A vision based multirotor aircraft for use in the security industry
- Authors: Nelson, Benjamin David
- Date: 2020
- Subjects: Drone aircraft -- South Africa , Mechatronics -- Research
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46816 , vital:39664
- Description: This research consisted of developing a vision based multirotor aircraft that could be used in the security industry. A second-hand aircraft was purchased and modified. The aircraft made use of a Pixhawk flight controller and a Odroid XU4 companion computer, which resulted in the computer injecting commands into the flight controller. Robot Operating System was installed and used on the companion computer to integrate the vision system and the aircraft. The vision system was designed to help develop a landing system where the aircraft would land on an ArUco marker. The vision system also allowed the aircraft to detect and follow humans. A Software in the Loop (SITL) was run alongside Gazebo, allowing the developed landing system and the human detecting system to be simulated and tested. The developed landing system was implemented on the aircraft, where the developed landing system was tested and compared to the aircraft’s current GPS based landing system. The developed landing system obtained a better overall accuracy , while also taking longer to land the aircraft compared to the GPS based landing system. There were also numerous manual and autonomous test flights implemented on the aircraft.
- Full Text:
- Date Issued: 2020
- Authors: Nelson, Benjamin David
- Date: 2020
- Subjects: Drone aircraft -- South Africa , Mechatronics -- Research
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46816 , vital:39664
- Description: This research consisted of developing a vision based multirotor aircraft that could be used in the security industry. A second-hand aircraft was purchased and modified. The aircraft made use of a Pixhawk flight controller and a Odroid XU4 companion computer, which resulted in the computer injecting commands into the flight controller. Robot Operating System was installed and used on the companion computer to integrate the vision system and the aircraft. The vision system was designed to help develop a landing system where the aircraft would land on an ArUco marker. The vision system also allowed the aircraft to detect and follow humans. A Software in the Loop (SITL) was run alongside Gazebo, allowing the developed landing system and the human detecting system to be simulated and tested. The developed landing system was implemented on the aircraft, where the developed landing system was tested and compared to the aircraft’s current GPS based landing system. The developed landing system obtained a better overall accuracy , while also taking longer to land the aircraft compared to the GPS based landing system. There were also numerous manual and autonomous test flights implemented on the aircraft.
- Full Text:
- Date Issued: 2020
Adaptive Neuro-Fuzzy Inference System modelling of surface topology in ultra-high precision diamond turning of rapidly solidified aluminium grade (RSA 443)
- Authors: Zvikomborero, Hweju
- Date: 2020
- Subjects: Mechatronics Surface roughness -- Measurement
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/49441 , vital:41721
- Description: Surface roughness prediction is a crucial stage during product manufacturing since it acts as a quality indicator. This investigative research thesis presents an online surface roughness prediction, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS) model during Ultra-High Precision Diamond Turning (UHPDT) of Rapidly Solidified Aluminium (RSA-443) using water and kerosene as coolants. Based on the Taguchi L9 orthogonal array, the cutting parameters (spindle speed, depth of cut and feed rate) are varied at three levels. Acoustic Emission (AE) signals are detected during the UHPDT process using a piezoelectric sensor. Spindle speed, depth of cut, feed rate, AE root mean square, prominent frequency and peak rate are considered as model inputs in this thesis. The experimental results reveal that a better surface finish is obtained using water coolant in comparison to kerosene coolant. Mean Absolute Percentage Error (MAPE) based comparison between ANFIS and Response Surface Method (RSM) is carried out. In this study, the ANFIS model has a prediction accuracy of 79.42% and 69.40% on water-based and kerosene-based results respectively. The RSM model yields higher prediction accuracies of 98.59% and 95.55% on water-based and kerosene-based results respectively.
- Full Text:
- Date Issued: 2020
- Authors: Zvikomborero, Hweju
- Date: 2020
- Subjects: Mechatronics Surface roughness -- Measurement
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/49441 , vital:41721
- Description: Surface roughness prediction is a crucial stage during product manufacturing since it acts as a quality indicator. This investigative research thesis presents an online surface roughness prediction, based on the Adaptive Neuro-Fuzzy Inference System (ANFIS) model during Ultra-High Precision Diamond Turning (UHPDT) of Rapidly Solidified Aluminium (RSA-443) using water and kerosene as coolants. Based on the Taguchi L9 orthogonal array, the cutting parameters (spindle speed, depth of cut and feed rate) are varied at three levels. Acoustic Emission (AE) signals are detected during the UHPDT process using a piezoelectric sensor. Spindle speed, depth of cut, feed rate, AE root mean square, prominent frequency and peak rate are considered as model inputs in this thesis. The experimental results reveal that a better surface finish is obtained using water coolant in comparison to kerosene coolant. Mean Absolute Percentage Error (MAPE) based comparison between ANFIS and Response Surface Method (RSM) is carried out. In this study, the ANFIS model has a prediction accuracy of 79.42% and 69.40% on water-based and kerosene-based results respectively. The RSM model yields higher prediction accuracies of 98.59% and 95.55% on water-based and kerosene-based results respectively.
- Full Text:
- Date Issued: 2020
Analytical evaluation of the effect of aggregate variation on Asphalt Mixture Properties
- Authors: Van Eck, Elandre
- Date: 2020
- Subjects: Aggregates (Building materials)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/49639 , vital:41743
- Description: This research study aimed to conduct an analytical evaluation of the effect of aggregate grading on the properties of asphalt mixtures. This was achieved by obtaining asphalt mix designs from approved civil engineering organisations and determining the relationship between the aggregate grading and the corresponding properties of the asphalt mix designs.
- Full Text: false
- Date Issued: 2020
- Authors: Van Eck, Elandre
- Date: 2020
- Subjects: Aggregates (Building materials)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/49639 , vital:41743
- Description: This research study aimed to conduct an analytical evaluation of the effect of aggregate grading on the properties of asphalt mixtures. This was achieved by obtaining asphalt mix designs from approved civil engineering organisations and determining the relationship between the aggregate grading and the corresponding properties of the asphalt mix designs.
- Full Text: false
- Date Issued: 2020
Development and process verification of a linear friction welding platform for small Ti6AI4V coupons
- Mohlala, Narishe Taetso Arnold
- Authors: Mohlala, Narishe Taetso Arnold
- Date: 2020
- Subjects: Friction welding , Pressure welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46196 , vital:39513
- Description: This thesis reports on a study conducted to establish the feasibility of implementing linear friction welding as a joining technique for small Ti6AI4V coupons. The main of this project is to facilitate the manufacturing of high-integrity near-net-shape components for aerospace, automotive and medical appliances. LFW is a solid-state welding technique that uses frictional heat generated by the rubbing of surfaces under an axially applied load, thereby forming a weld at temperature below beta tranus. This technique is advantageous as it has the potential to reduce defeats normally associated with conventional welding of this material. The first part of the study will describe the development of an experimental platform to facilitate the evaluation of the influence of selected process parameters on joint integrity.
- Full Text:
- Date Issued: 2020
Development and process verification of a linear friction welding platform for small Ti6AI4V coupons
- Authors: Mohlala, Narishe Taetso Arnold
- Date: 2020
- Subjects: Friction welding , Pressure welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46196 , vital:39513
- Description: This thesis reports on a study conducted to establish the feasibility of implementing linear friction welding as a joining technique for small Ti6AI4V coupons. The main of this project is to facilitate the manufacturing of high-integrity near-net-shape components for aerospace, automotive and medical appliances. LFW is a solid-state welding technique that uses frictional heat generated by the rubbing of surfaces under an axially applied load, thereby forming a weld at temperature below beta tranus. This technique is advantageous as it has the potential to reduce defeats normally associated with conventional welding of this material. The first part of the study will describe the development of an experimental platform to facilitate the evaluation of the influence of selected process parameters on joint integrity.
- Full Text:
- Date Issued: 2020
Friction stir welding of thin section aluminium extrusions for marine applications
- Authors: Chikamhi, Prince Philhelene
- Date: 2020
- Subjects: Friction welding , Welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46030 , vital:39410
- Description: This dissertation focuses on the development of a welding extrusion feeder, tool and schedule for implementation of defect-free butt welds on long, thin and complex-shape aluminium extrusions, as used by the marine industry. Viability of employing Friction Stir Welding (FSW) as a welding technology for joining long extrusions with a short-bed and bolt-on feeder to facilitate onsite fabrication of flat structures in shipbuilding is evaluated. An FSW feeder, tool and process control unit were designed, developed and integrated with an existing FSW platform, to facilitate implementation of continuous welds. Weld data acquired from literature review, experimentation, mechanical testing and metallographic analysis was used in design considerations for the development of a feeder. Subsequently, butt welds were implemented successfully on long 3 mm AA6082-T6 extrusions, during continuous FSW on the feeder. A specially adapted tool, the Floating Bobbin Tool, used with the feeder to implement butt welds was designed and developed from literature tool heuristics and weld trials. The tool eliminated the need for a backing bar and enabled tool-workpiece auto-alignment, beneficial with thin-section extrusions. Effect of rotational and weld speed and tool geometry of two tools (Tool 1 and 2), on weld forces and quality was tested, to establish optimum parameters for attaining high quality welds. Tool geometry had a profound effect on weld forces and integrity; Tool 2 welds exhibited superior and consistent weld quality, meeting maritime rules and standards and proving the adequacy of using FSW for joining long thin extrusions. Feeder process control, automation and optimisation, was implemented by process control unit devices, in addition to force and position control provided by the existing FSW platform. Owing to process control, automation and optimisation during continuous FSW of thin long and complex-shape aluminium extrusions, welding setup times and process variations are minimised and chances for defect-free welds increased, boosting production and cost savings in large panel fabrication in shipbuilding.
- Full Text:
- Date Issued: 2020
- Authors: Chikamhi, Prince Philhelene
- Date: 2020
- Subjects: Friction welding , Welding
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46030 , vital:39410
- Description: This dissertation focuses on the development of a welding extrusion feeder, tool and schedule for implementation of defect-free butt welds on long, thin and complex-shape aluminium extrusions, as used by the marine industry. Viability of employing Friction Stir Welding (FSW) as a welding technology for joining long extrusions with a short-bed and bolt-on feeder to facilitate onsite fabrication of flat structures in shipbuilding is evaluated. An FSW feeder, tool and process control unit were designed, developed and integrated with an existing FSW platform, to facilitate implementation of continuous welds. Weld data acquired from literature review, experimentation, mechanical testing and metallographic analysis was used in design considerations for the development of a feeder. Subsequently, butt welds were implemented successfully on long 3 mm AA6082-T6 extrusions, during continuous FSW on the feeder. A specially adapted tool, the Floating Bobbin Tool, used with the feeder to implement butt welds was designed and developed from literature tool heuristics and weld trials. The tool eliminated the need for a backing bar and enabled tool-workpiece auto-alignment, beneficial with thin-section extrusions. Effect of rotational and weld speed and tool geometry of two tools (Tool 1 and 2), on weld forces and quality was tested, to establish optimum parameters for attaining high quality welds. Tool geometry had a profound effect on weld forces and integrity; Tool 2 welds exhibited superior and consistent weld quality, meeting maritime rules and standards and proving the adequacy of using FSW for joining long thin extrusions. Feeder process control, automation and optimisation, was implemented by process control unit devices, in addition to force and position control provided by the existing FSW platform. Owing to process control, automation and optimisation during continuous FSW of thin long and complex-shape aluminium extrusions, welding setup times and process variations are minimised and chances for defect-free welds increased, boosting production and cost savings in large panel fabrication in shipbuilding.
- Full Text:
- Date Issued: 2020
Machinability of rapidly solidified aluminium alloy for optical applications
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
- Authors: Abbas, Abdalla Abbas Said
- Date: 2020
- Subjects: Aluminum alloys , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/45975 , vital:39402
- Description: The production of metal mirrors and critical components for optical devices and aerospace application requires extreme high accuracy and outstanding surface quality. Thus, to achieve such high dimensional accuracies, they are being mainly produced through ultra-high precision machining. Aluminium alloys have been used in the production of components for optics application as well as spaceborne for so many years but with the advancement in technology and demands for a superior material, a new modified grade of aluminium was developed by a rapid solidification process. These grades exhibit a much better mechanical and physical properties while having a finer microstructure. The only downside is the limited research in the correlation of surface roughness and reflectance when single point diamond turned. In this study, rapidly solidified aluminium RSA 905 were used to investigate the effect of varying the cutting parameters on the machined surface finish and its corresponding surface reflectance. The cutting parameters were cutting speed, feed rate and depth of cut. The surface roughness was measured using Taylor Hopson PGI Profilometer while the reflectance factor was measured by using VERTEX 80v Spectrometer. The results were used to develop two predictive models namely; response surface and artificial neural network which have indicated a very high accuracy to the experimental measurements. Finally, the results were very promising for the diamond turning of RSA 905 where it has achieved a very low values of surface roughness and high reflectance in the visual range without the need of any additional production/fabrication steps and to ensure that bi-metallic binding does not take place in extreme low temperatures. Therefore, RSA 905 is a very promising material for optical applications in the visual spectrum.
- Full Text:
- Date Issued: 2020
Optical diamond turning of rapidly solidified aluminium alloy grade - 431
- Authors: Oyekunle, Funsho Adekunle
- Date: 2020
- Subjects: Aluminum alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46860 , vital:39670
- Description: The high demand for ultraprecision machining systems is increasing day by day. The technology leads to increased productivity and quality manufactured products, with an excellent surface finish. Therefore, these products are in demand in many industrial fields such as space, national defence, the medical industry and other high-tech industries. Single point diamond turning (SPDT) is the core technology of ultraprecision machining, which makes use of single-point crystalline diamond as a cutting tool. This technique is used for machining an extensive selection of complex optical surfaces and other engineering products with a quality surface finish. SPDT can achieve dimensional tolerances in order of 0.01um and surface roughness in order of 1nm. SPDT is not restricted, but mostly applicable, to non-ferrous alloys; due to their reflective properties and microstructure that discourages tool wear. The focus of this study is the development of predictive optimisation models, used to analyse the influence of machining parameters (speed, feed, and depth of cut) on surface roughness. Moreover, the study aims to obtain the optimal machining parameters that would lead to minimum surface roughness during the diamond turning of Rapidly Solidified Aluminium (RSA) 431. In this study, Precitech Nanoform 250 Ultra grind machine was used to perform two experiments on RSA 431. The first machining process, experiment 1, was carried out using pressurized kerosene mist; while experiment 2 was carried out with water as the cutting fluid. In each experiment, machine parameters were varied at intervals and the surface roughness of the workpiece was measured at each variation. The measurements were taken through a contact method using Taylor Hobson PGI Dimension XL surface Profilometer. Acoustic emission (AE) was employed as a precision sensing technique – to optimize the machining quality process and provide indications of the expected surface roughness. The results obtained revealed that better surface roughness can be generated when RSA 431 is diamond-turned using water as a cutting fluid, rather than kerosene mist. Predictive models for surface roughness were developed for each experiment, using response surface methodology (RSM) and artificial neural networks (ANN). Moreover, RSM was used for optimisation. Time domain features acquired from AE signals, together with the three cutting parameters, were used as input parameters in the ANN design. The results of the predictive models show a close relationship between the predicted values and the experimental values for surface roughness. The developed models have been compared in terms of accuracy and cost of computation - using the mean absolute percentage error (MAPE).
- Full Text:
- Date Issued: 2020
- Authors: Oyekunle, Funsho Adekunle
- Date: 2020
- Subjects: Aluminum alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/46860 , vital:39670
- Description: The high demand for ultraprecision machining systems is increasing day by day. The technology leads to increased productivity and quality manufactured products, with an excellent surface finish. Therefore, these products are in demand in many industrial fields such as space, national defence, the medical industry and other high-tech industries. Single point diamond turning (SPDT) is the core technology of ultraprecision machining, which makes use of single-point crystalline diamond as a cutting tool. This technique is used for machining an extensive selection of complex optical surfaces and other engineering products with a quality surface finish. SPDT can achieve dimensional tolerances in order of 0.01um and surface roughness in order of 1nm. SPDT is not restricted, but mostly applicable, to non-ferrous alloys; due to their reflective properties and microstructure that discourages tool wear. The focus of this study is the development of predictive optimisation models, used to analyse the influence of machining parameters (speed, feed, and depth of cut) on surface roughness. Moreover, the study aims to obtain the optimal machining parameters that would lead to minimum surface roughness during the diamond turning of Rapidly Solidified Aluminium (RSA) 431. In this study, Precitech Nanoform 250 Ultra grind machine was used to perform two experiments on RSA 431. The first machining process, experiment 1, was carried out using pressurized kerosene mist; while experiment 2 was carried out with water as the cutting fluid. In each experiment, machine parameters were varied at intervals and the surface roughness of the workpiece was measured at each variation. The measurements were taken through a contact method using Taylor Hobson PGI Dimension XL surface Profilometer. Acoustic emission (AE) was employed as a precision sensing technique – to optimize the machining quality process and provide indications of the expected surface roughness. The results obtained revealed that better surface roughness can be generated when RSA 431 is diamond-turned using water as a cutting fluid, rather than kerosene mist. Predictive models for surface roughness were developed for each experiment, using response surface methodology (RSM) and artificial neural networks (ANN). Moreover, RSM was used for optimisation. Time domain features acquired from AE signals, together with the three cutting parameters, were used as input parameters in the ANN design. The results of the predictive models show a close relationship between the predicted values and the experimental values for surface roughness. The developed models have been compared in terms of accuracy and cost of computation - using the mean absolute percentage error (MAPE).
- Full Text:
- Date Issued: 2020
A monitoring and control system for an accelerated weather test chamber
- Authors: Harvey, Luke Gareth
- Date: 2019
- Subjects: Materials -- Deterioration -- Testing , Motor vehicles -- Testing Motor vehicles -- Automatic control Intelligent control systems
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/40360 , vital:36152
- Description: In the Automotive Sector, weathering tests of components are of paramount importance. The most critical components to the overall comfort and durability of a vehicle are the interior components and thus is important to guarantee the quality of these components. The interior components are generally made of plastic, fabric, leather and various painted components. These components are prone to fading, cracking and distortion which is caused by natural factors such as solar radiation, temperature and moisture. This is known as natural weathering. Over the years many weathering tests have been carried out on automotive components to address critical issues during the design process. Many of these tests are simulated in chambers to mimic real life cycles. Although these accelerated tests provide somewhat accurate results in much shorter periods, natural weathering is still essential as it is uncontrolled and unpredictable. This dissertation looks at the method of a metallic chamber used to carry out weathering tests on automotive components and to simulate the conditions inside a vehicle. It addresses the current state and improvement: accurate tracking, intelligent fuzzy logic control and cloud-based monitoring. Currently weather testing chambers are stationery, which does not allow for maximum exposer to solar radiation. Therefore, a system was designed to allow the weather testing chamber to track the azimuth and elevation of the sun to increase the solar radiation on the components tested, a GPS will achieve this. Currently systems lack remote monitoring. A further shortcoming is the lack of controlling the temperature and humidity inside the chamber for sufficient tests. The use of a fuzzy logic controller was implemented to achieve this. The fuzzy logic was compared to other types of logic controllers. To further IoT integration, two main control devices were used, these control devices were two Arduino Mega’s. One Arduino Mega was used for the intelligent fuzzy logic control and the second for solar tracking. The weathering system and controllers were powered by using solar power. The fuzzy logic controller was tested while tracking the sun and then not tracking the sun. The results obtained were compared and it was seen that the fuzzy logic performed very well in both instances, however, the test with tracking the sun performed better. A second test was performed. The second test was similar to the previously mentioned test, but the fuzzy logic had a set point control. It was concluded that both tests performed as expected as the fuzzy logic controlled the temperature and humidity at the given setpoint, but during the solar tracking test the fuzzy logic control performed the best. The fuzzy logic worked well in general use as well as set point control, both for tracking and non-tracking. The tracking performed better than the non-tracking.
- Full Text:
- Date Issued: 2019
- Authors: Harvey, Luke Gareth
- Date: 2019
- Subjects: Materials -- Deterioration -- Testing , Motor vehicles -- Testing Motor vehicles -- Automatic control Intelligent control systems
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/40360 , vital:36152
- Description: In the Automotive Sector, weathering tests of components are of paramount importance. The most critical components to the overall comfort and durability of a vehicle are the interior components and thus is important to guarantee the quality of these components. The interior components are generally made of plastic, fabric, leather and various painted components. These components are prone to fading, cracking and distortion which is caused by natural factors such as solar radiation, temperature and moisture. This is known as natural weathering. Over the years many weathering tests have been carried out on automotive components to address critical issues during the design process. Many of these tests are simulated in chambers to mimic real life cycles. Although these accelerated tests provide somewhat accurate results in much shorter periods, natural weathering is still essential as it is uncontrolled and unpredictable. This dissertation looks at the method of a metallic chamber used to carry out weathering tests on automotive components and to simulate the conditions inside a vehicle. It addresses the current state and improvement: accurate tracking, intelligent fuzzy logic control and cloud-based monitoring. Currently weather testing chambers are stationery, which does not allow for maximum exposer to solar radiation. Therefore, a system was designed to allow the weather testing chamber to track the azimuth and elevation of the sun to increase the solar radiation on the components tested, a GPS will achieve this. Currently systems lack remote monitoring. A further shortcoming is the lack of controlling the temperature and humidity inside the chamber for sufficient tests. The use of a fuzzy logic controller was implemented to achieve this. The fuzzy logic was compared to other types of logic controllers. To further IoT integration, two main control devices were used, these control devices were two Arduino Mega’s. One Arduino Mega was used for the intelligent fuzzy logic control and the second for solar tracking. The weathering system and controllers were powered by using solar power. The fuzzy logic controller was tested while tracking the sun and then not tracking the sun. The results obtained were compared and it was seen that the fuzzy logic performed very well in both instances, however, the test with tracking the sun performed better. A second test was performed. The second test was similar to the previously mentioned test, but the fuzzy logic had a set point control. It was concluded that both tests performed as expected as the fuzzy logic controlled the temperature and humidity at the given setpoint, but during the solar tracking test the fuzzy logic control performed the best. The fuzzy logic worked well in general use as well as set point control, both for tracking and non-tracking. The tracking performed better than the non-tracking.
- Full Text:
- Date Issued: 2019
Characterisation of single event effects and total ionising dose effects of an intel atom microprocessor
- Authors: Malinda, Muema
- Date: 2019
- Subjects: Microprocessors , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/41875 , vital:36605
- Description: The rapid advancements of COTS microprocessors compared to radiation hardened microprocessors has attracted the interest of system designers within the aerospace sector. COTS microprocessors offer higher performance with lower energy requirements, both of which are desired characteristics for microprocessors used in spacecraft. COTS microprocessors, however, are much more susceptible to radiation damage therefore their SEE and TID responses needs to be evaluated before they can be incorporated into spacecraft. This thesis presents the process followed to evaluate said characteristics of a COTS Intel Atom E3815 microprocessor mounted on a DE3815TYBE single board PC. Evaluation of the SEE response was carried out at NRF iThemba Labs in Cape Town, South Africa where the device was irradiated by a proton beam at 55.58 MeV and with varying beam currents. The device showed a higher sensitivity to functional interrupts when running with the onboard cache on compared to when running with the cache off, as would be expected. The cross-sections, respectively, are: 4.5𝑥 10−10 𝑐𝑚2 and 2.8 𝑥 10−10 𝑐𝑚2. TID testing on the other hand was carried out at the irradiation chamber of FruitFly Africa in Stellenbosch, South Africa. The test device was irradiated by gamma radiation from a Cobalt-60 source at a dose rate of 9.7kRad/h and to a total dose of 67.25kRad. Noticeable TID degradation, in the form of leakage currents, was observed once a total dose of about 20kRad was absorbed. The device then completely failed once a total dose of approximately 32kRad was absorbed. These results suggest that the E3815 microprocessor would not be suitable for long term missions that require higher TID survivability. The processor could however be considered for short term missions launched into polar or high incline orbits where the dose rate is relatively low, and the mission is capable of tolerating functional interrupts.
- Full Text:
- Date Issued: 2019
- Authors: Malinda, Muema
- Date: 2019
- Subjects: Microprocessors , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/41875 , vital:36605
- Description: The rapid advancements of COTS microprocessors compared to radiation hardened microprocessors has attracted the interest of system designers within the aerospace sector. COTS microprocessors offer higher performance with lower energy requirements, both of which are desired characteristics for microprocessors used in spacecraft. COTS microprocessors, however, are much more susceptible to radiation damage therefore their SEE and TID responses needs to be evaluated before they can be incorporated into spacecraft. This thesis presents the process followed to evaluate said characteristics of a COTS Intel Atom E3815 microprocessor mounted on a DE3815TYBE single board PC. Evaluation of the SEE response was carried out at NRF iThemba Labs in Cape Town, South Africa where the device was irradiated by a proton beam at 55.58 MeV and with varying beam currents. The device showed a higher sensitivity to functional interrupts when running with the onboard cache on compared to when running with the cache off, as would be expected. The cross-sections, respectively, are: 4.5𝑥 10−10 𝑐𝑚2 and 2.8 𝑥 10−10 𝑐𝑚2. TID testing on the other hand was carried out at the irradiation chamber of FruitFly Africa in Stellenbosch, South Africa. The test device was irradiated by gamma radiation from a Cobalt-60 source at a dose rate of 9.7kRad/h and to a total dose of 67.25kRad. Noticeable TID degradation, in the form of leakage currents, was observed once a total dose of about 20kRad was absorbed. The device then completely failed once a total dose of approximately 32kRad was absorbed. These results suggest that the E3815 microprocessor would not be suitable for long term missions that require higher TID survivability. The processor could however be considered for short term missions launched into polar or high incline orbits where the dose rate is relatively low, and the mission is capable of tolerating functional interrupts.
- Full Text:
- Date Issued: 2019
Improvements and optimization for a functional low-cost prosthetic hand
- Authors: Setty, Kiran
- Date: 2019
- Subjects: Biomechanics , Artificial limbs -- Design , Prosthesis -- Design
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/43655 , vital:36955
- Description: The following study investigates the work of the Touch Hand 4, which involves the development of a lowcost myoelectric prosthetic terminal hand device for transradial amputees. The Touch Hand 4 is an iteration of the Touch Hand project which attempts to make a functional, low-cost prosthetic hand which is capable of being accessible to more people relative to conventional myoelectric prosthetic hands as well as being used as a robotic UAV gripper. This research is motivated due to the lack of affordable myoelectric prosthetic hands in the global market. It is believed, with the current technology, it is capable of developing a prosthetic hand which can meet these needs. Research was performed through reviewing other prosthetic hands to understand the requirements for a prosthetic hand as well as understanding the market of prosthetic hands. Prosthetists were interviewed to obtain a perspective from medial professionals regarding the requirements for a prosthetic hand. Hand kinesiology was performed to understand the biomechanics of the human hand, which was emulated in the design of the Touch Hand 4. The mechanical design begun with developing and testing a concept design, which was used to design the general shape of the Touch Hand 4. SLS was chosen to print the prosthetic hand with. After performing a kinematics and static force simulation, the mechanical system was designed accordingly. Further research on EMG sensors was then performed to understand the requirements of using EMG signals to control a prosthetic hand. The electronics and control system were then designed according to the requirements of the prosthetic hand. Tests were performed, however, tests performed with an amputee using the device was affected to improper placement of the EMG sensors, leading to poor results. Tests performed without an amputee, however, showed that the prosthetic hand is capable of gripping various objects of different shapes and sizes. An investigation was also performed on the contributions the Touch Hand 4 could make as a UAV gripper, which showed that the Touch Hand 4 is more adaptable and versatile than any other UAV gripper available on the market.
- Full Text:
- Date Issued: 2019
- Authors: Setty, Kiran
- Date: 2019
- Subjects: Biomechanics , Artificial limbs -- Design , Prosthesis -- Design
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/43655 , vital:36955
- Description: The following study investigates the work of the Touch Hand 4, which involves the development of a lowcost myoelectric prosthetic terminal hand device for transradial amputees. The Touch Hand 4 is an iteration of the Touch Hand project which attempts to make a functional, low-cost prosthetic hand which is capable of being accessible to more people relative to conventional myoelectric prosthetic hands as well as being used as a robotic UAV gripper. This research is motivated due to the lack of affordable myoelectric prosthetic hands in the global market. It is believed, with the current technology, it is capable of developing a prosthetic hand which can meet these needs. Research was performed through reviewing other prosthetic hands to understand the requirements for a prosthetic hand as well as understanding the market of prosthetic hands. Prosthetists were interviewed to obtain a perspective from medial professionals regarding the requirements for a prosthetic hand. Hand kinesiology was performed to understand the biomechanics of the human hand, which was emulated in the design of the Touch Hand 4. The mechanical design begun with developing and testing a concept design, which was used to design the general shape of the Touch Hand 4. SLS was chosen to print the prosthetic hand with. After performing a kinematics and static force simulation, the mechanical system was designed accordingly. Further research on EMG sensors was then performed to understand the requirements of using EMG signals to control a prosthetic hand. The electronics and control system were then designed according to the requirements of the prosthetic hand. Tests were performed, however, tests performed with an amputee using the device was affected to improper placement of the EMG sensors, leading to poor results. Tests performed without an amputee, however, showed that the prosthetic hand is capable of gripping various objects of different shapes and sizes. An investigation was also performed on the contributions the Touch Hand 4 could make as a UAV gripper, which showed that the Touch Hand 4 is more adaptable and versatile than any other UAV gripper available on the market.
- Full Text:
- Date Issued: 2019
Vision-based autonomous aircraft payload delivery system
- Authors: Sewell, James Alderton
- Date: 2019
- Subjects: Airplanes -- Control systems , Systems engineering Engineering -- Data processing Artificial intelligence
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/43666 , vital:36960
- Description: This research sought to design and develop an autonomous aircraft payload delivery system which utilised an onboard computer vision system for drop-zone identification. The research was tasked at achieving a modular system which could be used in the delivery of a given payload within a 5 m radius of designated drop-zone identifier. An integrated system was developed, where an autonomous flight controller, an onboard companion computer and computer vision system formed the physical hardware utilised to achieve the desired objectives. A Linux-based Robotic Operating System software architecture was used to develop the control algorithms which governed the autonomous flight control, object recognition and tracking through image processing, and payload release trajectory modelling of the system. The hardware and software architectures were integrated into a remote control fixed-wing aircraft for testing. Implementation of the system through simulation and physical testing proved successful and payload delivery was achieved at an altitude of 75 m, within an average displacement of 1.82 m from the true drop-zone location, where drop-zone detection and location were determined through autonomous survey over the approximate drop-zone’s location. This research furthered the development of autonomous aircraft delivery systems by introducing computer vision as a means of drop-zone location confirmation and authentication, allowing for greater payload delivery security and efficiency. The results gathered in this research illustrated the possible applications of modular airborne payload delivery systems into Industry 4.0 through the use of such a system in the service delivery sector.
- Full Text:
- Date Issued: 2019
- Authors: Sewell, James Alderton
- Date: 2019
- Subjects: Airplanes -- Control systems , Systems engineering Engineering -- Data processing Artificial intelligence
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/43666 , vital:36960
- Description: This research sought to design and develop an autonomous aircraft payload delivery system which utilised an onboard computer vision system for drop-zone identification. The research was tasked at achieving a modular system which could be used in the delivery of a given payload within a 5 m radius of designated drop-zone identifier. An integrated system was developed, where an autonomous flight controller, an onboard companion computer and computer vision system formed the physical hardware utilised to achieve the desired objectives. A Linux-based Robotic Operating System software architecture was used to develop the control algorithms which governed the autonomous flight control, object recognition and tracking through image processing, and payload release trajectory modelling of the system. The hardware and software architectures were integrated into a remote control fixed-wing aircraft for testing. Implementation of the system through simulation and physical testing proved successful and payload delivery was achieved at an altitude of 75 m, within an average displacement of 1.82 m from the true drop-zone location, where drop-zone detection and location were determined through autonomous survey over the approximate drop-zone’s location. This research furthered the development of autonomous aircraft delivery systems by introducing computer vision as a means of drop-zone location confirmation and authentication, allowing for greater payload delivery security and efficiency. The results gathered in this research illustrated the possible applications of modular airborne payload delivery systems into Industry 4.0 through the use of such a system in the service delivery sector.
- Full Text:
- Date Issued: 2019
Characterization of residual stress driven deformation in terms of build height for thin walled laser metal deposition (Ti6AI4V) components
- Authors: Swan, Lindsay Jane
- Date: 2018
- Subjects: Titanium alloys Pulsed laser deposition
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/23537 , vital:30577
- Description: Ti6Al4V is the most commonly used of the titanium alloys and is known for its high strength to weight ratio and superb corrosion resistance compared to conventional steels. Ti6Al4V is used in applications in the aerospace, biomedical, automotive, power generation and oil and gas fields. Laser metal deposition (LMD) is an additive manufacturing (AM) platform used to build 3-D metal shapes. LMD is one of the most researched topics within the laser processing field currently and is advancing continuously. The rapid growth in the AM field is driven by market demands to reduce manufacturing costs, shorter lead times and an increasing demand for customized products. One of the major challenges facing the production of Ti6Al4V components using LMD is the high resultant residual stresses, limiting build size due to delamination or distortion. At the commencement of this study, little data pertaining to the residual stress build up in larger LMD components was available. This research was conducted to create an understanding of the relationship between build height and surface residual stresses and how they influence the dimensional stability of a part. Additionally, the relationship between build height and static mechanical properties was analysed. The effects of laser power, scanning speed and powder mass flow rate on the deposition layer were evaluated. The number of defects and the deposition build height were evaluated to determine the optimum process parameters for multi-layer components. An increase in laser power resulted in an increase in build height for the parameter window selected for the study. Similarly, an increase in build height was observed with an increase in powder mass flow rate, while an increase in scanning speed resulted in a decrease in build height. As laser power and scanning speed had inverse effects on the build height, heat input was evaluated to determine the optimum combination of the 2 parameters. Multilayer samples were produced with a laser power setting of 1900 W, a scanning speed of 0.01 m/s and a powder mass flow rate of 8 g/min. Fully dense components were produced with no notable defects. These components were analysed to reveal the relationship between build height and surface residual stresses and showed that the minimum residual stress observed in a component was related to an actual height from the base and was not affected by the build height of the sample. Maximum residual stresses were observed closest to the base of the cylinder and the stresses were larger in larger samples for both hoop and longitudinal surface residual stress. The micro-hardness of the samples increased as build height increased. The tensile strength remained within constant range between 1080 MPa and 1050 MPa for all samples successfully tested. Brittle failures were observed on the upper sections of the larger samples, attributed to the high micro-hardness observed in these areas. The study successfully evaluated the relationship between build height and surface residual stresses as well as build height and static mechanical properties thereby increasing the knowledge within this field.
- Full Text:
- Date Issued: 2018
- Authors: Swan, Lindsay Jane
- Date: 2018
- Subjects: Titanium alloys Pulsed laser deposition
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/23537 , vital:30577
- Description: Ti6Al4V is the most commonly used of the titanium alloys and is known for its high strength to weight ratio and superb corrosion resistance compared to conventional steels. Ti6Al4V is used in applications in the aerospace, biomedical, automotive, power generation and oil and gas fields. Laser metal deposition (LMD) is an additive manufacturing (AM) platform used to build 3-D metal shapes. LMD is one of the most researched topics within the laser processing field currently and is advancing continuously. The rapid growth in the AM field is driven by market demands to reduce manufacturing costs, shorter lead times and an increasing demand for customized products. One of the major challenges facing the production of Ti6Al4V components using LMD is the high resultant residual stresses, limiting build size due to delamination or distortion. At the commencement of this study, little data pertaining to the residual stress build up in larger LMD components was available. This research was conducted to create an understanding of the relationship between build height and surface residual stresses and how they influence the dimensional stability of a part. Additionally, the relationship between build height and static mechanical properties was analysed. The effects of laser power, scanning speed and powder mass flow rate on the deposition layer were evaluated. The number of defects and the deposition build height were evaluated to determine the optimum process parameters for multi-layer components. An increase in laser power resulted in an increase in build height for the parameter window selected for the study. Similarly, an increase in build height was observed with an increase in powder mass flow rate, while an increase in scanning speed resulted in a decrease in build height. As laser power and scanning speed had inverse effects on the build height, heat input was evaluated to determine the optimum combination of the 2 parameters. Multilayer samples were produced with a laser power setting of 1900 W, a scanning speed of 0.01 m/s and a powder mass flow rate of 8 g/min. Fully dense components were produced with no notable defects. These components were analysed to reveal the relationship between build height and surface residual stresses and showed that the minimum residual stress observed in a component was related to an actual height from the base and was not affected by the build height of the sample. Maximum residual stresses were observed closest to the base of the cylinder and the stresses were larger in larger samples for both hoop and longitudinal surface residual stress. The micro-hardness of the samples increased as build height increased. The tensile strength remained within constant range between 1080 MPa and 1050 MPa for all samples successfully tested. Brittle failures were observed on the upper sections of the larger samples, attributed to the high micro-hardness observed in these areas. The study successfully evaluated the relationship between build height and surface residual stresses as well as build height and static mechanical properties thereby increasing the knowledge within this field.
- Full Text:
- Date Issued: 2018
Computational analysis and cavity optimisation to achieve directional solidification in a cast aluminium alloy [Al7SiMg] component
- Authors: Nohanyaza, Melikhaya
- Date: 2018
- Subjects: Metal castings , Automobiles -- Materials , Alloys , Light metal alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/22913 , vital:30141
- Description: The study at hand focussed on A356.0 industrial and high production die casting alloy. Since the birth of metal casting, numerous researchers have addressed the multiple phenomena that influence the casting quality and mechanical properties of castable alloys. This study harnessed research findings on A356.0 alloy and the aluminium family as a whole, to improve the casting soundness of the component already in the production process. The local foundry showed interest in understanding solidification and quality of A356.0 alloy fluxed with NaCl+KCl melt cleaning flux plus 4 of TiB2 5:1 master alloy grain refining rods and A356.0 alloy processed with KCl+Ti (presumably KCl+TiB2) grain refining flux plus 4 of TiB2 5:1 master alloy rods. Numerical analysis was used to define the progressive nature and directional solidification of the alloy using MAGMA5. MAGMA5.3 virtual optimisation capabilities were used for development of future component casting methods and procedures to solve macro- and microporosity evident on the casting. To find a direct link between the virtual and foundry environment, a preliminary study was conducted on a simple foundry stage of cone billet casting for both alloys with and without mould/casting interface coating. The findings indicated that A356.0 maintained its shrinkage volume percentage at mould temperatures above 300 °C, but progressively increased at temperatures below. Furthermore, thermal insulation coat (also used on Right Hand Side [RHS] mould of the foundry component) influenced the shrinkage distribution on the casting while localised at the centre on non-coated mould/casting interfaces for both KCl+Ti and NaCl+KCl melt fluxed A356.0 at similar percentage shrinkage for mould temperatures greater or equal to 300 °C. Near thin foundry castings for both flux treatments indicated similar mechanical properties at similar casting stages. The mechanical properties of both conditions seemed to degrade as a function of die casting period. Secondary dendrite arm spacing microstructure parameter for NaCl+KCl and KCl+Ti fluxed alloy averaged 40 μm and 35 μm respectively across all test zones. However, individual SDAS definitions per test zone indicated possible micro segregation on NaCl+KCl fluxed alloy and instantaneous solidification as a result of constitutional supercooling on alloys fluxed with KCl+Ti alloy. The growth rate solidification parameter was symmetrical about the centre of the component, where the centre of the component experienced an exponential drop from the top (away from the filling gate) to the bottom (near the filling gate) of the component. A virtual approach to tooling geometrical design indicated a weak influence on both micro- and macroporosity. However, the introduction of low thermal capacity, high heat transfer at Left Hand Side [LHS] tooling and a new cooling system arrangement indicated a higher influence in achieving sound casting. Knowledge gained in this study will improve local foundry competitiveness and introduce cost effective virtual approach foundry developments. The study will also introduce new methods for industrial research and position Nelson Mandela University as a leader in this field.
- Full Text:
- Date Issued: 2018
- Authors: Nohanyaza, Melikhaya
- Date: 2018
- Subjects: Metal castings , Automobiles -- Materials , Alloys , Light metal alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/22913 , vital:30141
- Description: The study at hand focussed on A356.0 industrial and high production die casting alloy. Since the birth of metal casting, numerous researchers have addressed the multiple phenomena that influence the casting quality and mechanical properties of castable alloys. This study harnessed research findings on A356.0 alloy and the aluminium family as a whole, to improve the casting soundness of the component already in the production process. The local foundry showed interest in understanding solidification and quality of A356.0 alloy fluxed with NaCl+KCl melt cleaning flux plus 4 of TiB2 5:1 master alloy grain refining rods and A356.0 alloy processed with KCl+Ti (presumably KCl+TiB2) grain refining flux plus 4 of TiB2 5:1 master alloy rods. Numerical analysis was used to define the progressive nature and directional solidification of the alloy using MAGMA5. MAGMA5.3 virtual optimisation capabilities were used for development of future component casting methods and procedures to solve macro- and microporosity evident on the casting. To find a direct link between the virtual and foundry environment, a preliminary study was conducted on a simple foundry stage of cone billet casting for both alloys with and without mould/casting interface coating. The findings indicated that A356.0 maintained its shrinkage volume percentage at mould temperatures above 300 °C, but progressively increased at temperatures below. Furthermore, thermal insulation coat (also used on Right Hand Side [RHS] mould of the foundry component) influenced the shrinkage distribution on the casting while localised at the centre on non-coated mould/casting interfaces for both KCl+Ti and NaCl+KCl melt fluxed A356.0 at similar percentage shrinkage for mould temperatures greater or equal to 300 °C. Near thin foundry castings for both flux treatments indicated similar mechanical properties at similar casting stages. The mechanical properties of both conditions seemed to degrade as a function of die casting period. Secondary dendrite arm spacing microstructure parameter for NaCl+KCl and KCl+Ti fluxed alloy averaged 40 μm and 35 μm respectively across all test zones. However, individual SDAS definitions per test zone indicated possible micro segregation on NaCl+KCl fluxed alloy and instantaneous solidification as a result of constitutional supercooling on alloys fluxed with KCl+Ti alloy. The growth rate solidification parameter was symmetrical about the centre of the component, where the centre of the component experienced an exponential drop from the top (away from the filling gate) to the bottom (near the filling gate) of the component. A virtual approach to tooling geometrical design indicated a weak influence on both micro- and macroporosity. However, the introduction of low thermal capacity, high heat transfer at Left Hand Side [LHS] tooling and a new cooling system arrangement indicated a higher influence in achieving sound casting. Knowledge gained in this study will improve local foundry competitiveness and introduce cost effective virtual approach foundry developments. The study will also introduce new methods for industrial research and position Nelson Mandela University as a leader in this field.
- Full Text:
- Date Issued: 2018
Mitigation of single event upsets in a XILINX ARTIX-7 field programmable gate array
- Authors: Omolo, Joshua
- Date: 2018
- Subjects: Field programmable gate arrays -- Design and construction Prototypes, Engineering
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/22310 , vital:29942
- Description: Field programmable gate arrays are increasingly being used in harsh environments like space where high energy particles from radiation affect the integrity of the data. Before deployment of satellites in space, characterisation and consequently mitigation of radiation effects is necessary to avoid failure. By irradiating a digital microelectronic device, using accelerated energetic particles, it is possible to predict the likelihood of an event effect happening. Such irradiation tests can only be done at a particle accelerator facility such as iThemba LABS in Cape Town. It is the one of the few particle accelerators in the southern hemisphere and offers the capacity to perform these event effect characterisation tests. Triple Modular Redundancy (TMR) is a commonly used mitigation technique in microelectronics. Although effective, it has the downside of increased resource area. A DMR-Filter combination mitigation technique was developed at the Nelson Mandela University. It uses fewer resources than TMR and it is envisaged to significantly reduce event upsets in a FPGA. This research project seeks to investigate the effectiveness of the DMR-Filter combination mitigation technique in reducing the likelihood of event upsets occurring in Xilinx’s Artix-7 FPGA when exposed to highly accelerated particles, similar to those in space.
- Full Text:
- Date Issued: 2018
- Authors: Omolo, Joshua
- Date: 2018
- Subjects: Field programmable gate arrays -- Design and construction Prototypes, Engineering
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/22310 , vital:29942
- Description: Field programmable gate arrays are increasingly being used in harsh environments like space where high energy particles from radiation affect the integrity of the data. Before deployment of satellites in space, characterisation and consequently mitigation of radiation effects is necessary to avoid failure. By irradiating a digital microelectronic device, using accelerated energetic particles, it is possible to predict the likelihood of an event effect happening. Such irradiation tests can only be done at a particle accelerator facility such as iThemba LABS in Cape Town. It is the one of the few particle accelerators in the southern hemisphere and offers the capacity to perform these event effect characterisation tests. Triple Modular Redundancy (TMR) is a commonly used mitigation technique in microelectronics. Although effective, it has the downside of increased resource area. A DMR-Filter combination mitigation technique was developed at the Nelson Mandela University. It uses fewer resources than TMR and it is envisaged to significantly reduce event upsets in a FPGA. This research project seeks to investigate the effectiveness of the DMR-Filter combination mitigation technique in reducing the likelihood of event upsets occurring in Xilinx’s Artix-7 FPGA when exposed to highly accelerated particles, similar to those in space.
- Full Text:
- Date Issued: 2018
Solar thermal performance of a conical helix receiver tube mounted on a parabolic dish
- Nandjembo, Frans Nelongo Pandeni
- Authors: Nandjembo, Frans Nelongo Pandeni
- Date: 2018
- Subjects: Solar energy , Power resources Energy conversion
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/32860 , vital:32379
- Description: This report presents the investigation of a conical helix receiver tube with a zero shading factor to achieve optimal performance of a small concentrating solar thermal collector. In order to understand the working performance of the conical helix receiver tube, it was compared to that of a flat spiral receiver tube. This was done by measuring temperatures at various points as well as the volume airflow rate. Optical studies were achieved using SolTrace to quantify spillage losses and optical efficiency of the dish used in the study from the parabolic dish using a simulation in SolTrace. Comparative tests were conducted between the conical receiver tube and equivalent flat receiver tube at volume air flow rates between 30 m3.h−1 and 45 m3.h−1. The conical helix receiver tube showed a linear temperature distribution, from the outer surface tube towards the inner surface tube in an ascending order, while the flat spiral receiver tube showed a non-linear temperature distribution, its temperature increased in the middle section and decreased towards the inner surface tube. The research showed that an optimally configured helical receiver tube with linear temperature change along its length outperformed the flat receiver tube.
- Full Text:
- Date Issued: 2018
- Authors: Nandjembo, Frans Nelongo Pandeni
- Date: 2018
- Subjects: Solar energy , Power resources Energy conversion
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/32860 , vital:32379
- Description: This report presents the investigation of a conical helix receiver tube with a zero shading factor to achieve optimal performance of a small concentrating solar thermal collector. In order to understand the working performance of the conical helix receiver tube, it was compared to that of a flat spiral receiver tube. This was done by measuring temperatures at various points as well as the volume airflow rate. Optical studies were achieved using SolTrace to quantify spillage losses and optical efficiency of the dish used in the study from the parabolic dish using a simulation in SolTrace. Comparative tests were conducted between the conical receiver tube and equivalent flat receiver tube at volume air flow rates between 30 m3.h−1 and 45 m3.h−1. The conical helix receiver tube showed a linear temperature distribution, from the outer surface tube towards the inner surface tube in an ascending order, while the flat spiral receiver tube showed a non-linear temperature distribution, its temperature increased in the middle section and decreased towards the inner surface tube. The research showed that an optimally configured helical receiver tube with linear temperature change along its length outperformed the flat receiver tube.
- Full Text:
- Date Issued: 2018
A genetic algorithm to obtain optimum parameters for a halcon vision system
- Authors: Fulton, Dale Meares
- Date: 2017
- Subjects: Genetic algorithms , Artificial intelligence , Automation , User interfaces (Computer systems)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/29751 , vital:30774
- Description: This report discusses the optimisation of a HALCON vision system using artificial intelligence, specifically a genetic algorithm. Within industrial applications, vision systems are often used for automated part inspection and quality control. A number of vision system parameters are to be selected when setting up a vision system. Since each vision system application differs, there is no specific set of optimal parameters. Parameters are selected during installation using a trial and error method. As a result, there is a need for an automated process for obtaining suitable vision system parameters. Within this report, research was conducted on both vision systems, genetic algorithms and integration of the two. A physical vision system was designed and developed utilising HALCON vision software. A genetic algorithm was then developed and integrated with the vision system. After integration, experimental testing was performed on the genetic algorithm in order to determine the ideal genetic algorithm control parameters which yield ideal genetic algorithm performance. Once the ideal genetic algorithm was obtained, the genetic algorithm was applied to the vision system in order to obtain optimal vision system parameters. Results showed that applying the genetic algorithm to the vision system optimised the vision system performance well.
- Full Text:
- Date Issued: 2017
- Authors: Fulton, Dale Meares
- Date: 2017
- Subjects: Genetic algorithms , Artificial intelligence , Automation , User interfaces (Computer systems)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/29751 , vital:30774
- Description: This report discusses the optimisation of a HALCON vision system using artificial intelligence, specifically a genetic algorithm. Within industrial applications, vision systems are often used for automated part inspection and quality control. A number of vision system parameters are to be selected when setting up a vision system. Since each vision system application differs, there is no specific set of optimal parameters. Parameters are selected during installation using a trial and error method. As a result, there is a need for an automated process for obtaining suitable vision system parameters. Within this report, research was conducted on both vision systems, genetic algorithms and integration of the two. A physical vision system was designed and developed utilising HALCON vision software. A genetic algorithm was then developed and integrated with the vision system. After integration, experimental testing was performed on the genetic algorithm in order to determine the ideal genetic algorithm control parameters which yield ideal genetic algorithm performance. Once the ideal genetic algorithm was obtained, the genetic algorithm was applied to the vision system in order to obtain optimal vision system parameters. Results showed that applying the genetic algorithm to the vision system optimised the vision system performance well.
- Full Text:
- Date Issued: 2017
Diamond turning of contact lens polymers
- Authors: Liman, Muhammad Mukhtar
- Date: 2017
- Subjects: Diamond turning Contact lenses , Electrostatic lenses Lenses -- Design and construction Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/19223 , vital:28789
- Description: Contact lens production requires high accuracy and good surface integrity. Surface roughness is generally used to measure the index quality of a turning process. It has been an important response because it has direct influence toward the part performance and the production cost. Hence, choosing optimal cutting parameters will not only improve the quality measure but also the productivity. In this study, an ONSI-56 (Onsifocon A) contact lens buttons were used to investigate the triboelectric phenomena and the effects of turning parameters on surface finish of the lens materials. ONSI-56 specimens are machined by Precitech Nanoform Ultra-grind 250 precision machine and the roughness values of the diamond turned surfaces are measured by Taylor Hopson PGI Profilometer. Electrostatics values were measured using electrostatic voltmeter. An artificial neural network (ANN) and response surface (RS) model were developed to predict surface roughness and electrostatic discharge (ESD) on the turned ONSI-56. In the development of predictive models, turning parameters of cutting speed, feed rate and depth of cut were considered as model variables. The required data for predictive models were obtained by conducting a series of turning test and measuring the surface roughness and ESD data. Good agreement is observed between the predictive models results and the experimental measurements. The ANN and RSM models for ONSI-56 are compared with each other using mean absolute percentage error (MAPE) for accuracy and computational cost.
- Full Text:
- Date Issued: 2017
- Authors: Liman, Muhammad Mukhtar
- Date: 2017
- Subjects: Diamond turning Contact lenses , Electrostatic lenses Lenses -- Design and construction Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/19223 , vital:28789
- Description: Contact lens production requires high accuracy and good surface integrity. Surface roughness is generally used to measure the index quality of a turning process. It has been an important response because it has direct influence toward the part performance and the production cost. Hence, choosing optimal cutting parameters will not only improve the quality measure but also the productivity. In this study, an ONSI-56 (Onsifocon A) contact lens buttons were used to investigate the triboelectric phenomena and the effects of turning parameters on surface finish of the lens materials. ONSI-56 specimens are machined by Precitech Nanoform Ultra-grind 250 precision machine and the roughness values of the diamond turned surfaces are measured by Taylor Hopson PGI Profilometer. Electrostatics values were measured using electrostatic voltmeter. An artificial neural network (ANN) and response surface (RS) model were developed to predict surface roughness and electrostatic discharge (ESD) on the turned ONSI-56. In the development of predictive models, turning parameters of cutting speed, feed rate and depth of cut were considered as model variables. The required data for predictive models were obtained by conducting a series of turning test and measuring the surface roughness and ESD data. Good agreement is observed between the predictive models results and the experimental measurements. The ANN and RSM models for ONSI-56 are compared with each other using mean absolute percentage error (MAPE) for accuracy and computational cost.
- Full Text:
- Date Issued: 2017
Electrostatic discharge and roughness modelling in diamond turning of contact lenses
- Authors: Kopi, Fundiswa
- Date: 2017
- Subjects: Diamond turning Contact lenses
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18783 , vital:28723
- Description: With the increased application of ultra-high precision machining of polymers and the limited research in single point diamond turning (SPDT) of contact lens polymers, it became imperative to gather understanding on the production of contact lenses using the above-mentioned technology. A limiting factor in SPDT of polymers is wear of the diamond tool, resulting into poor surface finish due to unintended charges generated as a result of the contact/rubbing action between the cutting tool and the cut material. Central Composite Design (CCD) Face Centred experimental design was developed and applied to the SPDT of ONSI-56 and Polymethly methacrylate (PMMA) contact lens buttons. An electrostatic sensor coupled to a computer monitored the electrostatic discharge generated and a profilometer measured the surface roughness. The Response Surface Method (RSM) was utilised during the development of predictive models for both the surface roughness and the electrostatic discharge generated, to deduce the effects of cutting parameters during machining. The cutting speed and the feed rate deemed as the influential parameters on the surface roughness and electrostatic discharge, for both materials. The depth of cut induced more charge generation for PMMA. Predictive models were successfully developed and they were aimed at creating a database a guide to the SPDT of contact lens polymers.
- Full Text:
- Date Issued: 2017
- Authors: Kopi, Fundiswa
- Date: 2017
- Subjects: Diamond turning Contact lenses
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18783 , vital:28723
- Description: With the increased application of ultra-high precision machining of polymers and the limited research in single point diamond turning (SPDT) of contact lens polymers, it became imperative to gather understanding on the production of contact lenses using the above-mentioned technology. A limiting factor in SPDT of polymers is wear of the diamond tool, resulting into poor surface finish due to unintended charges generated as a result of the contact/rubbing action between the cutting tool and the cut material. Central Composite Design (CCD) Face Centred experimental design was developed and applied to the SPDT of ONSI-56 and Polymethly methacrylate (PMMA) contact lens buttons. An electrostatic sensor coupled to a computer monitored the electrostatic discharge generated and a profilometer measured the surface roughness. The Response Surface Method (RSM) was utilised during the development of predictive models for both the surface roughness and the electrostatic discharge generated, to deduce the effects of cutting parameters during machining. The cutting speed and the feed rate deemed as the influential parameters on the surface roughness and electrostatic discharge, for both materials. The depth of cut induced more charge generation for PMMA. Predictive models were successfully developed and they were aimed at creating a database a guide to the SPDT of contact lens polymers.
- Full Text:
- Date Issued: 2017
Friction welding of thin walled zircaloy-4 tubes for the nuclear industry
- Authors: Koloi, Nthatisi Dinah
- Date: 2017
- Subjects: Friction welding Zirconium alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18794 , vital:28724
- Description: This work reports on the process development of solid state welding as an alternative joining process for assembling Zircaloy-4 fuel rod components for the nuclear industry. A typical fuel rod consists of a thin tube that is blocked at both ends by end-caps. The welding of the thin wall tubes onto the end-caps is currently accomplished by employing fusion techniques. Due to limited thin wall Zircaloy-4 tube supplied, preliminary welding was initially performed with thin wall 316L stainless steel tube for the development of a joint geometry and establishment of an experimental welding and testing setup. A suitable joint geometry that would achieve higher static strength equal or above that of the parent material, as well as complete circumferential bonding was investigated through welding a tube on different volume interface geometries of the end-caps. Higher joint efficiency was obtained from a tube-to-tube joint geometry that allowed sufficient frictional heat input at the interface. Consequently, the successful joint geometry was employed to develop a friction welding process for the joining of thin wall Zircaloy-4 tubes. The influential process parameters, axial force, rotational speed and upset distance were varied during the investigation. The completed weld joints were evaluated by visual, metallurgical and mechanical means. Successful welds showed complete circumferential bonding and high joint efficiency that was above the parent plate material as well as parent tube material. The evaluation of the microstructure showed transformation of grain structure on the heat affected zone (HAZ) and friction weld zone when compared to the parent materials. Even though, this work could not resolve inner flash formation, there is enough evidence that friction welding can be used for assembling fuel rod components in the nuclear industry.
- Full Text:
- Date Issued: 2017
- Authors: Koloi, Nthatisi Dinah
- Date: 2017
- Subjects: Friction welding Zirconium alloys
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/18794 , vital:28724
- Description: This work reports on the process development of solid state welding as an alternative joining process for assembling Zircaloy-4 fuel rod components for the nuclear industry. A typical fuel rod consists of a thin tube that is blocked at both ends by end-caps. The welding of the thin wall tubes onto the end-caps is currently accomplished by employing fusion techniques. Due to limited thin wall Zircaloy-4 tube supplied, preliminary welding was initially performed with thin wall 316L stainless steel tube for the development of a joint geometry and establishment of an experimental welding and testing setup. A suitable joint geometry that would achieve higher static strength equal or above that of the parent material, as well as complete circumferential bonding was investigated through welding a tube on different volume interface geometries of the end-caps. Higher joint efficiency was obtained from a tube-to-tube joint geometry that allowed sufficient frictional heat input at the interface. Consequently, the successful joint geometry was employed to develop a friction welding process for the joining of thin wall Zircaloy-4 tubes. The influential process parameters, axial force, rotational speed and upset distance were varied during the investigation. The completed weld joints were evaluated by visual, metallurgical and mechanical means. Successful welds showed complete circumferential bonding and high joint efficiency that was above the parent plate material as well as parent tube material. The evaluation of the microstructure showed transformation of grain structure on the heat affected zone (HAZ) and friction weld zone when compared to the parent materials. Even though, this work could not resolve inner flash formation, there is enough evidence that friction welding can be used for assembling fuel rod components in the nuclear industry.
- Full Text:
- Date Issued: 2017
Hybrid additive manufacturing platform for the production of composite wind turbine blade moulds
- Authors: Momsen, Timothy Benjamin
- Date: 2017
- Subjects: Manufacturing processes -- Automation Production control -- Automation , Production management
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/19091 , vital:28772
- Description: This dissertation discusses the application of additive manufacturing technologies for production of a large-scale rapid prototyping machine, which will be used to produce moulds for prototype composite turbine blades for the emerging renewables energy industry within the Eastern Cape region in South Africa. The conceptualization and design of three complete printer builds resulted in the amalgamation of a final system, following stringent theoretical design, simulation, and feasibility analysis. Following the initial product design cycle stage, construction and performance testing of a large-scale additive manufacturing platform were performed. In-depth statistical analysis of the mechatronic system was undertaken, particularly related to print-head locational accuracy, repeatability, and effects of parameter variation on printer performance. The machine was analysed to assess feasibility for use in the mould-making industry with accuracy and repeatability metrics of 0.121 mm and 0.156 mm rivalling those produced by some of the more accurate fused deposition modellers commercially available. The research data gathered serves to confirm that rapid prototyping is a good alternative manufacturing method for wind turbine blade plug and mould production.
- Full Text:
- Date Issued: 2017
- Authors: Momsen, Timothy Benjamin
- Date: 2017
- Subjects: Manufacturing processes -- Automation Production control -- Automation , Production management
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/19091 , vital:28772
- Description: This dissertation discusses the application of additive manufacturing technologies for production of a large-scale rapid prototyping machine, which will be used to produce moulds for prototype composite turbine blades for the emerging renewables energy industry within the Eastern Cape region in South Africa. The conceptualization and design of three complete printer builds resulted in the amalgamation of a final system, following stringent theoretical design, simulation, and feasibility analysis. Following the initial product design cycle stage, construction and performance testing of a large-scale additive manufacturing platform were performed. In-depth statistical analysis of the mechatronic system was undertaken, particularly related to print-head locational accuracy, repeatability, and effects of parameter variation on printer performance. The machine was analysed to assess feasibility for use in the mould-making industry with accuracy and repeatability metrics of 0.121 mm and 0.156 mm rivalling those produced by some of the more accurate fused deposition modellers commercially available. The research data gathered serves to confirm that rapid prototyping is a good alternative manufacturing method for wind turbine blade plug and mould production.
- Full Text:
- Date Issued: 2017