Architectural design interventions toward improvement of construction health, safety, and ergonomics in South Africa
- Authors: Goldswain, Craig Colin
- Date: 2014
- Subjects: Construction industry -- Safety measures , Construction industry -- Accidents -- South Africa , Architectural design -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9717 , http://hdl.handle.net/10948/d1021060
- Description: The construction industry produces a high rate of accident statistics. Constructors are exposed to a range of construction hazards and risks which manifest themselves in accidents and lead to a high incidence of illnesses, injuries and fatalities. Despite evidence that up to 50 percent of construction accidents can be avoided through mitigation of hazards and risks in the design phase of construction projects, architectural designers do not adequately engage in designing for construction health, safety, and ergonomics. The research localises the problem in the context of South Africa and sets out to develop an architectural design oriented model toward a reduction of construction hazards and risks, which can be engendered through optimisation of tertiary architectural education and through continuing professional development (CPD) programmes. The ultimate aim is to realise a paradigm shift in architectural design relative to construction health, safety, and ergonomics as architectural designers in South Africa still view it as the constructor’s responsibility. The research intertwined a range of secondary data with four provisional studies undertaken in the Eastern Cape Province considered representative of South Africa. This involved both quantitative and qualitative methodologies and were directed at architectural designers registered with the South African Council for the Architectural Profession (SACAP). The provisional studies were published in international conference proceedings and served to gradually provide local insight, and ultimately provided a line of structured questions for use in the main study. The main study was positioned in the action research (AR) paradigm and used focus group (FG) methodology to solicit a vast richness of qualitative data from SACAP registered architectural designers who participated in the FG proceedings. Synthesis of data with literature and the provisional studies gave rise to a provisional model comprising six main model components and a range of sub-components. The provisional model was validated and refined while simultaneously testing the research hypotheses by means of questionnaires directed at the SACAP registered FG participants. The evolved model includes a core model embedded in a greater process model, and implementation and use of the core model relies on appropriate knowledge of architectural designers. It is ultimately recommended that tertiary architectural education institutions and those involved in architectural CPD programmes take ‘upstream design ownership’ and use the model as a basis for designing and implementing appropriate tertiary architectural programmes and architectural CPD offerings. Ultimately the model is not considered as a complete means to an end, and further investigation is needed in order to design and implement the recommended programmes. Only then can we begin to realise a paradigm shift in architectural thinking and practice.
- Full Text:
- Date Issued: 2014
Behaviour-based health and safety management in construction: a leadership-focused approach
- Authors: Okorie, Victor Nnannaya
- Date: 2014
- Subjects: Construction industry -- Safety measures , Construction industry -- Accidents -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9676 , http://hdl.handle.net/10948/d1021034
- Description: The construction industry remains a pillar in the South African economy, generating employment and wealth. Nonetheless, the industry is reportedly bedevilled by a high rate of accidents and serious injuries that often lead to permanent deformation and fatalities among workers and the general public. These accidents and injuries manifest due to poor construction health and safety (H&S) performance that is often related to poor H&S leadership of the key project leaders involved in the construction business. Shortcomings pertain to client leadership in terms of involvement and commitment to H&S and project H&S related decisions of professionals (designers, project managers, quantity surveyors and engineers). They also pertain to contractor related aspects such as H&S management systems and leadership at all levels of management. In addition, contractors’ inadequacies of H&S management relative to workplace planning and materials related issues have continued to marginalise H&S performance in construction. The H&S leadership of key project leaders is very important in creating a culture of H&S in the workplace. This study examined the H&S management practices and leadership of the key project leaders that contribute to at-risk work practices or unsafe behaviour of workers. Presently, there is limited or no research in South African construction on how the H&S leadership of the key project leaders contributes to at-risk work practices or unsafe behaviour of workers. The methodology employed in the study included an extensive review of relevant literature, which enabled the field work to proceed unhindered. The quantitative survey and qualitative inquiry was conducted with the key construction participants in South African construction. Focus group discussions and interviews were used in a complementary manner. Accordingly, the sampling technique for the study comprised simple random and purposive sampling. The study revealed apparent poor leadership and lack of involvement and commitment to workers’ H&S by the key project leaders. Notably, there is statistical evidence of poor H&S management practices among contractors in terms of top management commitment to and involvement in project H&S. This statistical evidence includes poor H&S education and training of workers and lack of workers’ involvement and participation in H&S matters, which is the tenet of behaviour-based H&S anagement. The model of leadership influence on worker H&S behaviour developed in this research constitutes an innovative contribution to construction H&S performance improvement through a leadership-focused approach. The study has established a basic level of awareness and understanding among key project leaders in that their upstream decisions during the project planning and construction phases have significant influence on workers’ safe or unsafe behaviour or at-risk work practices. The study strongly advocates transparent leadership, ethical behaviour among clients in public and private sectors, designers’ critical H&S decisions, project managers’ and quantity surveyors’ commitment towards project H&S and contractors’ adoption and implementation of behaviour-based H&S management systems. The developed leadership influence model of worker H&S behaviour in the study provides a useful guide for the key project leaders to realise the desired H&S performance improvement in the South African construction industry.
- Full Text:
- Date Issued: 2014
Construction and integration of a battery pack and management system into a solar car
- Authors: Kloeblen, Arne
- Date: 2013
- Subjects: Solar cars -- Batteries , Solar cars -- Design and construction
- Language: English
- Type: Thesis , Masters , MEngineering (Mechatronics)
- Identifier: vital:9653 , http://hdl.handle.net/10948/d1018654
- Description: In today’s world, we have reached the point where conventional energy forms are inevitably running out. At the same time, the technology for alternative energy harnessing is improving with big steps, especially with society rethinking their high consumption of finite energy and material. This opens the opportunity und increases acceptance for projects and research to prove its actual implementation and to push the boundaries of current technology further.One particular area of application is the automotive sector showcasing raise of costs due to depleting fuel. Solar powered cars are raising interest as it could be a way to complete independence of any resource that has to be produced, mined or in any way transported to the place of consumption. Involvement with the view to enhance their research in this field has become interesting for universities.With solar powered cars, new problems emerge, amongst others the amount of harnessed sun power and the storage to have it available at the point of use. Due to the low energy available, energy storage as light and as efficient as possible is needed. A system is required that allows to be operated independently of its surrounding in a way it is controllable.Lithium-ion based batteries were seen as the most applicable way to execute this, as they give the highest energy density with lower losses than stable, commercially available energy storage mediums.It was decided to design, build and integrate a battery system with its safety circuit into a solar car. After material selection suppliers were searched and contacted. With the successful manufacturing of this system combining different processing methods, partially at university and partially in the industry, the project included a monitoring and management system and protective measures. It was implemented so that neither the limitations of the chemistry and the physical cells nor the vibration occurring while driving the car prevents its proper use. Besides this, communication and dimensions to operate within the car followed, allowing the driver and convoy to access information and control the system.This battery system proved to be practical in street use comparable with that of regular cars and posed as a safe and effective energy supply for an electrically driven car, meeting the given demands.
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- Date Issued: 2013
The fatigue life cycle prediction of a light aircraft undercarriage
- Authors: Erasmus, Daniel Jacobus
- Date: 2010
- Subjects: Metals--Fatigue
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9614 , http://hdl.handle.net/10948/1527 , Metals--Fatigue
- Description: The reliability of systems relies heavily on accurate fatigue life prediction of related components. Fatigue life prediction is a complicated process requiring the correct methodology to determine accurate and reliable predictions. The Palmgren – Miner damage accumulation hypothesis is widely used in determining the fatigue life of components exposed to variable loading conditions. Modifications have been made to this hypothesis trying to achieve a greater degree of accuracy, of these the Liu – Zenner modification has been the most successful. In this report the systematic process of fatigue life prediction using the Liu – Zenner modification to achieve reliable results is calculated. A representative stress time history measured in service on the component forms the basis for defining a flight cycle which is the chosen unit in which to express the fatigue life. Rainflow cycle counting performed on the stress time history allowed the formulation of a load spectrum to which the component is exposed in one cycle. Combining the load spectrum with the developed SN curve of the component and using the Liu – Zenner modification to the Palmgren – Miner rule a reliable fatigue life in cycles is predicted.
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- Date Issued: 2010
Implementing the CoSaWoE models in a commercial workflow product
- Authors: Erwee, Carmen
- Date: 2005
- Subjects: Computers -- Access control , Workflow , Computer security , Data protection
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9732 , http://hdl.handle.net/10948/169 , Computers -- Access control , Workflow , Computer security , Data protection
- Description: Workflow systems have gained popularity not only as a research topic, but also as a key component of Enterprize Resource Planning packages and e- business. Comprehensive workflow products that automate intra- as well inter-organizational information flow are now available for commercial use. Standardization efforts have centered mostly around the interoperability of these systems, however a standard access control model have yet to be adopted. The research community has developed several models for access control to be included as part of workflow functionality. Commercial systems, however, are still implementing access control functionality in a proprietary manner. This dissertation investigates whether a comprehensive model for gain- ing context-sensitive access control, namely CoSAWoE, can be purposefully implemented in a commercial workflow product. Using methods such as an exploratory prototype, various aspects of the model was implemented to gain an understanding of the di±culties developers face when attempting to map the model to existing proprietary software. Oracle Workflow was chosen as an example of a commercial workflow product. An investigtion of the features of this product, together with the prototype, revealed the ability to affect access control in a similar manner to the model: by specifying access control constraints during administration and design, and then enforcing those constraints dynamically during run-time. However, only certain components within these two aspects of the model directly effected the commercial workflow product. It was argued that the first two requirements of context-sensitive access control, order of events and strict least privilege, addressed by the object design, role engineering and session control components of the model, can be simulated if such capabilities are not pertinently available as part of the product. As such, guidelines were provided for how this can be achieved in Oracle Workflow. However, most of the implementation effort focussed on the last requirement of context-sensitive access control, namely separation of duties. The CoSAWoE model proposes SoD administration steps that includes expressing various business rules through a set of conflicting entities which are maintained outside the scope of the workflow system. This component was implemented easily enough through tables which were created with a relational database. Evaluating these conflicts during run-time to control worklist generation proved more di±cult. First, a thorough understanding of the way in which workflow history is maintained was necessary. A re-usable function was developed to prune user lists according to user involvement in previous tasks in the workflow and the conflicts specified for those users and tasks. However, due to the lack of a central access control service, this re- usable function must be included in the appropriate places in the workflow process model. Furthermore, the dissertation utilized a practical example to develop a prototype. This prototype served a dual purpose: firstly, to aid the author's understanding of the features and principles involved, and secondly, to illustrate and explore the implementation of the model as described in the previous paragraphs. In conclusion the dissertation summarized the CoSAWoE model's compo- nents which were found to be product agnostic, directly or indirectly imple- mentable, or not implemented in the chosen workflow product. The lessons learnt and issues surrounding the implementation effort were also discussed before further research in terms of XML documents as data containers for the workfow process were suggested.
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- Date Issued: 2005
Material characterisation of laser formed dual phase steel components
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
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- Date Issued: 2005
The application of constraint management to a simulated manufacturing environment
- Authors: Van der Merwe, Karl Robert
- Date: 2005
- Subjects: Theory of constraints (Management) , Production management , Manufacturing processes -- Computer simulation , Production engineering -- Computer simulation
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9606 , http://hdl.handle.net/10948/409 , Theory of constraints (Management) , Production management , Manufacturing processes -- Computer simulation , Production engineering -- Computer simulation
- Description: South Africa endorsed a world trade accord ratified in Geneva on December 13, 1993. To promote world economic growth, the General Agreement on Tariffs and Trade (GATT) aimed to slash duties on 8000 categories of manufactured goods. Tariff barriers have declined significantly and are now approaching trivial levels (Hill, 1999, p163). Unfortunately, South Africa is ranked near the bottom of the World Competitiveness Report (Cheales, 1995, p8). Increased foreign competition has caused many South African companies to search for techniques that will improve their overall performance. Unless these techniques can be identified and implemented timeously, some companies may fail to remain competitive. This research addresses the lack of awareness in the Eastern Cape (SA) and utilisation of two techniques used successfully in the USA (and elsewhere in developed countries) namely, Constraint Management and simulation. The overall objective was to develop a method of convincing industry management of the benefits of the two techniques. The approach adopted was to use simulation to prove Constraint Management. To achieve this objective a comprehensive literature survey was performed to determine the logic of each technique and the associated benefits. The next step was to determine the levels of awareness among industry practitioners and managers. Managers, engineers and academics were requested to complete questionnaires in order to determine awareness and utilisation of each technique as well as factors that prevented the application of both. The simulation modeling process was examined in order to verify the logic of simulation and a model of a manufacturing system was developed. Constraint Management principles were then applied to the model in a series of experiments. This process was then developed into a manual that could be used to address the lack of awareness and utilisation of both Constraint Management and simulation. The manual was tested on a group of BTech students and industry practitioners in order to establish whether its use would be effective in raising awareness, understanding and utilisation. The outcome was positive and it was established that this technique was effective.
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- Date Issued: 2005
Design and implementation of robotic control for industrial applications
- Authors: Will, Desmond Jeffrey
- Date: 2004
- Subjects: Robotics
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10819 , http://hdl.handle.net/10948/213 , Robotics
- Description: Background: With the pressing need for increased productivity and delivery of end products of uniform quality, industry is turning more and more to computer-based automation. At the present time, most of industrial automated manufacturing is carried out by specialpurpose machines, designed to perform specific functions in a manufacturing process. The inflexibility and generally high cost of these machines often referred to as hard automation systems, have led to a broad-based interest in the use of robots capable of performing a variety of manufacturing functions in a more flexible working environment and at lower production costs. A robot is a reprogrammable general-purpose manipulator with external sensors that can perform various assembly tasks. A robot may possess intelligence, which is normally due to computer algorithms associated with its controls and sensing systems. Industrial robots are general-purpose, computer-controlled manipulators consisting of several rigid links connected in series by revolute or prismatic joints. Most of today’s industrial robots, though controlled by mini and microcomputers are basically simple positional machines. They execute a given task by playing back a prerecorded or preprogrammed sequence of motion that has been previously guided or taught by the hand-held control teach box. Moreover, these robots are equipped with little or no external sensors for obtaining the information vital to its working environment. As a result robots are used mainly for relatively simple, repetitive tasks. More research effort has been directed in sensory feedback systems, which has resulted in improving the overall performance of the manipulator system. An example of a sensory feedback system would be: a vision Charge-Coupled Device (CCD) system. This can be utilized to manipulate the robot position dependant on the surrounding robot environment (various object profile sizes). This vision system can only be used within the robot movement envelope
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- Date Issued: 2004
A generic simulation of energy consumption of automobile air conditioning systems
- Authors: Konz, Martin
- Date: 2003
- Subjects: Automobiles -- Air conditioning
- Language: English
- Type: Thesis , Masters , MTech (Engineering)
- Identifier: vital:10822 , http://hdl.handle.net/10948/129 , Automobiles -- Air conditioning
- Description: The air conditioning system in a car is, in addition to the heating system, installed to increase the comfort in the passenger compartment. Comfort is not the only reason for automotive air conditioning systems, as road safety also improves with the comfort of the driver, as a pleasant environment reduces driver fatigue. The rising environmental problems and, hence, resulting stringent legislation are forcing the automobile industry to develop cars with ever decreasing fuel consumptions. The question of better fuel consumption and energy utilisation does not stop with the engine and aerodynamics, but is required of the air-conditioning system as well. Thus, incessantly innovative technologies are developed to decrease the energy required by the air-conditioning systems. The interaction of the refrigerant cycle components and the rapidly changing operating conditions of the car (speed, revolutions per minute, etc.) places extensive demands on the control system. In addition, the air-conditioning system is also designed for high ambient temperatures (cool down), but is mostly used in fairly moderate conditions. This operation allows for energy saving control strategies such as externally controlled compressors, blower motor control, etc. The experimental comparison of different air-conditioning systems, components or control strategies is very time consuming and extensive, and the use of an air-conditioned wind tunnel is inevitable when experiments need to be done with reproducible ambient conditions.This, combined with the high costs of installation and operation of a wind tunnel is a major problem. Furthermore, the effect of component or control strategy enhancements should be available as soon as possible in the early stages of design. The above considerations have prompted the rapid development of new powerful simulation tools, but in most cases the simulation tools are focused on one specific component or problem only. A more holistic approach would be to combine the calculations of two or more programs. This implies the adaptation of the model to more programs which leads to a lack of transparency. Obviously, the entire development work cannot be done entirely by simulation, especially in the later phases of the development where it would still be necessary to build prototypes to evaluate the done work experimentally. However, in the early stages of development, it would be advantagous to work without expensive prototypes.
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- Date Issued: 2003
An automotive carbon dioxide air-conditioning system with heat pump
- Authors: Böttcher, Christof
- Date: 2003
- Subjects: Automobiles -- Air conditioning , Automobiles -- Heating and ventilation , Heat pumps
- Language: English
- Type: Thesis , Masters , MTech (Mechanical Engineering)
- Identifier: vital:10811 , http://hdl.handle.net/10948/206 , Automobiles -- Air conditioning , Automobiles -- Heating and ventilation , Heat pumps
- Description: The refrigerant circuits of car air-conditioning systems are fitted with so-called open type compressors, because there is only a lip seal preventing the refrigerant from leaking from the compressor housing to the atmosphere. In addition, the cycle uses damping elements between the compressor and the other components on the suction and pressure lines to reduce vibration and noise transfer from the engine to the car body. Both the lip seal and damping elements result in loss of refrigerant as they are made from elastomers and leak with age, and, under high temperature conditions inside the engine room, these elements also allow a relatively high permeation of the refrigerant gas to the atmosphere. With very high refrigerant losses in the older R12 -cooling cycles and the damage caused by this gas to the ozone layer in the stratosphere, the Montreal protocol phased out this refrigerant and the car industry was forced to revert completely to R134a until 1994/95. R134a has no ozone depletion potential, but it has a direct global warming potential, and, therefore, leakages also have to be minimised. R134a has, because of its molecular size, a high permeation potential and, hence, all the refrigerant hoses are lined internally. Unfortunately, these hoses also leak with age and significant refrigerant loss will occur [1] R134a can therefore only be viewed as a solution until an alternative refrigerant with no direct global warming potential has been developed. Candidates for new refrigerants are natural substances such as hydrocarbons or carbon dioxide [2]. Unfortunately, both substances have disadvantages and their use is restricted to special cases, for e.g. hydrocarbons are flammable and are not used in car air-conditioners, but in Germany it is used as a refrigerant in household refrigerators with hermetic cycles. What makes the implementation of carbon dioxide (CO2) difficult are the high system pressures and the low critical point [3].
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- Date Issued: 2003
Analysis of material flow around a retractable pin in a friction stir weld
- Authors: Georgeou, Zacharias
- Date: 2003
- Subjects: Friction welding , Aluminum alloys -- Welding
- Language: English
- Type: Thesis , Masters , MTech (Mechanical Engineering)
- Identifier: vital:10812 , http://hdl.handle.net/10948/196 , Friction welding , Aluminum alloys -- Welding
- Description: Friction StirWelding (FSW) has been researched for a number of years since its inception in 1991. The work thus far has been based on understanding the material and thermal flow using the standard fixed pin tool. The keyhole resulting during tool extraction in a FSW weld, is a disadvantage and a current limiting factor. Eliminating this effect from a weld using a movable pin tools would make FSW more commercially viable. This dissertation focuses on the design of a novel retractable pin tool, and highlights the problems encountered during the welding of Aluminum plates, Al2024 and Al5083. Previously studied techniques of material and thermal flow were used, to investigate the effect of the tool during extraction in a FSW weld. A prototype retractable tool was designed using parametric and axiomatic design theory, and implementing a pneumatic muscle actuation system. The resulting problems in the calibration of the retractable pin tool and the resulting welds are presented, these results confirming previous studies. The movable pin produced discrepancies the heat generation around the shoulder during a FSW weld. The failure of this tool to produce a reasonable weld showed that previous ideas into the workings of a retractable pin tool requires further investigation, furthermore a fresh approach to the interpretation and understanding of the FSW weld process needs consideration.
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- Date Issued: 2003
Design and development of a remote reconfigurable internet embedded I/O controller
- Authors: Phillips, Grant
- Date: 2003
- Subjects: Embedded computer systems -- Design and construction , Computer input-output equipment , Programmable controllers , Electronic controllers -- Design and construction
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10817 , http://hdl.handle.net/10948/116 , Embedded computer systems -- Design and construction , Computer input-output equipment , Programmable controllers , Electronic controllers -- Design and construction
- Description: The use of embedded Internet systems is growing rapidly in the manufacturing sector. These systems allow the monitoring and controlling of plant machinery and manufactured items from a remote location via a standard Web interface. In a manufacturing environment, it is inevitable that long running processes will require support for dynamic reconfiguration because, for example, machines may fail, services may be moved or withdrawn and user requirements may change. In such an environment it is essential that the operation and architecture of such processes can be modified to reflect such changes. This research project will present methods and ideas for establishing a reconfigurable remote system by using standard 8-bit microcontrollers and reconfigurable hardware. It will allow a manufacturing process to be modified and changed within minutes without even having to be physically present at the location where the process is running.
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- Date Issued: 2003
Hybrid field generator controller for optimised perfomance
- Authors: Moleli, Christopher Teboho
- Date: 2003
- Subjects: Hybrid power systems , Wind turbines , Electric power production
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10818 , http://hdl.handle.net/10948/236 , Hybrid power systems , Wind turbines , Electric power production
- Description: Battery charging wind turbines like, Hybrid Field Generator, have become more popular in the growing renewable energy market. With wind energy, voltage and current control is generally provided by means of power electronics. The paper describes the analytical investigation in to control aspects of a hybrid field generator controller for optimized performance. The project objective is about maintaining the generated voltage at 28V through out a generator speed range, between 149 rpm and 598 rpm. The over voltage load, known as dump load, is connected to the control circuit to reduce stress on the bypass transistor for speeds above 598 rpm. Maintaining a stable voltage through out the speed range, between 149rpm and 598rpm, is achieved by employing power electronics techniques. This is done by using power converters and inverters to vary the generator armature excitation levels hence varying its air gap flux density. All these take place during each of the three modes of generator operation, which are: buck, boost and permanent magnet modes. Although the generator controller is power electronics based, it also uses software to optimize its performance. In this case, a PIC16F877 microcontroller development system has been used to test the controller function blocks.
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- Date Issued: 2003
Intelligent monitoring and control system for a friction stir welding process
- Authors: Kruger, Grant
- Date: 2003
- Subjects: Friction welding
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10823 , http://hdl.handle.net/10948/273 , Friction welding
- Description: A Friction Stir Welding machine is proposed and built to allow future research into the process and to provide a framework from which the application of intelligent manufacturing to industrial processes can be investigated. Initially a literature survey was conducted upon which the design of the machine could be based. The conversion of a conventional milling machine into a Friction Stir Welding machine by applying modern monitoring and control systems is then presented. Complete digital control was used to drive actuators and monitor sensors. A wireless chuck mounted monitoring system was implemented, enabling forces, torques, temperature and speed of the tool to be obtained directly from the process. Software based on a hierarchical Open Systems Architectural design, incorporating modularity, interoperability, portability and extensibility is implemented. This experimental setup is used to analyze the Friction Stir Welding process by performing data analysis using statistical methods. Three independent variables (weld speed, spindle speed and plunge depth) were varied and the independent variables (forces, torques, power, temperature, speed, etc) recorded using the implemented software. The statistical analysis includes the analysis of variants, regression analysis and the creation of surface plots. Using these results, certain linguistic rules for process control are proposed. An intelligent controller is designed and discussed, using the derived rules to improve and optimize certain aspects of the process encountered during the experimental phase of the research.
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- Date Issued: 2003
Design, development and analysis of the friction stir welding process
- Authors: Blignault, Calvin
- Date: 2002
- Subjects: Friction welding
- Language: English
- Type: Thesis , Masters , MTech (Mechanical Engineering)
- Identifier: vital:10809 , http://hdl.handle.net/10948/1350 , Friction welding
- Description: The development of a CNC-based technology FSW machine to accurately produce friction stir weld samples that can be analyzed for research purposes is implemented and discussed. A process diagnosis and control scheme to improve the process monitoring and weld evaluation capabilities of an FSW machine are proposed and implemented. Basic CNC-based hardware implementation such as optical encoders and inverters for process control are explained and verified. The control scheme and framework of interfaces to the digital I/O cards for PC user interface are explained. An advanced monitoring system which senses process performance parameters such as tool temperature, 3-axis tool forces, torque and spindle speed are explained. Mechanical designs and manufacturing techniques such as tool, clamp and backing plate designs are explained and verified. The process parameters for quality optimization are investigated and optimized by making use of Correlation and Regression Analysis. The statistical data and analytical relationships between welding parameters (independent) and each of the performance parameters (dependent) are obtained and used to simulate the machining process. The weld research samples are tested for strength and integrity making use of various scientific testing techniques. The reliability of the samples are also evaluated and compared to that of other institutions. Process variables and the optimum operating range of the Friction Stir Welding machine is determined and a framework for further research into weld quality optimization is set.
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- Date Issued: 2002
Intelligent gripper design and application for automated part recognition and gripping
- Authors: Wang, Jianqiang
- Date: 2002
- Subjects: Automatic control , Robots, Industrial , Robotics
- Language: English
- Type: Thesis , Doctoral , DTech (Engineering)
- Identifier: vital:10816 , http://hdl.handle.net/10948/102 , Automatic control , Robots, Industrial , Robotics
- Description: Intelligent gripping may be achieved through gripper design, automated part recognition, intelligent algorithm for control of the gripper, and on-line decision-making based on sensory data. A generic framework which integrates sensory data, part recognition, decision-making and gripper control to achieve intelligent gripping based on ABB industrial robot is constructed. The three-fingered gripper actuated by a linear servo actuator designed and developed in this project for precise speed and position control is capable of handling a large variety of objects. Generic algorithms for intelligent part recognition are developed. Edge vector representation is discussed. Object geometric features are extracted. Fuzzy logic is successfully utilized to enhance the intelligence of the system. The generic fuzzy logic algorithm, which may also find application in other fields, is presented. Model-based gripping planning algorithm which is capable of extracting object grasp features from its geometric features and reasoning out grasp model for objects with different geometry is proposed. Manipulator trajectory planning solves the problem of generating robot programs automatically. Object-oriented programming technique based on Visual C++ MFC is used to constitute the system software so as to ensure the compatibility, expandability and modular programming design. Hierarchical architecture for intelligent gripping is discussed, which partitions the robot’s functionalities into high-level (modeling, recognizing, planning and perception) layers, and low-level (sensing, interfacing and execute) layers. Individual system modules are integrated seamlessly to constitute the intelligent gripping system.
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- Date Issued: 2002
Sensorless speed estimation in three phase induction motors
- Authors: Govindsamy, Matthew
- Date: 2002
- Subjects: Electric motors, induction , Electronic controllers
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10810 , http://hdl.handle.net/10948/139 , Electric motors, induction , Electronic controllers
- Description: This thesis proposes a technique to determine and improve the performance of a sensorless speed estimator for an induction motor based on Motor Current Signature Analysis (MCSA). The theoretical concepts underlying the parameter based observer are developed first and then the model of the observer is built using Simulink. The observer is developed based on Model Reference Adaptive System (MRAS). The dynamic performance of the observer and its behavior due to variation of machine parameters is studied. The error in speed estimated using this observer is shown and the ability of MCSA to retune the rotor speed from the stator current spectrum. The spectrum estimation technique has been implemented using a software routine in Matlab. Both the observer and MCSA techniques were implemented practically on an induction motor. The performance of the combined sensorless speed estimation system was tested and verified.
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- Date Issued: 2002
An investigation into the use of electrode mass measurement to optimise an electrostatic precipitator unit
- Authors: Pershad, Sathish Kumar
- Date: 2001
- Subjects: Electrostatic precipitation
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10815 , http://hdl.handle.net/10948/66 , Electrostatic precipitation
- Description: Electrostatic precipitators (ESP’s) can be simply described as particle collection devices and service a wide variety of industries. This particle collection can either be classed as a cleansing or product recovery (or both) process. They can be found in fossil fueled power generation plant (municipal incinerators, iron and steel industries (sinter plants, coke ovens), non ferrous industries, rock products (cement, lime), chemical and petrochemical (detarrers, de-oilers) They have been around for approximately 70 years and their fundamental principle of operation has not changed much during this time. What has changed is the demand on their operating efficiency. Environmental pressure as well as the loss of product has forced ESP’s to perform even better than before. This performance enhancement is two-fold : an increase in collection efficiency and a reduction in maintenance and wear costs. This project researches the use of mass measurement techniques to optimise the operation of ESP’s from both the above mentioned perspectives.
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- Date Issued: 2001
Monitoring a diagnosis for control of an intelligent machining process
- Authors: Van Niekerk, Theo
- Date: 2001
- Subjects: Expert systems (Computer science) -- Industrial applications , System design
- Language: English
- Type: Thesis , Doctoral , DTech (Engineering)
- Identifier: vital:10814 , http://hdl.handle.net/10948/70 , Expert systems (Computer science) -- Industrial applications , System design
- Description: A multi-level modular control scheme to realize integrated process monitoring, diagnosis and control for intelligent machining is proposed and implemented. PC-based hardware architecture to manipulate machining process cutting parameters, using a PMAC interface card as well as sensing processes performance parameters through sampling, and processing by means of DSP interface cards is presented. Controller hardware, to interface the PC-based PMAC interface card to a machining process for the direct control of speed, feed and depth of cut, is described. Sensors to directly measure on-line process performance parameters, including cutting forces, cutting sound, tool-workpiece vibration, cutting temperature and spindle current are described. The indirect measurement of performance parameter surface roughness and tool wear monitoring, through the use of NF sensor fusion modeling, is described and verified. An object based software architecture, with corresponding user interfaces (using Microsoft Visual C++ Foundation Classes and implemented C++ classes for sending motion control commands to the PMAC and receiving processed on-line sensor data from the DSP) is explained. The software structure indicates all the components necessary for integrating the monitoring, diagnosis and control scheme. C-based software code executed on the DSP for real-time sampling, filtering and FFT processing of sensor signals, is explained. Making use of experimental data and regression analysis, analytical relationships between cutting parameters (independent) and each of the performance parameters (dependent) are obtained and used to simulate the machining process. A fuzzy relation that contains values determined from statistical data (indicating the strength of connection between the independent and dependent variables) is proposed. The fuzzy relation forms the basis of a diagnostic scheme that is able to intelligently determine which independent variable to change when a machining performance parameter exceeds control limits. The intelligent diagnosis scheme is extensively tested using the machining process simulation.
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- Date Issued: 2001
The control of a multi-variable industrial process, by means of intelligent technology
- Authors: Naidoo, Puramanathan
- Date: 2001
- Subjects: Fuzzy systems , Intelligent control systems
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10813 , http://hdl.handle.net/10948/48 , Fuzzy systems , Intelligent control systems
- Description: Conventional control systems express control solutions by means of expressions, usually mathematically based. In order to completely express the control solution, a vast amount of data is required. In contrast, knowledge-based solutions require far less plant data and mathematical expression. This reduces development time proportionally. In addition, because this type of processing does not require involved calculations, processing speed is increased, since rule process is separate and all processes can be performed simultaneously. These results in improved product quality, better plant efficiency, simplified process, etc. Within this project, conventional PID control has already been implemented, with the control parameter adjustment and loop tuning being problematic. This is mainly due to a number of external parameters that affects the stability of the process. In maintaining a consistent temperature, for example, the steam flow rate varies, the hot well temperature varies, the ambient may temperature vary. Another contributing factor, the time delay, also affects the optimization of the system, due to the fact that temperature measurement is based on principle of absorption. The normal practice in industry to avoid an unstable control condition is to have an experienced operator to switch the controller to manual, and make adjustments. After obtaining the desired PV, the controller is switched back to automatic. This research project focuses on eliminating this time loss, by implementing a knowledge-based controller, for intelligent decision-making. A FLC design tool, which allows full interaction, whilst designing the control algorithm, was used to optimize the control system. The design tool executed on a PC is connected to a PLC, which in turn is successfully integrated into the process plant.
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- Date Issued: 2001