No description available.

No description available.

Manufacturing firms strive to improve existing methods or develop new ideas to reduce production costs and lead time in order to rapidly provide quality assured parts to customers. Maintaining control over the processes involved in manufacturing is. therefore, vital. With the widespread use of CNCs in the industry, controlling their manufacturing processes has become pertinent.

No description available.

The design of complex control systems for industrial processes is in general still based on experience and trial and error rather than on systematic process analysis and control system design. Typically control systems in the process industry comprise either single PID control loops with clear association of the process input and controlled signal or standard control schemes developed by intuition through the years (e.g. cascade control using an underlying flow control loop). Although many of these control schemes seem to work rather satisfactorily, in most major control systems several poorly tuned or switched off controllers are encountered leading to unsatisfactory process behaviour or manual operation of the process. The subject of this work is the development of a structured approach to industrial control system design which makes the potential of systematic process analysis and controller design methods developed by control theory available for industrial users with limited control experience. This aspect has been addressed within the collaboration research project between the University of Glamorgan and the Fachhochschule Hannover, of which the work presented in this thesis is a substantial part. Therefore, the ICACSD (Industrial Computer Aided Control System Design) scheme has been developed to allow the design of PID based control structures for nonlinear single- and multivariable processes that are as simple as possible and as good as required. Beyond this an industrial standardised controller design procedure for nonlinear and multivariable processes has been elaborated. For the validation of the proposed approach, a prototype control system design tool has been programmed, which can be integrated into the ICACSD scheme using a blockoriented simulation environment. The approach for industrial control system design presented shows the benefits of applying advanced control system design methods which are usable by industrial users when provided with an intuitive and usable graphical user interface. In order to validate the work the proposed control design procedure has been made accessible in the form of a software prototype with an economically designed graphical user interface allowing easy application of the developed methods. The prototype realisation for the Industrial Computer Aided Control (ICAC) toolbox supplies the new structured approach to control system design for industrial processes within a block-oriented simulation environment.

The objective of the dissertation is to improve the understanding of the complicated dynamics of the bubbling process in a fluidised bed. This will enable the implementation of effective control to achieve a desirable fluidisation quality. Techniques in the field of dynamics and automatic control were employed to study the bed. A planar fluidised bed was used to enable bubbling to be directly observable and measurable using real-time image analysis instrumentation. The bubble void fraction, BVF, in the bed was measured, which is the proportion of the bed occupied by the voids associated with bubbles. A simulated bubbling bed devised based on the Clift & Grace (1970, 1971a, 1971b) bubble interaction model was validated experimentally using frequency domain analysis techniques. This led to the dynamical modelling of the fluidised bed by capturing the important features that governs the overall dynamics of the bed. The fluidised bed can be thought to be a temporary store of gas and the model related the introduction of a packet of gas and its nucleation as a bubble, to the changes in the bed BVF. The model works for cases of single bubbles and freely bubbling beds, showing that activities such as bubble interaction and coalescence cause non-linearity within the bed. The criteria for good fluidisation quality were defined and were related closely to bubble population and spatial distribution in the bed. The major causes affecting it were identified as bubble interaction and the influence of geometry allowing techniques to improve the quality of the process to be proposed. A closed-loop system permitted thorough system identification of the bubbling fluidisation process, enabling the process dynamics to be extracted for controller design purposes. Fixed gain (Proportional + Integral + Derivative) and adaptive (Minimal Control Synthesis) controller schemes were implemented to control the process producing good experimental results.

Few significant changes in Programmable Logic Controller (PLC) software design techniques have taken place since PLC's were first introduced in the 1960's. Programs written in the traditional language used in PLC's, ladder logic, are generally thought to be difficult to maintain and modify, and thus ill suited to the support of modem flexible manufacturing processes. This work demonstrates that the choice of PLC software structure used in a project has an impact on process flexibility with an appropriate choice providing significant cost savings in development time. An overview of work on formalised programming tools conducted in academia is provided together with a report on the PLC software structures used in industry. The factors influencing the choice of PLC and software structure are identified. Familiarity was found to be a major factor influencing selection. A method for comparing code structures, which allows the results to be expressed as a time saving (and consequently a cost) has been created. Implementation of this approach was used to show that the formalised programming tool under test provides a 33% increase in "right first time" rate together with an 80% time saving over traditional contact based ladder logic. Among experienced practitioners, performance with step-based ladder logic was found to be a close match to the formalised tool, demonstrating that the commonly perceived limitations are the result of the structure in which the language is used rather than a function of the programming tool itself. Further investigation of participant preferences among skilled PLC users showed a mismatch between their performance with a tool and their preference, with at least 25% selecting a tool based on their prior knowledge rather than performance. This highlights the need for the use of objective measures when conducting evaluations between products and technologies. With the information provided in this work, automation end users are provided with a mechanism for ensuring the selection of automation tools best suited to their business needs, whilst at the same time providing automation vendors with the ability to best demonstrate the strengths of the products.

A thesis which models the DNP3 and IEC 61850 protocol in OPNET / Supervisory Control and Data Acquisition (SCADA) is a critical part of monitoring and controlling of the electrical substation. The aim of this dissertation is to investigate the performance of the Distributed Network Protocol Version 3.3 (DNP3) protocol and to compare its performance to that of International Electro-technical Commission (IEC) 61850 protocol in an electrical substation communication network environment. Building an electrical substation control room and installing the network equipment was going to be expensive and take a lot of time. The better option was to build a model of the electrical substation communication network and run simulations. Riverbend modeller academic edition known as Optimized Network Engineering Tool (OPNET) was chosen as a software package to model substation communication network, DNP3 protocol and IEC 61850 Protocol stack. Modelling the IEC 61850 protocol stack on OPNET involved building the used Open System Interconnection (OSI) layers of the IEC 61850 protocol stack onto the application definitions of OPNET. The Transmission Control Protocol/Internet Protocol (TCP/IP) configuration settings of DNP3 protocol were also modelled on the OPNET application definitions. The aim is to compare the two protocols and determine which protocol is the best performing one in terms of throughput, data delay and latency. The substation communication model consists of 10 ethernet nodes which simulate protection Intelligent Electronic Devices (IEDs), 13 ethernet switches, a server which simulates the substation Remote Terminal Unit (RTU) and the DNP3 Protocol over TCP/IP simulated on the model. DNP3 is a protocol that can be used in a power utility computer network to provide communication service for the grid components. DNP3 protocol is currently used at Eskom as the communication protocol because it is widely used by equipment vendors in the energy sector. DNP3 protocol will be modelled before being compared to the new recent robust protocol IEC 61850 in the same model and determine which protocol is the best for Eskom on the network of the power grid. The network load and packet delay parameters were sampled when 10%, 50%, 90% and 100% of devices are online. The IEC 61850 protocol model has three scenarios and they are normal operation of a Substation, maintenance in a Substation and Buszone operation at a Substation. In these scenarios packet end to end delay of Generic Object Oriented Substation Event (GOOSE), vi © University of South Africa 2020 Generic Substation Status Event (GSSE), Sampled Values (SV) and Manufacturing Messaging Specification (MMS) messages are monitored. The throughput from the IED under maintenance and the throughput at the Substation RTU end is monitored in the model. Analysis of the results of the DNP3 protocol simulation showed that with an increase in number of nodes there was an increase in packet delay as well as the network load. The load on the network should be taken into consideration when designing a substation communication network that requires a quick response such as a smart gird. GOOSE, GSSE, SV results on the IEC 61850 model met all the requirements of the IEC 61850 standard and the MMS did not meet all the requirements of the IEC standard. The design of the substation communication network using IEC 61850 will assist when trying to predict the behavior of the network with regards to this specific protocol during maintenance and when there are faults in the communication network or IED’s. After the simulation of the DNP3 protocol and the IEC 61850 the throughput of DNP3 protocol was determined to be in the range (20 – 450) kbps and the throughput of IEC61850 protocol was determined to be in the range (1.6 – 16) Mbps. / College of Engineering, Science and Technology / M. Tech. (Electrical Engineering)