A study of optimization for vibration performance and electromagnetic force of the bone conduction speaker actuator asymmetry

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Abstract
This study derives an optimal design of electromagnetic force, verifies the analysis of the optimum, and runs the vibration test to consider various properties of the optimal design in order to optimize the performance of the bone conduction speakers used in Smart Glasses, one of smart wearable devices. For performance factors that affect the electromagnetism of actuator in a bone conduction speaker which holds a magnetic structure, the diaphragm height, yoke pole height, magnet height, magnet and plate width, and coil turn number were selected. To analyze the properties of the performance factors, responsive factors needed to be classified first using fractional factorial design and full factorial design was used for influence analysis. The F-test was done as the means to conduct the valence test to show the independence and reciprocal action for selected performance factors, and it concluded that three independence factors were valid. Based on the valid performance factors, a regression equation to predict its performance was deducted and using the equation, an optimal design to maximize the electromagnetic force performance per component. To verify the characteristics of the optimal model, the finite element method (FEM) was used for analysis. Through electromagnetic analysis, magnetic flux density was obtained, and the particular information along with current and coil length contributed to deriving 0.052 N of electromagnetic force. After completing the frequency response analysis based on the electromagnetic force, it resulted in the 0.0772 mm of displacement at 590.12 Hz of resonant frequency. A sample model was fabricated, followed by vibration testing, after optimal design and analytical verification. Hence, it is verified that the optimal design method and the credibility of the analysis of this study is deemed very high. Furthermore, utilizing this mechanism would inspect the effect of the design parameter performance and increase the credibility and efficiency of a design.

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