Ce travail de thèse a été effectué au sein du Laboratoire GIPSA-Lab de Grenoble, sous la direction de Carlos Canudas de Wit et co-encadré par Franck Quaine et Violaine Cahouët.Ce travail a été réalisé dans le cadre du projet ANR-09-VTT-14-01/06 « VOLHAND ». Il s’inscrit dans le contexte général des nouvelles générations de Direction Assistée Electrique (DAE, ou EPAS en anglais pour Electronic Power Assistance Steering) avec pour objectif spécifique de tenir compte des caractéristiques des conducteurs à mobilité réduite. En effet, à ce jour, il n’existe pas de système de direction assistée adapté aux capacités articulaires (rhumatismes divers), musculaires (diminution de force, sénescence), ou encore aux douleurs ressenties par le conducteur. Le principal objectif de cette thèse est donc de proposer une méthodologie générale permettant d'adapter une DAE standard aux conducteurs à mobilité réduite. Le mémoire est organisé en cinq chapitres.Chapitre 1, intitulé Context and objectives of the study presente l’impact économique et sociétal, la problématique et l’objectif. Ensuite, la stratégie permettant d’atteindre l’objectif ainsi spécifié est précisée.Chapitre 2, intitulé Models for simulation, est dédié à l’établissement d’un modèle mathématique du système de DAEs prenant bien en compte l’élasticité en torsion de la colonne de direction due à la présence d’un capteur de couple. Parmi les entrées de ce modèle à deux degrés de liberté, une attention est faite en ce qui concerne la description du couple de frottement du contact pneumatique-route. Un modèle de frottement dynamique, basé sur le modèle de LuGre, est développé pour décrire ces phénomènes. Une amélioration du modèle est ainsi proposée.Chapitre 3, intitulé Oscillation annealing and torque observer design, commence par mettre en évidence les conséquences de la présence du mode souple associé à l’élasticité en torsion du capteur de couple sur le ressenti au niveau du volant. Une commande LQ est proposée pour limiter les oscillations dues à ce mode souple. Enfin, un observateur pour estimer le couple conducteur et le couple résultant du frottement pneumatique route est développé.Chapitre 4, intitulé Power steering booster stage, se focalise dans un premier temps sur la nature des courbes d’assistance utilisées dans le cadre des DAE. En effet, l’état de l’art sur le sujet met en évidence l’absence de justification de la forme de ces courbes généralement fonction de la vitesse du véhicule et du couple appliqué par le conducteur. Dans ce chapitre on propose de calculer de nouvelles lois en se fondant sur l’approche par optimisation (minimisation du jerk couplé avec la loi de puissance de Steven). Les résultats obtenus montrent que la minimisation du critère fondé sur le jerk du volant et la loi de puissance de Steven peut permettre de reproduire les lois existantes d’assistance et leur apportent une justification. Ils confirment également la forte influence du frottement (couple) au niveau du contact roue-sol. La seconde partie de ce chapitre est consacrée au développement d’une méthodologie générale d’adaptation des lois d’assistance (cartographie standard initiale) aux exigences du conducteur à mobilité réduite (typiquement ici une personne présentant une asymétrie.Chapitre 5, intitulé Experimental validation NeCS-Car benchmark, commence par détailler la plateforme expérimentale présente au laboratoire GIPSA-LAB et utilisée pour évaluer et valider les nouvelles lois d’assistance adaptées au conducteur à mobilité réduite. La stratégie globale d’assistance de couple au volant pour un conducteur présentant une asymétrie, est testée sur le banc avec la NeCS-Car. Les résultats issus du protocole montrent la validité de la stratégie proposée.Ce mémoire se termine avec une partie General conclusions and perspectives où les principales contributions sont d’abord rappelées, puis où des perspectives pour compléter et prolonger ce travail sont proposées. / Nowadays, vehicles have been widely equipped with power assistance steering systems and the way of providing assist torque is various. Electronic Power Assistance Steering (EPAS) systems have the tendency to replace the Hydraulic Power Assistance Steering (HPAS) systems, due to better fuel consumption, better road feel feedback to the driver and better return-to-center performance of the steering system. Actual EPAS systems are designed basing on a general driver’s profile and they try to mimic the behavior of the HPAS system. Main goal of this thesis is to propose a general methodology to adapt standard EPAS for drivers with reduced mobility. Toward this general goal, following contributions are integrant part of this thesis.First, a mathematical model of the steering system that keeps into account the torsion of the steering column is introduced. This model is influenced by two exogenous inputs: the tire-road friction torque and the driver's torque. Mathematical models for these inputs are also proposed. Due its importance on the steering system, great attention is dedicated to the description of the tire-road friction torque. This torque includes the contribution of two main phenomena: the self-alignment and the sticking friction torques. They appear, respectively, at high and low speeds of the vehicle. Dynamical friction models, based on the LuGre theory, are used to describe these phenomena.Then, a study of the steering model subject to the influence of exogenous inputs is done in open loop. This study shows that the steering column starts to oscillate when an exogenous input is applied. To delete low-frequency oscillations of the column, an optimal state-space control is introduced. Moreover, an observer is designed to estimate state variables of the system and exogenous inputs, acting on it.Third contribution of the thesis deals with the aim to provide some rationality to actual methods that are used to implement electronic power assistance on commercial vehicles. Indeed, investigations about actual assistance systems do not provide ground foundations or evidence that the current assistance is optimal for the driver in any sense. At this aim, an optimization procedure is proposed to retrieve the shape of the steering assistance, starting from the analysis of the steering movement, in case of a general driver's profile, and the analysis of the human perception face to an external stimulus.After that, a procedure to adapt the standard steering assistance to the driving of disabled people is proposed. As there is not any classification of drivers according to their pathology, attention focuses on drivers affected by diseases to the upper limbs that cause an asymmetry into the torque production on the steering wheels. A study about main problems that these patients are dealing during some critical driving manoeuvres is done. Starting from this, a compensation procedure is proposed to modify the standard power steering assistance. This procedure is validated in simulation. Moreover, objective evaluation criteria are derived to test improvements due to the proposed assistance.Finally, the experimental validation of all elements proposed in the general methodology is done on the tele-operation platform, present at the laboratory Gipsa-LAB. This system is made up of a control station with the operator, a pc-unit and a tele-operated vehicle, that allows retrieving a real profile of tire-road friction torque. Results about these experimental tests validate benefits of the adaptation methodology. They represent also the starting point for the installation of the proposed assistance on a real vehicle and set the basis for the application of the methodology for a wider class of patients, affected by different pathologies.

Orientador: Ulisses Rocha Antuniassi / Banca: Edivaldo Domingues Velini / Banca: José Armando Furlani Junior / Banca: José Paulo Molin / Banca: Otávio Jorge G. Abi Saab / Resumo: O uso do Sistema de Posicionamento Global (GPS) em uma propriedade agrícola não está limitado ao monitoramento georreferenciado de fatores produtivos, mas cada vez mais esta tecnologia está sendo utilizada como um equipamento disponível dentro da propriedade e que deve ser utilizada o máximo possível para a diluição do seu custo. Uma utilização cotidiana desta tecnologia é em sistemas de direcionamento via satélite. No entanto, ensaios destes sistemas de direcionamento operando em curva estão ainda no início. Poucas também são as informações relacionadas à análise de custo de investimento desta tecnologia. Os objetivos deste trabalho foram desenvolver uma metodologia de campo para ensaios de sistemas de direcionamento via satélite e/ou convencionais em sua utilização terrestre operando em reta e em curva, avaliar a acurácia de diferentes sistemas de orientação seguindo a metodologia desenvolvida e realizar uma breve análise de investimento para aquisição de um sistema de direcionamento via satélite. Para tanto, foram realizados quatro ensaios de campo em que foram ensaiados sete sistemas de direcionamento por barra de luz, um sistema de auto-direcionamento, um sistema de direcionamento por monitor eletrônico, um sistema de direcionamento por cabo-de-aço e um sistema de orientação por marcador de espuma. Em cada ensaio de campo foi aplicada a mesma metodologia desenvolvida para avaliação da acurácia destes sistemas de direcionamento. Esta metodologia se baseou na mensuração direta em campo dos desvios dos alinhamentos orientados pelos sistemas de direcionamento em relação ao alinhamento programado. Os ensaios foram realizados em reta e em curva. A metodologia de campo apresentada neste trabalho para ensaios de sistemas de direcionamento pôde ser aplicada com sucesso...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of the Global Positioning System (GPS) in a farm is not limited to monitor productive factors involved on the yield production, but the GPS have been used as equipment available into the farm that can be used to another issues and it must be used a lot into the farm to dilute the initial cost. A daily use of this technology is on steering systems. However, we do not have results of field tests of these steering systems operating in curve. Few also are the information related to the cost analysis of investments on this technology. The purposes of this work were develop a field test methodology to evaluate the accuracy of conventional steering systems and/or satellites steering systems operating in straight line or curve operations, evaluate the accuracy of several steering systems according to the developed methodology and perform a brief cost analysis to buy a satellite steering system. Four field test evaluations were performed where were evaluated seven light bar steering systems, one auto-steering system, one steering system operated by an electronic monitor, a steering system operated by a steel cable and a system oriented by a foam marker. The same developed methodology was applied on these four field test. This developed methodology was based on measure the steering error compared to the programmed alignment directly on the field, where an operator was guided by the evaluated steering system. The tests were made in straight line and curve operations. The field methodology presented in this work was successful. The advantage of this methodology is the possibility of reflection of all factors involved in the errors and the possibility of the errors measured in the field directly by the final user...(Complete abstract click electronic access below) / Doutor

A microestrutura de uma peça temperada determina suas características mecânicas. Dessa forma, torna-se fundamental conhecer os parâmetros que influenciam na formação da estrutura do componente tratado com função dos tratamentos térmicos aplicados, permitindo obter melhorias de qualidade de uma peça frente a sua aplicação. Métodos distintos podem ser empregados para obtenção da camada de têmpera. Entretanto, esses métodos devem ser parametrizados adequadamente para garantir a qualidade do produto final. No trabalho em questão, aplicaram-se dois metódos distintos de têmpera: por indução e por condução para obtenção da camada martensítica, dureza e durabilidade requerida em cremalheiras de aço SAE 1045, utilizadas em mecanismo de direção automotiva. Fabricou-se um lote de peças, do qual metade das peças foram tratadas por indução e a outra por condução. Após a têmpera e após o revenido, foi avaliado o nível de empenamento, a dureza superficial, a microdureza, a microestrutura formada. A peças após o término do processo de fabricação, foram montadas no sistema caixa de direção, sendo realizados ensaios de durabilidade e impacto dos mesmos. Os tratamentos realizados demonstraram resultados de empenamento, dureza, microestrutura e ensaios de durabilidade e impacto no produto final, dentro das especificações. O processo de têmpera por condução levou a melhor micrestrutura, mais alta dureza e menores níveisde empenamento comparado com o processo de têmpera por indução. Mas, também constatou-se que é possível desenvolver melhorias no processo de indução para atingir-se resultados melhores. / The microstructure of a hardened part is determining its mechanical characteristiscs. Thus, the knowledge of pararameters influencing the heat treated part’s microstructure is of fundamental importance. This allows to obtain quality improvements for specific applications. Diferent methods can be used for the obtation of a hardened layer. However, in these methods the parameters have to be correctly set to reach the final product quality. In this work, two diferente techniques were applied, induction and conduction surface hardening to obtain a required martensitic layer depth, hardness and durability of SAE 1045 steel racks used in automotive driving systems. A batche of parts were manufactured, being half of the parts surface hardened by Induction and half by conduction. After hardening and after tempering, the warpage level, surface hardness, microhardness and microstructure were investigated. The parts were mounted in a steering gear system and then endurance tests and impact tests were carried out. The results of warpage levels, hardness, microstructure and endurance tests, as well as the impact tests were in the range of the specifications. The conduction hardening process leads to better microstructure, higher hardness and lower warpage levels compared to induction hardening. But it was found that the Induction hardening can be optimized to reach better results.

Existe necessidade de se desenvolver modelos teóricos e testes experimentais, que nos permitam ter plenas condições de melhor avaliar e concluir sobre o comportamento dinâmico dos ônibus, ao trafegar sobre diferentes pistas e realizar diversos tipos de manobras. O objetivo do trabalho é avaliar e otimizar simultaneamente o comportamento dinâmico lateral e vertical de um ônibus modelado como um sistema multicorpo. A metodologia utilizada no trabalho é dividida em duas partes. A primeira parte consiste na programação de um modelo multicorpo de ônibus que possa ser utilizado para fins de otimização do seu comportamento de dinâmica lateral via programação matemática; o desenvolvimento de uma manobra do tipo mudança dupla de faixa - DLC (Double Lane Change), adaptada da combinação da norma ISO 3888-1:1999 que envolve mudança dupla de faixa para carros de passeio e a norma ISO 14791:2000 que envolve mudança simples de faixa para veículos comerciais, na ausência de normas específicas; e finalmente a validação de resultados através de testes experimentais e simulações computacionais. A segunda parte consiste na programação de um modelo multicorpo de ônibus para fins de otimização do seu comportamento de dinâmica vertical via programação matemática, neste caso sujeito a uma pista da classe C segundo classificação da norma ISO 8608:1995. Os resultados específicos da programação das manobras laterais do modelo de ónibus foram validados experimentalmente, bem como comparados através da simulação das manobras num modelo virtual implementado num software multicorpo comercial. O conjunto das soluções atingidas mostraram boa correlação, possibilitando a posterior otimização dos parâmetros concentrados da suspensão do modelo multicorpo de ônibus, através da técnica de algoritmos genéticos. A função objetivo implementada consiste da composição penalizada do valor RMS do ângulo de rolagem da manobra lateral quanto ao handling, e de parâmetros associados ao conforto e segurança, como o valor RMS da aceleração vertical, do deslocamento máximo da suspensão, e da deflexão máxima do pneu de forma a garantir aderência continua à pista. Os resultados otimizados dos parâmetros concentrados conseguem uma negociação dos objetivos conflitantes. / There is a need for theoretical models and experimental tests to be developed that allow for better assessments and conclusions about the dynamic behavior of buses driving on different lanes and performing various types of maneuvers. The purpose of this work is to evaluate and optimize both the lateral and the vertical dynamic behavior of a bus modeled as a multibody system. The methodology employed comprises two parts. The first part consists in programming a bus multibody model that can be used to optimize the lateral dynamic behavior of buses via mathematical programming; developing a type of maneuver known as Double Lane Change (DLC), adapted from a combination of the ISO 3888-1:1999 standard, which involves double lane changes for passenger cars, and the ISO 14791:2000 standard, which involves single lane changes for commercial vehicles, in the absence of specific standards; and lastly, validating the results by means of experimental tests and computational simulations. The second part consists in programming a bus multibody model to optimize the vertical dynamic behavior via mathematical programming, in this case for a class C road, according to the classification of the ISO 8608:1995 standard. The specific results of the programming of the lateral maneuvers of the bus model were validated experimentally and then compared with simulations of the maneuvers by a virtual model developed using commercial multibody software. The results showed a good correlation, enabling subsequent optimization of the lumped parameters of the suspension of the bus multibody model using the genetic algorithm optimization technique. The objective function consists of the penalized composition of some terms, including the RMS value of the roll angle of the lateral handling maneuver and of parameters associated with comfort and safety, such as the RMS value of vertical acceleration, the maximum suspension working space, and the maximum tire deflection to ensure continuous adherence on the road surface. The optimized results of the lumped parameters of the suspension enable an alignment of the conflicting goals.

The automotive industry is currently undergoing a paradigm shift. One such example in the next generation steering is the Steer-by-Wire (SbW) technology. SbW comes with a lot of advantages but one of the big challenges is to provide the driver with a realistic steering feel. More precisely, steering feel can be defined as the relationships between the steering wheel torque, the steering wheel angle and the dynamics of the vehicle. Accordingly, the first contribution of this work will be to present transfer functions between these quantities that resemble those observed in traditional steering systems. The steering feel/feedback is then achieved by an electric motor which can be controlled by different control strategies. In this thesis three different control strategies are investigated. The first straightforward strategy is called open loop since there is no feedback controller in the system. The second strategy is torque feedback control and the third strategy is angle feedback control. All three systems are evaluated in terms of reference tracking, stability, robustness and sensitivity. Here reference tracking is defined as tracking a desired transfer function. The desired transfer function is denoted as the reference generator. When fulfilling the requirements the analysis shows that the torque feedback system has a better reference tracking than the other evaluated systems. It is also concluded that the open loop system has a compromised reference tracking compared to the torque and angle feedback systems. Since the SbW technology is still an undergoing area of research within the automotive sector this work can be used as a basis for choice of control strategy for steering feedback systems and also as a guideline for future hardware choices.

O sistema de produção canavieiro e dependente da sequência de cortes e rebrota das plantas de cana-de-açúcar. O trafego sobre a soqueira deve ser evitado para garantir a integridade fisiológica da rebrota e possibilitar a obtenção de elevada produtividade. Essa necessidade de exatidão no trafego de maquinas canavieiras impulsionou a adoção de sistemas de direcionamento automático para a otimização do trafego dos conjuntos mecanizados nas lavouras, especialmente em colhedoras. No entanto, os conjuntos de tratores e carretas de transbordo apresentam o risco de desvios do trafego ideal e trafegam sobre o terreno em igual intensidade ao das colhedoras, porem comumente sem sistemas de direcionamento automático ou com sistemas simplificados. Além disso, as carretas sofrem desvios em percursos curvos e em terrenos inclinados, o que frequentemente ocorre nas áreas produtoras. O desempenho dos sistemas de direcionamento automático está frequentemente associado aos erros transversais a trajetória, os quais devem estar abaixo de 0,1 m para evitar danos as soqueiras. Deste modo, este trabalho objetivou quantificar os desvios a que os tratores e carretas de transbordo estão submetidos sob diferentes tipos de percursos em terrenos planos e inclinados. Utilizou-se do sistema de transporte interno composto por um trator e duas carretas de transbordo com três eixos, sendo todos equipados com receptores GNSS e sistema de correção tipo RTK para a obtenção de suas respectivas posições. Os erros entre as passadas foram avaliados pela diferença da distância ortogonal entre os pontos de posição das antenas, no centro do trator e no centro do último eixo de cada carreta, em relação a linha referencia. Os resultados obtidos mostraram que, quando analisado o impacto do relevo no direcionamento manual em função dos tipos de percurso, os maiores desvios ocorreram em terreno inclinado e, nesse caso, os erros são maiores em percursos curvos, pois as carretas de transbordo tem a tendência de diminuir o raio de curvatura. Observando os valores de desalinhamento em áreas de pequena inclinação, com ambos os direcionamentos, constatou-se que o sistema de direcionamento automático auxilia para minimizar os erros de desalinhamento no ultimo transbordo. No entanto, quando o direcionamento passa a ser manual, esses erros aumentam em ate cinco vezes acima do aceito. A medida que os desalinhamentos são relacionados as inclinações laterais, seus valores crescem sensivelmente, mesmo utilizando sistema de direcionamento automático. Sugere-se a adaptação e avaliação do desempenho de sistemas com atuadores nos rodados ou no cabeçalho dos transbordos e a utilização de transbordos montados em chassi de caminhão. Conclui-se que a metodologia desenvolvida foi eficiente para quantificar os erros de percursos do conjunto trator-transbordo de cana-de-açúcar e que a inclinação do terreno, mesmo com variações sutis, exerce forte influência para o desalinhamento do conjunto. / Sugarcane production system is dependent on the sequence of cuts and regrowth of sugarcane plants. The traffic on the ratoon should be avoided to ensure physiological integrity of the regrowth and enable high productivity. This need for accuracy in traffic of sugarcane machines boosted the adoption of automatic guidance systems for mechanized sets in crops, especially harvesters. However, tractors with transshipment trailers usually present the risk of deviation from the ideal path, since they rarely employ automatic steering systems, or use simplified ones, and travel on the ground at the same intensity as that of the harvesters. In addition, trailers are subject to deviations in curved paths and sloping terrain, which often occurs in producing areas. The performance of automatic steering systems is often associated with traverse errors, which should be less than 0.1m in order to avoid damage to the ratoon. Thus, this study aims to quantify deviations to which tractors and transshipment trailers are submitted under different paths on flat and inclined terrain. The transport system used in this study is composed of a tractor and two transshipment trailers with three axes, all of which are equipped with GNSS receivers and a RTK type correction system to obtain their respective positions. The errors between the passes were evaluated by the difference in the orthogonal distance between the antenna position points at the center of the tractor and at the center of the last axis of each truck, relative to the reference line. The obtained results showed that, when analyzing the impact of the relief on the manual steering according to the types of route, the greater deviations occurred in inclined terrain and, in this case, the errors are larger in curved routes, since the transshipment trailers tend to decrease the radius of curvature. Observing the values of misalignment in areas of small inclination, in both directions, it was verified that the automatic steering system helps to minimize misalignment errors of the last transshipment in the correct route. However, when steering becomes manual, these errors increase by up to five times what is accepted. As the misalignments are related to the lateral slopes, the values of misalignments increase significantly, even using an automatic steering system. Adaptations and evaluation of performance of systems with actuators in the wheels or in the heading of the transshipment and the use of transshipment mounted in truck are suggested. It is concluded that the developed methodology was efficient to quantify the errors of trajectories of the tractor-transshipment set of sugarcane and the inclination of the terrain, even with subtle variations, exerts a strong influence for the misalignment of the set.

O uso de tintas à base de solventes tem acarretado problemas ambientais, gerando a necessidade de pesquisas para o desenvolvimento de materiais com baixo teor de compostos orgânicos voláteis (VOC) para redução do impacto ao meio ambiente. Os efeitos do VOC ao meio ambiente motivaram este estudo, que tem como objetivos desenvolver uma nova tinta de base aquosa para a aplicação na fabricação de volantes automotivos. O presente trabalho tem como objetivo estudar o desempenho por meio de medição de camada de tinta, resistência aos reagentes químicos, combustibilidade e resistência ao desgaste da pintura obtida com tintas baseadas em 1) solventes orgânicos e 2) água, aplicadas em volantes automotivos constituídos de poliuretano (PU). Os resultados demonstram que a pintura à base de água possui uma espessura de camada maior e menor velocidade de combustão em relação à pintura à base de solventes orgânicos, porém apresenta um menor desempenho no ensaio de resistência à abrasão e aos reagentes químicos em relação à tinta à base de solventes orgânicos. / The use of solvent-based paints has caused environmental problems, creating the need for research to develop materials with low volatile organic compound (VOC) to reduce the environmental impact. The effect of volatile organic compound (VOC) to the environment motivated this study, which aims to develop a new water-based paint for application in the manufacture of automotive steering wheels. The present work aim to study the performance by measuring the layer thickness, resistance to chemical reagents, combustibility and wear resistance obtained with paints based on 1) organic solvents and 2) water, applied in automotive steering wheels made of polyurethane (PU). The results has showed that water-based paint has a layer thickness greater and lower burning rate than solvent-based paint, but it has a lower performance in the test for resistance to abrasion and resistance to chemical reagents in relation to organic solvent-based paint.

By using existing knowledge from the game community, which have had a long experience from game artificial intelligence, and new research from the field of artificial intelligence I have implemented REACT, a crowd simulation system for visual effects. REACT is based on high-level behaviour that uses an underlying layer of low-level behaviour. The high-level capabilities gives the digital character means to reasoning about how to achieve certain goals based on a knowledge base of rules and facts that are present in the virtual world. This gives the digital character a degree of autonomous intelligent behaviour. REACT is designed to integrate directly into the 3D animation package Maya as a plug-in. This means that the animators can continue to animate their characters via their animation package of choice, rather than having to learn a new technology. In addition, many animators are already familiar with the workflow of Maya, so learning curves are reduced. REACT is already in use in the visual effects industry where it has proven itself to be a worthy competitor to the existing systems on the market.

The mining industry desires to cut costs and to operate in more dangerous mines, which is why companies such as Atlas Copco are developing autonomous vehicles. The problem to navigate autonomously is however complex, so the vehicles have in the recent years become more intelligent; the number of computers, actuators and sensors are increasing. For example, an autonomous LHD (Loading – Hauling – Dump) vehicle has sensors including: inertial measurement unit (IMU), odometer, hinge angle sensor, laser range finders and cameras. The parameters for the sensors needs to be calibrated before the vehicle can be used in a mine. There are also a number of electrical currents which needs to be calibrated for the actuators.The calibration of parameters has traditionally been made manually, but Atlas Copco realizes that manual calibration is not feasible once the sales of intelligent mine vehicles increases. Effort is therefore put into automation of the calibration procedures.Interviews with employees were carried out at Atlas Copco to identify the most time consuming procedures during calibration and installation of autonomous mine vehicles. The calibration of steering currents was not only identified as the most time consuming procedure, but also as one of the most complex procedures.The goal of this thesis is to enable easier and quicker installation of mine vehicles. This is done through investigation of methods for automatic calibration of steering currents. The problem is approached from two angles: a grey box model using system identification and a black box model using neural network with resilient backpropagation. The models are compared to a search algorithm, used for simulation of the manual calibration method. In the end, the models are evaluated with regard to performance and ease of implementation.The hypothesis was that the more complex grey box or black box model would have higher accuracy than a simple search algorithm. However, the search algorithm proves to outperform the other models both with regard to accuracy and calibration time, and is also easier to implement. The search algorithm is thus suggested to be implemented instead of a complex model. Moreover, it is suggested that a straightforward mapping of 20 currents may outperform even the search calibration. It is also concluded that calibration of steering currents can be done when the vehicle is standing still.

M.Ing. / This study considers improving the azimuth beam steering resolution of the circular Switched Parasitic Array (SPA) antennas (made up of dipoles) by a factor of two or more. In circular SPA antennas, beam steering is conventionally achieved by open-circuiting and shortcircuiting different parasitic elements and usually only one parasitic element is open-circuited at a time. However, such an approach results in low beam steering resolutions especially for the SPA antennas with few parasitic elements. In order to increase the azimuth beam steering resolution for the circular SPA antennas, two beam steering methods are proposed in this research work. In the first method, parasitic elements are open-circuited and short-circuited based on different combinations of the parasitic elements and the possible switch states. The proposed method was first validated by simulation tests using the MATLAB tool and WIPL-D. A prototype of the circular SPA antenna consisting of five elements was then implemented. It is noted that the simulation and measurement results match very well at 2.4 GHz. In order to have at least two combinations (from the first method) with almost similar gain and return loss, another simpler beam steering method was developed. The latter method is based on simultaneously open-circuiting either two or three neighbouring parasitic elements. The performance of the second method was studied through simulations using the circular SPA antenna geometries consisting of five, seven and nine elements. These geometries were first optimized (for gain and input impedance) and then modelled using WIPL-D. It was observed that the two methods double the azimuth beam steering resolution of the circular SPA antennas when compared to the conventional beam steering approaches of open-circuiting one parasitic element at a time. Variations in the structural parameters of the five elements circular SPA antenna at 2.4GHz were also investigated. In this procedure, the effects of variations (also considered as random errors) in the structural parameters (or antenna dimensions) on the performance of the SPA antennas were examined. Firstly, variations in each structural parameter were modelled with other structural parameters fixed as per specifications. Thereafter, effects of combined errors were also investigated. The simulation results demonstrated that variations in the structural parameter can either increase or decrease the gain and input impedance of the SPA antenna depending on the given specifications. The gain and input impedance sensitivities per variations in each structural parameter were computed to determine the degree at which the gain and input impedance can vary for a predefined change (error) in the structural parameter.