Run-of-mine ore milling circuits are generally difficult to control owing to the presence of strong external disturbances, poor process models and the unavailability of important process variable measurements. These shortcomings are common for processes in the mineral-processing industry. For processes that fall into this class, the peripheral control tools in the control loop are considered to be as important as the controller itself. This work addresses the implementation of peripheral control tools on a run-of-mine ore milling circuit to help overcome the deteriorated control performance resulting from the aforementioned shortcomings. The effects of strong external disturbances are suppressed through the application of a disturbance observer. A fractional order disturbance observer is also implemented and a novel Bode ideal cutoff disturbance observer is introduced. The issue of poor process models is addressed through the detection of significant mismatch between the actual plant and the available model from process data. A closed-form expression is given for the case where the controller has a transfer function. If the controller does not have a transfer function, a partial correlation analysis is used to detect the transfer function elements in the model transfer function matrix that contain significant mismatch. The mill states and important mill parameters are estimated with the use of particle filters. Simultaneous state and parameter estimation is compared with a novel dual particle filtering scheme. A sensitivity analysis shows the class of systems for which dual estimation would provide superiorestimation accuracy over simultaneous estimation. The implemented peripheral control tools show promise for current milling circuits where proportional-integral-derivative (PID) control is prevalent, and also for advanced control strategies, such as model predictive control, which are expected to become more common in the future. AFRIKAANS : Maalkringe wat onbehandelde erts maal is oor die algemeen moeilik om te beheer as gevolg van die teenwoordigheid van sterk eksterne steurings, onakkurate aanlegmodelle en metings van belangrike prosesveranderlikes wat ontbreek. Hierdie probleme is algemeen vir aanlegte in die mineraalprosesseringsbedryf. Vir aanlegte in hierdie klas word die randbeheerinstrumente as net so belangrik as die beheerder beskou. Hierdie verhandeling beskryf die implementering van randbeheerinstrumente vir ’n maalkring wat onbehandelde erts maal, om die verswakte beheerverrigting teen te werk wat veroorsaak word deur bogenoemde probleme. Die impak van sterk eksterne steurings word teengewerk deur die implementering van ’n steuringsafskatter. ’n Breuk-orde-steuringsafskatter is ook geïmplementeer en ’n nuwe Bode ideale afsnysteuringsafskatter word voorgestel. Die kwessie van onakkurate aanlegmodelle word hanteer deur van die aanlegdata af vas te stel of daar ’n verskil is tussen die aanleg en die beskikbare model van die aanleg. ’n Uitdrukking word gegee vir hierdie verskil vir die geval waar die beheerder met ’n oordragsfunksie voorgestel kan word. Indien die beheerder nie ’n oordragsfunksie het nie, word van ‘n parsiële korrelasie-analise gebruik gemaak om die element, of elemente, in die aanleg se oordragsfunksiematriks te identifiseer wat van die werklike aanleg verskil. Die toestande en belangrike parameters in die meul word beraam deur van partikel-filters gebruikte maak. Gelyktydige toestand- en parameter-beraming word vergelyk met ’n nuwe dubbel-partikelfilter skema. ’n Sensitiwiteitsanalise wys die klas van stelsels waarvoor dubbel-afskatting meer akkurate waardes sal gee as gelyktydige afskatting. Die voorgestelde randbeheerinstrumente is toepaslik vir huidige maalkringe waar PID-beheer algemeen is, asook vir gevorderde beheerstrategieë, soos model-voorspellende beheer, wat na verwagting in die toekoms meer algemeen sal word. Copyright / Dissertation (MEng)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

Text in Afrikaans / Die doel van die ondersoek sentreer rondom die verband tussen denkontwikkeling (‘n kognitiewe veranderlike) en prestasie in Afrikaans as tweede taal. Denkont-wikkeling is egter nie die enigste kognitiewe veranderlike wat prestasie in ‘n taal kan beïnvloed nie. Verbale begrip en geheue is ook as vername kognitiewe verander-likes geïdentifiseer. Affektiewe veranderlikes soos motivering, selfkonsep en angs, kan ook met prestasie in Afrikaans as tweede taal in verband gebring word. ‘n Empiriese ondersoek is uitgevoer waarby 174 hoërskoolleerders betrek is. Kognitiewe en affektiewe veranderlikes, asook leerstyl, is gemeet. Uit die empiriese ondersoek blyk dit dat selfkonsep, geheue, verbale begrip en motivering as die vernaamste veranderlikes beskou kan word wat met prestasie in Afrikaans as tweede taal verband hou. Denkontwikkeling is nie as ‘n vername faktor geïdentifiseer nie. Die bevindinge in die literatuurstudie en die empiriese ondersoek is bespreek om ouers en onderwysers van riglyne te voorsien om prestasie in Afrikaans te verhoog. / The aim of the research focusses on the relationship between thought development (a cognitive variable) and achievement in Afrikaans as a second language. Besides thought development, verbal understanding and memory recollection are also identified as distinctive cognitive variables. Affective variables such as motivation, self-concept and anxiety could also relate to performance in Afrikaans as a second language. Empirical research was conducted amongst 174 High School learners. Cognitive variables, affective variables and learning styles were measured. Resulting from the empirical research, it appears that self-concept, memory recollection, verbal comprehension and motivation are the main variables that impact on the performance of Afrikaans as a second language. Thought process development was not identified as a main factor. Results from the literature study and the empirical research are discussed in order to assist parents and teachers with guidelines to increase achievement in Afrikaans as a second language. / Psychology of Education / M. Ed. (Sielkundige Opvoedkunde)

Text in Afrikaans / Die doel van die ondersoek sentreer rondom die verband tussen denkontwikkeling (‘n kognitiewe veranderlike) en prestasie in Afrikaans as tweede taal. Denkont-wikkeling is egter nie die enigste kognitiewe veranderlike wat prestasie in ‘n taal kan beïnvloed nie. Verbale begrip en geheue is ook as vername kognitiewe verander-likes geïdentifiseer. Affektiewe veranderlikes soos motivering, selfkonsep en angs, kan ook met prestasie in Afrikaans as tweede taal in verband gebring word. ‘n Empiriese ondersoek is uitgevoer waarby 174 hoërskoolleerders betrek is. Kognitiewe en affektiewe veranderlikes, asook leerstyl, is gemeet. Uit die empiriese ondersoek blyk dit dat selfkonsep, geheue, verbale begrip en motivering as die vernaamste veranderlikes beskou kan word wat met prestasie in Afrikaans as tweede taal verband hou. Denkontwikkeling is nie as ‘n vername faktor geïdentifiseer nie. Die bevindinge in die literatuurstudie en die empiriese ondersoek is bespreek om ouers en onderwysers van riglyne te voorsien om prestasie in Afrikaans te verhoog. / The aim of the research focusses on the relationship between thought development (a cognitive variable) and achievement in Afrikaans as a second language. Besides thought development, verbal understanding and memory recollection are also identified as distinctive cognitive variables. Affective variables such as motivation, self-concept and anxiety could also relate to performance in Afrikaans as a second language. Empirical research was conducted amongst 174 High School learners. Cognitive variables, affective variables and learning styles were measured. Resulting from the empirical research, it appears that self-concept, memory recollection, verbal comprehension and motivation are the main variables that impact on the performance of Afrikaans as a second language. Thought process development was not identified as a main factor. Results from the literature study and the empirical research are discussed in order to assist parents and teachers with guidelines to increase achievement in Afrikaans as a second language. / Psychology of Education / M. Ed. (Sielkundige Opvoedkunde)