Hägglund Fredrik, Martinsson Jesper, Carlson Johan E
EISLAB, Department of Computer Science and Electrical Engineering, Luleå University of Technology, Luleå, Sweden.
IEEE Trans Ultrason Ferroelectr Freq Control. 2009 Aug;56(8):1689-702. doi: 10.1109/TUFFC.2009.1233.
In ultrasonic measurement situations, when dealing with media of multi-layered structures consisting of 1 or more thin layers, analysis of the measured ultrasonic waveform can be difficult because of overlapping and reverberant echoes. Information from the individual layers is then difficult to extract because the individual echoes cannot be detected. In this study, we use a parametric layer model to analyze the multi-layered material in a system identification approach. The parameters of the model are connected to physical properties of the investigated material, e.g., the reflection coefficients, the time-of-flight, and the attenuation. The main advantage using this model is that the complexity of the model is connected to the number of layers rather than the number of observable echoes in the received ultrasonic waveform. A system of linear equations is presented, giving the opportunity to find the model for both pulse-echo and through-transmission measurements. A thorough effort is made on the parameter estimation and optimization algorithm. The model is validated with practical measurements on a 3-layered structure using both pulse-echo and through-transmission techniques. The 3-layered material consists of a thin embedded middle layer with the time-of-flight in that layer shorter than the emitted signal's time support, giving rise to overlapping echoes. Finally the relation between the model parameters and physical properties of the material is established.
在超声测量情况下，当处理由一层或多层薄层组成的多层结构介质时，由于回波重叠和混响，对测量到的超声波形进行分析可能会很困难。由于无法检测到各个回波，因此难以从各层中提取信息。在本研究中，我们使用参数层模型以系统识别方法分析多层材料。该模型的参数与被研究材料的物理特性相关，例如反射系数、飞行时间和衰减。使用此模型的主要优点是模型的复杂性与层数相关，而不是与接收到的超声波形中可观测回波的数量相关。提出了一个线性方程组，为脉冲回波测量和穿透传输测量找到模型提供了机会。在参数估计和优化算法方面进行了深入研究。使用脉冲回波和穿透传输技术对三层结构进行实际测量，对该模型进行了验证。该三层材料由一个薄的嵌入式中间层组成，该层中的飞行时间短于发射信号的时间支持，从而产生重叠回波。最后建立了模型参数与材料物理特性之间的关系。
