Simulation Research Of High-Power Flextensional Transducer Based On Magnetostriction

The underwater acoustic parametric array can generate a secondary wave signal through the nonlinear effect of acoustic wave in water.This secondary wave signal has the characteristics of low frequency and narrow directivity.Moreover,this form of signal can be transmitted by using a small transmitting transducer.In the parametric matrix theory,the relationship between the primary excitation signal and the secondary wave signal is not linear,so in order to obtain the secondary wave signal with the same waveform as the preset signal at the receiving end,the preset signal needs to be pre-tuned at the transmitting end.The modulated signal can obtain the preset signal form without distortion at the receiving end through the self-demodulation of the water medium.The quality of the acoustic parametric array modulation algorithm directly affects the quality of the received secondary wave signal,so this thesis studies the key technology of the acoustic parametric array modulation algorithm.Based on Berktay theory,this thesis analyzes the nonlinear relationship between the preset signal and the secondary wave received by the receiving end,and provides a design idea for a new parametric array modulation algorithm.Two common parametric array modulation algorithms and three new modulation algorithms based on function approximation are studied,and five algorithms are analyzed through simulation results,and it is concluded that although the fully modulated amplitude modulation algorithm and the square root modulation algorithm are common transmission methods of parametric arrays,they will cause distortion of the secondary wave signal,and the fully modulated modulation algorithm should also consider the problem of DC bias.The Fourier series modulation algorithm can obtain good performance when the fitting coefficient value is appropriate,but the selection of the fitting coefficient requires a long operation time.Chebyshev,Fourier series,and cubic spline interpolation modulation algorithms can approximate distortion-free waveforms and obtain high-quality secondary waves in signal transmission.In terms of calculation rate,the algorithm of full amplitude modulation,square root modulation and cubic spline interpolation is basically the same,and the time is about 1/3 faster than Chebyshev interpolation modulation algorithm.Then the coefficient compensation of the modulation algorithm based on function approximation is carried out to solve the problem of signal divergence caused by integral error.In this thesis,the above five different modulation algorithms of underwater acoustic parametric array are tested in the pool.After the experiment,the signal processing is carried out,and the received secondary wave signal is filtered.The frequency doubling phenomenon of the full amplitude modulation algorithm in the simulation is indirectly optimized.After verifying the simulation data,the influence of the frequency response of the transmitting system on the secondary wave is studied.By measuring the frequency response of the transmitting system,the preset signal is corrected and then modulated and transmitted through the modulation algorithm,and the corrected secondary wave is finally obtained.The results show that the correlation coefficient of the secondary wave increases after correction,and the shape of the secondary wave is controlled.This means that the secondary wave behaves better after correction and is more consistent with the desired waveform characteristics than before correction.