção. A segunda solução desenvolvida permite que os motores comuniquem, através de uma ligação de rádio frequência, com um dispositivo central. O dispositivo central dispõe de um processador ARM Cortex-M4, o qual é responsável pelo processamento de toda a informação recebida dos motores e de a reenviar para uma base de dados. Por fim, toda a informação armazenada na base de dados pode ser consultada e analisada, em tempo real, pelo utilizador através de um website desenvolvido para o efeito