High power ultrasonic application using a multi-mode ultrasonic transducer

近场声悬浮是一种基于非线性现象的高功率超声应用。NFAL通过悬浮千克级物体实现非接触式运输。到目前为止，各种NFAL的研究已被报道，但他们只使用简单的正弦振动波的悬浮力。在这项研究中，我们建议利用各种波形，以提高NFAL的性能。为此，研制了一种谐振频率比可精确控制的超声换能器，其谐振频率比f3/f1 = 2。使用这种传感器，基本和第二振动模式很容易组合。从实验结果中，我们证实了空气的非线性体积模量对NFAL的贡献显着，并找到了合适的模型，使用泊松定律。根据该计算，可以清楚地看出，形状控制波是有效的，特别是在高负载条件下。

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.