Issue 51

K. Li et alii, Frattura ed Integrità Strutturale, 51 (2020) 386-397; DOI: 10.3221/IGF-ESIS.51.28 388 interface. The transmission actuator is driven by a stepping motor to output a high-precision, controllable lifting movement. The drive control unit consists of a stepper motor driver, PLC and related components. The control slider performs a uniform linear ascending and descending motion on the slide rail through the M programming language. In order to control the uniform linear lifting scanning action of the laser ranging sensor, it is fixedly mounted on the slider through the connecting plate. The sensor scan plane is parallel to the ground and perpendicular to the drive direction. The parameters of the laser sensor are set on the surface of the sensor control interface, so that the scanning optical center lifting speed is consistent with the linear sliding group motion output. Figure 1 : Design drawing of 3d laser scanning system. System measurement principle Two coordinate systems for the structural characteristics of the 3D laser measurement system are defined as followed: 1) The coordinate system of laser ranging sensor position: {O A -X A Y A Z A }; 2) The coordinate system of the image acquired by laser scanning: {O-XYZ}. The origin of the {O A -X A Y A Z A } coordinate system is located at the sensor transmission port, X A O A Y A is parallel to the scanning surface of the two-dimensional laser, and Z A is the transmission direction. The moving speed of the laser sensor in the Z direction is v (m / s), and the movement time is t (s). In the initial state, the laser emitting end (red circle) coincides with the origin. The angle between the laser emitted by the transmitting end and X A is α , and the coordinate of the intersection with the object to be detected is S (x a ,x b ,x c ). The laser is emitted to the object, and the reflected light on the object is reflected to the receiving end (green circle). The angle between the emitted light and the reflected light is θ. The X-axis of the {O-XYZ} coordinate system is parallel to the intersection of the scanning plane and the detected object. The Y-axis is parallel to the scanner drive direction. The Z-axis represents the distance from the laser emitting end of the scanning plane to the detected object. Figure 2 : Laser ranging sensor coordinate system {O A -X A Y A Z A }