| 1. |
- Berglund, Martin, 1985-, et al.
(författare)
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Dynamic characterization and modelling of a dual-axis beam steering device for performance understanding, optimization, and control design
- 2013
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:4, s. 045020-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a lumped thermal model of a dual-axis laser micromirror device for beam steering in a free-space optical (FSO) communication system, designed for fractionated spacecraft. An FSO communication system provides several advantages, such as larger bandwidth, smaller size and weight of the communication payload and less power consumption. A dual-axis mirror device is designed and realized using microelectromechanical systems technology. The fabrication is based on a double-sided, bulk micromachining process, where the mirror actuates thermally by joints consisting of v-grooves filled with the SU-8 polymer. The size of the device, consisting of a mirror, which is deflectable versus its frame in one direction, and through deflection of the frame in the other, is 15.4 × 10.4 × 0.3 mm3. In order to further characterize and understand the micromirror device, a Simulink state-space model of the actuator is set up using thermal and mechanical properties from a realized actuator. A deviation of less than 2% between the modelled and measured devices was obtained in an actuating temperature range of 20–200 °C. The model of the physical device was examined by evaluating its performance in vacuum, and by changing physical parameters, such as thickness and material composition. By this, design parameters were evaluated for performance gain and usability. For example, the crosstalk between the two actuators deflecting the mirror along its two axes in atmospheric pressure is projected to go down from 97% to 6% when changing the frame material from silicon to silicon dioxide. A feedback control system was also designed around the model in order to examine the possibility to make a robust control system for the physical device. In conclusion, the model of the actuator presented in this paper can be used for further understanding and development of the actuator system.
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| 2. |
- Jonsson, Jonas, et al.
(författare)
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Instrumentation and vehicle platform of a miniaturized submersible for exploration of terrestrial and extraterrestrial aqueous environments
- 2012
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Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 79, s. 203-211
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Tidskriftsartikel (refereegranskat)abstract
- An example of an extraterrestrial environment likely to support life is the vast liquid body believed to hide underneath the frozen crust of Jupiter's moon Europa. The hypothetical exploration of this, as well as the more accessible subglacial lakes on Earth, has been used as model applications for the development of a heavily miniaturized, yet qualified, submersible with the potential to be deployable either in itself through a long and narrow borehole or as the daughter craft of an ice-penetrating cryobot.Onboard the submersible, which is only 20 cm in length and 5 cm in diameter, accommodation of a versatile set of sensors and instruments capable of characterizing and imaging the surroundings, and even collecting water samples with microorganisms for return, is facilitated through the use of miniaturization technologies. For instance, together with a small camera, a laser-based, microoptic device enables the 3-D reconstruction of imaged objects for topographical measurements. As a complement, when the water is turbid or a longer range is wanted, the world's smallest side-scanning sonar, exhibiting centimeter resolution and a range of over 30 m, has been developed. The work on miniaturizing a CTD, which is a widely employed oceanographic instrument used to measure and correlate conductivity, temperature, and depth, has commenced. Furthermore, a device employing acoustics to trap microscopic particles and organisms, and, by this, enrich water samples, is under development. To ensure that the gathered samples are pristine until analyzed at the end of a mission, the device is equipped with high-pressure, latchable valves.Remote operation and transfer of measurement data and images, or even live streaming of video, is made possible through a kilometer-long fiber optic cable being reeled out from the vehicle underway and tethering it to a terminal. To extend the missions, the same fiber shall also be capable of charging the onboard batteries.In this paper, the vehicle and its subsystems are summarized. Subsystems essential for the vehicle's operation, e.g., hull structure, communication and power management, are treated separately from those of more mission-specific nature, like the instruments mentioned above.
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| 3. |
- Jonsson, Jonas, et al.
(författare)
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Miniaturized submersible for exploration of aqueous environments on Earth and beyond
- 2011
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Konferensbidrag (refereegranskat)abstract
- Some of the most likely environments to support extraterrestrial life in our solar system are the ice-covered moons, suchas Europa, thought to harbor a liquid ocean underneath its frozen crust. Exploration, however, necessitates an ice-penetratingcryobot, or a long and narrow borehole, and the subsequent deployment of a small submersible, a hydrobot, with severe sizerestrictions imposed on its scientific payload. As a stepping stone for exploration of such environments, a small instrumentladenedsubmersible vehicle is currently under development.Employment of a large set of instruments capable of characterizing the aqueous environment, imaging the surroundingsand collecting microorganisms is essential for the determination of habitability. Despite the submersible being only 20 cm inlength and 5 cm in diameter, a high degree of functionality is facilitated here through the use of miniaturization technologies. Forinstance, a compact laser-illuminated diffractive optical element, paired with a high-resolution camera, enable photogrammetryand the reconstruction of objects’ shapes in 3-D space. Also for imaging, the world’s smallest side-scanning sonar has beendeveloped to acoustically image, either where water is too turbid for the camera, or where longer range is necessary. Currently,the sonar exhibits centimeter resolution and ranges over 30 meters. On the sensor side, a most vital oceanographic instrument, theCTD, used to measure the conductivity, temperature, and depth of water, has been heavily miniaturized and preliminaryevaluated. Additionally, a water sampler combining integrated selection and enriching capabilities to filter out and accommodate,e.g., microbes in the size range of 1-10 μm, is under development. Among other parts, its high-pressure valves and microfluidicacoustic traps have already been realized.For remote operation and upload of measurement data or images, or even live streaming of video, the submersible will betethered with a bi-directionally transmitting fiber optic cable, also capable of charging the onboard batteries for long missions.The one kilometer long fiber will be fitted within the hull, and by reeling out the fiber from the submersible, drag will be reduced.Herein, test results and images of the vehicle and its complete, and continuously developed, subsystems are presented.The vehicle, and its subsystems as stand-alone instruments, will enable the exploration of previously unreachable analogenvironments on Earth, vital to the field of astrobiology, and act as a forerunner to a submersible hydrobot that can explore icecoveredoceans elsewhere in our solar system.
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| 4. |
- Jonsson, Jonas, et al.
(författare)
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Miniaturized submersible for exploration of small aqueous environments
- 2011
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Ingår i: Oceans’11 MTS/IEEE Kona, Hilton Waikoloa Village, Kona, Hawai‘i September 19-22, 2011.
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Konferensbidrag (refereegranskat)abstract
- Remotely operated vehicles (ROVs) are commonlyused for sub-surface exploration. However, multi-functionalROVs tend to be fairly large, while preferred small and compactROVs suffer from limited functionality. The Deeper Access,Deeper Understanding (DADU) project aims to develop a smallsubmersible concept using miniaturization technologies to enablea high functionality. An operator is able to maneuver the vehiclewith five degrees of freedom using eight small thrusters, while aset of accelerometers and gyros monitor the orientation of thesubmersible. A single fiber optic cable will connect thesubmersible to a control station and enable simultaneous dataand command transfers. Rechargeable battery packs providepower to the submersibles subsystems during operation. Thesewill be rechargeable through the fiber connection. A forwardlooking camera is aided by a laser topography measurementsystem, where distances, sizes and shapes of objects in view canbe determined to within 0.5 cm. For murkier environments, orwhen a more extensive mapping of the surroundings is needed,the small high-frequency side-scanning sonar can be used.Salinity calculations of the water will be available throughmeasurements of the conductivity, temperature and depth.Samples of water and particles within it will be enabled through awater sampler with an enriching capability. Flow sensors will beable to measure the water movement around the submersible’shull. The submersible and its subsystems are under continuousdevelopment. The vehicle itself, and its subsystems as stand-aloneinstruments, will enable the exploration of previouslyunreachable submerged environments, such as the sub-glaciallakes found in Iceland and Antarctica, or other submerged smallenvironments, such as pipe and cave systems.
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| 5. |
- Lekholm, Ville, 1976-, et al.
(författare)
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Ceramic cold gas microthruster with integrated flow sensor
- 2011
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Ingår i: PowerMEMS 2011 Technical digest. - Daejeon, Republic of Korea : Cell Bench Research Center, KAIST. - 9788996759102 ; , s. 167-170
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Konferensbidrag (refereegranskat)abstract
- For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding very high temperatures. Samples have been shown capable of achieving temperatures locally exceeding 1000ºC.
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| 6. |
- Lekholm, Ville, 1976-, et al.
(författare)
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Ceramic microcomponents for high-temperature fluidics
- 2010
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Ingår i: Technical DigestPowerMEMS 2010, The 10th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Leuven, Belgium, December 1-3, 2010. - 9789073802889 ; , s. 291-294
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Konferensbidrag (refereegranskat)abstract
- For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as abundant for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. A major reason is the lack of means for high-resolution structuring. This paper describes the application of silicon-based manufacturing processes in the fabrication of ceramic yet truly micromechanical structures and devices for very high-temperature applications, and demonstrates the technique’s implementation in, and significance for, high-temperature microfluidics. Embossing of structures down to 2 µm wide is demonstrated, as well as deep embossing (50 µm), punching through 15 µm tape, and lamination of structured layers. The resulting samples survive temperatures of 1400ºC.
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| 7. |
- Lekholm, Ville, 1976-, et al.
(författare)
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High-temperature zirconia microthruster with integrated flow sensor
- 2013
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:5, s. 055004-
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the design, fabrication and characterization of a ceramic, heated cold-gas microthruster device made with silicon tools and high temperature co-fired ceramic processing. The device contains two opposing thrusters, each with an integrated calorimetric propellant flow sensor and a heater in the stagnation chamber of the nozzle. The exhaust from a thruster was photographed using schlieren imaging to study its behavior and search for leaks. The heater elements were tested under a cyclic thermal load and to the maximum power before failure. The nozzle heater was shown to improve the efficiency of the thruster by 6.9%, from a specific impulse of 66 to 71 s, as calculated from a decrease of the flow rate through the nozzle of 13%, from 44.9 to 39.2 sccm. The sensitivity of the integrated flow sensor was measured to 0.15 m Omega sccm(-1) in the region of 0-15 sccm and to 0.04 m Omega sccm(-1) above 20 sccm, with a zero-flow sensitivity of 0.27 m Omega sccm(-1). The choice of yttria-stabilized zirconia as a material for the devices makes them robust and capable of surviving temperatures locally exceeding 1000 degrees C.
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| 8. |
- Lekholm, Ville, 1976-, et al.
(författare)
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Schlieren Imaging of Microthruster Exhausts for Qualitative and Quantitative Analysis
- 2012
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Ingår i: Measurement science and technology. - : Institute of Physics (IOP). - 0957-0233 .- 1361-6501. ; 23:8, s. 085403-
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. Schlieren imaging is a method used to visualize differences in refractiveindex within a medium. It is a powerful and straightforward tool for sensitiveand high-resolution visualization of, e.g., gas flows. Here, heated cold gasmicrothrusters were studied with this technique. The thrusters are manufacturedusing microelectromechanical systems technology, and measure 22×22×0.85 mm. Thenozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit.Through these studies, verification of the functionality of the thrusters, and directvisualization and of the thruster exhausts was possible. At atmospheric pressure,slipping of the exhaust was observed, due to severe overexpansion of the nozzle. Invacuum (3 kPa), the exhaust was imaged while feed pressure was varied from 100 to450 kPa. The nozzle was overexpanded, and the flow was seen to be supersonic. Theshock cell period was linearly dependent on feed pressure, ranging from 320 to 610 µm.With activated heaters, the shock cell separation increased. The effect of the heaterswas more prominent at low feed pressure, and an increase in specific impulse of 20%was calculated. It was also shown that schlieren imaging can be used to detect leaks,making it a valuable, safe, and noninvasive aid in quality control of the thrusters.
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| 9. |
- Lekholm, Ville, 1976-, et al.
(författare)
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Verifying microexhausts with schlieren imaging
- 2010
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Ingår i: Proceedings of the 2nd International Conference on Space Propulsion, San Sebastián, Spain, May 3-6, 2010.
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Konferensbidrag (refereegranskat)abstract
- Schlieren imaging is a method to visualize differences in refractive index within a medium. It is an inexpensive, yet powerful and straightforward tool, for sensitive and high-resolution visualization of gas flows. Here, heated cold gas microthrusters were studied with schlieren imaging techniques. The thruster chips are manufactured using MEMS technology, and measure 22*22*0.85 mm. The nozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit. Through these studies, verification and direct visualization of the functionality of the thrusters were possible. At atmospheric pressure, slipping of the exhaust was observed, due to the severe overexpansion of the nozzle. In vacuum, the nozzle was underexpanded, and the flow was seen to be supersonic. There was a measurable change in the exhaust with heaters activated. It was also shown that the method can be used to detect leaks, making it a valuable, quick, safe, and inexpensive aid in quality control of the thrusters.
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| 10. |
- Palmer, Kristoffer, et al.
(författare)
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A highly integratable silicon thermal gas flow sensor
- 2012
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 22:6, s. 065015-
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Tidskriftsartikel (refereegranskat)abstract
- Thermal flow sensors have been designed, fabricated, and characterized. All bulk material in these devices is silicon so that they are integratable in silicon-based microsystems. To mitigate heat losses and to allow for use of corrosive gases, the heating and sensing thin film titanium/platinum elements, injecting and extracting heat, respectively, from the flow, are placed outside the channel on top of a membrane consisting of alternating layers of stress-balancing silicon dioxide and silicon nitride. For the fabrication, an unconventional bond surface protection method using sputter-deposited aluminum instead of thermal silicon dioxide is used in the process steps prior to silicon fusion bonding. A method for performing lift-off on top of the transparent membrane was also developed. The sensors, measuring 9.5 x 9.5 mm(2), are characterized in calorimetric and time-of-flight modes with nitrogen flow rates between 0 sccm and 300 sccm. The maximum calorimetric sensor flow signal and sensitivity are 0.95 mV and 29 mu V sccm(-1), respectively, with power consumption less than 40 mW. The time-of-flight mode is found to have a wider detectable flow range compared with calorimetric mode, and the time of flight measured indicates a response time of the sensor in the millisecond range. The design and operation of a sensor with high sensitivity and large flow range are discussed. A key element of this discussion is the configuration of the array of heaters and gauges along the channel to obtain different sensitivities and extend the operational range. This means that the sensor can be tailored to different flow ranges.
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