High power ultrasonic application using a multi-mode ultrasonic transducer

近场声悬浮是基于非线性现象的高功率超声应用之一。nal通过悬浮公斤级物体实现非接触式运输。迄今为止，已有各种NFAL研究报道；然而，他们只使用简单的正弦振动波作为悬浮力。在本研究中，我们建议利用各种波形来改善nal性能。为此，设计了一种新型超声换能器，其谐振频率比可精确控制，f3/f1 = 2。使用这种传感器，基本和第二振动模式很容易结合。从实验结果中，我们证实了空气的非线性体积模量对nal有显著的贡献，并利用泊松定律建立了合适的模型。通过计算，明确了形式控制波在高负荷工况下是有效的。

Near-field acoustic levitation (NFAL) is one of the high-power ultrasonic applications that are based on the nonlinear phenomena. The NFAL enables non-contact transportation by levitating kg-order objects. Until now, various NFAL researches had been reported; however they used only the simple sinusoidal vibration wave for a levitation force.In this study, we propose to utilize various wave forms to improve NFAL performances. For this purpose, new designed ultrasonic transducer was fabricated, whose resonant frequencies ratio can be controlled precisely, f3/f1 = 2. Using this transducer, fundamental and second vibration modes are easily combined. From the experimental results, we confirmed the nonlinear bulk modulus of air contributes to NFAL significantly and found the appropriate model using Poisson's law. According to this calculation, it was clarified that the form controlled wave is effective especially in the case of highly-loaded conditions.