A Novel Threshold Accelerometer With Postbuckling Structures for Airbag Restraint Systems

Zhao, Jian; Jia, Jianyuan; Wang, Hongxi; Li, Wanli

doi:10.1109/jsen.2007.897936

Cited by 70 publications

(25 citation statements)

References 21 publications

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“…This is perhaps since these structures represent the simplest architectures employed in demonstrating a wide spectrum of complex phenomena typically exhibited in bistable devices. In addition to a small footprint of this device and a possibility of dimensional downscaling to the nanoscale regime, these devices provide attractive platforms in applications spanning non-volatile memory [17][18][19][20], switches [8] and sensors [21,22], wherein the use of other designs is precluded.…”

Section: Introductionmentioning

confidence: 99%

Bistability of curved microbeams actuated by fringing electrostatic fields

2011

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In this work we investigate the feasibility of two-directional switching of an initially curved or pre-buckled electrostatically actuated microbeams using a single electrode fabricated from the same structural layer. The distributed electrostatic force, which is engendered by the asymmetry of the fringing fields in the deformed state, acts in the direction opposite to the deflection of the beam and can be effectively viewed as a reaction of a nonlinear elastic foundation with stiffness parameterized by the voltage. The reduced order model was built using the Galerkin decomposition with linear undamped modes of a straight beam as base functions and verified using the results of the numerical solution of the differential equation. The electrostatic force was approximated by means of fitting the results of three-dimensional numerical solution of the electrostatic problem. Static stability analysis reveals that the presence of the restoring electrostatic force may result in the suppression of the snapthrough instability as well as in the appearance of additional stable configurations associated with higher buckling modes of the beam that are not observed in "mechanically" loaded structures. We show that two-directional switching of a pre-buckled beam between two stable configurations cannot be achieved using quasistatic loading. Furthermore, we show that switching is both associated with the dynamic snapthrough mechanism and possible within certain interval of actuation voltages. Using a single-degree-offreedom (lumped) model, estimation voltage boundaries are obtained. Theoretical results illustrate the feasibility of the suggested operational principle as an efficient mechanism in the arena of non-volatile mechanical memory devices.

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Section: Introductionmentioning

confidence: 99%

Bistability of curved microbeams actuated by fringing electrostatic fields

2011

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“…Taking the automotive airbag system as an example, merely an inertial micro-switch can achieve the same function as the complex system composed of three components: an accelerometer monitoring the car's acceleration, a decision/controller unit processing the acceleration signal, and a switch to fire the airbag when the acceleration exceeds a certain threshold due to impact (Younis et al 2007). What's better, the use of the inertial switch can eliminate the risk of mis-operation by an electromagnetic noise (Tadao and Masayoshi 2002;Zhao et al 2007). …”

Section: Introductionmentioning

confidence: 99%

Dynamic simulation of a contact-enhanced MEMS inertial switch in Simulink®

et al. 2011

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A novel contact-enhanced design of MEMS (micro-electro-mechanical system) inertial switch was proposed and modeled in Simulink Ò . The contact effect is improved by an easily realized modification on the traditional design, i.e. introducing a movable contact point between the movable electrode (proof mass) and the stationary electrode, therefore forming a dual mass-spring system. The focus of this paper is limited to a vertically driven unidirectional one for the purposes of demonstration, but this design concept and Simulink Ò model is universal for various kinds of inertial micro-switches. The dynamic simulation confirmed the contact-enhancing mechanism, showing that the switch-on time can be prolonged for the dynamic shock acceleration and the bouncing effect can be reduced for the quasi-static acceleration. The threshold acceleration of the inertial switch is determined by the proof mass-spring system's natural frequency. Since the inertial switches were fabricated by the multilayer electroplating technology, the proof mass thickness were assigned two values, 100 and 50 lm, in order to get threshold levels of 56 and 133 g respectively for the dynamic acceleration of half-sine wave with 1 ms duration. Other factors that influence the dynamic response, such as the squeeze film damping and the contact point-spring system's natural frequency were also discussed. The fabricated devices were characterized by the drop hammer experiment, and the results were in agreement with the simulation predictions. The switch-on time was prolonged to over 50 ls from the traditional design's 10 ls, and could reach as long as 120 ls. Finally, alternative device configurations of the contact-enhancing mechanism were presented, including a laterally driven bidirectional inertial switch and a multidirectional one.

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“…The relation between the two relative coordinates can be expressed as . Based on the magnetic-charge model [32], [33] and the superposition principle of magnetic force, the total magnetic force applied by the two fixed magnets in the direction can be obtained as (2) where is the number of the fixed magnets, the distance between the two interactive magnets, and the magnetic permeability. The intermediate variables appearing in (3) are given at the bottom of the page.…”

Section: Bistable Permanent Magnetic Structurementioning

confidence: 99%

A Novel Magnetic Actuated Bistable Acceleration Switch With Low Contact Resistance

et al. 2010

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A novel unsymmetrical bistable mechanism with a parallel beam and three magnets arranged in the three-dimensional space is proposed, and the combined effect of the magnetic force and the mechanical force on the bistability of such a structure is analyzed based on the magnetic-charge model and the material mechanics theory. By employing the nonlinear combined force during the snap-through procedure to enhance the contact force, a novel fast response threshold acceleration switch with low contact resistance is designed and fabricated, which consists mainly of an inertial mass supported by two parallel elastic beams, one metal contact point, and three permanent magnets with one imbedded in the inertial mass and the other two fixed in the case along the vertical direction. The dynamic design model subjected to different shock pulses is proposed to optimize the design process, and the effect of the pulse shapes on the switch's sensing threshold and response time is investigated, and the simulation results show that the acceleration switch is closed in less than 9.0 ms after being triggered by the rectangular shock pulse of amplitude of 50.0 g, and also, the contact force is greater than 0.5 N, which can reduce the contact resistance to an acceptable value and guarantee the contact reliability.According to the working principle of the acceleration switch, a series of test benches are established to test the static and dynamic performance of the switch. The contact resistance is less than 1.9 with a minimum resistance only 0.5 . The average threshold acceleration of the switch sample is 51.4 g with only 2.8% deviation from the design value of 50.0 g. Both the dynamic simulation results and experiments validate the feasibility of introducing permanent magnetic actuated bistable structures in designing the threshold acceleration switch.

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A Novel Threshold Accelerometer With Postbuckling Structures for Airbag Restraint Systems

Cited by 70 publications

References 21 publications

Bistability of curved microbeams actuated by fringing electrostatic fields

Bistability of curved microbeams actuated by fringing electrostatic fields

Dynamic simulation of a contact-enhanced MEMS inertial switch in Simulink®

A Novel Magnetic Actuated Bistable Acceleration Switch With Low Contact Resistance

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