Abstract
Squeeze-film damping and acceleration load are two major issues in the design of inertial micro-switches. In order to deeply and systematically study these two issues, this paper proposes a typical vertically-driven inertial micro-switch, wherein the air and electrode gaps were chosen to design the required damping ratio and threshold value, respectively. The switch was modeled by ANSYS Workbench, and the simulation program was optimized for computational accuracy and speed. Transient analysis was employed to investigate the relationship between the damping ratio, acceleration load, and the natural frequency, and the dynamic properties (including contact bounce, contact time, response time, and threshold acceleration) of the switch. The results can be used as a guide in the design of inertial micro-switches to meet various application requirements. For example, increasing the damping ratio can prolong the contact time of the switch activated by short acceleration duration or reduce the contact bounce of the switch activated by long acceleration duration; the threshold value is immune to variations in the damping effect and acceleration duration when the switch is quasi-statically operated; the anti-jamming capability of the switch can be improved by designing the sensing frequency of the switch to be higher than the acceleration duration but much lower than the other order frequencies of the switch.
Highlights
As a typical inertial device for acceleration sensing, the inertial switch has been extensively investigated over the last several decades
We propose an inertial micro-switch of typical vertically-driven structure, wherein the required damping ratio and threshold value can be separately determined by the air and electrode gaps, facilitating the single factor comparison of different dynamic responses of the switch under various damping ratios and acceleration loads
The explanation of the results is as follows: the rebound motion of the proof mass is constrained by the squeeze-film damping, and the protrusion can be held near the substrate under the continuous action of the acceleration
Summary
As a typical inertial device for acceleration sensing, the inertial switch has been extensively investigated over the last several decades. Younis et al [9] indicated that the squeeze-film damping effect becomes a major factor when the switch is excited dynamically, while the effect is significantly weakened in the case of quasi-static impact load. Dehkordi et al [11] adjusted the squeeze-film damping effect to reduce the response delay of the switch and to increase the contact time Another important factor influencing the dynamics of the inertial micro-switch is the applied acceleration load, mainly including the amplitude and duration (pulse width). Transient analysis of ANSYS Workbench is employed to investigate the relationship between the damping ratio, acceleration load, and the natural frequency, and the dynamic properties (including contact bounce, contact time, response time, and threshold acceleration) of the switch. The results can provide guidance for future research into the design of inertial micro-switches
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