# Research on Three-Dimensional Scanning Path Planning of Casing Parts Based on Industrial Robot
## 2 Automated Tracking Type 3D Scanning Measurement System  
### System Composition  
In the manufacturing process of aeroengine large parts, it is necessary to quickly measure the geometric dimensions of the part to guide the manufacturing process and evaluate the processing quality. This paper designed an automatic tracking 3D scanning-measurement system with a laser 3D scanner and industrial robot as the core, which mainly includes a 3D scanning data acquisition subsystem (3D scanning head, laser positioning tracking instrument), motion control subsystem (industrial robot, safety protection), turntable support subsystem and software system (automatic scanning and detection software, system automatic control software), as shown in Figure 2. The motion control subsystem includes a six degrees of freedom industrial robot (called a scanning robot), which can flexibly scan the 3-D scanning head in the trapezoidal working space of the laser positioning tracker to realize the automatic acquisition of the point cloud of the casing engine. The turntable support subsystem is a six degrees of freedom parallel-motion platform, which can fix the measured workpiece in the measurement space of the laser positioning tracker, to realize the scanning measurement of multiple poses of the large aviation components.  
The I/O module software system was developed to connect the scanning robot to the laser scanner through the I/O signal communication. The communication structure is shown in Figure 3. The I/O control signal was written into the robot scanning trajectory program, and the signal received/sent by the I/O module controls the three-dimensional scanning probe, laser positioning tracker and safety protection accessories for automatic scanning operations to complete the acquisition of the point cloud data of the measured workpiece.  
Figure 2: Automatic tracking type 3D scanning measurement system.  
The operation process of the automatic tracking-type 3D scanning measurement system to collect the point cloud data and measurement of casing parts: (1) the laser scanner, optical tracker, scanning robot and six degrees of freedom motion platform were calibrated in advance; (2) the measured casing was placed on a six degrees of freedom parallel motion platform, and the platform pose was adjusted to expose the inner and outer surfaces of the casing to the binocular camera of the laser location tracker as much as possible; (3) the laser scanner parameters were configured according to the material and reflectivity of the measured workpiece, and the scanning template was established; (4) the scanning path *.TB program of the scanning robot was established by teaching pendant or off-line programming method; (5) start the automatic control system, invocation of the scanning template and the scanning path *.TB program to scan the measured workpiece area by area to obtain its point cloud data; (6) the point cloud data of the workpiece were post-processed and imported into the measurement software. The casing wall thickness was measured according to the pre-established measurement program, and the measurement report was generated.