Power line communication systems for industrial control applications

For almost as long as the electricity distribution industry itself has existed, so also has the idea of utilising the transmission grid, be it over a wide area or on a local basis, for the transmission of 'intelligence'. This might be in the form of voice transmissions, or for the purposes of monitoring or controlling electrical devices attached to the network. This thesis specifically concerns itself with the potential applications of power-line-carrier (PLC) communications technology within the field of industrial plant/equipment control, as it is within this field that the author works. We look at the entire subject area of industrial control, starting from a historical viewpoint, and consider the special needs and requirements that a proposed PLC solution must offer for this application, especially based on the noise conditions likely to be experienced on a `real' power line. A proposal is made for a `Power Bus', intended for use within certain areas of industrial control, and decisions are made based on the projected link response times for such applications. The experimental phase of the research is practical in nature and consists of a raft of tests and evaluations of the performance of power line modem technologies, under controlled and repeatable noise conditions. To complement these results, further tests are carried out under `real world' conditions, within an actual factory environment. Based on the results of all of these tests, the suitability of a PLC solution for this type of industrial control application is considered. The Thesis concludes with a look at recent developments in, as well as the future of, Power Line Communication techniques

Dynamic topology management unit for a fieldbus

Mestrado em Engenharia Electrónica e TelecomunicaçõesA redundância, mudança de topologia, detecção e isolamento de falhas pode aumentar a fiabilidade de um barramento de campo, como o Controller Area Network – CAN. A Dynamic Topology Management (DTM) em CAN faz uso da redundância e da detecção e contenção de falhas. Esta solução possui duas entidades fundamentais: a Unidade de Gestão de Topologia (Topology Management Unit – TMU) e a Unidade de Comutação de Rede (Network Switch Unit – NSU). A TMU é responsável pela gestão dos meios de comunicação e pelo acesso de cada NSU a pelo menos um meio de comunicação. A própria TMU possui redundância, havendo sempre uma TMU master e pelo menos uma TMU slave num sistema DTM em CAN. Um dos pontos fulcrais nesta rede é a necessidade da TMU Slave possuir os mesmos dados que a TMU Master. Isto implica a existência de um método que garanta a consistência de dados replicados. Quando ocorre um sincronismo dos dados entre o slave e o master, o mecanismo de consistência de dados replicados deverá ocupar os canais de comunicação o menos possível. Neste trabalho a arquitectura interna da TMU é analisada e é apresentada uma proposta para uma implementação em FPGA. Vários problemas relacionados com a gestão dos canais de comunicação são levantados e solucionados. O principal tema desta dissertação é o estudo de um módulo interno da TMU que executa um mecanismo de consistência de dados replicados. Um algoritmo de pesquisa em árvore em conjunto com o cálculo de CRC de porções de informação é utilizado para comparar dados entre o TMU master e slave. Esta técnica demonstra a eficiência em termos de taxa de ocupação dos canais de comunicação quando comparado com a técnica de reenvio de todos os dados. A implementação em FPGA deste módulo, denominado Distributable Table Content Consistency Checker – DT3C, demonstra a viabilidade da solução em hardware. A simulação, em Matlab, do algoritmo de pesquisa em árvore permite verificar as vantagens e limites. ABSTRACT: The dependability of a fieldbus such as the Controller Area Network can be improved by adapting redundancy, improving its topology, detecting and isolating failures. The Dynamic Topology Management (DTM) in CAN is a solution that makes extensive use of redundancy and also of failure detection and isolation. This solution is composed by two main elements: The Topology Management Unit – TMU and the Network Switch Unit – NSU. The TMU is responsible for managing the redundant communication medium and guaranteeing the access of each NSU to at least one communication medium. There is also redundancy at the TMU level, which signifies that there is always one TMU master and at least one TMU slave. One of the key points in this network is the ability of the TMU slave to have the exact same data as the TMU master. This implies that there must be a rigorous consistency scheme of replicated data. Moreover, the consistency scheme should occupy as less as possible the communication medium when a synchronization between the TMU master and TMU slave is scheduled. I analyze and propose a TMU internal architecture for FPGA based implementation. Various issues related to the redundancy management of the communication medium are analyzed. The main focus of this work is a simple replicated data consistency mechanism module that is present inside the TMU. A tree search algorithm combined with cyclic redundancy check calculations of portions of data is used to compare data between the TMU slave and master. This technique proves to be bandwidth efficient when compared to the option of resending all the data from the TMU master to the slave. The implementation in FPGA of this module, denominated Distributable Table Content Consistency Checker - DT3C, demonstrates that the proposed solution is achievable in hardware. Furthermore, a Matlab simulation of the tree search algorithm reveals the efficiency and limitations of the DT3

Commissioning and implementing a PROFIBUS network in the Universal Water System

The Universal Water System (UWS) was built for instrumentation and control engineering students to design, implement and test different control schemes. The system has been primarily developed and designed by fourth year undergraduate and master’s students with the help of on-site technicians and electricians for installation of high voltage wiring, hardware equipment and IT related tasks. As the UWS is a learning tool that provides hands on experience with an industrial grade environment and equipment, improvement and maintenance of its functionality is a vital part of the on-going thesis projects. The main objectives of this work are split into three major segments. The first was commissioning the UWS, which consisted of updating the system’s software, replacing faulty equipment and ensuring appropriate functionality of the plant’s hardware. Two PROFIBUS Decentralised Peripherals (DP) flowmeters had been purchased to replace two faulty positive displacement flowmeters in the system. Hence the second objective was implement a PROFIBUS DP communication network for the new devices. The last objective was to design, implement and test more advanced control schemes through Open Platform Communication for the newly upgraded plant. With the project now complete, the UWS is operational with a fully functioning PROFIBUS DP communication network. The server computer’s operating system has been upgraded, while the Compact RIO’s firmware and the programming software has been updated to the latest version. Faulty equipment has been replaced and commissioned. Namely, two replacement flowmeters and an electric flow valve. A PROFIBUS DP network has been implemented to communicate with the two replacement flowmeters. An unexpected technical difficultly led to 5 variable speed drives being added to the PROFIBUS DP network. Additionally, the compact RIO’s code has been redesigned to improve efficiency, provide cyber-security, and to reduce the complexity of the client program. Due to unforeseen circumstances and time constraints the time taken to commission the plant and implement PROFIBUS was far greater than expected; two of the three project objectives were completed, pushing the advanced control schemes and Open Platform Communication to future work. Overall, the main accomplishment of this thesis besides the project objectives, is that the system has been updated, refitted and ready for operation for the next thesis student; so they do not run into the tedious and painful issues found during this project

A conformance test framework for the DeviceNet fieldbus

The DeviceNet fieldbus technology is introduced and discussed. DeviceNet is an open standard fieldbus which uses the proven Controller Area Network technology. As an open standard fieldbus, the device conformance is extremely important to ensure smooth operation. The error management in DeviceNet protocol is highlighted and an error injection technique is devised to test the implementation under test for the correct error-recovery conformance. The designed Error Frame Generator prototype allows the error management and recovery of DeviceNet implementations to be conformance tested. The Error Frame Generator can also be used in other Controller Area Network based protocols. In addition, an automated Conformance Test Engine framework has been defined for realising the conformance testing of DeviceNet implementations. Automated conformance test is used to achieve consistent and reliable test results, apart from the benefits in time and personnel savings. This involves the investigations and feasibility studies in adapting the ISO 9646 conformance test standards for use in DeviceNet fieldbus. The Unique Input/Output sequences method is used for the generation of DeviceNet conformance tests. The Unique Input/Output method does not require a fully specified protocol specification and gives shorter test sequences, since only specific state information is needed. As conformance testing addresses only the protocol verification, it is foreseen that formal method validation of the DeviceNet protocol must be performed at some stage to validate the DeviceNet specification

Phasing of Periodic Tasks Distributed over Real-time Fieldbus

In designing a distributed hard real-time system, it is important to reduce the end-to-end delay of each real-time message in order to ensure quick responses to external inputs and a high degree of synchronization among cooperating actuators. In order to provide a real-time guarantee for each message, the related literature has focused on the analysis of end-to-end delays based on worst-case task phasing. However, such analyses are too pessimistic because they do not assume a global clock. With the assumption that task phases can be managed by using a global clock provided by emerging real-time fieldbuses, such as EtherCAT, we can try to calculate the optimal task phasing that yields the minimal worst-case end-to-end delay. In this study, we propose a heuristic to manage the phase offsets in the distributed tasks to reduce the theoretical end-to-end delay bound. The proposed heuristic reduces the search time for a solution by identifying time intervals where actual communication occurs among inter-dependent tasks. Furthermore, to analyze the distribution of endto- end delays in different phases, we implemented a simulation tool. The simulation results showed that the proposed heuristic can reduce worst-case end-to-end delay as well as jitter in end-to-end delays

Towards an In-depth Understanding of Deep Packet Inspection Using a Suite of Industrial Control Systems Protocol Packets

Industrial control systems (ICS) are increasingly at risk and vulnerable to internal and external threats. These systems are integral part of our nation’s critical infrastructures. Consequently, a successful cyberattack on one of these could present disastrous consequences to human life and property as well. It is imperative that cybersecurity professionals gain a good understanding of these systems particularly in the area of communication protocols. Traditional Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are made to encapsulate some of these ICS protocols which may enable malicious payload to get through the network firewall and thus, gain entry into the network. This paper describes technical details on various ICS protocols and a suite of ICS protocol packets for the purpose of providing digital forensic materials for laboratory exercises toward a better understanding of the inner workings of ICS communications. Further, these artifacts can be useful in devising deep packet inspection (DPI) strategies that can be implemented in network firewalls, in expanding challenge materials for cyber competitions, and in attribution, vulnerability assessment, and penetration testing research in ICS security. We also present software tools that are available for free download on the Internet that could be used to generate simulated ICS and Supervisory Control and Data Acquisition (SCADA) communication packets for research and pedagogical purposes. Finally, we conclude the paper by presenting possible research avenues that can be pursued as extensions to this seminal work on ICS security. Prominent among these possible extensions is the expansion of the ICS packet suite to include those protocols in the wireless domain such as Wi-Fi (802.11), Bluetooth, Zigbee, and other protocols that utilizes proprietary Radio Frequency