In this master thesis, a new method for estimating the position of the moving parts of avoice coil is presented. Instead of using a position sensor the method exploits the connectionbetween the position and the inductance of the voice coil. This is done by superpositioning a small sine voltage signal and the voice coil voltage control signal. By measuring thevoltage and current and using the fourier transform, the impedance and phase difference iscalculated which are used to compute the inductance. A medical ventilator (also known as a respirator) concept is developed with a control systemwhich takes the expiratory pressure from a higher to a lower level. The position estimationalgorithm is then used in an attempt to improve the pressure control. The result is a slightlymore stable control system. The master thesis is conducted at Maquet Critical Care (MCC) in Solna, Sweden. MCC is amedical technology company working with high performance medical ventilators. The longterm goal of this work is to develop a ventilator which is more comfortable for the patient.

Today, 3D models of cities are created from aerial images using a camera rig. Images, together with sensor data from the flights, are stored for further processing when building 3D models. However, there is a market demand for a more mobile solution of satisfactory quality. If the camera position can be calculated for each image, there is an existing algorithm available for the creation of 3D models. This master thesis project aims to investigate whether the iPhone 4 offers good enough image and sensor data quality from which 3D models can be created. Calculations on movements and rotations from sensor data forms the foundation of the image processing, and should refine the camera position estimations. The 3D models are built only from image processing since sensor data cannot be used due to poor data accuracy. Because of that, the scaling of the 3D models are unknown and a measurement is needed on the real objects to make scaling possible. Compared to a test algorithm that calculates 3D models from only images, already available at the SBD’s system, the quality of the 3D model in this master thesis project is almost the same or, in some respects, even better when compared with the human eye.

In industrial drives market, speed and position estimation are one of the most important subjects for accurate motor drives. Vector controlled drives has the best dynamic performance among AC motor drives. Sensorless vector control is one of the most studied one. However, sensorless drive systems fail at low or zero speeds and may not have enough accuracy. For better accuracy and speed range speed sensors or position encoders are usually essential. However, coupling of sensor and sensor prices introduces extra cost on the drive. Thus in order to reduce the cost of the drive a cheap and easy to mount speed sensor is essential. Throughout this study, a speed and position sensor using an external search coil placed between cooling fins on the frame of an induction machine is proposed. The search coil utilizes the fringing flux outside the frame of induction motor. Using the induced voltage on the external search coil, a new method that estimates the flux and rotor position is proposed. In this study, the induced voltage on the search coils are investigated with different types of search coils placed on various positions. The frequency domain and time domain analysis are performed in order to build a model that can estimate machine flux, rotor speed and rotor position. As a result of this study, a low cost, easy to mount speed and position sensor is designed and implemented. Experiment results are presented.

Thesis (M.Ing. (Electronical Engineering))--North-West University, Potchefstroom Campus, 2010.

The ability to localise objects and persons is a useful ability, that is currently used in everyday life in the form of Global Positioning System (GPS) navigation. Localisation is also useful in data networks. The ability to localise nodes in a network paves the way for applications such as location based services, beamforming and geographic routing. The Radio Interferometric Positioning System (RIPS), is a method originally designed for localisation in wireless sensor networks. RIPS is a promising method due to the fact that it is capable of localisation with high accuracy over long ranges. This is something which other existing methods are not capable of. RIPS makes localisation measurements in a different manner from conventional methods. Instead of making pairwise measurements between a transmitter and receiver, RIPS uses sets of four nodes in each of its measurements. Furthermore, RIPS requires multiple measurements to obtain the correct RIPS measurement value. This value is referred to as a q–range. Multiple q–ranges are required in order to localise a node. This creates overhead in terms of co–operation between the nodes participating in a RIPS measurement. The focus of this research is to provide a possible solution to this problem of overhead. In this dissertation an investigation is launched into the considerations and benefits of implementing RIPS on a single node. This is done by creating a conceptual design for a single wireless node capable of implementing RIPS through the use of multiple antennas. In order to test this conceptual device, a simulation model is created. This simulation model is then validated, verified and used in experiments designed to test the effects of certain design considerations and variables on the conceptual device’s localisation accuracy. The analysis of the results from these experiments shows that the conceptual device’s use of multiple antennas makes RIPS sensitive to errors. Increasing the distances separating the conceptual device’s antennas is found to decrease this sensitivity to errors. This is shown to be caused by the distances separating the antennas imposing limits on the range of q–ranges values that are possible, with smaller distances resulting in smaller ranges of possible q–range values. It is also found that the use of higher frequencies in RIPS measurements results in greater accuracy. This is with the assumption that these frequencies can be accurately transmitted. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

Thesis (M.Ing. (Electronical Engineering))--North-West University, Potchefstroom Campus, 2010.

The ability to localise objects and persons is a useful ability, that is currently used in everyday life in the form of Global Positioning System (GPS) navigation. Localisation is also useful in data networks. The ability to localise nodes in a network paves the way for applications such as location based services, beamforming and geographic routing. The Radio Interferometric Positioning System (RIPS), is a method originally designed for localisation in wireless sensor networks. RIPS is a promising method due to the fact that it is capable of localisation with high accuracy over long ranges. This is something which other existing methods are not capable of. RIPS makes localisation measurements in a different manner from conventional methods. Instead of making pairwise measurements between a transmitter and receiver, RIPS uses sets of four nodes in each of its measurements. Furthermore, RIPS requires multiple measurements to obtain the correct RIPS measurement value. This value is referred to as a q–range. Multiple q–ranges are required in order to localise a node. This creates overhead in terms of co–operation between the nodes participating in a RIPS measurement. The focus of this research is to provide a possible solution to this problem of overhead. In this dissertation an investigation is launched into the considerations and benefits of implementing RIPS on a single node. This is done by creating a conceptual design for a single wireless node capable of implementing RIPS through the use of multiple antennas. In order to test this conceptual device, a simulation model is created. This simulation model is then validated, verified and used in experiments designed to test the effects of certain design considerations and variables on the conceptual device’s localisation accuracy. The analysis of the results from these experiments shows that the conceptual device’s use of multiple antennas makes RIPS sensitive to errors. Increasing the distances separating the conceptual device’s antennas is found to decrease this sensitivity to errors. This is shown to be caused by the distances separating the antennas imposing limits on the range of q–ranges values that are possible, with smaller distances resulting in smaller ranges of possible q–range values. It is also found that the use of higher frequencies in RIPS measurements results in greater accuracy. This is with the assumption that these frequencies can be accurately transmitted. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

This master thesis is about providing the implementation of synthesis, detection of spiral symbols and estimating the pan/tilt angle and position by using camera calibration. The focus is however on the latter, the estimation of parameters of localization. Spiral symbols are used to be able to give an object an identity as well as to locate it. Due to the spiral symbol´s characteristic shape, we can use the generalized structure tensor (GST) algorithm which is particularly efficient to detect different members of the spiral family. Once we detect spirals, we know the position and identity parameters of the spirals within an apriori known geometric configuration (on a sheet of paper). In turn, this information can be used to estimate the 3D-position and orientation of the object on which spirals are attached using a camera calibration method.   This thesis provides an insight into how automatic detection of spirals attached on a sheet of paper, and from this, automatic deduction of position and pose parameters of the sheet, can be achieved by using a network camera. GST algorithm has an advantage of running the processes of detection of spirals efficiently w.r.t detection performance and computational resources because it uses a spiral image model well adapted to spiral spatial frequency characteristic. We report results on how detection is affected by zoom parameters of the network camera, as well as by the GST parameters; such as filter size. After all spirals centers are located and identified w.r.t. their twist/bending parameter, a flexible technique for camera calibration, proposed by Zhengyou Zhang implemented in Matlab within the present study, is performed. The performance of the position and pose estimation in 3D is reported. The main conclusion is, we have reasonable surface angle estimations for images which were taken by a WLAN network camera in different conditions such as different illumination and different distances.

A estimação de posição é o resultado direto da reconstrução de cenas, um dos ramos da visão computacional. É também uma informação importante para o controle de sistemas mecatrônicos, e em especial para os sistemas robóticos autônomos. Como uma aplicação de engenharia, o desempenho de tal sistema deve ser avaliado em termos de eficiência e eficácia, medidas traduzidas respectivamente pelo custo de processamento e pela quantificação do erro. A geometria epipolar é um campo da visão computacional que fornece formalismo matemático e técnicas de reconstrução de cenas a partir de uma par de imagens, através de pontos correspondentes entre elas. Através deste formalismo é possível determinar a incerteza dos métodos de estimação de posição, que são relativamente simples e podem atingir boa precisão. Dentre os sistemas robóticos autônomos destacam-se os ROVs - do inglês \"Remotely Operated Vehicles\" - ou veículos operados remotamente, muito utilizados em tarefas submarinas, e cuja necessidade crescente de autonomia motiva o desenvolvimento de um sensor de visão com características de baixo consumo de energia, flexibilidade e inteligência. Este sensor pode consistir de uma câmera CCD e algoritmos de reconstrução de cena baseados em geometria epipolar entre imagens. Este estudo visa fornecer um comparativo de resultados práticos da estimação de posição através da geometria epipolar entre imagens, como parte da implementação de um sensor de visão para robôs autônomos. Os conceitos teóricos abordados são: geometria projetiva, modelo de câmera, geometria epipolar, matriz fundamental, reconstrução projetiva, re-construção métrica, algoritmos de determinação da matriz fundamental, algoritmos de reconstrução métrica, incerteza da matriz fundamental e complexidade computacional. Os resultados práticos baseiam-se em simulações através de imagens geradas por computador e em montagens experimentais feitas em laboratório que simulam situações práticas. O processo de estimação de posição foi realizado através da implementação em MATLAB® 6.5 dos algoritmos apresentados na parte teórica, e os resultados comparados e analisados quanto ao erro e complexidade de execução. Dentre as principais conclusões é apresentado a melhor escolha para a implementação de sensor de visão de propósito geral - o Algoritmo de 8 Pontos Correspondentes Normalizado. São apresentadas também as condições de utilização de cada método e os cuidados necessários na interpretação dos resultados. / Position estimation is the direct result of scene reconstruction, one of computer vision\'s fields. It is also an important information for the control of mechanical systems - specially the autonomous robotic systems. As an engineering application, those systems\' performance must be evaluated in terms of efficiency and effectiveness, measured by processing costs and error quantification. The epipolar geometry is a field of computer vision that supply mathematical formalism and scene reconstruction techniques that are based on the correspondences between two images. Through this formalism it is possible to stipulate the uncertainty of the position estimation methods that are relatively simple and can give good accuracy. Among the autonomous robotic systems, the ROVs - Remotely Operated Vehicles - are of special interest, mostly employed in submarine activities, and whose crescent autonomy demand motivates the development of a vision sensor of low power consumption, flexibility and intelligence. This sensor may be constructed with a CCD camera and the scene reconstruction algorithms based on epipolar geometry. This work aims to build a comparison of practical results of position estimation through epipolar geometry, as part of a vision sensor implementation for autonomous robots. The theory presented in this work comprises of: projective geometry, camera model, epipolar geometry, fundamental matrix, projective reconstruction, metric reconstruction, fundamental matrix algorithms, metric reconstruction algorithms, fundamental matrix uncertainty, and computational complexity. The practical results are based on computer generated simulations and experimental assemblies that emulate practical issues. The position estimation was carried out by MATLAB® 6.5 implementations of the algorithms analyzed in the theoretical part, and the results are compared and analyzed in respect of the error and the execution complexity. The main conclusions are that the best algorithm choice for the implementation of a general purpose vision sensor is the Normalized 8 Point Algorithm, and the usage conditions of each method, besides the special considerations that must be observed at the interpretation of the results.

This thesis focuses on developing algorithms for brushless AC motor control. First part of the thesis contains derivation of mathematical model and overview of selected sensor and sensorless control methods. Second part introduces simulation model of the motor, developed in Matlab/Simulink environment, with usage of SimPowerSystems toolbox. Following chapter describes realization of control algorithm, utilizing Hall sensors and position estimation. After that, sensorless rotor position estimation module is developed, and its implementation into the model is mentioned. Last chapters deal with development of graphical user interface, meant for changing selected motor and control parameters, and they also summarize and compare achieved results.