不同激励方式对矩形声场均匀性的影响

发布时间：2017-12-28 17:14

本文关键词：不同激励方式对矩形声场均匀性的影响　出处：《陕西师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：大功率超声设备一般由超声波发生器和超声波换能器两部分组成。由信号发生器产生特定频率的信号激励换能系统,使系统保持在谐振状态下工作。在大功率超声的各类应用中,声场的分布情况对应用效果的影响起着重要的作用。本文根据声波叠加原理和波动声学理论,利用声波的不相干性和扩散声场的特点设计出一种频率连续变化的窄带多频合成信号激励相应换能系统工作,并结合实验研究对比分析了不同激励方式下矩形声场的分布情况。具体工作包括以下几个方面：1根据波动声学理论和声波叠加原理分析了单频声波和多频不相干声波在矩形空间的分布情况。研究表明：多频下的声场是由单频大量的简正振动方式叠加与多频不相干声波叠加而成的,且频率越高,简正振动方式越多,声场越均匀。2根据白噪声信号在固定频带宽度时频谱连续且均匀的特点,设计出经带通滤波器滤波之后的白噪声信号作为多振子换能系统的激励信号,可以满足系统保持长期稳定工作的需求。本文采用Matlab软件编程生成信号,并经过第三方软件UltraWave将信号引入函数发生器,实现信号的分析。结果发现：白噪声信号经滤波之后幅值很低,不能驱动相应换能系统工作。进一步提出并确定等幅正弦叠加的多频合成信号作为系统的激励信号。3将矩形超声换能系统的谐振特性分别在小信号模式和大信号模式下进行测量与分析,以便对合成信号的带宽进行准确设计。研究发现：两种激励方式下系统的谐振特性是不同的,主要表现在：两种方式下系统的谐振带宽均随着频率的增加而加宽；系统在大信号激励方式下谐振频率fs和谐振带宽△fs整体偏大。根据大功率超声换能系统实际工作需要,确定依据大信号激励方式下的谐振频率和谐振带宽作为合成信号参数设计的标准。4基于大信号方式下测得的谐振带宽△fs,对信号分别在带宽△f△fs、Δf=Δfs、ΔfΔfs进行合成信号设计,结合系统工作时的电参数和染色法声场分布与正弦信号激励下的情况进行对比分析。结果表明：合成信号带宽范围设计在△f△fs时,系统整体的性能较好,且在高频系统中更为稳定；电参数下的有功功率和电效率相比正弦信号呈现出稍微降低的趋势,且在低频信号表现更为明显,但声场的均匀性都得到一定的改善。而在△f≥△fs,不论是电参数还是声场均匀性方面,效果均不如△f△fs信号的情况。综合分析指出合成信号的最佳带宽选取在谐振带宽一般时,即△f=△fs/2,系统的各方面性能最好。5测试信号分别选取正弦信号和最佳带宽的合成信号激励矩形换能系统,并通过铜版纸染色法和水听器声压测量法对矩形槽内的声场进行了测量与分析。实验结果表明：在声场均匀性方面,高频声场优于低频声场,合成信号优于正弦信号。声压测点的平均效果表现为合成信号声压相对值大于对应位点正弦信号声压相对值,间接地说明了合成信号的电声转化效率要高于正弦信号。
[Abstract]:The high power ultrasonic equipment is usually composed of two parts: ultrasonic generator and ultrasonic transducer. A signal generator is generated by a signal generator to stimulate the energy exchange system to keep the system working in a resonant state. In the various applications of high power ultrasound, the distribution of sound field plays an important role in the effect of the application. According to the principle of superposition and acoustic wave acoustics theory, the coherence and diffuse field acoustic features designed to change a narrow-band continuous frequency multi frequency synthesis signal excitation corresponding transducer system, and combined with the experimental study on comparative analysis of the distribution of rectangular field under different seismic excitations. The specific work includes the following aspects: 1. According to the wave acoustic theory and the superposition principle, the distribution of single frequency and multi frequency incoherent sound waves in rectangular space is analyzed. The research shows that the sound field at multiple frequencies is superimposed by a large number of single mode normal mode superposition and multiple frequency uncorrelated sound waves, and the higher the frequency, the more the normal mode of vibration is, the more uniform the sound field is. 2, according to the continuous and uniform spectrum of white noise signal in fixed band width, we design a white noise signal filtered by bandpass filter as the excitation signal of multi oscillator energy conversion system, which can meet the needs of long-term stable work of the system. In this paper, the signal is generated by Matlab software programming, and the signal is analyzed by introducing the signal into a function generator through third party software UltraWave. The results show that the amplitude of the white noise signal is very low after filtering, and it can not drive the work of the corresponding energy exchange system. The multi frequency synthetic signal with equal amplitude sinusoidal superposition is further proposed and determined as the excitation signal of the system. 3, the resonant characteristics of the rectangular ultrasonic energy conversion system are measured and analyzed under small signal mode and large signal mode respectively, so as to accurately design the bandwidth of the synthetic signal. The study found that: the resonant characteristics of two kinds of incentive modes of system is different, mainly in two ways: the resonant bandwidth system was widened with the increase of frequency; large signal excitation system in the resonant frequency of FS resonant FS overall larger bandwidth. According to the actual working needs of the high-power ultrasonic energy conversion system, we must determine the resonance frequency and the vibration bandwidth according to the large signal excitation mode as the design criteria of the synthetic signal parameters. 4 based on the mode of large signal measurement of the resonant bandwidth FS, the signal which are synthesized signal design in bandwidth delta f delta FS, Delta f=, delta FS, delta f delta FS, combined with the electrical parameters and dyeing method and field distribution of sine signal excitation system is working under the condition of comparative analysis. The results show that the synthetic signal bandwidth design in delta f delta FS, the overall system performance is better, and in the high frequency system is more stable; electrical parameters of the active power and power efficiency compared to the sinusoidal signal shows a slightly decreasing trend, and the performance in the low frequency signal is more obvious, but the uniformity of sound field to get some improvement. In the delta f delta FS, whether electric parameters or acoustic field uniformity, the effects are not the delta f delta FS signal. Comprehensive analysis points out that the optimum synthetic bandwidth signal selection in resonant bandwidth, namely Delta f= Delta fs/2, the best performance of the system. 5, the test signal selects the sinusoidal signal and the best bandwidth synthetic signal excitation rectangle energy conversion system respectively, and the sound field in the rectangular groove is measured and analyzed by the method of the coated paper stain and the hydrophone's sound pressure measurement. The experimental results show that the high frequency sound field is superior to the low frequency sound field in the field uniformity, and the synthetic signal is better than the sinusoidal signal. The average effect of sound pressure measurement points is that the relative value of synthetic signal pressure is greater than that of corresponding location sinusoidal signal, which indirectly indicates that the efficiency of synthetic signal's electroacoustic conversion is higher than that of sinusoidal signal.
【学位授予单位】：陕西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB55

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