Procedia

Engineering Procedia Engineering 00 (2009) 000 000

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Proc. Eurosensors XXIV, September 5-8, 2010, Linz, Austria

Experimental Research on Temperature Characteristics of Two-Dimensional Micro Scanner

Chi Zhang, Hu Huang, Zheng You State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments and Mechanology, Tsinghua

University, Beijing, China

Abstract

Two-dimensional micro scanner which used for space laser detection is affected by the space environment. The scanning and piezoresistive measuring performances of the two-dimensional micro scanner are affected by the temperature change. In order to test the space temperature adaptability, the temperature characteristics of scanning and piezoresistive measuring performances are researched in this paper. According to the temperature change in space, the temprature effects on the scanning and piezoresistive measuring performances are measured in the range of -20 to 80 . The experimental results indicate that there are minor change in the two resonant frequencies and always linear relationships of the piezoresistive measuring results. The reasons of the effects on measuring sensitivity and linearity are analyzed and the optimal temperature range is presented. Through the temperature adaptation experiments, a basis of the temperature compensation and space application of the two-dimensional micro scanner is provided. © 2009 Published by Elsevier Ltd. Keywords: micro scanner, temperature characteristic, space environment

1. Introduction

Two-dimensional micro scanner, which used for space laser detection, is affected by the space environment with large temperature changes [1]. The scanning and piezoresistive measuring performances of the two-dimensional micro scanner are affected by the temperature change. In order to test the space temperature adaptability, the temperature characteristics of scanning and piezoresistive measuring performances are researched in this paper, which can provide experimental evidence for space application and temperature compensation of the two-dimensional micro scanner.

2. Two-Dimensional Micro Scanner

2.1. Prototype

c© 2010 Published by Elsevier Ltd.

Procedia Engineering 5 (2010) 568–571

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1877-7058 c© 2010 Published by Elsevier Ltd.doi:10.1016/j.proeng.2010.09.173

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The two-dimensional micro scanner with piezoresistors is shown in Fig.1, which is packaged in a stainless steel case with the size of 28 mm × 20 mm × 18 mm. It has two resonance vibration modes of twisting and bending, which is also has two piezoresistive Weatstone bridges for measuring deflection angles in both modes [2].

Fig. 1. Photograph of two-dimensional micro scanner with piezoresistors

2.2. Characteristics

The scanning amplitude frequency responses of the two modes in room temperature are shown in Fig.2. The two resonance frequencies of the two-dimensional micro scanner are measured by the frequency sweeping method and the scanning amplitude is detected by a laser interferometer measurement system. The results indicate that the resonance frequencies are 216.8 Hz and 464.8 Hz, respectively.

The piezoresistive Wheatstone bridge characteristics of the two modes in room temperature are shown in Fig.3. The deflection angles of the two-dimensional micro scanner are measured by the piezoresistors detection circuits and the piezoresistor characteristics are indicated by the output voltages of the two Wheatstone bridges. There are linear relationships between each piezoresistor output voltage and each deflection angle [3]. The deflection angles measurement sensitivities for two directions are 59 mV/deg and 30 mV/deg, respectively.

(a) (b)

Fig. 2. (a) Scanning amplitude frequency responses of two modes in room temperature; (b) Piezoresistive Wheatstone bridge characteristics of two modes in room temperature

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3. Temperature Characteristics

3.1. Experimental Method

In order to adequately simulate the space temperature condition [4,5], the experiment is achieved in the dry temperature chamber with the range of -20 to 80 and the interval of 5 . The two resonant frequencies and two piezoresistive Weatstone bridges characteristics are repeatedly measured in each temperature point.

3.2. Resonant frequencies

The two resonant frequencies are measured by a frequency sweeping method and the temperature characteristics are shown in Fig.3. The experimental results indicate that two resonant frequencies slowly decreased with a rise of temperature. The resonant frequency of twisting mode ranges from 219Hz to 215Hz, while the other one of bending mode ranges from 468Hz to 460Hz.

The main reason is that the resonant frequency is related to the length of the flexible beam and Young's modulus. The thermal expansion of the silicon beam and the temperature dependence of Young's modulus cause the decrease. However, the minor change in the two resonant frequencies has litter effect on the scanning characteristics.

Fig. 3. Temperature characteristics of two resonant frequencies

3.3. Piezoresistive measuring performances

In the temprature range, the piezoresistors have a good stress sensing performance. There are always linear relationships between Weatstone bridge output and actuation displacement. As shown in Fig.4 and Fig.5, the piezoresistive Wheatstone bridge sensitivity ranges from 116mV/µm to 157mV/µm and the measuring linearity ranges from 2.0% to 4.1% in the twisting mode. While in the bending mode, the piezoresistive Wheatstone bridge sensitivity ranges from 48mV/µm to 104mV/µm and the measuring linearity ranges from 0.9% to 6.3%. The experimental results indicate that temperature change has a very significant and irregular effect on the piezoresistive measuring performances.

The measuring sensitivities caused by temperature changes may be due to many factors. The temperature dependence of piezoresistive coefficient, thermal expansion of micro-structure and temperature dependence of Young's modulus can lead to decreased measurement sensitivities [6,7]. However, the measurement sensitivity increases may be due to the ideal gas equation of state in the constant pressure. The temperature increase causes the gas density decreased, the number of molecules reduced and the damping coefficient decreased, which cause the measurement sensitivity increased [8]. Therefore, these reasons lead to the nonuniform temperature dependences of piezoresistance measuring sensitivities.

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(a) (b)

Fig. 4. (a) Temperature characteristics of two piezoresistive Wheatstone bridge sensitivities; (b) Temperature characteristics of two piezoresistive Wheatstone bridge linearities

4. Conclusion

The space temperature adaptability of the two-dimensional micro scanner is tested and the temperature characteristics of scanning and piezoresistive measuring performances are presented in this paper. The experimental results indicate that in the range of 10 to 30 , the two-dimensional micro scanner has two steady resonant frequencies, smooth piezoresistive measuring sensitivities and better linearities which are less than 0.9% and 6.3%, respectively. Therefore, the range of 10 to 30 is the optimal temperature range for space application.

References

[1] H. Daniel, G. Henry. Spacecraft-Environment Interactions. Cambridge, UK: Cambridge University Press, 2004. [2] C. Zhang, G. F. Zhang, Z. You. A two-dimensional micro scanner integrated with a piezoelectric actuator and piezoresistors. Sensors, 2009,

9(1):631-644. [3] C. Zhang, G. F. Zhang, Z. You. Piezoresistor design for deflection angles decoupling measurement of two-dimensional MOEMS scanning

mirror. Proc. of the 7th IEEE International Conference on Nanotechnology, Hong Kong, China, 2007: 150-153. [4] B. C. Huang, Y. L. Ma. Spacecraft Environmental Testing Technology. Beijing, China: National Defence Industry Press, 2002. [5] Z. You, S. J. Shi, Y. Lin. Remote sensing system for nanosatellite with CMOS imaging sensor. Journal of Tsinghua University (Sci & Tech),

2004, 44(8):1047-1050. [6] B. A. Nelsona, W. P. Kingb. Temperature calibration of heated silicon atomic force microscope cantilevers. Sensors and Actuators A:

Physical, 2007, 140(1): 51-59. [7] Y. N. Li, J. Zhao, T. Guo, Y. Li, X. Fang, X. Fu, X. T. Hu. Resonant Drift of Microcantilever Caused by Temperature Variation. Journal of

Tianjin University, 2008, 41(1):7-10. [8] K. Yum, Z. Wang, A. P. Suryavanshi, M. F. Yu. Experimental measurement and model analysis of damping effect in nanoscale mechanical

beam resonators in air. Journal of Applied Physics, 2004, 96: 3933.

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