Cette thèse présente la conception d'un microgyromètre MEMS triaxial. Les microgyromètres ont de nombreuses applications telles que le contrôle d'attitude de drones ou l'interfaces homme/machine. Les microgyromètres triaxiaux sont particulièrement avantageux car ils permettent de déterminer les trois composantes de la vitesse de rotation à partir d'un seule structure monolithique et planaire. Le principe de fonctionnement des gyromètres vibrants à effet Coriolis (CVG) a été étudié analytiquement, puis une structure originale de gyromètre triaxial monolithique et planaire a été conçue. Cette structure est constituée de quatre poutres encastrées sur un cadre déformable. Des prototypes en silicium ont été réalisés et caractérisés. L’arséniure de gallium (GaAs) a été sélectionné pour la réalisation en raison de ses propriétés piézoélectriques et de son fort potentiel de miniaturisation. Un système d’électrodes pour l'excitation et la détection des vibrations mécaniques a été mis au point. Deux procédés d'usinage du GaAs ont été développés, un procédé de gravure chimique et un procédé de gravure plasma permettant tous les deux de graver verticalement le GaAs sur 450 micromètres de profondeur. Le procédé de gravure plasma est compatible avec la réalisation du CVG triaxial. Des résonateurs de test en GaAs dopé Carbone ont été réalisés par gravure chimique pour mesurer l'évolution en température de la résistivité et des propriétés électromécaniques de ce matériau. Ces mesures ont permis d'estimer que les marches aléatoires angulaires du CVG triaxial sont inférieures à 0,025 degré par racine d'heure sur la gamme de température [-40°C +80°C] pour les trois axes de mesure. Ceci situe le potentiel du CVG triaxial conçu parmi les CVG MEMS les plus performants. / This PhD present the conception of a triaxial MEMS microgyro. Microgyros offer a wide range of applications varying from drones attitude control to human interface devices. The triaxial microgyros offer great benefits because they allow determination of the three rotation rate components with only one monolithic planar structure. The operating principle of Coriolis Vibrating Gyro (CVG) has been studied analytically and an original structure has been designed. This structure consists of four beam clamped into a deformable frame. Some silicon prototypes have been machined and characterised. The gallium arsenide (GaAs) has been chosen for the realisation because of its piezoelectric properties and its great miniaturization potential. A transduction system based on GaAs piezoelectricity was developed. Two GaAs machining processes have been developed: a chemical etching process and a plasma etching process which both enable 450 micrometers deep vertical etching. The plasma etching technique allows high fidelity enough machining to be compatible with the triaxial CVG realisation. Some C-doped GaAs test resonators have been realised to measure the resistivity temperature dependency and electromechanical properties of this material. Those characterisations lead to estimate the angular random walk for the three axis ranges below 0,025 degree per square root hour on the temperature range [-40°C +80°C]. This sets the triaxial CVG together with the best monoaxial MEMS CVG.

This internship's objective is to implement modeling of uncut chip thicknesses and milling forces in 3-axis milling, and apply it to orbital drilling. The goal is to understand deeper the process, and develop a tool which permits to model a wide range of end-mill tool geometries, and most of 3-axis milling operations.In this report, the following axis will be developed: • The modeling of the complex tool geometry • The modeling of uncut chip thicknesses in slot milling, and for any 3-axis milling operation • The strategy which has been chosen to identify cutting forces coefficients, and their use. • The obtained results and prospects for development.

This diploma thesis focuses on the design and production technology of making pattern and core box by milling. The theoretical part summarizes the issue of production models, CAD / CAM technology and milling technology. The practical part is elaborates engineering design of machined parts focused on the specific requirements for application in the foundry. For designing of milling technology was used CAM system. This milling technology was programmed and optimized. Parts are finally produced on 3-axis milling machine. In the end there is technical-economic evaluation of production and discussion of results.

No description available.

Thesis (MscEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The Cape Peninsula University of Technology, in collaboration with Stellenbosch University, is developing a 3-unit CubeSat for a low earth polar orbit. The two main payloads are a camera and a radio frequency beacon. This beacon will be used to calibrate the radar antenna patterns of an antenna of the Hermanus Magnetic Observatory at their base in Antarctica. This thesis describes the development of an aerodynamic attitude determination and control system needed to achieve three-axis stabilisation of the satellite and to perform accurate pointing of the camera. The satellite structure is designed to utilise aerodynamic means of control. It includes four feather antennae for passive pitch-yaw stabilisation and two active aerodynamic roll control paddles. The sensors used are a three-axis magnetometer, ne sun sensor and nadir sensor. Three attitude determination methods are investigated, namely the Triad, Rate Kalman Filter and Extended Kalman Filter algorithm. Apart from the aerodynamic control elements of the satellite, three magnetic torque rods and three nano-reaction wheels are also included in the design. Three control modes for the satellite are identi ed and various control methods are investigated for these control modes. The various attitude determination and control methods are evaluated through simulations and the results are compared to determine the nal methods to be used by the satellite. The magnetic Rate Kalman Filter is chosen as attitude determination method to be used when the satellite is tumbling and a combination of the sun Rate Kalman Filter and the Triad algorithm is to be used when the satellite experiences low angular rates. The B-dot and Y-spin controller is chosen for the detumbling control mode, the aerodynamic and cross-product control method for the three-axis stabilisation control mode and the quaternion feedback control method for the pointing control mode of the satellite. The combination of magnetic and aerodynamic control proved to be su cient for the initial stabilisation of the satellite, but the three nano-reaction wheels are required for the pointing control of the imaging process. / AFRIKAANSE OPSOMMING: Die Kaapse Skiereiland Universiteit van Tegnologie, in samewerking met die Universiteit van Stellenbosch, is tans besig met die ontwikkeling van 'n 3-eenheid CubeSat vir 'n pol^ere, lae aard-wentelbaan. Die twee loonvragte van die satelliet bestaan uit 'n kamera en 'n radiofrekwensie-baken. Die radiofrekwensie-baken sal gebruik word om 'n antenna van die Hermanus Magnetiese Observatorium, by hul basis in Antarktika, se radar antenna patrone te kalibreer. Hierdie tesis beskryf die ontwikkeling van 'n aerodinamiese ori entasiebepaling en -beheerstelsel wat benodig word om die satelliet in drie asse te stabiliseer en om die kamera noukeurig te rig. Die satelliet se struktuur word ontwerp vir aerodinamiese beheer. Dit sluit vier veerantennas in vir passiewe duik-gier beheer, asook twee aerodynamiese rolbeheer appies vir aktiewe beheer. Die sensors wat gebruik word sluit 'n drie-as magnetometer, fyn sonsensor en nadirsensor in. Drie ori entasiebepalingsmetodes word ondersoek, naamlik die Drietal, Tempo Kalman lter en die Uitgebreide Kalman lter algoritmes. Buiten die aerodinamiese beheerelemente van die satelliet, word daar ook drie magneetstange en drie nano-reaksiewiele ingesluit in die ontwerp. Daar word onderskeid getref tussen drie beheermodusse en verskeie beheermetodes word ondersoek vir hierdie beheermodusse. Die verskeie ori entasiebepalings- en ori entasiebeheermetodes word ge evalueer deur middel van simulasies en die resultate word vergelyk om die beste metodes vir die satelliet se gebruik te bepaal. Die magnetiese Tempo Kalman lter word gekies as ori entasiebepalingsmetode vir 'n tuimelende satelliet en die kombinasie van die son Tempo Kalman lter en Drietal algoritme word gebruik vir 'n satelliet met lae hoektempos. Die B-dot en Y-spin beheerder word gekies vir die tuimelbeheermodus, die aerodinamiese en kruisproduk beheermetode vir die drie-as-stabilisasie-beheermodus en die kwaternioon terugvoer beheermetode vir die rigbeheermodus van die satelliet. Daar word bepaal dat die samespanning van magnetiese en aerodinamiese beheer voldoende is vir die aanvanklike stabilisering van die satelliet, maar dat die drie nano-reaksiewiele benodig word om die kamera te rig tydens die beeldvormingproses.

Des capteurs MEMS variés peuvent être fabriqués dans une technologie CMOS standard associée à une ou plusieurs étapes de gravure supplémentaires. Dans ce contexte, le micro-usinage du substrat par la face avant permet la fabrication de capteurs résistifs bas coût, basés sur des effets piezorésistifs ou thermiques, mais non optimaux en terme de bruit et de consommation. Cependant, au lieu d'envisager une optimisation technologique du procédé, ce travail s'est plutôt concentré sur le design du capteur et de son interface électronique afin d'améliorer les performances ci-dessus. L'objet de cette thèse est un accéléromètre convectif 3 axes basé sur une topologie initialement prévue pour des mesures suivant 2 axes, dans le plan de la puce, et utilisant une mesure de température différentielle. La mesure de l'accélération dans la direction perpendiculaire au plan de la puce, sans ajouter de structure supplémentaire, est donc étudiée ainsi que l'interface électronique associée. L'originalité de la mesure suivant ce 3ème axe réside dans la mesure de la température de mode commun de la structure existante. Cette étude est réalisée par l'intermédiaire de modélisations multi-physiques et électriques du capteur, de la conception et de la simulation de l'interface électronique et enfin de la caractérisation d'un prototype complet. / In the field of MEMS, various sensors can be manufactured using a standard CMOS technology and subsequent etching techniques. In this context, The Front-Side Bulk Micromachining (FSBM) approach allows the fabrication of low-cost resistive transducers based on either piezoresistive or thermal effects. Nevertheless, such fabrication method leads to non-optimized devices in terms of noise and power consumption. Instead of constraining fabrication technology, and in order to keep fabrication costs as low as possible, this work focuses on sensor design and electronic interfaces to address both issues. In this thesis, the device under study is a 3-axis CMOS thermal accelerometer. The sensor is based on a topology that was primarily introduced for 2-axis measurements only (in-plane acceleration, xy), using differential voltage across sensing thermistors. This work addresses the overall sensing performance by using dedicated front-end electronic and also investigates an opportunity to measure out-of-plane acceleration without the requirement of an additional device. The third axis (z) is provided by measuring a shift in the common-mode temperature, which is clearly an original approach. The study is carried out by means of both physical and electrical modeling of the transducer, electronic design and simulation, and prototype characterization.

The purpose of the project is to implement a control system for a 3- axis camera stabilizer. The stabilization is done by controlling three blushless DC motors driving the yaw, pitch and roll movements of the camera stabilizer's frame, respectively. The stabilizer's frame (equipped with three motors) is used in this project, and it is directly taken from a commercial product, Feiyu Tech G4S. The control system concerned in this project consists of a Teensy 3.6 microcontroller unit (MCU) implemented with three PID controllers, the motor drivers to drive the three motors, and an inertial measurement unit (IMU) of 9 degrees of freedom.The MCU is also used to process the IMU angle measurements of the camera position in 3- axis motion, in particular, it converts the IMU raw data to an angle for each of the axis, it then processes the angle data using a Kalman filter to reduce the noise. In the end of the project a prototype has been built and tested, it uses the control system to run the stabilizing process. It is shown to work quite successfully. In particular, it can run smoothly in the roll and pitch axes and compensate for unwanted movement, however the yaw axis does not function as intended due to a misplacement as well as poor calibration process of the magnetometer sensor in the IMU, which is left for future work.

The dissertation work focuses on the design and optimization of the castings and foundry technology and the production a particular model for the casting. The technology proposal and the pattern set building in 3D using CAD system. The casting simulation in CAE MAGMAsoft® system and evaluation of the proposed casting technology. Production of the pattern using CAD/CAM software and CNC machine tools with a focus on 3-axis and 5-axis machining. The economic benefits for the company.

In 1905 Albert Einstein developed the theory of Special Relativity. This theory describes the relation between space and time and revolutionized the understanding of the universe. While the concept is generally accepted new experimental setups are constantly being developed to challenge the theory, but so far no contradictions have been found. One of the postulates Einsteins theory of Relativity is based on states that the speed of light in vacuum is the highest possible velocity. Furthermore, it is demanded that the speed of light is independent of any chosen frame of reference. If an experiment would find a contradiction of these demands, the theory as such would have to be revised. To challenge the constancy of the speed of light the socalled Kennedy Thorndike experiment has been developed. A possible setup to conduct a Kennedy Thorndike experiment consists of comparing two independent clocks. Likewise experiments have been executed in laboratory environments. Within the scope of this work, the orbital requirements for the first space-based Kennedy Thorndike experiment called BOOST will be investigated.BOOST consists of an iodine clock, which serves as a time reference, and an optical cavity, which serves as a length reference. The mechanisms of the two clocks are different and can therefore be employed to investigate possible deviations in the speed of light. While similar experiments have been performed on Earth, space offers many advantages for the setup. First, one orbit takes roughly 90 min for a satellite based experiment. In comparison with the 24 h duration on Earth it is obvious that a space-based experiment offers higher statistics. Additionally the optical clock stability has to be kept for shorter periods, increasing the sensitivity. Third, the velocity of the experimental setup is larger. This results in an increased experiment accuracy since any deviation in the speed of light would increase with increasing orbital velocity. A satellite planted in a Low Earth Orbit (LEO) travels with a velocity of roughly 7 km/s. Establishing an Earth-bound experiment that travels with a constant velocity of that order is impossible. Finally, space offers a very quiet environment where no disturbances, such as vibrations, act upon the experiment, which is practically unavoidable in a laboratory environment. This thesis includes two main chapters. The chapter titled "Mission Level" exploits orbital candidates. Here, possible orbits are explained in detail and the associated advantages and problems are investigated. It also contains a discussion about ground visibility and downlink feasibility for each option. Finally, a nominal mission scenario is sketched. The other chapter is called "Sub-Systems". Within this chapter the subsystems of the spacecraft are examined. To examine the possible orbits it is necessary to define criteria according to which the quality of the orbits can be determined. The first criterion reflects upon the scientific outcome of the mission. This is mainly governed by the achievable velocity and the orbital geometry. The second criterion discriminates according to the mission costs. These include the launch, orbital injection, de-orbiting, satellite development, and orbital maintenance. The final criteria defines the requirements in terms of mission feasibility and risks, e.g. radiation. The criteria definition is followed by explaining the mission objectives and requirements. Each requirement is then discussed in terms of feasibility. The most important parameters, such as altitude, inclination, and the right ascension of the ascending node (RAAN), are discussed for each orbital option and an optimal range is picked. The optimal altitude depends on several factors, such as the decay rate, radiation concerns, experimental contributions, and eclipse duration. For the presented mission an altitude of 600 km seems to be the best fit. Alongside the optimal altitude possible de-orbiting scenarios are investigated. It is concluded that de-orbiting of the satellite is possible without any further external influence. Thus, no additional thrusters are required to de-orbit the satellite. The de-orbiting scenario has been simulated with systems tool kit (STK). From the simulation it can be concluded, that the satellite can be deorbited within 25 years. This estimation meets the requirements set for the mission. Another very important parameter is the accumulative eclipse duration per year for a given orbit. For this calculation it is necessary to know the relative positions and motion of the Earth and the Sun. From this the eclipse duration per orbit for different altitudes is gained. Ground visibilities for orbital options are examined for two possible ground stations. The theory is based on the geometrical relation between the satellite and the ground stations. The results are in an agreement with the related STK simulations. Finally, both ground stations are found adequate to maintain the necessary contact between the satellite and the ground station. In the trade-off section, orbit candidates are examined in more detail. Results from the previous sections with some additional issues such as the experiment sensitivities, radiation concern and thermal stability are discussed to conclude which candidate is the best for the mission. As a result of the trade-off, two scenarios are explained in the "Nominal Mission Scenario" section which covers a baseline scenario and a secondary scenario. After selecting a baseline orbit, two sub-systems of the satellite are examined. In the section of "Attitude Control System (ACS)" where the question of "Which attitude control method is more suitable for the mission?" is tried to be answered. A trade-off among two common control methods those are 3-axis stabilization and spin stabilization is made. For making the trade-off possible external disturbances in space are estimated for two imaginary satellite bodies. Then, it is concluded that by a spin stabilization method maintaining the attitude is not feasible. Thus, the ACS should be built on the method of 3-axis stabilization. As the second sub-system the possible power system of the satellite is examined. The total size and the weight of the solar arrays are estimated for two different power loads. Then, the battery capacity which will be sufficient for the power system budget is estimated together with the total mass of the batteries. In the last section, a conclusion of the thesis work is made and the possible future works for the BOOST mission are stated.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This thesis describes the development of attitude sensors required for the Attitude Determination and Control System (ADCS) for a Cubesat. The aim is to find the most suitable sensors for use on a small picosatellite by implementing miniaturised sensors with available commercial-off-the-shelf (COTS) technology. Specifically, the algorithms, hardware prototypes, software and filters required to create accurate sensors to determine the 3-axis orientation of a CubeSat are discussed. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van oriëntasiesensors wat benodig word vir die oriëntasiebepaling en -beheerstelsel (Engels: ADCS) van ’n CubeSat. Die doelwit is om sensors te vind wat die geskikste is om in ’n klein picosatelliet te gebruik, deur miniatuursensors met kommersiële maklik verkrygbare tegnologie (Engels: COTS technology) te implementeer. Daar word in die bespreking veral aandag geskenk aan die algoritmes, hardewareprototipes, programmatuur en filters wat benodig word om akkurate sensors te skep wat op hul beurt 3-as oriëntasie van die CubeSat kan bepaal.