Design, manufacture and test of a magnetic encoder

An new eddy current based magnetic position encoder structure is proposed and studied in this thesis. The encoder is composed of one read head and one scale with metal plates placed periodically on a substrate. The read head contains one emitter and two receiver pairs which are all rectangular planar coils. The electromagnetic coupling between the emitter and receivers were affected by the relative position of the scale. A system level analytical model of the proposed encoder structure has been derived, from which three different encoder signals forms were generated. An amplification and synchronous demodulation circuit has been designed and fabricated. The circuit board was used successfully to process the encoder output signals in the measurement. Four PCB encoder prototypes were fabricated. These encoder structures were studied using the ANSYS MaxwellTM software package. The simulated and measured results were compared. The best accuracy performance of the PCB encoder is -15 μm to 15 μm from the simulation results and -35 μm to 25 μm from the corresponding measurement. An alternative manufacturing process of the magnetic encoder based on multilayer Low Temperature Co-fired Ceramic (LTCC) technology has also been presented. The fabrication process of the LTCC encoder and equipment used were described. Two different methods were used to characterise the LTCC encoder with good agreement between all approaches attempted. The best accuracy performance of the LTCC encoder was -30 μm to 25 μm and after lookup table correction the improved accuracy ranged from -10 μm to 10 μm

SIRU development. Volume 1: System development

A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results

MEMS Accelerometers

Micro-electro-mechanical system (MEMS) devices are widely used for inertia, pressure, and ultrasound sensing applications. Research on integrated MEMS technology has undergone extensive development driven by the requirements of a compact footprint, low cost, and increased functionality. Accelerometers are among the most widely used sensors implemented in MEMS technology. MEMS accelerometers are showing a growing presence in almost all industries ranging from automotive to medical. A traditional MEMS accelerometer employs a proof mass suspended to springs, which displaces in response to an external acceleration. A single proof mass can be used for one- or multi-axis sensing. A variety of transduction mechanisms have been used to detect the displacement. They include capacitive, piezoelectric, thermal, tunneling, and optical mechanisms. Capacitive accelerometers are widely used due to their DC measurement interface, thermal stability, reliability, and low cost. However, they are sensitive to electromagnetic field interferences and have poor performance for high-end applications (e.g., precise attitude control for the satellite). Over the past three decades, steady progress has been made in the area of optical accelerometers for high-performance and high-sensitivity applications but several challenges are still to be tackled by researchers and engineers to fully realize opto-mechanical accelerometers, such as chip-scale integration, scaling, low bandwidth, etc

Eddy current angular position sensor for automotive

Programa doutoral em Líderes para Indústrias TecnológicasOs sensores angulares usados em aplicações automóveis, requerem uma boa resolução, fiabilidade, baixa manutenção, baixo custo de produção e capacidade de trabalhar sob condições adversas. Devido a estes requisitos, os sensores mais utilizados são os magnéticos, indutivos e magneto-indutivos. Outro fator crítico é a dimensão do sensor, quanto mais reduzido e compacto, maior é o número de aplicações em que pode ser aplicado. No caso dos sensores magneto-indutivos e indutivos, uma forma de reduzir o seu tamanho é através do uso de a bobines planares impressas em placas de circuito impresso (PCB). Estas, para além de mais compactas, conseguem também reduzir os custos de produção, otimizar a repetibilidade e assemblagem, e permitir que o seu desenho seja facilmente adaptado às suas aplicações. No desenvolvimento de sensores indutivos, obter a indutância das bobinas, que funcionam como elemento transdutor, é essencial e desafiador no caso de bobinas planas. Atualmente, há duas abordagens no estado da arte: fórmulas de aproximação (para geometrias regulares), e simulações de modelos de elementos finitos (FEM). As simulações são demoradas e recorrem a ferramentas de software dispendiosas e que exigem muitos recursos computacionais. Esta tese tem como objetivo desenvolver uma ferramenta de cálculo analítico para obter a indutância de bobinas planas genéricas, reduzindo o tempo de desenvolvimento. A ferramenta possibilita ainda o cálculo da interferência que um alvo planar condutivo tem na indutância da bobine, tornando assim possível obter a resposta de um sensor indutivo baseado em eddy currents durante a sua fase de desenvolvimento. Esta tese, além de detalhar o desenvolvimento da ferramenta mencionada, também descreve todos os processos de validação implementados, através de simulações FEM e testes experimentais. A metodologia proposta foi aplicada com sucesso no desenvolvimento de um sensor de posição angular automotivo baseado em eddy currrents. Foi possível comprovar que a precisão da ferramenta desenvolvida está de acordo com as metodologias usualmente utilizadas, com a vantagem de ser mais rápida e económica.Angular sensors used in automotive applications require good precision, reliability, low maintenance, low production costs and the ability to work in harsh conditions. Due to these requirements, magnetic, inductive and magneto-inductive sensors are preferred and are used in current generations of automotive angular position sensors. The size of the sensors is another relevant factor in the development of new solutions. The smaller and more compact, the larger the number of applications in which they can be applied. In the case of magneto-inductive and inductive sensors, one way to reduce their size is to use planar coils printed on printed circuit boards (PCBs). These, in addition to occupy a smaller volume when compared to solenoids, also reduce production costs and optimize repeatability and simplify assembly. When developing inductive sensors, knowing the required inductance value of its coils is essential and this task can be challenging in the case of planar coils. Currently, two approaches are used to calculate the inductances of planar coils. When the coils have regular geometry approximation formulas are used, configuring some parameters. When they have irregular geometry or a more accurate result is desired, simulations using finite element methods (FEM) are chosen. These simulations have the disadvantage of being time-consuming, requiring expensive software applications and a huge computing resources. In view of the budget and the reduction of development time, this thesis provides an analytical calculation tool for the inductance of generic multi-layer planar coils. In this way, it is possible to develop dedicated applications in reduced time. The tool also allows to calculate the interference that a planar conductive target, of arbitrary geometry, can have on the coil inductance. Thus, it is possible to obtain the response of an inductive sensor based on eddy currents during its development phase. This thesis, in addition to detailing the development of the aforementioned tool, also describes all the validation processes implemented using FEM simulations and experimental tests. The proposed methodology was successfully applied in the development of an automotive angular position sensor based on eddy currents. It was possible to prove that the precision of the developed analytical tool is in concordance with the methodologies usually used, with the advantage of being faster and open source.Fundação para a Ciência e a Tecnologia (FCT) - bolsa de doutoramento PD/BD/128142/201

Motion control design of a PMSM and FPGA implementation for the Beam Wire Scanner at CERN

This thesis work describes the modelling, simulation, implementation and testing of a motion controller for a Permanent Magnet Synchronous Motor, used as an actuator for the Beam Wire Scanner at CERN. The dissertation, after a brief introduction to the subject, focuses on the design of the control system starting for the basics of motion control and the mathematical equations describing the various parts of the system. The architecture of the controller is explained as well as the design choices and their reasons. It consists in a three-level cascade feedback loop, regulated through three variable structure, saturated PID controllers with anti-windup architecture. Also, three feedforward actions are included, as well as a static decoupler and a steady-state Kalman filter. In the last chapters, the implementation of the control system on an ALTERA FPGA board is described and its performances are verified through a serie of experiments

A method for the mechatronico analysis of parallel kinematics manipulators based on decoupling the dynamics of actuators and mechanism

287 p

The 31st Aerospace Mechanisms Symposium

The proceedings of the 31st Aerospace Mechanisms Symposium are reported. Topics covered include: robotics, deployment mechanisms, bearings, actuators, scanners, boom and antenna release, and test equipment. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms