Theoretical And Experiment Research On The Calibration Method Of 3d Laser Scanning System

Dimensional measurement of large forgings in real-time plays an important role in open die forgings process. In order to evaluate the hot parts in real-time, acquiring both of the dimension parameters and shape when .Traditionally, open die forgings are measured while hot, using contact measurement equipment. This is inconvenient because of the difficulty in working with very hot workpieces. Compared with contact measurement, non-contact gauging methods have many advantages in hot large forging measurement such as rapidity, high precision, good repeatability and noncontact.Laser range sensor based on time of flight is a typical non-contact gauging equipment, which is applied in many fields such as localization and navigation of mobile robots, object recognition and tracking, environment reconstruction. In order to acquire 3D data of large forgings, we constructs a non-contract 3D laser scanning system with key components of a 2D laser range sensor and a servo motor. For the measurement systems, calibration is a very crucial step, it is the assurance of the accurate measurement. Around calibration of the 3D laser scanning system, this paper conducted the following research works:1, Research on the calibration method of 3D laser scanning system. We defined three Cartesian coordinates systems according to configuration of our measurement system. Accordingly, calibration parameters of the measurement system are equivalent to two parameter matrices, which include an interior parameter matrix and an exterior parameter matrix. We presented solutions to the two parameter matrices based on virtual closed kinematic chain. According to projective geometry and matrix transformations, we proposed a calibration method to calculate the two parameter matrices of the measurement system, based on an exterior calibration applied in the field of mobile robot localization.2, Research on line extraction of calibration target from planar scanning data. In the implementation process of the calibration method proposed in this paper, we need to extract the straight lines of the calibration object and their intersections from the planar scanning data firstly. After summarizing a number of line extraction method, we proposed a line extraction method with corresponding to characteristics of data of the calibration object, applying the idea of processing the data step by step. Finally, we obtained straight lines corresponds to the calibration object, as well as the intersections of these lines.3, Experiment and analysis of calibration method. First, we validated the feasibility of the calibration method by simulated data, and then, we carried out experiments on the platform of 3D laser scanning system. Finally, according to experiments results, we analyzed the causes of errors, and proposed methods for improvement.This paper constructed a 3D laser scanning system on the background of dimensional measurement of large forgings in real-time. According to the characteristics of this measurement system, we studied the calibration method and related content. Finally, we carried out experiments and analyzed the results based on the measurement system. These studies were the basis of following researches of our topic, and the calibration method can be applied to similar measurement system with 2D laser range sensor.