Papers by Keyword: Coordinate Measurement

Abstract: In the paper we propose an approximation model of the measured point cloud for machined cylindrical surfaces. The developed model is different from the traditional view because it relies on the contact of mating surfaces. The model allows to determine the parameters of cylindrical surfaces such as the coordinates of the center and the radius. To evaluate the geometrical parameters of the model the objective function is formulated, which characterizes the nature of the interface and a number of limitations. The approximation problem is solved by use of nonlinear optimization methods. The model takes into account the surfaces contact, which influences in deformation of its irregularities. The irregularities it is form deviations and surface roughness. The application of the model on the example of the shaft coupling with the inner ring of the bearing. There is given an estimate of geometric parameters for interfacing compared to method of least squares, which is widely used for coordinate measurements. As a result of research it was obtained that the proposed method can predict more accurately the parameters, which describe the location of the cylindrical surfaces made during assembly.

Abstract: For getting the coordinate of contactor on CCL, the measurement system transformed resistance into voltage by providing constant current on CCL. The system includes MCU, 3A constant current source, MOSFET switch circuit, signal amplifier circuit and A/D converter. By the curve-fitting method, the equipotent lines of CCL were simulated with MATLAB according to the discrete data. The equations of equipotent lines were obtained with second-order polynomial fitting method. The two curves which the contactor located in were acquired with local linearization method, and the coordinate was gained by calculating solving equation groups.

Abstract: In order to improve the intelligent level of path planning in coordinate measurement, the algorithm of path planning based on theory of polychromatic sets and ant colony algorithm is proposed. The model of the relation about measured geometrical features, probe angles and inspection planes is established, and the sub path is got by grouping for the global path on the basis of conjunctive operation of polychromatic sets. The global path is optimized by planning the sub paths with ant colony algorithm. The practical example verified the validity and reliability of the proposed method.

Abstract: For a coordinate measurement system based on binocular vision, system calibration is an important factor for measurement accuracy. In this paper we present a flexible calibration method for the axis calibration of rotation stage which is installed in front of the binocular vision system to increase the system measurement range. By putting a standard ball in front of the binocular vision system, a sequence of pictures is taken by the two cameras with a few different rotation angles of the rotation stage. With the method of space intersection of two straight lines, the reference points (the ball centers at each rotation angles) for axis calibration are figured out. The trail of standard ball is a circle. Since all ball centers of rotation are on a plane perpendicular to the axis, the center of circle is on the axis of rotation stage. The rotation axis of stage is then calibrated according to the calibration model.

Abstract: The process of coordinate measurement involves a large amount of data. This paper uses the IDEF0 and DFD model to analyze the measuring function requirements for solving the problem of ambiguous internal information flow and material flow during the measuring process and uses IDEF1X method to constitute information model of coordinate measurement. The information is extended on the three-dimensional model generated by using the MBD (model based definition) technology. It enables us to specify the measurement process and reduce the specification uncertainty of the digital measuring system. In addition, the extended information could have been inputted for the subsequent process such as process planning, data analysis and evaluation of measurement results.

Abstract: In order to provide accurate and robust indoor location service for large-scale mechanical manufacturing, a sensor network consisting of laser transmitters and optical receivers is proposed in a distributed framework. Geometric model described by rotating plane equations is established, re-ceiver’s location algorithm is achieved by utilizing intersection constraint of multiple laser planes form different transmitters. A self-monitoring mechanism for sensor network is also presented by introducing redundant fixed receivers as reference. Experiment has shown that the measuring accu-racy of a minimal sensor network is better than 0.2mm and self-monitoring mechanism can effectively guarantee the accuracy of the measurement results.

Abstract: Due to the range of the measuring system is limited in the measurement of large aspheric optical elements, test is hard to be once fulfilled, so coordinate measurement based on multi-section stitching is proposed, and the least square mathematical model of large aperture optical elements multi-section stitching is built. Moreover, the profiler Talysurf PGI 1240 made by Taylor Hobson company is used for study. The result shows that, the method is suitable for multi-section data stitching for large aspheric optical elements, and possesses many advantages, such as fast speed, high accuracy and strong operability, etc.

Abstract: A rapid casting method for complex parts is presented. In this method, casting moulds with complex cavity are manufactured by self-created rapid prototyping approach which called Selected Laser Partitioning for Prototyping. After surface coating treatment for moulds, complex parts are obtained by centrifugal casting. As application cases, metal impeller was casted by this method. A self-developed five-axis coordinate measurement machine was used to process the surface measuring of impeller. The Dimension accuracy grade of impeller is CT-3 and the surface roughness is Ra 6.3µm through making comparisons directly between CAD model and point cloud data of impeller surface. The result shows that this rapid casting method which has the characters of simple technology and low production cost reaches the level of precision casting.

Abstract: A novel workspace measurement positioning system based on optical scanning and wireless sensor network is presented in this paper. Coordinate measurement principle through angle intersection is detailed discussed. According to analysis of system requirement, a Zigbee wireless sensor network is designed for data transmission; routing algorithm and flowchart of nodes software are also given. A platform consists of two planar laser transmitter and optical receivers is set up for verification. Experiments result demonstrates that the accuracy of new angle measurement method is better than 1mm.

Abstract: The uncertainty estimation of coordinate and profile measurement is essential for accurate measurement and establishment of traceability. We proposed an uncertainty propagation method to estimate the uncertainty of coordinate and profile measurement. In this article, the multi sensor algorithm with uncertainty estimation method is described for the profile measurement. Additionally, two examples of multi sensor method are introduced. According to the simulation results of assessing uncertainty and the experimental results, the validity of the method was confirmed.