Research On Simulation And Optimization Design Of Broadband Longitudinal Transducer

With the further development of underwater detection technology,stricter and newer requirements for the performance of underwater acoustic transducers have been put forward.Pony-size,high power and medium-high frequency performances have become new development trends.For widely used longitudinal vibration transducer,how to further obtain wider bandwidth and higher transimission voltage response(TVR)is two of the major sticking points in underwater acoustic transducer research field.This paper mainly take the longitudinal vibration broadband transducer as a research subject combing of the equivalent circuit method and the finite element method(FEM).By adjusting the size of structure,changing the excitation mode and importing the external circuit of the device,the use of longitudinal vibration mode,head mass bending mode,radial vibration mode of the piezoelectric stacks and their couplings,thus achieving broadening the bandwidth.of frequency.Firstly,by deducing the equivalent circuit method of the longitudinal vibration transducer,it is used to analyze admittance curve of double-excited wideband transducer,and calculate the resonant frequency of the transducer.Then,the size of structure of the transducer is initially determined.Based on this,the FEM model of the transducer is established,and ANSYS software is used to analyze the modal and harmonic analysis of the transducer.The multi-resonant frequency and the TVR of the transducer are obtained.The results show that it can be within frequency range 22~49kHz which does not exceed ±2.7dB with peak TVR of 143.3dB,however,it is found that there is a deep valley between high frequencies above 55 kHz,the TVR produced a deep valley in TVR curve,and the fluctuation was too large to meet the practical application.On this basis,FEM is used to optimize the structural model of the transducer,thus studying the the effects of structure parameters,series resistance and excitation mode on the electroacoustic characteristics of the transducer.The change of structure size has a influence on the TVR of the double-excited longitudinal vibration transducer within frequency range 24.0-55.5kHz which does not exceed ±3.4dB with peak TVR of 143.9dB,but the change of excitation mode has a significant impact on the TVR in high frequency band,which slows the downward trend of TVR compared with same-phase condition,thus further expanding the bandwidth of the transducer.The TVR is within frequency range 28-99 kHz which does not exceed ±7.5dB with peak TVR of 148.2dB.Finally,a one-side exciting broadband transducer sample is fabricated according to the theoretical design later,impedance characteristic,the TVR and the directivity are also measured.The anechoic pool experiment shows that the sample is observed within frequency range 25-61 kHz with peak TVR 148 dB,and the fluctuation within the frequency range is less than ±6dB.In summary,the means of reverse excitation of the front stack of the longitudinal vibration transducer can solve the problem of deep valleys between the high resonant frequencies,thus effectively expanding the bandwidth,and optimizing the structural size can also help with broadning the bandwidth and decreasing the fluctuation.