基于Barker编码发射的MIMO超声测量方法及误差补偿

发布时间：2018-07-02 20:12

本文选题：Barker码 + MIMO　；参考：《南京信息工程大学》2014年硕士论文

【摘要】：液位超声测量方法的准确性是超声测量领域中的一个重要问题,为此,本文基于MIMO超声测量系统的基础之上实现动态液位测量,并从信号的角度提出了测量误差的补偿方法,进一步提高动态液位状态下的测量准确性。本文首先研究单通道编码发射的超声测量系统误差来源并进行了分析,假设测量误差来源于回波信号波形的畸变,回波信号除了在时间上被延迟外,信号幅度上是由于噪声干扰影响而产生改变,码元宽度上是由于声波传播非线性因素影响产生的改变,为此,研究码元宽度变化引起的测量误差问题,并在超声测量过程中,先估计码元宽度的增加量,再对测量结果进行相应的误差补偿。除此之外,在测量之前,采用自适应滤波器对回波信号进行平滑,滤除噪声成分,获得较好的回波信号波形,实验仿真结果证明了该方法的可行性,并获得了较好的结果；其次,对常规的单通道超声液位测量方法在动态液位测量的准确性存在的问题进行了分析,提出了基于Barker码发射的MIMO超声测量方法,并对其构成的主要关键技术进行介绍,如阵元阵列结构设计、发射信号波形优化、合成聚焦技术、脉冲压缩及通道分离系统,仿真并构建实际的MIMO超声测量系统进行了相关验证,证明了采用Barker码发射的MIMO超声测量方法可以有效的提高超声测量准确性,改善测量精度,优于传统的单通道编码发射的超声测量方法；再次,结合Barker编码发射的单通道超声液位测量系统的误差补偿方法,对波束合成后的信号码元宽度进行估计,并利用Barker码发射的单通道超声测量误差补偿方法进行测量结果修正,也获得了较好的测量结果,并提高了超声测量精度。在Barker码发射的MIMO超声测量系统中,并未采用自适应滤波器,主要是因为在对回波信号进行合成处理时,在信号同相位处,信号合成处理对噪声成分起到了平均处理作用,“削弱”了噪声成分对超声测量结果的影响,此外,也对引起Barker码发射的MIMO超声液位测量误差的其它因素进行研究,包括采样精度、液位波动幅度过高,为Barker码发射的MIMO超声测量系统构造提供了一定的理论基础。最后,通过实验结果证明,采用Barker码发射的MIMO超声测量方法不仅可行,而且,结合相应的测量误差补偿方法,可以提高超声测量精度,改善测量系统稳定性。实验仿真结果表明：当回波信号码元宽度变化时,采用新方法对设置液面空间采样点的测量误差在±0.06cm之间,通过最小二乘拟合法进行修正后得到测量误差在±0.015cm之间；当被测液面波动时,若液面波动平均速度v1.67m/s,采用直接多普勒频移补偿法进行速度补偿,若液面波动平均速度v1.67m/s,采用多支路多普勒补偿法进行速度补偿。
[Abstract]:The accuracy of liquid level ultrasonic measurement method is an important problem in the field of ultrasonic measurement. In this paper, the dynamic liquid level measurement is realized based on MIMO ultrasonic measurement system, and the compensation method of measurement error is proposed from the point of view of signal. The accuracy of dynamic liquid level measurement is further improved. In this paper, the error sources of single-channel coded ultrasonic measurement system are studied and analyzed. It is assumed that the measurement error originates from the distortion of echo signal, which is delayed in time. The amplitude of signal is changed by noise interference, and the width of symbol is changed by nonlinear factor of acoustic wave propagation. Therefore, the measurement error caused by variation of symbol width is studied, and in the process of ultrasonic measurement, The increment of symbol width is estimated first, then the measurement result is compensated accordingly. In addition, before the measurement, adaptive filter is used to smooth the echo signal, filter the noise component, and obtain a better echo signal waveform. The experimental results show that the method is feasible and the better results are obtained. Secondly, the problems existing in the accuracy of the conventional single channel ultrasonic liquid level measurement method in dynamic liquid level measurement are analyzed, and the MIMO ultrasonic measurement method based on Barker code is proposed, and the main key technologies are introduced. For example, array structure design, waveform optimization of transmitting signal, synthesis focusing technology, pulse compression and channel separation system, simulation and construction of the actual MIMO ultrasonic measurement system are verified. It is proved that the MIMO ultrasonic measurement method using Barker code can effectively improve the accuracy of ultrasonic measurement and improve the measurement accuracy, which is superior to the traditional single-channel coded ultrasonic measurement method. Thirdly, Combining the error compensation method of single channel ultrasonic liquid level measurement system with Barker code, the width of signal number element after beam-forming is estimated, and the measurement result is corrected by using the single channel ultrasonic measurement error compensation method which is transmitted by Barker code. Good results are obtained and the accuracy of ultrasonic measurement is improved. In the MIMO ultrasonic measurement system transmitted by Barker code, the adaptive filter is not used, mainly because when the echo signal is synthesized, at the same phase of the signal, the signal synthesis process plays an average role in processing the noise component. The effect of noise components on ultrasonic measurement results is "weakened". In addition, other factors causing MIMO ultrasonic level measurement error caused by Barker code transmission are studied, including sampling accuracy and excessive fluctuation amplitude of liquid level. It provides a theoretical basis for the construction of MIMO ultrasonic measurement system based on Barker code. Finally, the experimental results show that the MIMO ultrasonic measurement method based on Barker code is not only feasible, but also can improve the accuracy of ultrasonic measurement and improve the stability of measurement system. The experimental results show that when the width of echo signal is changed, the measurement error of the sampling point in liquid level space is 卤0.06cm by using the new method, and the measurement error is between 卤0.015cm by the least square fitting method. When the measured liquid level fluctuates, if the average velocity of the liquid surface fluctuation is v1.67 m / s, the direct Doppler frequency shift compensation method is used to compensate the velocity, and if the average velocity of the liquid surface fluctuation is v1.67 m / s, the multi-branch Doppler compensation method is used to compensate the velocity.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB551

【参考文献】