OpenUCT :: Browsing by Author "Tapson, Jonathan"

Browsing by Author "Tapson, Jonathan"

Now showing 1 - 20 of 38

Open Access
Analysis and design of a 1 kW Class-GD ultrasonic generator
(2006) Wheeler, Jacques; Tapson, Jonathan; Davies, J
Open Access
Analysis and design of a high frequency induction-heating system
(2003) Khan, Irshad; Tapson, Jonathan
Advances in power electronic semiconductor technology are making high frequency converters for induction heating more feasible at power levels up to 50kW. This research presents the development and analysis of a solid-state induction-heating system, operating directly off single-phase mains frequency, which enables optimum and efficient operation over a frequency range of 80kHz to 200kHz. The system essentially comprises a DC-DC converter configured as a controlled current source, which feeds a load resonant DC-AC inverter, driving a parallel resonant load circuit. The load circuit comprises an induction-heating coil and a reactive power compensating capacitor. The systems active switching elements comprise power MOSFET's but can be extended to almost any other controlled power devices such as IGBT's, BJT's, SCR's, GTO's or SIT's. An automatic frequency control system ensures that the DC-AC inverter drives the load at its resonant frequency, thereby achieving zero voltage switching of the power semiconductors. This operating mode always ensures maximum power transfer to the load as well as maximum operating efficiency of the DC-AC inverter. Driving the load at resonance presents an essentially resistive load to the DC-DC converter, thereby reducing the losses associated with a reactive load. A compact circuit layout combined with this optimum mode of operation eliminates the need for any snubber circuit components in both the DC-DC and DC-AC converters at this power level. An overview into various applications and technologies of induction-heating is presented in this research. A detailed analysis of the induction-heating coil and work- piece are presented in order to aid the design of the load circuit. The induction-heating technology overview presents various induction-heating power sources, discussing the configurations of various topologies. A brief mathematical analysis is used to describe the operation of power electronic converters employed in the induction-heating system developed for this research. The parallel resonant induction-heating load circuit is characterised mathematically, allowing for the determination of the optimum operating conditions. This is followed by a simulation analysis, which is used to gain insight into the problem of frequency control. The frequency control system is modelled and the steady-state error response evaluated under different input conditions. Experimental results on the system implemented, based on operating waveforms and efficiency measurements of the solid-state induction-heating system are presented along with recommendations for future work. The implemented power source was tested at a maximum power of 2.3kW at 151kHz. A system efficiency of 86% at 1.3kW was measured when operating at 138kHz. This design however, provides for scaling to power levels up to 50kW. The induction-heating system's frequency tracking capability is evaluated by heating a steel work-piece through its Curie transition temperature. The induction-heating system is used to heat a 26mm x 35mm stainless-steel billet (work-piece) to 1200°C in 130 seconds using the calculated power of 1.35kW .
Open Access
An application of Hierarchical Temporal Memory (HTM)
(2011) Liddiard, Ashley; Tapson, Jonathan; Verrinder, Robyn
While a number of neuromorphic studies have been based on understanding and building the brain in software and hardware, a recent theory has been presented from a high level, top down approach, with the view of understanding how the human brain performs higher reasoning, and then designing software infrastructure based on that theory - namely Hierarchical Temporal Memory (HTM). Current opinion raises question marks as to whether this theory is sound, feasible, coherent, logical and correct. This thesis aims to, if not answer some of those questions, at least get closer to understanding the brain and therefore implementing HTM theory in software for further use in an embedded environment. This paper begins by reviewing the discovery of the sensory input and chemical makeup of the signals in the brain, and then introduces mathematical abstraction to form a software program node.
Open Access
Continuous wave mode locking for the determination of the acoustic nonlinearity parameter B/A
(2001) Davies, Jevon Raymond; Tapson, Jonathan; Mortimer, Bruce
The acoustic nonlinearity parameter B/A of the nonlinearity of the equation of state for a fluid. Its significance can be found in numerous fields including shockwaves, bio-chemistry and medicine. Recent studies in the field of biomedical ultrasound have necessitated a simple and accurate means of measuring B/A in vitro.
Open Access
The control of semi-autonomous robots
(2004) McPhillips, Graeme; Tapson, Jonathan
Robotic soccer is an international area of research which involves multiple robots collaborating in an adversarial and dynamic environment. Although many different forms gf robotic soccer are played, the University of Cape Town (UCT) chose the RoboCup smallÂ» sized robot league, officially known as the F180 RoboSoccer league, as a means of pursuing robotics research within the institution. The robot soccer game is played between two teams of ï¬ ve robots on a carpeted surface that is 2.8 m long by 2.3 m wide. The robots have their own on-board controllers that execute instructions sent to them from a computer-based artiï¬ cial intelligence (AI) system. In order for the AI system to keep track of all the robots and the ball (an orange golf ball), a global vision system is utilised. This global vision system uses images captured from either one or multiple digital cameras mounted above the ï¬ eld of play to determine the position and orientation of the team's robots, the position of the other teams' robots and ï¬ nally the position of the ball. In the true spirit of competition and furthering research, the rules which govern F180 RoboSoccer league cover only the basic format of the game thereby leaving various aspects of the robots, global vision system and AI design open for development. Since there was no RoboSoccer research in existence at UCT prior to the inception of this researcher's Masters' thesis the task included both the establishment of this format of robotics research at the institution as well as the actual design and development of the robots and the associated components as outlined below. Developing a team of robots requires a wide array of knowledge and the research undertaken was accordingly broken into three key components; the design of the robots (which included their related electronics and on-board controller), the design of a vision system and the design of an Al system. The main focus of this author's work was on the design of the robots as well as the overall structuring and integration of the UCT F180 RoboSoccer team. In addition, the areas of the global vision system and AI system that were covered within the scope of this thesis, are also presented. Prototypes were developed and in the ï¬ rst the main emphasis was placed on the movement of the robot, with the design of the kicking mechanism only occurring subsequent to this. After the ï¬ rst competition in 2002, this ï¬ rst design was abandoned in favour of developing a simpler robot with which to continue development. This simpler robot became the second prototype which, after testing, was reï¬ ned into the competition robot for 2003. During this period, the Al and global vision systems were developed by undergraduate thesis students. This research was then incorporated where applicable and, ï¬ nally, the residual problem areas were again addressed by a collaboration of staff and students. Whilst the design and implementation of the robots was very successful, the vision system was not successfully implemented before the competition in 2003. Although an autonomous game of soccer was not successfully played in the 2003 competition, the UCT F180 RoboSoccer team had made a great deal of progress towards this goal and, consequently, a strong foundation for future robotic soccer research within UCT has been established.
Open Access
The design and commissioning of a laboratory thickener test plant for measurement and control investigations
(2006) Roeble, Adrian; Tapson, Jonathan
This thesis discusses the design, construction, and commissioning of a laboratory scale thickener test plant to carry out measurement and control tests under controlled conditions. The laboratory scale thickener simulates the settiling conditions found in full scale high compression thickeners. A review of thickener technology, applicable measurements and control strategies was carried out.
Open Access
The design and construction of a flying bird robot
(2011) Bensch, Marius; Tapson, Jonathan
The purpose of this project is to investigate the issues surrounding the design and construction of a flying bird robot. The ideal would be to re-create a model of a bird that looks like bird, functions like a bird with regard to the biomechanical issues involved in flight and uses control systems that emulate the ones used by the bird to control the flight path.
Open Access
Design and construction of a vibration data logging prototype board for overland conveyor belts
(2006) Verrinder, Robyn A; Tapson, Jonathan
Overland conveyor belt systems form a vital part of modern transportation systems in the mining and mineral processing industries. It is vital that the system is well maintained in order to minimise system downtime and maximise profit. The conveyor belt is the single most expensive item in the system. It must be monitored to pick up potential problems before they cause belt failure. The majority of conveyor belt monitoring methods identify belt failure events rather than belt failure causes. The purpose of this project was to research and design a belt condition monitoring board which could be physically embedded in the conveyor belt. This would then be used to monitor the condition of the conveyor idlers whose failure can result in major system damage. The venture was split into two areas of research: the design of a vibration data logging board and the design of a power generation system. The thesis focused on the design of a DSP vibration data logging prototype board, while S.A. Williams investigated the design of a power generation system.
Open Access
Design and implementation of a six-degree of freedom robotic platform for measuring the forces of flying objects
(2011) Banda, Richard; Tapson, Jonathan
The purpose of this project was to research, design and build a six-degree of freedom platform that measures the forces of flying animal robotics. The platform had to have an embedded force sensing mechanism and should be able to move in response to forces detected and measured. The platform had to measure the forces in six different orthogonal axes. The course of action and focus of the thesis was to research, design, build and control the robotic platform and it was an individual project.
Open Access
Design of a high intensity ultrasound dispersion cell
(2003) Foster, Clinton; Tapson, Jonathan; Mortimer, Bruce
The aim of this project was to provide detailed research on the factors causing mechanical damage in a high power ultrasound environment, and to give recommendations for the production of an ultrasonic dispersion cell with a removable treatment vessel. The primary mechanism for causing this dispersion was cavitation: a void of air or vapour in a liquid medium that grows and collapses in an intense ultrasonic sound field. The secondary mechanism was a phenomenon called acoustic streaming which provides a macro mixing effect, also caused by intense ultrasound. Streaming and, even more so, cavitation were difficult to measure and for this reason a refinement of a method to map cavitation fields with aluminium foil was developed. This involved using digital image processing to extract quantitative information from damaged foil samples. A large portion of the project focused on the overcoming of absorption and subsequent rapid attenuation of sound between the transducer (ultrasonic source) and the treatment vessel. This absorption was due to a number of interrelated factors: reflection of sound at material boundaries; cavitation clouds causing sound scattering; energy absorption; and conventional absorption in liquids due to viscous damping. A number of strategies were employed to overcome this absorption problem: the use of increased static pressure to suppress cavitation in certain areas; the use of multiple transducers; and, as a result, multiple paths for the sound to enter the vessel. A combination of static pressure and multiple transducers were also tested. A number of different media were tested for their ability to transmit sound and an optimum solution was recommended. Streaming and the physical constraints affecting streaming in the treatment vessel were tested to give a practical guide to the factors producing streaming. Then, as the temperature of the liquid affects absorption, cavitation threshold, and the ability of a solvent to dissolve, a look at the thermal aspects of the system was discussed.
Open Access
Design of a low pressure system to determine the acoustic nonlinearity parameter B/A for small volumes of sample liquids
(2003) Prenzlow, Bjorn; Tapson, Jonathan; Davies, J
This thesis aimed to design a measurement system to obtain B/A readings for different liquids using the isentropic phase method. The resulting system uses a sinusoidal wave source that operates on less than 20kPa to pressurize a sample liquid of less than 0.2 ml. The advantage of the system is that it can obtain measurements using relatively few parameters of the liquid, requiring only density and sound speed, and that it can obtain a result in a relatively short amount of time (less than 15 minutes after system has reached thermal equilibrium).
Open Access
The design of high power ultrasonic transducers
(2002) Green, A G; Tapson, Jonathan
The purpose of this thesis is to investigate the design and construction of high power ultrasound transducers as well as some of the effects of high power ultrasound. The two design approaches that are researched and applied are the equivalent circuit method and Finite Element Method (FEM). These methods are used in conjunction with each other to design three different transducers, which are then built and tested at low and high powers.
Open Access
Development and prototyping of a Point Coupled Linear Transformer (PCLT) displacement sensor
(2005) Walton, Michael; Tapson, Jonathan
The main aims of this project were to develop and prototype a Point Coupled Linear Transformer (PCLT) displacement sensor, and to perform a general exploration of the PCLT technology. The PCLT is a recent invention that has planar PCB windings and a non-contacting movable core, and relies on variable induction to detect displacement. Different core materials and shapes are investigated. The transformer windings layout is optimized for symmetrical response and high primary to secondary voltage coupling.
Open Access
Development of a cellphone based monitoring and management-support system for anti-retroviral therapy
(2005) Anand, Samir Aneil; Tapson, Jonathan
HIV/Aids has had a major impact on global society since its discovery in 1981.Over the last two decades, HIV treatment research has resulted in the developmentof antiretroviral (ARV) drug therapy and treatment. However, there are many challenges to ARV Therapy (ART) and these challenges are further extended in the resource limited developing world, where the majority of infections occur. Therefore, ART is regarded as not only a medical challenge, but a logistical, monitoring and management challenge that requires the development and implementation of supporting systems. The Cell-Life system is a prototype engineering concept that uses locally available ICTs (Information and Communication Technologies), such as GSM (Global System for Mobile) and Internet connectivity to provide monitoring and management support for ART. This dissertation is an investigation and development of the system in order to create an effective solution for public health sector clinics.The investigation process is based upon a user-centred HCI (Human Computer Interface) model and it is carried out on five components of the system: cellphonemenu applications, SMS data submission and database integration, web applications, servers and user guide and training. This research has resulted in a progressive advancement and transformation of the prototype concept through the development, testing and pilot site implementation of an updated suite of components with valuable findings from usability testing. This study confirms that locally available ICTs can be developed to empower the resource limited clinic level public health sector to overcome some of the challenges of ART. This essentially contributes to bridging the “digital divide” and providing support in the developing context.
Open Access
The development of an on-chip-metering solution
(2001) Kaplen, David; Tapson, Jonathan
Energy Measurements Ltd (EML), a joint venture partnership between Siemens and Spescom, manufacture prepaid electricity utility meters for both the local and international markets. Under the brand name CASHPOWER 2000, EML produces single and polyphase prepayment utility meters. Currently, these meters currently utilise a separate module for the measuring of electrical energy. In order to reduce component costs, EML proposed the energy measurement be conducted by the onboard Microcontroller Unit (MCU), a term known as On-Chip-Metering (OCM). It is envisioned that this would quickly translate in an increase in revenue. However, a major concern regarding this has been the increase in the required processor overhead. The CASHPOWER 2000 embedded MCU would be required to conduct all the present metering functionality in addition to the energy measurement. This, together with the cost analysis and compliance with the stipulated IEC1036 regulations, constitute the key criteria in determining the projects viability. This dissertation represents the investigative and development stages of a prototype algorithm and accompanying peripheral hardware as a possible solution for OCM. As part of the preliminary research, several examples of digital power and energy-measurement techniques were investigated. A comparative analysis of these was performed to facilitate the development of a unique solution based on the research conducted. This completed, a prototype was developed and preliminary testing was conducted to determine its compliance with the stipulated regulations for a class 2 meter, as per IEC1O36 speciﬁcations.
Open Access
An extensible computational cochlear modelling framework
(2012) Rapson, Michael James; Tapson, Jonathan
Cochlear models are used by many people for many purposes. Each purpose has different accuracy and complexity requirements, so no single model will be suitable for every purpose. A wide range of cochlear models has already been proposed, and the diversity in the field is only increasing. The proposed framework allows a large subset of models to be implemented and compared, facilitating modelling efforts. It uses the finite element method and state space techniques in an object orientated library, and is suitable for time domain cochlear models. In the face of the diversity noted, the physiology of the cochlea itself limits the scope of the possible models to consider. A general modelling framework is described in broad strokes, narrowing to provide full details of its implementation and use for a smaller set of models. Various published models were accurately replicated in the framework, and it was used to verify a silicon cochlea model. Studies into the mathematics behind fluid-structure interaction in the cochlea show that the set of models considered is characteristic of cochlear models in general, ensuring the desired extensibility of the modelling framework. These studies also have various implications for the cochlear modelling community at large.
Open Access
A handheld DSP based vibration analyzer
(2001) Ginsberg, Samuel Isaac; Tapson, Jonathan
This dissertation investigates the design and implementation of a hand held vibration analyzer for use on electrical rotating machinery. The analyzer gathers data from an accelerometer and can present either acceleration, velocity or displacement information. Any information can be presented to the user in either the time or frequency domain. Numerical measurements can be made on the readings and readings can be stored onto a CompactFlash memory card. The instrument features its own type of file system and data storage metaformats. Facilities exist for the instrument to upload data to a computer or to download information from a computer. The instruments is made ergonomic by means of an extensive menu and hotkey system and by means of automated route tracking facilities.
Open Access
Image reconstruction on electrical resistance tomography measurements in a settling process
(2004) Herholdt, Siegfried; Tapson, Jonathan
This thesis uses Electrical Resistance Tomography (ERT) to measure a settling process. The measurement hardware for this system was developed during previous work carried out by the author. This research is the continuation of this work by focusing on image reconstruction from the measured data. The reconstruction algorithm attempts to find the conductivity distribution of the interior of a rig from measurements made on its boundary. The method used in this thesis is the Newton-Raphson (NR) Algorithm, which employs iterative solutions of the Finite Element Method (FEM) in order to converge to a solution for conductivity. FEM is a numerical simulation method that discretises a region into elements and performs a global optimisation or minimisation in order to arrive at a solution. The NR-method is similar in principle to Newton's method, but is designed to operate on complex data and matrix equations in multiple dimensions. This thesis discusses the methods in reasonable detail and highlights several issues, including ill-conditioning, and regularisation as a method to improve the conditioning of the data. The results contain images of successful reconstruction of a settling process.
Open Access
Imitating human motion using humanoid upper body models
(2012) Dube, Chioniso; Tsoeu, Mohohlo Samuel; Tapson, Jonathan
This thesis investigates human motion imitation of five different humanoid upper bodies (comprised of the torso and upper limbs) using human dance motion as a case study. The humanoid models are based on five existing humanoids, namely, ARMAR, HRP-2, SURALP, WABIAN-2, and WE-4RII. These humanoids are chosen for their different structures and range of joint motion.
Open Access
Improving sports vision diagnostics using wireless electro-oculography
(2006) Wills, Dominic A; Tapson, Jonathan
Traditional techniques such as eye hand coordination tests have difficulty isolating the pure eye movement data as their results are reliant on subjects performing physical responses to visual stimuli. What is needed in this field is diagnostic equipment that can give information on eye motion alone. Electro-Oculography was investigated as a form of eye tracking as it is an inexpensive, simple, underdeveloped and primary method of eye tracking that required low data transmission rates.