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Daeban Seo,Yongdae Kim,Sejin Kwon IEEE 2014 IEEE Sensors Journal Vol. No.
<P>A micro shear-stress sensor (MiSS) for real-time detection of flow separation in unmanned aerial vehicles was presented. The direct method was selected for the MiSS, and movement of its floating element was measured using a simple and highly reliable piezoresistive scheme. To realize the MiSS, a polysilicon strain gauge of the piezoresistor type with a very low temperature coefficient of resistivity (TCR) and high gauge factor was first developed. These two characteristics were adjusted by varying the boron concentration during fabrication. The strain gauge was also designed to evaluate the effect of size (width) on these characteristics. The TCR was almost zero and the gauge factor was 32 at a boron concentration of 1.5×10<SUP>19</SUP> cm<SUP>-3</SUP>. The characteristics were unaffected by its width (in the tens of micrometer range). The MiSS was designed and fabricated using the developed polysilicon strain gauge, and its performance was evaluated using a NACA0012 airfoil section in a wind tunnel. At a 0 <SUP>°</SUP> angle of attack (AOA), the resistance of MiSS increased with the flow. At a 20 <SUP>°</SUP> AOA, the resistance did not change owing to detachment of the flow caused by separation. In the real-time separation detection test, the resistance of MiSS decreased as soon as separation occurred. Hence, the separation detection ability of the developed MiSS using a polysilicon strain gauge was verified.</P>
Seo, Daeban,Kim, Yongdae,Kwon, Sejin IEEE Sensors Council 2014 IEEE SENSORS JOURNAL Vol.14 No.4
A micro shear-stress sensor (MiSS) for real-time detection of flow separation in unmanned aerial vehicles was presented. The direct method was selected for the MiSS, and movement of its floating element was measured using a simple and highly reliable piezoresistive scheme. To realize the MiSS, a polysilicon strain gauge of the piezoresistor type with a very low temperature coefficient of resistivity (TCR) and high gauge factor was first developed. These two characteristics were adjusted by varying the boron concentration during fabrication. The strain gauge was also designed to evaluate the effect of size (width) on these characteristics. The TCR was almost zero and the gauge factor was 32 at a boron concentration of 1.5 x 10(19) cm(-3). The characteristics were unaffected by its width (in the tens of micrometer range). The MiSS was designed and fabricated using the developed polysilicon strain gauge, and its performance was evaluated using a NACA0012 airfoil section in a wind tunnel. At a 0 degrees angle of attack (AOA), the resistance of MiSS increased with the flow. At a 20 degrees AOA, the resistance did not change owing to detachment of the flow caused by separation. In the real-time separation detection test, the resistance of MiSS decreased as soon as separation occurred. Hence, the separation detection ability of the developed MiSS using a polysilicon strain gauge was verified.
A MEMS glass membrane igniter for improved ignition delay and reproducibility
Seo, Daeban,Jeong, Juyoung,Kim, Taekyu,Lee, Jongkwang Elsevier Sequoia 2017 Sensors and actuators. A Physical Vol.258 No.-
<P><B>Abstract</B></P> <P>A MEMS igniter with improved ignition characteristics and reproducibility is described. A glass wafer was selected as the igniter material for high membrane structural stability. To improve the reproducibility of the igniter, the membrane was designed to realize a flat surface and uniform thickness, which are essential factors for reproducibility. A heater is designed at the under surface of the membrane for direct contact with the propellant. It was expected that this would improve ignition delay compared with the previous glass-ceramic membrane igniter. Numerical simulations are performed to predict and compare ignition characteristics. The designed glass membrane igniter is realized as an array-type using a MEMS fabrication process with a glass wafer. Performance evaluation of the fabricated igniter is conducted through a firing test. At the cubesat’s operational voltage of 15V, the measured ignition delay was 17.1ms, which is almost the same as the numerical simulation result. Additionally, this result is 34.45% shorter than the measured ignition delay of the previous glass ceramic membrane igniter. The reproducibility is evaluated by consecutively igniting five igniters at 15V. The calculated average ignition delay and its coefficient of variation are 17.08ms and 12%, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study describes a MEMS igniter for improved ignition characteristics with high structural stability and a uniform membrane thickness. </LI> <LI> A glass membrane which had a flat surface and uniform thickness was selected as the igniter material for high membrane structural stability. </LI> <LI> Numerical simulations were performed to predict and compare ignition characteristics. </LI> <LI> The designed glass membrane igniter was realized as an array-type using a MEMS fabrication process with a glass wafer. </LI> <LI> The measured average ignition delay and ignition energy were 17.08ms and 25.6mJ, respectively. </LI> </UL> </P>