Multirotor UAV-based autonomous rural security system
- Authors: Welgemoed, Jacques Christian
- Date: 2022-04
- Subjects: Mechatronics , Computer security -- Software
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/58544 , vital:59761
- Description: This dissertation presents the development, implementation and experimental verification of a multirator UAV-based autonomous rural security system. this system is capable of autonomously responding to security-related events, broadcasting and analysing a video feed of the event, returning to a home position, and performing a precision landing using onbroad intelligence, computer vision, and state-of-the-art flight control software. this research is intended to address some of the issues associated with security in rural areas, for example, farmlands by providing a rapid response mechanism. An integrated hardware and software architecture was developed to achieve the aim and objectives of this research. , Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 2022
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- Date Issued: 2022-04
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.
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- Date Issued: 2020
Optical surface quality and molecular dynamics modelling of ultra-high precision optical silicon machining
- Authors: Abdulkadir, Lukman Niyi
- Date: 2019-04
- Subjects: Engineering design -- Data processing , Manufacturing processes -- Data processing , Mechatronics
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/66552 , vital:75601
- Description: Hard and brittle materials, such as silicon, silicon carbide etc., are widely used in aerospace, integrated circuit, and other fields due to their excellent physical and chemical properties. However, these materials display poor machinability owing to hardness, brittleness, non-linearity in machining process and complexities in selecting suitable machining parameters and tool geometry. These leads to low quality lenses due to subsurface damage and surface micro-crack. Additionally, it is experimentally very difficult to observe all nanoscale physical phenomena due to in-process measurement problems, inaccessible contact area of tool and workpiece, and the difficulty of surface analysis. With the use of molecular dynamics (MD) which is a comprehensive nanoscale modelling technique, proper selection of process parameters, tool geometry and online monitoring techniques, production of freeform optics is possible through Ultra-high precision diamond turning (UHPDT). Though, depending on view point, machinability in UHPDT may be in terms of tool wear rate, hardness, chip morphology, surface roughness, and other benchmarks. These situations have called for more insights, which on the long run will help to achieve high precision manufacturing with predictability, repeatability, productivity and high infrared (IR) optical quality. In this thesis, UHPDT of monocrystalline silicon at atomistic scale was conducted to investigate combined effects of edge radius, feed rate, cutting speed, depth of cut, rake and clearance angles hitherto not done so far. Using appropriate potential functions with the MD algorithm, comprehensive analysis of thermal effects, diamond tool wear, phase change, cutting forces and machining stresses (normal, shear, hydrostatic and von Mises) were carried out. Dislocation extraction algorithm (DXA) and radial distribution function (RDF) were used to evaluate dislocation nucleation, variations in bond lengths, microstructural transformation and represents structural changes in histogram form. Selected parameters for optical quality surface roughness were afterwards compared and optimized through response surface methodology (RSM) based on Box Behnken (BBD) and Taguchi L9 methods. The results indicated that, silicon atoms in the chip formation zone undergo high pressure phase transformation (HPPT) at high hydrostatic pressure and temperature.Silicon microstructure transformed from four-coordinated diamond cubic structure (Si- I) to unstable six-coordinated body-centered tetragonal structure (β-silicon) which then transformed to amorphous silicon atoms (a-Si) through amorphization. These resulted in plastic deformation and defects in the machining zone causing subsurface damage. Stress analysis indicated that the compressive stress in the machining zone (i.e. amorphous region) suppressed crack formation contributing to continuous plastic flow which is responsible for silicon ductile-mode cutting. Furthermore, formation of silicon carbide which constituted diamond wear was observed to be by sp3 - sp2 diamond carbon atom disorder and tribochemistry. The tribochemistry occurred through both multiphase and solid-state single-phase reaction between diamond tool and silicon workpiece at cutting temperatures above and below 959 K. Both the experimental findings and the simulation results reveal that, at edge radius less than uncut chip thickness, tool wear was more of rake wear than flank wear. Tool wear and kinetic friction reduced as the edge radius approached the uncut chip thickness while forces, stresses and SCE increased. When machining silicon at differentratio, silicon stress state, SCE, SSD, forces (reduced with increase in clearance angle), shear plane, chip velocity and chip ratio increased as edge radius and rake angle increased, while, kinetic friction, chip length and thickness reduced. The crystal lattice of the machined surfaces and subsurface deformed layer depth increased with increase in edge radius, feed and rake angle. Amongst all tested and analysed parameters, feed rate had the highest influence on surface quality while depth of cut showed the least. Acoustic emission was also monitored during machining and its results statistically analysed. The trends of the monitored acoustic emissions showed its capability to adequately represent and predict surface roughness results. Based on the developed simulation model a novel method for quantitative assessment of tool wear was proposed. The proposed model can be used to compare tool wear using graphitization and tribochemistry to decide the path and mode of the diamond tool wear. Finally, based on the experiment results and predictive model, a novel combination and hierarchical arrangement of the considered factors capable of suppressing tool wear and improve attainable machined surface roughness when turning hard-to-machine materials was proposed. , Thesis (D.Phil) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2019
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- Date Issued: 2019-04
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.
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- Date Issued: 2019
Energy management system for the diagnosis and control of an automatic guided vehicle
- Authors: Church, Stuart Michael
- Date: 2016
- Subjects: Automated guided vehicle systems , Mechatronics
- Language: English
- Type: Thesis , Masters , MEng
- Identifier: http://hdl.handle.net/10948/4798 , vital:20681
- Description: With the increase in electronic equipment implemented in various systems, as well as the increase in calculating power that these devices offer, designers are being empowered to make use of this power in real-time systems to diagnose and protect the systems themselves. This reasoning is too compounded by the focus on efficiency and safety in the design of complex systems, as well as the increasing expense and sensitivity of the electronic components themselves. With this in mind, this dissertation aims at developing a comprehensive measurement, control and reaction system for the electrical diagnosis and ultimately optimisation of complex electrical and electronic systems. This system will serve as a real-time diagnosis tool, which will enable the real-time diagnosis of various components in an electro-mechanical system, which can then be interpreted to determine the working state of the various components. Another sphere of this project will involve the accurate monitoring of the battery status as well as actively balancing the series connected batteries. The focus on the batteries will seek to prolong the life of the batteries, while being able to squeeze as much capacity out of them. The initial design and testing will be based on an AGV system implemented at VWSA, however a main goal throughout the design process will be modularity, i.e. the ease of implementation of this system in other systems. The key technologies used in the development of this system will still comprise of the components used in the original AGV, however new prototype components sourced from Microcare are used for the battery management system, while current sensors directly connected to the PLC’s analog input ports will be used for the active monitoring of currents distributed through the AGV.
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- Date Issued: 2016
Development of a navigation system for an autonomous guided vehicle using android technology
- Authors: Snyman, Christo Johannes
- Date: 2012
- Subjects: Mechatronics , Engeering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9654 , http://hdl.handle.net/10948/d1020025
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- Date Issued: 2012