Browsing by Author "Boje, Edward Sidney."

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Application of quantitative feedback theory to robust power system stabiliser design.
(2003) Chetty, Paramasivan.; Boje, Edward Sidney.
This thesis aims to verify the use of quantitative feedback theory (QFT) as a viable tool for designing power system stabilisers (PSS) for a single machine infinite bus system. The result of the QFT design is verified by simulation of the linear and nonlinear models representing the power system, and also by experimental procedures carried out in a laboratory. QFT falls into the classical control category, and is a frequency domain design method. It is an alternative to other design methods such as root locus and Hoo . The QFT design procedure can be extended to a multimachine system and QFT designs of MIMO systems has gained impetus. From theory, through simulation, and to the final laboratory testing on a single machine, infinite bus system, it will be shown that the application of QFT to robust PSS design does indeed work. QFT is a design method that allows the designer to choose a set of realistic operating points and to produce a design that include those points. Other methods allow the designer to produce a design for single operating point, and one has no idea how the design performs at the other operating points.
Development of a model helicopter based flight test platform for multivariable feedback control.
(2009) Moodley, Thessygan.; Boje, Edward Sidney.
The dissertation describes the development of a model helicopter based flight test platform for implementing autonomous six degree of freedom flight by a multiple input multiple output automatic control system. The focus of the research is two fold: i. Navigation system design centred about fusing multiple data and measurement sources using Kalman filtering techniques. ii. Electrical engineering of a complete avionics package to support guidance, navigation and control functions. Included are the results from several experiments conducted on the test platform, highlighting salient aspects and performance of the electrical and navigation systems.
Modelling, simulation and robust control of a Benson boiler during hot startup.
(2005) Mukosa, Dunn.; Boje, Edward Sidney.
Large boilers have typically been designed for continuous operation from 60-100% load. With restructuring of electrical supply and in some cases because of local fuel supply constraints, some of these boilers are run for only two shifts per day and this entails warm start ups. A reasonable objective is to bring the plant online as quickly as possible within the equipments constraint and without risk of tripping major plant equipment such as feed pumps and circulation pumps. The project required the development of a model accurate enough to represent the boiler thermal dynamics. The thesis compares the simulated model results with the measured results from a Benson boiler from Majuba power station. The developed model is then used to investigate gain scheduled and robust control approaches to the design of the control system for collector vessel level and evaporator flow rate. Once the control problems are clearly understood, an investigation into fast start up is undertaken. The subject of the start up of Benson boilers has limited open literature. This is because flexibility in plant operation has only recently become an important issues with electricity utilities. The limited research in the field of robust control of start up of Benson boiler has made the extensive work done by both Eitelberg and Boje [2001,2002,2004] state of the art. Most of the research done in this thesis follows from the work done by Eitelberg and Boje.
Obstacle avoidance and trajectory optimisation for a power line inspection robot.
(2012) Rowell, Timothy.; Boje, Edward Sidney.
This dissertation presents the research, development and application of trajectory creation, obstacle avoidance and trajectory optimisation methods for an existing serial manipulator power line inspection robot (PLIR). The obstacle avoidance implementation allows the robot to navigate around an obstacle obstructing its navigation along the line. The algorithm generated end effector trajectory waypoints autonomously based on bounding box obstacle descriptions in Cartesian space, and connected them with a fifth order basis-spline end effector trajectory command. The trajectories were created taking into account the dynamic torque and velocity constraints of the robot while ignoring non-linearities. Performance was inspected and evaluated in a simulated workspace environment. The trajectory optimisation was designed to maximise the robot’s operating range, with constraints on the battery power supply, by minimising charge consumed during obstacle avoidance trajectories. The temporal components of the basis-spline trajectories were optimised by minimising a timeenergy type of cost function subject to the dynamic constraints of the robot. Cost function analyses are presented for a simple frictionless robot model based on the recursive Newton-Euler method, and for a more realistic model including viscous, Coulomb and static friction as well as gearbox backlash. It is shown that the Nelder-Mead simplex method was appropriate for optimisation. For representative trajectories that were studied, the optimiser was capable of finding global minima with satisfactory speed and accuracy in simulation. The validity of trajectory optimisation with regard to the cost function behaviour was confirmed. This was based on experiments carried out on the robot hardware in the laboratory, examining the predicted and actual actuator current profiles. The engineering design and implementation of hardware and software for the base station and on-board system is presented, together with the layout of the PLIR’s control system and PID (proportional-integral-derivative) controller design. Trajectory commands are sent from the base station to the robot via Wi-Fi for execution. Furthermore, live video feed from the robot can be sent to the ground station computer. Furthermore, high voltage testing of the PLIR showed that the engineering design of the robot and communication platform is robust.
Quantitative feedback design and construction of a two by two system with large disturbances.
(1989) Boje, Edward Sidney.; Eitelberg, Eduard.
The quantitative feedback theory (QFT) of Horowitz is theoretically well developed for multivariable systems but there is not sufficient knowledge on its application to practical problems. A "flying machine" consisting of an airframe with two independently controlled sets of wings has been designed and constructed as a 2-input 2-output control problem. The airframe is constrained to move vertically on guide wires and to rotate about a pivot. Air flow over the wings is provided by two 7.SkW fans operated without any attempt at providing non-turbulent flow. The arrangement of the wings is such that in open loop, the dynamic behaviour of the airframe from the rear set of wings to the height is non-minimum phase. Additionally, the airframe is unstable for some flight conditions. This uncertain, non-linear and highly disturbed plant provides an ideal practical environment in which to test controller design theory. The construction, modelling, parameter estimation and simulation of the flying machine is described. Three different controller structures are disGussed, with actual controller designs arrived at from QFT understanding. The controller designs for the flying machine take into account parameter uncertainty and trade off disturbance attenuation against rate and amplitude saturation at the wing angle inputs.
Research and design of an embedded controller and GUI for the automation of the armature Volt-Drop test.
(2009) Matadin, Sunveer.; Boje, Edward Sidney.
In a rapidly evolving technological and industrialised society, automation is a current and growing trend. The concept is typically applied to uneconomical processes and extends from the automation of highly complex processes to those that are less complex. This dissertation discusses the automation of a previously mundane, manual, time-consuming and inefficient task using an embedded controller with dual enhanced microcontrollers as its core. Spoornet recognised the need to automate this and other processes hence a drive was initiated by Spoornet’s Engineering and Technology department into the study of automation principles and techniques that can be used as a basis for the automation of workshops and test centers. This research stems from the above mentioned drive. The Volt-Drop Test was the process that was used as a model to investigate the considerations, boundaries, design concepts and the hardware and software development that is inherent in the automation of a process. The design of the controller that facilitates the automation of the Volt-Drop Test was completed after research into embedded systems, embedded microcontrollers, programming languages and techniques, digital electronics, analogue electronics, digital system design concepts and techniques, analogue system design concepts and techniques, and the latest available electronic components. A Graphic User Interface (GUI) was developed to interface with the controller to set up test parameters, display the present test status, perform calculations on the data received from the controller and display faults in the armature under test. Further, the GUI has the functionality to save all test data in a predefined and secure location to be retrieved and viewed as historical data or used for trending. A Remote Graphic User Interface (RGUI) was also developed. This interface is used solely to view test data (retrieved from the saved history files), from any geographic location provided that the user has been granted access to the secure location in which this data is saved. In the testing phase, all tests were carried out using high quality, high accuracy and recently calibrated instrumentation. The test results obtained largely reflected what was expected from the system when compared to simulations that were carried out on the controller and the GUI during their development. With regard to the automation process, the system follows the procedure as it was designed with respect to correct switching sequences, response to system errors, timing of events and correct and efficient communication between the controller and the GUI. In terms of the data acquisition aspects the system captures, converts, calculates, analyses and logs data, within the expected input range with a level of accuracy that is considered to be high (a maximum percentage error of 0.75% - expressed as a percentage of the injected test supply) for this type of application when compared to the accuracy of present test methods.
Robust multivariable control design : an application to a bank-to-turn missile.
(2011) Reddi, Yashren.; Boje, Edward Sidney.
Multi-input multi-output (MIMO) control system design is much more difficult than single-input single output (SISO) design due to the combination of cross-coupling and uncertainty. An investigation is undertaken into both the classical Quantitative Feedback Theory (QFT) and modern H-infinity frequency domain design methods. These design tools are applied to a bank-to-turn (BTT) missile plant at multiple operating points for a gain scheduled implementation. A new method is presented that exploits both QFT and H-infinity design methods. It is shown that this method gives insight into the H-infinity design and provides a classical approach to tuning the final H-infinity controller. The use of “true” inversionfree design equations, unlike the theory that appears in current literature, is shown to provide less conservative bounds at frequencies near and beyond the gain cross-over frequency. All of the techniques investigated and presented are applied to the BTT missile to show their application to a practical problem. It was found that the H-infinity design method was able to produce satisfactory controllers at high angles of attack where there were no QFT solutions found. Although an H-infinity controller was produced for all operating points except the last, the controllers were found to be of very high-order, contain very poorly damped second order terms and generally more conservative, as opposed to the QFT designs. An investigation into simultaneous stabilization of multiple plants using Hinfinity is also presented. Although a solution to this was not found, a strongly justified case to entice further investigation is presented.
Robust power system stabilizer design.
(2002) Moodley, Devandren.; Boje, Edward Sidney.
This thesis investigates the design of damping controllers to alleviate the problem of low frequency electro-mechanical oscillations in power systems. The operating point and network parameters of power systems are continually changing, resulting in changes in system dynamics. The conventional controller design methodology has therefore come under increasing scrutiny for its lack of considerations for robustness. The thesis first outlines the conventional design of a power system stabilizer (PSS) and then applies two robust techniques (Hoo and Quantitative Feedback Theory, QFT) to the design problem. The single machine infinite bus (SMIB) model is used to illustrate the procedure for all three design techniques. The final design is undertaken to illustrate the more important problem of robust multi-machine PSS design using QFT. The design requires linearised models of the multi-machine system. A brief discussion is given on how these can be obtained. An introduction to decentralized control design in QFT is included to support the multi-machine design. Chapter three proceeds through the design steps required to generate a conventional PSS. The technique is shown to be simple for a given set of operating conditions. The controller is shown to be adequately robust over the given set of operating conditions albeit not by design. Chapter four introduces a design technique that directly addresses robustness issues during the controller design. For a restricted range of operating conditions the designed controller demonstrates the desired robustness and performance characteristics. The inherent difficulties with Hoo in PSS design become more apparent as the operating range is extended. Chapter five introduces the second robust controller design technique. QFT is shown to be more adept at dealing with increased operating ranges and changing specifications in the single-machine infinite-bus case. The controller is easy to generate and performs well over the entire range of operating conditions. QFT is also applied to the controller design for a four-machine study system. The design is a marginally more complex than in the single machine case but is still easily accomplished. This thesis confirms previous attempts at solving the design problem using the methods outlined above. The performance of all controllers is assessed for small and large disturbances using non-linear time domain simulations with models developed using PSCAD/EMTDC and MATLAB.