During the manufacturing process of heavy forgings, simple contact measuring techniques are still used to check the dimensions, therefore an optical measuring system is in demand. In this paper, a camera calibration method for the passive measuring system, which is being developed in collaboration with an industrial partner, is proposed. Our approach is based on space resection and works with robust coded targets, which are distributed in the field of view. The coordinates of targets are measured using TRITOP (GOM) measuring system. This solution allows to build a large calibration field, without a need of large calibration objects. The camera calibration works in 2 steps - at first, the intrinsic parameters of the camera, including lens distortion, are calibrated. These parameters are considered as stable, due to the use of special camera covers. Multi-image version of the calibration method and dense field of calibration targets are used. The second step is performed from every image and employs a single-image extrinsic camera parameters calibration method. Only a few coded calibration targets, mounted on stable objects in the scene, are required. The calibration method was tested in industrial conditions. The method showed great results, the average reprojection error was under 0.1 px. The effect of thermally affected zone on the calibration process is discussed.
The paper presents the development of a system for the measurement of the shapes and dimensions of rotationally symmetric forgings under high temperature. These large semi-finished products are measured with demands for accuracy on the order of millimeters. The challenge is to design a measurement system that overcomes the problems caused by high temperature and provides results instantly without interrupting the production process. The proposed approach exploits the fact, that the measured parts have simple rotationally symmetric shape. It is based on the assumption that (in the simplest case) the actual shape can be determined from four boundary curves which lie in two mutually perpendicular planes. These four boundary curves can be obtained by determining the edges of the forging in two images. The proposed approach has been incorporated into a software application created in Matlab programming environment. Hence the system does not use added illumination resolving edge detection and scale calculation is a crucial step. The main parts of the system, such as calibration, edge detection, spatial orientation, and the evaluation of information about the shapes and dimensions of the measured parts, have been designed so that the entire measurement process takes only a few seconds. The article focuses on the individual parts of the software application. It discusses the suitability of using particular mathematical models and the designed multi-step edge detection method, which is based on thresholding, directional median filtering and validation and correction of detected edge points.
Dimension measurement of hot large forgings is necessary for manufacturing process and quality control. Conventional
non-contact optical measurement methods are not applicable, mainly because of high temperature and large dimensions.
A novel approach to the axis staightness measurement of the cylindrical forging, based on the principle of
photogrammetry and edge detection, is described in this paper. Proposed system is developing under laboratory
conditions, but the actual conditions of steel production are also considered. Demands on the measurement system were
set by our industrial partner, producer of cylindrical forgings with length of 4 to 20 m and diameter up to 1.4 m. The
system should be able to detect axis straightness deviations higher than 5 mm (system accuracy has to be better than 5
mm). Cylindrical forgings are 4 to 20 m long with diameter up to 1.4 m.
The approach is based on the assumption that the actual shape of the cylindrical forging axis can be determined (in the
simplest case) using four boundary curves which lie in two mutually perpendicular planes. Four boundary curves can be
obtained by detecting the forgings edges in two images. The article provides results of first validation of proposed
method in laboratory conditions. Measurement repeatability was validated by carrying out ten measurements of a
deformed rod. Each measurement was compared with a measurement performed by industrial fringe projection scanner
Atos III Triple Scan in order to verify the accuracy of the proposed method.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.