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.
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.
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.
Composition and principle of 2m laser automatic interferometric comparator were introduced. A novel contact aiming system based on high precision inductance sensor was designed. The zero-cross trigger signal of inductance sensor output voltage was treated as the aiming signal. A rotating mechanism was designed and a segmental shifting motion control model was established. Two key problems, avoiding probe crash and aiming repeatability, were solved. The one dimension end standards such as gauge block, step gauge could be measured directly by this means. The data of test revealed that aiming repeatability was less than 0.2μm.
In order to improve the evaluation precision of spatial straightness error, new measurement setup using 4 LaserTRACERs were built at National Institute of Metrology (NIM). The LaserTRACER is a length measurement device with sub-micron accuracy. In principle, the LaserTRACER is a traceable interferometer. Experiment was implemented on a granite rail with air-suspending slider to test the spatial straightness of the rail. In the experiment, the retroreflector was mounted on slider and moves alone the rail after the spatial frame of axes was built. Using 4 LaserTRACERs, the spatial coordinates can be calculated by Multilateration algorithm. The optimal arrangement of LaserTRACERs is studied by simulation and experiment. The mathematical model based on GBT11336-2004 was built, and Least squares method is used in the spatial line fitting. The measurement principle and results were verified by comparison with SpatialAnalyzer and Metrolog XG.
Photomask is a kind of 2-D optical standard with etched orthogonal coordinates made of a glass substrate chrominged or
filmed with other metal. In order to solve the problems of measurement and traceability of ultra precision photomasks
used in advanced manufacturing industry, 2-D photomask optical standard was calibrated in high precision laser two
coordinate standard device. A high precision differential laser interferometer system was used for a length standard, a
high magnification optical micro vision system was used for precision optical positioning feedback. In this paper, a
image measurement model was purposed; A sampling window auto identification algorithm was designed. Grid stripe
image could be identified and aimed at automatically by this algorithm. An edge detection method based on bidirection
progressive scanning and 3-sigma rule for eliminating outliers in sampling window was found. Dirty point could be
removed with effect. Edge detection error could be lowered. By this means, the measurement uncertainty of 2-D optical
standard's ruling span was less than 0.3 micrometer (k=2).
Large-scale measurement systems of range over 30m are main traceable devices of dimensional measurement for modern
large-scale advanced manufacture domain. High precision large-scale dimensional measurement devices with flexibility
and openness are made up of length measurement system, environmental measuring system, guiding rail system and
control system. In length measurement system using laser interferometers, zero error should be taken into account. This
paper proposed a novel method to eliminate zero error in large-scale laser interferometric measurement system. The
uncertainty of this system is improved experimentally.
In close-range photogrammetry, a length scale of photogrammetric system was given by a scale-bar. To achieving a
precision result which uncertainty is less than 10 micrometers, the uncertainty of scale-bar measurement should be less
than 3 micrometers. For this purpose, an approach was proposed according to the feature of retroreflective target (RRT)
on scale-bar; a measurement system consisted of a high resolution CCD camera, a laser interferometer and the lights was
established. The RRTs at two ends of the scale-bar was aimed by the CCD camera. The distance between two aiming
positions was measured by the laser interferometer. In this paper, a linear direct measurement model was founded; an
algorithm calculating RRT's gray centroid was presented. A series of tests were carried out under different light, different
illuminance and different aiming method respectively. The results indicated that the uncertainty satisfying the request of
scale-bar measurement in close-range photogrammetry.
According to camera calibration requirements of close-range photogrammetry system, novel camera calibration method
based on dynamic three-dimensional (3-D) optical plate is proposed. The dynamic 3-D optical plate is realized by
translational moving a 2-D optical mask plate with elaborately designed targets alone a granite linear guiding rail. 2-D
direct linear transformation for camera external parameter decomposition is studied, and mathematical model for camera
internal parameter calibration is built based on bundle adjustment. The feasibility of dynamic 3-D optical plate and
camera calibration method are experimentally demonstrated.