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
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