The dynamic envelope measurement plays very important role in the external dimension design for high-speed train. Recently there is no digital measurement system to solve this problem. This paper develops an optoelectronic measurement system by using monocular digital camera, and presents the research of measurement theory, visual target design, calibration algorithm design, software programming and so on. This system consists of several CMOS digital cameras, several luminous targets for measuring, a scale bar, data processing software and a terminal computer. The system has such advantages as large measurement scale, high degree of automation, strong anti-interference ability, noise rejection and real-time measurement. In this paper, we resolve the key technology such as the transformation, storage and calculation of multiple cameras’ high resolution digital image. The experimental data show that the repeatability of the system is within 0.02mm and the distance error of the system is within 0.12mm in the whole workspace. This experiment has verified the rationality of the system scheme, the correctness, the precision and effectiveness of the relevant methods.
The article proposed a method to quantify corrosion characteristics of high strength alloy steel samples using digital image processing technique in color spaces. The distribution histograms in different channels of different spaces in corrosion images are plotted and analyzed. Select the proper color channel to extract the corrosion characteristics among three different spaces of RGB space, HSV space, YCbCr space. Combined the theory of corrosion generation, the data of color channels is processed and the feature of metal material salt spray corrosion is recognized. Through processing several sample color images of alloy steel, it is proved that the feature extracted by this procedure has better accuracy and the corrosion degree is quantifiable and the precision of discriminating the corrosion is improved.
This paper proposes a new strategy of extracting boundary points from scanning point cloud (SPC) data of sheet metal parts (SMPs). This strategy is suitable for bending SMPs with slowly changing surfaces. To cope with the problem that the SMP is too thin to have enough points of its lateral surface to be calculated for the boundary outline, the boundary points are obtained by moving ridge points which is the maximum curvature points on the marginal of parts along theoretical position direction. In this article, the strategy is explained firstly and then carried out on two different experimental SMPs. The strategy contains several steps. Firstly, we construct a slice set called multiple direction slices (MDS) along a curve fitted by boundary points of SPC. Then marginal point data (MPD) is obtained completely and accurately by MDS. And then the chamfer arc data is extracted from MPD by setting identification model of chamfer arc’s two endpoints. Then the ridge points which are the maximal curvature points of chamfer arc data are picked out from chamfer arc data. Finally, by moving the ridge points along a certain direction for a fixed distance, the boundary points are calculated out. Two experiments are carried out to identify position error and form error of the extracted boundary points. The measurement results of boundary outlines of a 6mm thick SMP from a three coordinate measuring machine (CMM) is taken as reference in the first experiment. The second experiment regards theoretical boundary outline as reference. Both two experiments demonstrate the effectiveness of the strategy.
For the purpose to measure a rotation angle around the axis of an object, a non-contact rotation angle measurement method based on solo camera was promoted. The intrinsic parameters of camera were calibrated using chessboard on principle of plane calibration theory. The translation matrix and rotation matrix between the object coordinate and the camera coordinate were calculated according to the relationship between the corners’ position on object and their coordinates on image. Then the rotation angle between the measured object and the camera could be resolved from the rotation matrix. A precise angle dividing table (PADT) was chosen as the reference to verify the angle measurement error of this method. Test results indicated that the rotation angle measurement error of this method did not exceed ± 0.01 degree.
With the gradual promotion of Microsoft.NET platform, C# as an object-oriented programming language based on the platform has been widely used. Therefore, more attention is concentrated on how to achieve the communication between Panasonic PLC and PC efficiently and fast in C#.NET environment. In this paper, a method of using SerialPort control which could be used for achieving communication between PLC and PC is introduced. Meanwhile, the reason of abnormal thread when displayed the receiving data in form is analyzed and the programming method to solve the problem of thread safety is designed. Achieving the communication of Panasonic PLC and PC in C#.NET environment can give full play to the advantages of the .NET framework. It is practical, easy communication, high reliability and can combine with other measurement and calibration procedures effectively and conveniently. Configuration software is expensive and can only communicate with PLC separately, but these shortcomings can be solved in C#.NET environment. A well-designed user interface realized real-time monitoring of PLC parameters and achieved management and control integration. The experiment show that this method of data transfer is accurate and the program’ running is stable.
Indoor GPS measurement network is a space coordinate measuring system, which is composed of more than one transmitter. The number and location of the transmitter determine the measurement range and accuracy of the measurement network. Therefore, how to correctly evaluate the measurement network is a key issue. By analyzing the error model of a measuring system, which is composed of two transmitters, we acquired the main cause of the measurement uncertainty. Through MATLAB simulation, we are able to get the effective measurement conditions, in order to meet specific requirement of measurement uncertainty. Meanwhile, total uncertainty of the measurement network, which is composed of measurement uncertainty, location uncertainty, receiver uncertainty and other uncertainties, is analyzed. We proposed the evaluation method based on the reference length, and at the same time, optimized the position of the reference position, posture and length, in order to meet the evaluation requirements of the entire measurement space. Finally, we simulated the measurement network for aircraft assembly in measurement space of 20m×20m×5m, and the measurement network for car assembly in measurement space of 5m×5m×2m. We evaluated the measurement network according to the above principles and estimated the uncertainty of the measurement network trough measurement bias of reference length at different locations.