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2-Step Drop Impact Analysis of a Miniature Mobile Haptic Actuator Considering High Strain Rate and Damping Effects

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2-Step Drop Impact Analysis of a Miniature Mobile Haptic Actuator Considering High Strain Rate and Damping Effects

Byungjoo Choi et al. Micromachines (Basel).

Abstract

In recent times, the haptic actuators have been providing users with tactile feedback via vibration for a realistic experience. The vibration spring must be designed thin and small to use a haptic actuator in a smart device. Therefore, considerable interests have been exhibited with respect to the impact characteristics of these springs. However, these springs have been difficult to analyze due to their small size. In this study, drop impact experiments and analyses were performed to examine the damages of the mechanical spring in a miniature haptic actuator. Finally, an analytical model with high strain rate and damping effects was constructed to analyze the impact characteristics.

Keywords: 2-step analysis; damping; haptic actuator; high strain rate effect; impact analysis.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A haptic actuator for a smart device.
Figure 2
Figure 2
Stress–strain curve of SUS304 based on strain rate variations.
Figure 3
Figure 3
Stress–strain curve of SUS301 based on strain rate variations.
Figure 4
Figure 4
Drop impact analysis model.
Figure 5
Figure 5
Analysis of the undamped impact force of first-step drop.
Figure 6
Figure 6
Fast Fourier transform (FFT) for residual force vibration (undamped area shown in Figure 5) in the frequency domain.
Figure 7
Figure 7
Damped impact force of the first-step drop-test and analysis.
Figure 8
Figure 8
Plastic strain of the dummy after (a) the impact test and (b) analysis.
Figure 9
Figure 9
Velocity profile of haptic attachment surface to dummy in first-step analysis.
Figure 10
Figure 10
Y-displacement of the spring with and without damping in the second-step analysis.
Figure 11
Figure 11
FFT for residual vibration (residual vibration area from Figure 9) in the frequency domain.
Figure 12
Figure 12
Effective stress of haptic spring at the moment of impact.
Figure 13
Figure 13
Effective plastic strain of haptic spring at steady state after impact (with number of elements).
Figure 14
Figure 14
Effective plastic strain of the damage area (with the number of elements shown in Figure 10).
Figure 15
Figure 15
Comparison of the vibration acceleration of the haptic actuator before and after the drop impact tests (a) No. 1 specimen (b) No. 2 specimen.

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