Publicação
Micro-g MEMS accelerometer based on time measurement
| Resumo: | The MEMS sensor market has experienced an amazing growth on the last decades, with accelerometers being one of the pioneers pushing the technology into widespread use with its applications on automotive industry. Since then, accelerometers have been gradually replacing conventional sensors due mainly to its lower cost. As the performance of MEMS accelerometers improves, the applications range where they replace conventional accelerometers increases. Nowadays, there is still a large range of applications for which suitable MEMS accelerometers are yet to be developed. This work focuses on the development of a high performance accelerometer taking advantage of the high sensitivity of a non-linear phenomenon that occurs in electrostatically actuated movable capacitive microdevices: electrostatic pull-in. Although the pull-in effect has been known for more than 40 years, it is usually avoided when dealing with movable microstructures as it leads to a region of instability, where the position of movable parts cannot be fully controlled. In the last decade, the pull-in displacement profile of 1-DOF parallel-plates devices has been the subject of research that revealed the presence of a so-called meta-stability. This meta-stability occurs in specific damping and voltage actuation conditions and translates as a non-linear displacement profile, rather than simple time-of-flight. This feature makes the pull-in time duration significantly longer, and it happens to be extremely sensitive to intervenient forces, such as external acceleration. Basically, measuring the pull-in time of specifically designed microstructures (while maintaining the other parameters constant) allows the measurement of the external acceleration that acts on the system. Using a pull-in time measurement rather than direct capacitance/displacement/acceleration transduction presents several advantages. The most important is the fact that time can be measured very accurately with technology readily available. For instance, if one uses a 100MHz clock on the time counting mechanism, which corresponds to a time measurement resolution of 100 ns, given the 0.26 μs/μg sensitivity of the accelerometer developed in this work, an acceleration resolution of 0.38 μg could be achieved. One of the main challenges of the time based accelerometer development is the damper design, as damping is of outmost importance in defining the accelerometer performance parameters, namely sensitivity and noise. A new squeeze-film damper geometry design has been presented and studied. It consists of flow channels implemented on the parallel-plates that relieve the squeeze-film damping pressures generated when the device is moving. This geometry has proved to be very effective in increasing the capacitance/damping ratio in parallel-plates, which was up to now a great challenge of in-plane parallel-plates design. This work reports the development of an open-loop accelerometer with 0.26 μs/μg sensitivity and 2.7 μg /√Hz noise performance. The MEMS structures used for its experimental implementation were fabricated using a commercially available SOI micromachining process. The main drawbacks of this accelerometer were the low system bandwidth and non-linearity. Closed-loop approaches using electrostatic feedback were explored in this work in order to overcome these limitations, and the dynamic range was successfully extended to 109 dB along with improvements on the linearity. From the thorough damping study performed in this work, a new application for the pullin time using the same microstructures was developed. It consists of a gas viscosity sensing application. At the low frequencies operated, damping is directly proportional to the viscosity of the gas medium. The experimental results obtained with gases with viscosities ranging from 8 μP to 18 μP have shown a sensitivity of 2 ms/μP, making the pull-in time viscosity sensor a very promising approach. |
|---|---|
| Autores principais: | Dias, Rosana Maria Alves |
| Assunto: | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| Ano: | 2013 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| _version_ | 1866877992281571328 |
|---|---|
| author | Dias, Rosana Maria Alves |
| author_facet | Dias, Rosana Maria Alves |
| author_role | author |
| contributor_name_str_mv | Rocha, Luís A. Correia, J. H. Universidade do Minho |
| country_str | PT |
| creators_json_txt | [{\"Person.name\":\"Dias, Rosana Maria Alves\"}] |
| datacite.contributors.contributor.contributorName.fl_str_mv | Rocha, Luís A. Correia, J. H. Universidade do Minho |
| datacite.creators.creator.creatorName.fl_str_mv | Dias, Rosana Maria Alves |
| datacite.date.Accepted.fl_str_mv | 2013-05-27T00:00:00Z |
| datacite.date.available.fl_str_mv | 2013-07-31T09:10:56Z |
| datacite.date.embargoed.fl_str_mv | 2013-07-31T09:10:56Z |
| datacite.rights.fl_str_mv | http://purl.org/coar/access_right/c_abf2 |
| datacite.subjects.subject.fl_str_mv | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| datacite.titles.title.fl_str_mv | Micro-g MEMS accelerometer based on time measurement |
| dc.contributor.none.fl_str_mv | Rocha, Luís A. Correia, J. H. Universidade do Minho |
| dc.creator.none.fl_str_mv | Dias, Rosana Maria Alves |
| dc.date.Accepted.fl_str_mv | 2013-05-27T00:00:00Z |
| dc.date.available.fl_str_mv | 2013-07-31T09:10:56Z |
| dc.date.embargoed.fl_str_mv | 2013-07-31T09:10:56Z |
| dc.format.none.fl_str_mv | application/pdf |
| dc.identifier.none.fl_str_mv | https://hdl.handle.net/1822/24893 |
| dc.language.none.fl_str_mv | eng |
| dc.rights.none.fl_str_mv | http://purl.org/coar/access_right/c_abf2 |
| dc.subject.none.fl_str_mv | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| dc.title.fl_str_mv | Micro-g MEMS accelerometer based on time measurement |
| dc.type.none.fl_str_mv | http://purl.org/coar/resource_type/c_db06 |
| description | The MEMS sensor market has experienced an amazing growth on the last decades, with accelerometers being one of the pioneers pushing the technology into widespread use with its applications on automotive industry. Since then, accelerometers have been gradually replacing conventional sensors due mainly to its lower cost. As the performance of MEMS accelerometers improves, the applications range where they replace conventional accelerometers increases. Nowadays, there is still a large range of applications for which suitable MEMS accelerometers are yet to be developed. This work focuses on the development of a high performance accelerometer taking advantage of the high sensitivity of a non-linear phenomenon that occurs in electrostatically actuated movable capacitive microdevices: electrostatic pull-in. Although the pull-in effect has been known for more than 40 years, it is usually avoided when dealing with movable microstructures as it leads to a region of instability, where the position of movable parts cannot be fully controlled. In the last decade, the pull-in displacement profile of 1-DOF parallel-plates devices has been the subject of research that revealed the presence of a so-called meta-stability. This meta-stability occurs in specific damping and voltage actuation conditions and translates as a non-linear displacement profile, rather than simple time-of-flight. This feature makes the pull-in time duration significantly longer, and it happens to be extremely sensitive to intervenient forces, such as external acceleration. Basically, measuring the pull-in time of specifically designed microstructures (while maintaining the other parameters constant) allows the measurement of the external acceleration that acts on the system. Using a pull-in time measurement rather than direct capacitance/displacement/acceleration transduction presents several advantages. The most important is the fact that time can be measured very accurately with technology readily available. For instance, if one uses a 100MHz clock on the time counting mechanism, which corresponds to a time measurement resolution of 100 ns, given the 0.26 μs/μg sensitivity of the accelerometer developed in this work, an acceleration resolution of 0.38 μg could be achieved. One of the main challenges of the time based accelerometer development is the damper design, as damping is of outmost importance in defining the accelerometer performance parameters, namely sensitivity and noise. A new squeeze-film damper geometry design has been presented and studied. It consists of flow channels implemented on the parallel-plates that relieve the squeeze-film damping pressures generated when the device is moving. This geometry has proved to be very effective in increasing the capacitance/damping ratio in parallel-plates, which was up to now a great challenge of in-plane parallel-plates design. This work reports the development of an open-loop accelerometer with 0.26 μs/μg sensitivity and 2.7 μg /√Hz noise performance. The MEMS structures used for its experimental implementation were fabricated using a commercially available SOI micromachining process. The main drawbacks of this accelerometer were the low system bandwidth and non-linearity. Closed-loop approaches using electrostatic feedback were explored in this work in order to overcome these limitations, and the dynamic range was successfully extended to 109 dB along with improvements on the linearity. From the thorough damping study performed in this work, a new application for the pullin time using the same microstructures was developed. It consists of a gas viscosity sensing application. At the low frequencies operated, damping is directly proportional to the viscosity of the gas medium. The experimental results obtained with gases with viscosities ranging from 8 μP to 18 μP have shown a sensitivity of 2 ms/μP, making the pull-in time viscosity sensor a very promising approach. |
| dirty | 0 |
| eu_rights_str_mv | openAccess |
| format | doctoralThesis |
| fulltext.url.fl_str_mv | https://prod-dspace.uminho.pt/bitstreams/ac4a0183-b535-482c-8c49-8c82629220d6/download |
| id | rum_fbff4cbacb40b7a85adc44f6cdb4ff7a |
| identifier.url.fl_str_mv | https://hdl.handle.net/1822/24893 |
| instacron_str | repositorium |
| institution | Universidade do Minho |
| instname_str | Universidade do Minho |
| language | eng |
| network_acronym_str | rum |
| network_name_str | RepositóriUM - Universidade do Minho |
| oai_identifier_str | oai:repositorium.uminho.pt:1822/24893 |
| organization_str_mv | urn:organizationAcronym:repositorium |
| person_str_mv | Dias, Rosana Maria Alves |
| publishDate | 2013 |
| reponame_str | RepositóriUM - Universidade do Minho |
| repository_id_str | urn:repositoryAcronym:rum |
| service_str_mv | urn:repositoryAcronym:rum |
| spelling | engThe MEMS sensor market has experienced an amazing growth on the last decades, with accelerometers being one of the pioneers pushing the technology into widespread use with its applications on automotive industry. Since then, accelerometers have been gradually replacing conventional sensors due mainly to its lower cost. As the performance of MEMS accelerometers improves, the applications range where they replace conventional accelerometers increases. Nowadays, there is still a large range of applications for which suitable MEMS accelerometers are yet to be developed. This work focuses on the development of a high performance accelerometer taking advantage of the high sensitivity of a non-linear phenomenon that occurs in electrostatically actuated movable capacitive microdevices: electrostatic pull-in. Although the pull-in effect has been known for more than 40 years, it is usually avoided when dealing with movable microstructures as it leads to a region of instability, where the position of movable parts cannot be fully controlled. In the last decade, the pull-in displacement profile of 1-DOF parallel-plates devices has been the subject of research that revealed the presence of a so-called meta-stability. This meta-stability occurs in specific damping and voltage actuation conditions and translates as a non-linear displacement profile, rather than simple time-of-flight. This feature makes the pull-in time duration significantly longer, and it happens to be extremely sensitive to intervenient forces, such as external acceleration. Basically, measuring the pull-in time of specifically designed microstructures (while maintaining the other parameters constant) allows the measurement of the external acceleration that acts on the system. Using a pull-in time measurement rather than direct capacitance/displacement/acceleration transduction presents several advantages. The most important is the fact that time can be measured very accurately with technology readily available. For instance, if one uses a 100MHz clock on the time counting mechanism, which corresponds to a time measurement resolution of 100 ns, given the 0.26 μs/μg sensitivity of the accelerometer developed in this work, an acceleration resolution of 0.38 μg could be achieved. One of the main challenges of the time based accelerometer development is the damper design, as damping is of outmost importance in defining the accelerometer performance parameters, namely sensitivity and noise. A new squeeze-film damper geometry design has been presented and studied. It consists of flow channels implemented on the parallel-plates that relieve the squeeze-film damping pressures generated when the device is moving. This geometry has proved to be very effective in increasing the capacitance/damping ratio in parallel-plates, which was up to now a great challenge of in-plane parallel-plates design. This work reports the development of an open-loop accelerometer with 0.26 μs/μg sensitivity and 2.7 μg /√Hz noise performance. The MEMS structures used for its experimental implementation were fabricated using a commercially available SOI micromachining process. The main drawbacks of this accelerometer were the low system bandwidth and non-linearity. Closed-loop approaches using electrostatic feedback were explored in this work in order to overcome these limitations, and the dynamic range was successfully extended to 109 dB along with improvements on the linearity. From the thorough damping study performed in this work, a new application for the pullin time using the same microstructures was developed. It consists of a gas viscosity sensing application. At the low frequencies operated, damping is directly proportional to the viscosity of the gas medium. The experimental results obtained with gases with viscosities ranging from 8 μP to 18 μP have shown a sensitivity of 2 ms/μP, making the pull-in time viscosity sensor a very promising approach.application/pdfporMicro-g MEMS accelerometer based on time measurementDias, Rosana Maria AlvesRocha, Luís A.Correia, J. H.HostingInstitutionOrganizationalUniversidade do Minhoe-mailmailto:repositorium@usdb.uminho.ptrepositorium@usdb.uminho.ptURNurn:tid:1013622772013-07-31T09:10:56Z2013-05-272013-03-262013-05-27T00:00:00ZHandlehttps://hdl.handle.net/1822/24893http://purl.org/coar/access_right/c_abf2open accessPull-inMEMSaccelerometernoiseparallel-platesdampingelectrostatic feedbackgas viscosityacelerómetroplacas-paralelasamortecimentofeeback electrostáticoviscosidade de gas8517105 bytesliteraturehttp://purl.org/coar/resource_type/c_db06doctoral thesishttp://purl.org/coar/access_right/c_abf2application/pdffulltexthttps://prod-dspace.uminho.pt/bitstreams/ac4a0183-b535-482c-8c49-8c82629220d6/download |
| spellingShingle | Micro-g MEMS accelerometer based on time measurement Dias, Rosana Maria Alves Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| status | SINGLETON |
| subject.fl_str_mv | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| title | Micro-g MEMS accelerometer based on time measurement |
| title_full | Micro-g MEMS accelerometer based on time measurement |
| title_fullStr | Micro-g MEMS accelerometer based on time measurement |
| title_full_unstemmed | Micro-g MEMS accelerometer based on time measurement |
| title_short | Micro-g MEMS accelerometer based on time measurement |
| title_sort | Micro-g MEMS accelerometer based on time measurement |
| topic | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| topic_facet | Pull-in MEMS accelerometer noise parallel-plates damping electrostatic feedback gas viscosity acelerómetro placas-paralelas amortecimento feeback electrostático viscosidade de gas |
| url | https://hdl.handle.net/1822/24893 |
| visible | 1 |