10 documents found, page 1 of 1
Low-pressure resonant MEMS accelerometers for automotive applications
Moreira, Eurico EstevesOs acelerómetros MEMS têm um papel importante no desenvolvimento de novas soluções/funcionalidades para a indústria automóvel, nomeadamente na melhoria das condições de segurança e de condução. Não obstante, dispositivos com melhor performance, dimensões mais reduzidas e menor custo possibilitariam a implementação de mais casos de uso/funcionalidades. A encapsulação em vácuo tem sido alvo de estudo para desenvo...
Influence of mechanical stress in a packaged frequency-modulated MEMS accelerom...
Moreira, Eurico Esteves; Kuhlmann, Burkhard; Alves, Filipe Manuel Serra; Dias, Rosana Maria Alves; Cabral, Jorge; Gaspar, JoaoFrequency modulated accelerometers composed of two double-ended tuning fork (DETF) resonators on a differential configuration were characterized for their sensitivity to force applied to their package. Commonly, differential architectures are employed to cancel common mode errors, such as the mechanical stress or temperature dependency. The device dependence to mechanical stress was experimentally measured for ...
Resonant accelerometer based on double-ended tuning fork and a force amplificat...
Moreira, Eurico Esteves; Kuhlmann, Burkhard; Gaspar, João; Rocha, Luís Alexandre MachadoResonant accelerometers are an alternative to amplitude modulated devices due to their higher integration capabilities, since they are encapsulated in vacuum and are stable at low pressures. Vacuum is required for some sensors (i.e., gyroscopes) but amplitude modulated accelerometers tend to be unstable under such conditions and therefore cannot be integrated in the same package. Herewith, a device composed by ...
Frequency modulated magnetometer using a double-ended tuning fork resonator
Moreira, Eurico Esteves; Gaspar, João; Rocha, Luís Alexandre MachadoA Lorentz force MEMS magnetometer based on a double-ended tuning fork (DETF) for out-of-plane sensing is presented here. A novel configuration using a hexagonal-shaped Lorentz force transducer is used, which simplifies the sensor configuration and improves its sensitivity. Frequency modulated devices were fabricated in an in-house process on silicon on insulator wafers (SOI) and then tested in vacuum. The final...
High-resolution seismocardiogram acquisition and analysis system
Leitão, Fábio André Costa; Moreira, Eurico Esteves; Alves, Filipe; Lourenço, Mário; Azevedo, Olga; Gaspar, João; Rocha, Luis A.Several devices and measurement approaches have recently been developed to perform ballistocardiogram (BCG) and seismocardiogram (SCG) measurements. The development of a wireless acquisition system (hardware and software), incorporating a novel high-resolution micro-electro-mechanical system (MEMS) accelerometer for SCG and BCG signals acquisition and data treatment is presented in this paper. A small accelerom...
Novel magnetic readout for hybrid spintronic MEMS devices
Dias, Rosana A.; Moreira, Eurico Esteves; Ribeiro, Igor; Costa, Margaret; Fonseca, Helder; Cardoso, Susana; Freitas, PauloThis digest reports for the first time on the concept, fabrication and characterization of a spintronics magnetic readout for hybrid MEMS. The method uses magnetic sensors (spin valves) and permanent magnets (on both the movable and the fixed parts of the MEMS structure) to detect displacement. The use of such transduction method has several potential advantages: it allows a small form factor, straightforward r...
Full-gap tracking system for parallel plate electrostatic actuators using close...
Moreira, Eurico Esteves; Lima, Vasco António Lourenço; Alves, Filipe Manuel Serra; Cabral, Jorge; Gaspar, João; Rocha, Luís Alexandre MachadoBi-directional full-gap tracking on parallel-plate electrostatic actuators using closed-loop control is demonstrated in this paper. On-Off control is explored, where the actuator position is controlled by actuating or releasing the actuator based on the actual position (weather it is above or below the desired position). Noise and delays introduced by the readout circuit compromise the performance of this contr...
Low-voltage, high-tuning range MEMS variable capacitor using closed-loop control
Moreira, Eurico Esteves; Cabral, Jorge; Gaspar, J.; Rocha, Luís Alexandre MachadoA low-voltage, high-tuning range variable MEMS capacitor using parallel-plates electrostatic microactuators operated in close-loop is introduced in this paper. The structures were fabricated using an in-house 2-masks process on SOI wafers and the use of a closed-loop controller increases the stable displacements of the structure beyond the pull-in limitation along the full available gap (the limitation are the ...
Bi-directional extended range parallel plate electrostatic actuator based on fe...
Moreira, Eurico Esteves; Alves, Filipe Manuel Serra; Dias, R. A.; Costa, M.; Fonseca, H.; Cabral, Jorge; Gaspar, J.; Rocha, Luís Alexandre MachadoIn this paper, we present a bi-directional extended range parallel-plate electrostatic actuator using feedback linearization control. The actuator can have stable displacements up to 90% of the full-gap (limited by mechanical stoppers) on both directions, i.e., the device can move +/- 2 mu m within a +/- 2.25 mu m gap. The system has successfully tracked references until 1kHz (limited by the dynamics of the dev...
Controlo de micro-atuadores eletrostáticos na zona de instabilidade
Moreira, Eurico EstevesNos dias de hoje, os dispositivos baseados em MEMS (Micro-electromechanical systems) são uma constante no mercado, desempenhando as mais diversas tarefas, desde a medição da aceleração ou pressão, até à utilização como microfones. Dispositivos MEMS são também usados como micro-atuadores, sendo que no caso dos micro-atuadores electroestáticos, devido às suas características, foram desenvolvidos sistemas contendo...