X-ray motion analysis of charge particles in a laboratory mill

 

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dc.contributor.advisor Powell, Malcolm en_ZA
dc.contributor.author Govender, Indresan en_ZA
dc.date.accessioned 2014-10-20T07:41:35Z
dc.date.available 2014-10-20T07:41:35Z
dc.date.issued 2005 en_ZA
dc.identifier.citation Govender, I. 2005. X-ray motion analysis of charge particles in a laboratory mill. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/8642
dc.description Includes bibliographical references (p. [266]-273). en_ZA
dc.description.abstract The work reported herein is of an automated X-ray vision system used to track the 3D trajectories of a typical bulk charge particle within an experimental Perspex mill, the intention of which is to simulate the grinding motion of rock found in typical industrial mills The experimental rig is constructed through an optimisation scheme that determines the maximum allowed dimensions of the mill that can be imaged by the X-ray system, however, the optimisation principle is not limited to the current study and can be employed to maximise any volume being investigated with the X-ray system. The raw data for each position of the tracked particle comprises of two X-ray images of the tumbling mill generated orthogonal to each other, with a phase lag between them. The correction of the phase lag between the biplanar images is a new addition to the usual usage of the system resulting in an effective sampling rate of 100 frames per second, thereby ensuring that the resolution is sufficient to conduct detailed kinematic studies. The processing of the raw images are achieved with a dynamic template matching algorithm followed by a modified, and improved, implementation of the Canny edge detector, while the centering of the edge images are based on an adapted conic fitting routine, resulting in an overall subpixel centering accuracy. The processed images are then mapped to object space using the direct linear transformation (DLT), equipped with a physically valid variance model that is shown to improve the standard implementation even when robust solvers are employed. The final reconstruction accuracy of the tracked particle was shown to be 0.15 mm and is achieved without iteration due to the appropriateness of the variance model. The high accuracy data. was initially used to benchmark the discrete element method (DEM), providing the first numerical comparisons that surpassed the usual end-window snapshots employed by other investigators for the purpose of validation. The analysis of the data was not restricted to DEM verification, and in some sense, surpassed the initial objective by yielding trends useful to communication practices. Amongst these analyses was the finding that the circulation rate of the charge is not once per mill revolution but greater, depicting a linear trend with mill speed. The slip between charge layers was shown to follow a linear pattern, with the degree of slip increasing linearly with mill speed. The phenomenon of charge surging was quantified, resulting in a trend for the variation of the surge amplitude with mill speed. A mechanism for the surging phenomenon was also proposed in this study. A particularly useful outcome of the data analyses was the formulation of a power model through heuristic trends of the center of mass (CoM) and center of circulation (CoC) of the charge. The methodology outlined by the model was shown to be robust, providing a correct approach to obtaining a truly fundamental power model based on generally applicable principles. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Mechanical Engineering en_ZA
dc.title X-ray motion analysis of charge particles in a laboratory mill en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Engineering and the Built Environment
dc.publisher.department Department of Mechanical Engineering en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Govender, I. (2005). <i>X-ray motion analysis of charge particles in a laboratory mill</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering. Retrieved from http://hdl.handle.net/11427/8642 en_ZA
dc.identifier.chicagocitation Govender, Indresan. <i>"X-ray motion analysis of charge particles in a laboratory mill."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2005. http://hdl.handle.net/11427/8642 en_ZA
dc.identifier.vancouvercitation Govender I. X-ray motion analysis of charge particles in a laboratory mill. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 2005 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/8642 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Govender, Indresan AB - The work reported herein is of an automated X-ray vision system used to track the 3D trajectories of a typical bulk charge particle within an experimental Perspex mill, the intention of which is to simulate the grinding motion of rock found in typical industrial mills The experimental rig is constructed through an optimisation scheme that determines the maximum allowed dimensions of the mill that can be imaged by the X-ray system, however, the optimisation principle is not limited to the current study and can be employed to maximise any volume being investigated with the X-ray system. The raw data for each position of the tracked particle comprises of two X-ray images of the tumbling mill generated orthogonal to each other, with a phase lag between them. The correction of the phase lag between the biplanar images is a new addition to the usual usage of the system resulting in an effective sampling rate of 100 frames per second, thereby ensuring that the resolution is sufficient to conduct detailed kinematic studies. The processing of the raw images are achieved with a dynamic template matching algorithm followed by a modified, and improved, implementation of the Canny edge detector, while the centering of the edge images are based on an adapted conic fitting routine, resulting in an overall subpixel centering accuracy. The processed images are then mapped to object space using the direct linear transformation (DLT), equipped with a physically valid variance model that is shown to improve the standard implementation even when robust solvers are employed. The final reconstruction accuracy of the tracked particle was shown to be 0.15 mm and is achieved without iteration due to the appropriateness of the variance model. The high accuracy data. was initially used to benchmark the discrete element method (DEM), providing the first numerical comparisons that surpassed the usual end-window snapshots employed by other investigators for the purpose of validation. The analysis of the data was not restricted to DEM verification, and in some sense, surpassed the initial objective by yielding trends useful to communication practices. Amongst these analyses was the finding that the circulation rate of the charge is not once per mill revolution but greater, depicting a linear trend with mill speed. The slip between charge layers was shown to follow a linear pattern, with the degree of slip increasing linearly with mill speed. The phenomenon of charge surging was quantified, resulting in a trend for the variation of the surge amplitude with mill speed. A mechanism for the surging phenomenon was also proposed in this study. A particularly useful outcome of the data analyses was the formulation of a power model through heuristic trends of the center of mass (CoM) and center of circulation (CoC) of the charge. The methodology outlined by the model was shown to be robust, providing a correct approach to obtaining a truly fundamental power model based on generally applicable principles. DA - 2005 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2005 T1 - X-ray motion analysis of charge particles in a laboratory mill TI - X-ray motion analysis of charge particles in a laboratory mill UR - http://hdl.handle.net/11427/8642 ER - en_ZA


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