Dynamic resonant frequency control system of ultrasonic transducer for non-sinusoidal waveform excitation
Dynamic resonant frequency control system of ultrasonic transducer for non-sinusoidal waveform excitation
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DOI：
10.1016/j.sna.2021.113124
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
Satori Hachisuka;Hiroki Yokozawa;Fangyi Wang;Susumu Miyake;J. Twiefel;Takeshi Morita
中科院分区：
文献类型：
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作者：
Satori Hachisuka;Hiroki Yokozawa;Fangyi Wang;Susumu Miyake;J. Twiefel;Takeshi Morita
本研究验证了换能器动态谐振频率控制系统的有效性。该系统使得换能器的谐振频率能够匹配驱动频率。通常，超声换能器的谐振频率基于其设计和材料特性而固定。因此，在驱动换能器时难以主动控制频率。然而，对于大功率压电致动器，重要的是将纵向振动的基本谐振频率和高阶谐振频率的比率精确地控制在1：2。高功率和高机械品质因数（高Q）超声换能器需要精确控制其谐振频率。然而，在驱动超声换能器时，谐振频率可能由于边界条件的变化或压电振动中的非线性现象而偏移。为了使超声换能器的谐振频率比保持在1：2，我们提出动态地控制谐振频率比恒定。在本研究中，我们提出了两个主要的建议，我们的动态谐振频率控制系统。一种是变频器的阶梯式结构，另一种是全自动控制。在阶梯结构中，朗之万换能器被设计成在初始条件下对于第一和第三纵模具有几乎1：2的谐振频率比。此外，这种结构可以实现对换能器的两个谐振频率中的仅一个的控制。在全自动控制系统中，引入压电元件对谐振频率比进行精确控制。为此，通过连接到超声换能器的MOSFET来切换这些压电元件的电边界条件，并通过我们的反馈系统自动控制其最佳占空比。该系统实现了谐振频率的动态控制。结果，换能器的谐振频率在从23.23 kHz到23.93 kHz的频带中与驱动频率匹配。还确认了可以通过使用谐振频率控制来控制激励的非正弦波形的形状。
This study verifies the effectiveness of a dynamic resonant frequency control system for transducers. This system enables the resonant frequency of the transducer to match the driving frequency. In general, the resonant frequency of an ultrasonic transducer is fixed based on its design and material properties. Therefore, it is difficult to actively control the frequency when driving the transducer. However, for high-power piezoelectric actuators, it is important to control the ratio of the fundamental and higher-order resonant frequency of the longitudinal vibration precisely at 1:2. A high-power and high mechanical quality factor (high-Q) ultrasonic transducer requires precise control of its resonant frequency. However, the resonant frequency may shift due to changes in boundary conditions or non-linear phenomena in piezoelectric vibration while driving the ultrasonic transducer. To maintain the resonant frequency ratio of the ultrasonic transducer at 1:2, we propose to dynamically control the resonant frequency ratio constant. In this study, we made two main proposals to our dynamic resonant frequency control system. One is the stepped structure of the transducer, and the other is the completely automatic control. In the stepped structure, a Langevin transducer was designed to have a resonant frequency ratio of almost 1:2 for the first and third longitudinal mode in the initial condition. Additionally, this structure could achieve control of only one of two resonant frequencies of the transducer. For the utterly automatic control system, piezoelectric elements were introduced for controlling the resonant frequency ratio precisely. For this propose, switching the electrical boundary conditions of these piezoelectric elements was carried out by MOSFETs connected to the ultrasonic transducer and control its optimum duty ratio automatically by our feedback system. This system realized dynamic control of the resonant frequency. As a result, the resonant frequency of the transducer matched the driving frequency in the frequency band from 23.23 kHz to 23.93 kHz. It was also confirmed that the shape of the excited non-sinusoidal waveform could be controlled by using resonant frequency control.