# An Advanced Vehicle Body Part Inspection Scheme Based on Scattered Point Cloud Data
## Related Work
### Parts Inspection  
In the field of parts inspection, [PERSON] et al. designed a robotic virtual disassembling system based on Agent technology in 1999 [21]. [PERSON] et al. developed a virtual assembly system based on virtual reality (VR) technology and computer aided design (CAD). This system first used computer graphics to position the parts and then applied the kinematic principle to assemble the parts [22]. [PERSON] et al. built a set of virtual assembly modeling systems for a satellite. This technique improved the assembly efficiency of the satellite parts through a tree structure [23]. [PERSON] et al. combined Unity 3D and Computer Aided Three-dimensional Interactive Application (CATIA) to build a virtual assembly training platform based on the Kinect V2 technology. The platform was tested and good experimental results were obtained [24]. For the above techniques, parts inspection technology is a more design-oriented process and based more strongly on an ideal model than measured data; thus, it cannot simulate a real state. Thus, the actual state of the parts cannot be evaluated. At present, the development of non-contact laser scanning technology has helped improve inspection objectivity and simulate a real matched state based on PCD. This research is developing rapidly and has made significant advancements in many areas, there are many scholars and engineers apply it to all walks of life [25; 26], [PERSON] provided new technology for a complex curved surface quality inspection method based on PCD [27]. An experimental analysis of complex parts proved the efficiency of the algorithm. [PERSON] et al. proposed a quasi-physical assembly method and successfully applied it to the aerospace cabin inspection process [28]. [PERSON] et al. used PCD inspection technology, such as the trial assembly process, for mining machinery equipment, thereby providing a new method for the inspection process of mining machinery and equipment [29]. [PERSON] studied composite part inspection based on PCD [30]. [PERSON] applied PCD inspection technology to the automobile body inspection field by using a non-contact measuring device to obtain the PCD [31]. The essence of the part inspection process is the processing and analysis of PCD. The PCD obtained by non-contact measurements can reflect the actual state of the parts more truly and can help analyze the actual matching position of the parts more accurately. For the initial PCD, the problems of noise data, large data volumes and inaccurate spatial positions greatly affect the quality of PCD. In the above studies, most PCDs were handled by manual operation or commercial software. Although these methods function, they are usually inefficient and require a large workload. Moreover, at present, most of the research in this field is limited to one of the modules such as denoising or registration and there are few studies on the systematic process of body parts inspection. Therefore, based on the relevant research, a new vehicle body part inspection framework is established in this paper. Firstly, a hybrid filtering denoising algorithm is designed for point cloud noise. Secondly, a point cloud simplification algorithm based on FCM is designed to solve the lightweight point cloud problem. This method simplifies the point cloud by obtaining the normal vector, curvature and point density of the PCD based on the 3D coordinates of the point cloud and constructs eight-dimensional PCD sets using the FCM clustering algorithm to classify the characteristics area and non-characteristics area of the PCD. The curvature method and bounding box method are used to simplify the different areas. Finally, a point cloud fine registration algorithm based on the TLBO algorithm is designed to solve the point cloud positioning problem. This method constructs a mathematical model of point cloud registration based on the Iterative Closest Point (ICP) principle and then uses the TLBO algorithm for further calculations to obtain the best registration position.