The systematic development of a machine vision based milking robot

Agriculture involves unique interactions between man, machines, and various elements from nature. Therefore the implementation of advanced technology in agriculture holds different challenges than in other sectors of the economy. This dissertation stems from research into the application of advanced technology in dairying - focusing on the systematic analysis and synthesis of concepts for a robotic milking machine for cows. The main subsystems of the milking robot are identified as a machine perception subsystem and a mechanical manipulator subsystem. The machine perception subsystem consists of one or more sensors and a signal processor; while the manipulator subsystem typically consists of a robot arm; a robot hand; actuators; and a controller. After the evaluation of different sensor concepts in terms of a defined set of technical performance requirements, television cameras are chosen as a suitable sensor concept for a milking robot. Therefore the signal processor is only concerned with image processing techniques. The primary task of the milking robot's image processor is to derive a computerized description of the spatial positions of the endpoints of a cow's four teats, in terms of a pre-defined frame of reference (called the word coordinates ). This process is called scene description ; and based on extensive experimental results, three-dimensional scene description - making use of a stereo-vision set-up - is shown to be feasible for application as part of a milking robot. Different processes are involved in stereo machine vision - such as data reduction, with the minimum loss of Image information (for which the Sobel edge enhancement operator is used); the accurate localisation of target objects in the two stereo images (for which the parabolic Hough transform is used); and correlation of features in the two stereo images. These aspects are all addressed for the milking robot, by means of concept analysis, trade-oft, and experimental verification. From a trade-off, based on a set of performance requirements for the manipulator subsystem, a cartesian robot arm is chosen as a suitable configuration for the milking robot; while sealed direct current servo motors are chosen as a suitable actuator concept. A robot arm and its actuators are designed by means of computer-aided design techniques; and computer simulation results are presented for the dynamic response of the arm and its actuators. A suitable robot hand is also designed - based on systematic trade-oft for different parts of a robot hand. From an analysis of the desired controller functions, and of different control concepts, it is concluded that a positional controller, making use of on-line obstruction avoidance, is required for the milking robot. Because this research project involved systematic concept exploration, there are still some details to be sorted out in a follow-up development phase. The basic principles of a machine vision based milking robot are however established; and the work in this dissertation represents a suitable baseline for further development

A Review of Current Research Trends in Power-Electronic Innovations in Cyber-Physical Systems.

In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.post-print2.019 K

Creating a 'black film industry' : state intervention and films for African audiences in South Africa, 1956-1990.

Includes abstract.Includes bibliographical references (leaves 217-239).This thesis examines one aspect of cinema in South Africa, namely, the historical construction of a 'black film industry' and the development of a 'black' cinema viewing audience. It does so by focusing on films produced specifically for an African audience using a state subsidy. This subsidy was introduced in 1972 and was separate from the general or A-Scheme subsidy that was introduced in 1956 for the production of English- and Afrikaans-language or 'white' films. This thesis is a critical assessment of the actual film products that the B-Scheme produced. The films are analysed within the broader political, economic and social context of their production and exhibition. The films are used as historical sources for the way in which African identities were constructed. Through critical analyses of the selected films, the thesis examines the manner in which African people, culture, gender and family relations, as well as class and/or political aspirations were represented in film. Africans had very little opportunity or power to represent themselves and where this had been possible, it was within the ideological and political boundaries set by the apartheid government

African field reports, 1952-1961

Mr. Edwin S. Munger is a successful experiment. The experiment started a number of years ago. It was an experiment with a new method of producing an expert. After World War II ten million men returned from overseas to the United States. Many of them had been in Africa, Asia, Europe and elsewhere for years on end. But the country to which they returned was deeply ignorant of the very world which it had helped to save from conquest by Germany and Japan. There were some experts on Russia and China, fewer still on India and Southeast Asia. On Africa there were a couple of lonely men with no one to talk to and nobody much who wanted to listen. Expertness in the American university world, especially in those days, was often training in the difficult art of looking at the world through the eye of a needle. Geographers of China without history, historians of Russia without economics, economists of Japan without anthropology, anthropologists of Africa without geography - this gave concentration, good thesis titles and no community of discourse. But help was at hand. During the war a few bright spirits recognized that fighting Japan and then making peace with Japan might be carried on more successfully if the geography, history, economics and anthropology were regarded as aspects of a total Japanese culture. Moreover, it did not seem to be quite so ridiculous or impossible for well-trained men to acquire an expert understanding of a whole people, an entire country or a large and even diverse area. Universities experimented with area studies, and for a while the experts permitted the upstarts to look round instead of through the eye of a needle. Of the many excellent things about America is a readiness to try something that has not been tried before, even though it may look silly or wrong. And so a bold foundation undertook the experiment of trying to create an expert generalist or a general expert. There appeared in India, South Africa, East Africa, Brazil and elsewhere able young men with the mission of seeing all they wanted to see, learning each according to his qualities, all they could learn, and setting down in writing their opinions, observations and conclusions. If any of them had a thesis, or wanted a Ph.D., or planned ultimately to get back of the eye of a needle, that was incidental. Otherwise, it was not cricket. Edwin Munger was one of these people. He was a geographer, which meant that he had his own eye of a needle. With a Ph.D. under his belt, he could run for cover if he had to. But he did not. As any reading of his published work shows, he became very skillful at looking at Africa from all sorts of angles. He skipped over the Germanic spirit of the nineteenth century scholarship into a free-ranging eighteenth century Voltairean spirit willing to look at geography, history, politics and even Afrikaans poetry. It was not a pure zest for scholarship that caused him to marry a South African girl, but his admirers know that this was helpful. Of Voltaire the historians of the day said that he was a master of all knowledge except history. Mathematicians, philosophers and divines made the same exception in the case of their own subjects. Scholars may want to express the same qualifications about a geographer who writes on constitutions, ethnology, penal codes and even rape. But they would miss the point. Ten years of traveling, looking, learning, writing and talking have produced in Mr. Munger an expert generalist. He has much of Africa, and certainly South Africa, in his veins and in his pores. His has been a systemic as well as a cerebral education. For the United States the appearance of a growing number of men with this systemic, visceral, pervasive understanding of other lands and peoples is a superb enrichment. It means that Americans are less prone to fashion their opinions out of theoretical deductions from their own history. This bad habit explains much of the naive or clumsy handling of America's foreign policy. A position based on American political thought does, of course, lead to more sympathy for Julius Nyerere than for Verwoerd. But the new generation of scholars like Edwin Munger make it possible for American public opinion to understand that Mr. Verwoerd is a man involved in one of the most difficult problems of modern history. If one, indeed, accepts Mr. Verwoerd's assumptions, which I cannot, then Mr. Verwoerd becomes a very logical man, acting according to principle, and in a spirit of great courage. One of the saddest paradoxes about Africa is that it needs literally millions of fresh highly skilled experts. But the clash of grinding racial antagonisms may be leading to the expulsion of nearly four million people already in Africa who have many of the skills that Africa must have in order to prosper. Maybe the dams have already burst, and the destroying floods are inexorably on their way. Mr. Verwoerd is certainly in their path. But meanwhile it is valuable to read the understanding and thoughtful things Mr. Munger has to say about Germans and Afrikaners, Jews and Indians, black men and colored men. He knows that if there is hope in South Africa it must come from Afrikaner liberals, although here I myself would wish that he had more to say of the now lonely, and courageous and generously minded English liberals. It is always a little harder to see the virtues of a people whose language is the same as your own. There is a special bias towards people whose tongue you have arduously learned to speak. All this will be written again, later on, in fuller knowledge, maybe not through a haze of tears or after the atomic dust has settled upon a broken world. If the fates are very kind, this may be written again by men free of the angers that now rack Africa. That Mr. Munger has written so fully, so variously means that the final and more definitive story will be better and more fairly told

The South African Philatelist : 1945

The Philatelic Federation of South Africa (PFSA) is a voluntary association organised as a federation of clubs & societies for stamp collectors and philatelists of all ages and all types. To produce the up-to-date journal locally is no easy matter, but we shall continue to give our readers what we think they will appreciate most. The journal is managed by a collector for the benefit of collectors, and as no dealer has any choice in the management, philatelists will realise that they have a paper which will cater for their wants, and give them reliable, unbiassed advice.The South African Philatelist, January - December (1945)Digitised by the Department of Library Services in support of Open Access to information, University of Pretoria.pm202

The lived experiences of African women transitioning from professional services firms to corporate environments

A research report submitted to the Faculty of Commerce, Law and Management, University of Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Management in Business Executive Coaching Wits Business School, Johannesburg February 2017This research was conducted to explore the career experiences and career transitions of African women Chartered Accountants in the South African business environment where employment equity of race groups is sought. The international pursuit of gender transformation at the executive level, together with the South African employment equity targets, makes professional African women a key group for employers. Their lived experiences and career transitions challenges were the focus of this study. Qualitative research was deemed the most suitable approach to obtain depth of understanding of an area that has not previously been researched. Semi-structured interviews provided insight to participants who experienced transitions within professional services firms (PSF), returned to PSF, and transitioned out of PSF to other corporates. Since career transitions of this group of professionals did not appear in the literature, a theoretical framework of related literature was derived, which informed the development of a semi-structured interview guide. Sixteen interviews were conducted with participants from South Africa’s Gauteng province. Participants fell into four groups: those who remained in PSF, those who returned to PSF after having left, those who left and were at a managerial level, and finally, those who had left and were at executive levels. Interviews, with permission of the participants, were recorded, transcribed and analysed using ATLAS.ti software. The analysis resulted in 145 codes, 23 categories and 10 themes. The increase in black women professionals in organisations is slower than would have been expected, with monitoring emphasis placed on overall racial transformation rather than gender-specific change. This research found that African women CAs experienced being regularly targeted by recruiters and employers for positions. Participant career transitions were found to be impacted by South Africa’s employment equity legislation, resulting in career fast-tracking initiatives and being targeted as new hires by organisations. Participants’ lived experiences highlighted that their first transition into the work environment established a basis for comparison when experiencing subsequent transitions. Career transition challenges experienced include racial tensions resulting from perceived fast-tracking, organisational unpreparedness in assisting newcomers, and a lack of role models and structured support. Tenure is impacted by ineffective transition experiences. Organisations lack sufficient programmes to cater to the unique challenges faced in these career transitions. Thus, coaching is proposed as a suitable intervention. Family backgrounds, role models and other significant networks are not generally available as support resulting in a need for coaching. Based on different types of transitions identified in the study, a model was developed to guide business coaches in assisting future clients in preparing for transitions, going through career transitions, as well as establishing themselves within new organisations. Further research should take in a wider sample, as this study was limited to participants within Gauteng. Studies focussing on other professions such, as the legal, medical and engineering profession, are recommended to establish the lived experiences of African women’s career transitions.MT201

A study of the interaction in book selection between provincial library systems and their affiliated public libraries in South Africa

Bibliography: leaves 360-395.Current methods of book selection in provincial library services in South Africa are examined with a view to establish whether they are the most effective possible from the point of view of the affiliated public libraries throughout the country. This involved tracing the history and development of the four provincial library services and examining their current selection practices. A well-organised network of affiliated public libraries making provision for white, and to a lesser extent coloured, South Africans has been established since World War II, with the strongly centralised provincial services providing the book stock. It appeared from the study that relatively little change had occurred in either the organisational structures or the book selection methods of these services since their inception, and that the involvement of local librarians in book selection was negligible. Instead of their role increasing as more public libraries were staffed by qualified librarians, financial pressures had resulted in even less initiative being permitted and an increase in centralised control. To establish the ideal model against which the performance of the provincial library services could be evaluated, contemporary professional opinion on public library objectives, management and book selection, as also the developments in rural systems in selected countries was surveyed. Compared to the static local picture of service which emerged from the empirical investigation, overseas advances in goals and management as reported in the literature had seen exciting professional advances, with librarians accepting, and going out to meet, the challenge of the changes in society. Strong communication links between users and selectors were emphasised. Rural networks in the foreign countries surveyed had grown to improve in efficiency and in economic terms, but in all cases the local librarian selected his own book stock, which seems more satisfactory than the current South African practice. To further test this hypothesis an empirical investigation by means of a questionnaire was circulated to all affiliated public libraries circulating more than 60 000 books annually. The findings confirmed the surmised lack of interaction in book selection between provincial and public librarians, and there was dissatisfaction, particularly among the very biggest libraries with experienced qualified staff, at the present system. The thesis concludes with recommendations made towards remedying this situation

Analysis and design of a high frequency induction-heating system

Includes bibliographical references.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