This paper presents the design and working principle of a pneu-pin sensor based on a gas path with differential pressure,
and the study on its curve-baffle characteristics. The measurement range of the sensor is about 32 &mgr;m, with a resolution
of 0.03 &mgr;m and less than an uncertainty of 0.3 &mgr;m. It is found through research on the curve-baffle characteristics with
different curvature radius of steel balls that the axis of the pneumatic probe does not need to go through the geometric
centre of work-piece, and so, the high accuracy positioning of the work-piece is avoided. Therefore, the pneumatic
measurement technology researched in this paper can be applied to high accuracy non-contact dimension of
measurement of different curvature radius of work-pieces.
Cold-test characteristics including dispersion and coupling impedance of a coupled-cavity slow-wave structure for space
TWT working in millimeter band have been simulated by self-designed software. The slow-wave structure has been
modeled and cold-test characteristics data were obtained. The interaction between electromagnetic wave and electron
beam has also been analyzed qualitatively. The study in the paper can provide some references for the design of coupled-cavity
slow-wave structure for space TWT.
Dimension and form of a train wheel tread contour are the key controlled parameters in manufacturing and running process. Projecting laser light line to the tread contour, the left image and the right one of the light line in the measured countour are caught by using two CCD cameras. After calibrating the two images and other processing, the two images are pieced together to form a free-form curve. Measuring and data processing are completed in two steps as using "Bi-measurement Evaluation Test", the first step is modeling and the second is testing. Comparing the real coordinate values of Testing points with their theoretical ones reconstructed from the form model, the problem whether the model expresses the contour features enough can be resolved. If the answer is yes, the number and position distribution of sampling points are rational, then we can estimate the standard deviation (σ) of noise in the measuring sequence made up of coordinate values of sampling points. The fact that the standard deviation (σ) of noise in the real measuring sequence is about 0.1600mm is estimated by real measuring and data analysis.
An active vision detection technology based on laser target is proposed in this paper for measuring the dimensions of thermal train wheels in workshop. A mapping transorm of histogram is used to restrain thermal background and extrude the laser target, therefore, it is necessary to search the transform threshold value. The color weights of the image background are analysed. A contrast of the laser targe stripe and a recognized error are pursued to a best threshold for image mapping transform. The experiments prove that the useful information of the laser target image is extruded and the recognized errors caused by the mapping transorm are less than 0.04 pixel. A theoretical foundation is set up for the laser target pick-up correctly and other image processing expediently.
Camera calibration is an important step in machine vision for dimensional measurement. Based on analyzing the photogrammetric calibration and self-calibration methods, a new planar way is proposed in this paper for calibrating the camera for the 2D objects. Induced some non-linear distortion factors, a fast algorithm is adopted to solve the complicated non-linear equations in calibration model. With this algorithm, a concatenation technique is used to reconstruct a 3D object from two 2D planar photos. In the second part of this paper, a calibration method using only one plane, which can be moved on some simple equipment, is deduced for 3D object dimensional measurement. Mathematic model and its transformation process are discussed in detail. This method can be used especially for profile inspection of machine parts in industrial working-field. An application to inspect the profile of train wheel is given in this paper. Experimental results are given to show the parameters of camera system and the measuring accuracy.