This paper proposes a system for a laser ultrasonic inspection of fixed non-planar composite structures. A pulse-echo configuration is used by which both the sensing and excitation lasers hit the same point on the structure, utilizing bulk waves for a through-the-thickness defect evaluation. A high signal-to-noise ratio is ensured by mounting a laser Doppler vibrometer (LDV), used as the sensing laser, on a 6 degree-of-freedom robot arm, thus allowing the correct distance and angle of the laser incident on the inspected structure to be maintained throughout the scan. The excitation laser is steered separately through a laser mirror scanner (LMS) to keep the robot payload sufficiently low, allowing the use of a lightweight portable robot arm. This robot arm can be mounted on a moveable platform suitable for in-situ inspections. An RGB-D camera is used for imaging the structure in front of the system, and a scan area with the required size can be delimited on the image produced by the camera. A scan path for the robot arm and laser mirror scanner is automatically generated by keeping the shape and distance of the structure within the delimited scan area. A graphical user interface allows the control of all individual blocks and contains the necessary algorithms for image capture of a specimen, geometry calculations, scan-path generation, signal acquisition, signal processing, and display of the results. This is a multithreaded software, ensuring a fast calculation of the structural geometry and scan path prior to the inspection and real-time updating of the results during the inspection. Composite specimens consisting of radial and conic sections with subsurface defects were inspected using the system. The test results show that the system is extremely reliable in detecting defects, particularly in the non-planar parts of the specimen.

本文提出了一种用于固定非平面复合结构激光超声检查的系统。使用脉冲回波配置，通过该配置，感测激光和激发激光都击中结构上的同一点，并利用体波进行整个厚度的缺陷评估。通过在6自由度机械臂上安装用作感测激光器的激光多普勒振动计（LDV），可以确保较高的信噪比，从而允许正确的距离和入射角度入射到激光器上。在整个扫描过程中要维护的受检查结构。激发激光分别通过激光反射镜扫描仪（LMS）进行操纵，以使机器人的有效载荷保持足够低，从而允许使用轻巧的便携式机器人手臂。该机械手可以安装在适用于现场的可移动平台上检查。RGB-D照相机用于对系统正面的结构进行成像，并且可以在照相机产生的图像上划分所需大小的扫描区域。通过将结构的形状和距离保持在限定的扫描区域内，可以自动生成机械臂和激光镜扫描仪的扫描路径。图形用户界面允许控制所有单独的块，并包含用于标本图像捕获，几何计算，扫描路径生成，信号采集，信号处理和结果显示的必要算法。这是一个多线程软件，可确保在检查之前快速计算结构几何形状和扫描路径，并在检查期间实时更新结果。使用该系统检查了由具有地下缺陷的径向和圆锥形截面组成的复合试样。测试结果表明，该系统在检测缺陷（特别是在样品的非平面部分）方面极为可靠。