Design and Simulation of a MEMS High G Inertial Impact Sensor

1. Design and Simulation of a MEMSHigh G Inertial Impact Sensor Y.P. Wang1, R.Q. Hsu1, C.W. Wu2 1Department of Mechanical Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, 300 Hsinchu, Taiwan Phone: +886-3-5712121 Ext.31934, Email: anitawu.wlh@msa.hinet.net 2Department of Mechanical and Mechatronic Engineering, National Taiwan Ocean University 2, Pei-Ning Road, Keelung, Taiwan. Speaker: Jing-Wen Shih

2. Outline • Introduction • The major goal of Inertial impact sensor • The micro impact sensor proposed in this study • Simulation • Conclusion • Reference

3. Introduction • Inertial sensors have been extensively utilized in science like inertial navigation systems and airbag triggers . • For high G(>300G) applications. Reaction times for conventional mechanical type impact sensors are not fast enough.

4. The major goal of inertial impact sensor • Designing an impact sensor that has a faster reaction time than conventional sensors and a mechanism that is sufficiently robust to survive the impact when a vehicle collides with a hard target is the major goal of this study.

5. Conventional inertial impact sensor • (a)cantilever beam type • (b)axial spring type

6. MDS System trigger • MDS: Mass- Damper- Spring Dynamic

7. Proof mass expressed by dynamic equation lamped system:

8. Use Laplace transformation to the second –order function for acceleration mass:

9. The micro impact sensor proposed in this study

10. To evaluate system reaction time, 4 different arrangements of spring and proof mass were tested.

11. The proof mass scale and coil number of the sensor

12. Simulation • Displacement versus applied forces for each sensor

13. The response time of the micro-sensor

14. Proof mass increases from 0.62 to 1.0, and thespring constant remains unchanged, the reaction time isdecreased.

15. Minimum G values for the sensors to be triggered

16. Reducing the spring constant, and retaining the proof mass, the reaction time decreased and the trigger G value decreased for sensors

17. Minimum G values for the sensors to be triggered

18. The plastic strain of the type 1 sensor in 21000G • With no significant interference in the x and z axis; consequently,sensor stability is very good.

19. Conclusion • This proposed impact sensor is intended for use at 8,000–21,000G. Four different designs were analyzed. • The impact sensors were sufficiently robust to survive the impact of at least 21,000G, four times higher than that of conventional inertial impact sensors.

20. References • F. Goodeough, Airbag boom when IC accelerometer sees 50 G,Electronics Design, pp.45-56, August. 8, 1991. • Tadao Matsunaga, Masayoshi Esashi, Acceleration switch with extended holding time using squeeze film effect for side airbag systems, Sensors and Actuators A：physical, vol. 100, Issue 1, pp.10-17 , August. 2002. • Military Standard, Mechanical Shock Test, MIL-STD-883E Method 2002.4, US Dept. of Defense, 2004. • Donald R. Ask eland, The science and engineering of materials, 1st edn,Taipei, Kai Fa, 1985, ch. 6, pp. 126-127. • Trimmer, W.S.N, Microrobots and Micromechanical Systems, Sensors and Actuators vol.19 no.3, pp. 267-287, 1989. • M. Elwenspoek, R. Wiegerink, Mechanical Microsensors, Germany,Springer, 2001. • Tai-Ran Hsu, MEMS & Microsystems Design and Manufacture,international edition 2002, Singapore, McGraw-Hill, pp. 157-159.

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