Novel three-dimensional data conversion technique and profile measurement system for engine cylinder head blank

Abstract

In order to obtain three-dimensional data of engine cylinder head blank, a passive line structured light system with camera coordinates as the measurement coordinates is designed in this paper. Data in different local coordinates can be converted to a global coordinate system, by calculating the camera moving distance and cosines of the moving direction. In addition, the direction cosine of the camera optical center movement is calibrated based on the principle of virtual stereo vision. The virtual stereo vision system consists of a camera moving along a one-dimension guide rail. The cosines calibration method has three major steps: (1) The rotation matrix R and translation vector T from local coordinate to global coordinate system are calculated by stereo calibration. (2) The origin of the local coordinate system is converted to the global coordinate system. (3) The camera movement along the guide rail is fitted and its direction cosine is calculated. By measuring the high-precision calibration board, the designed system demonstrates a higher accuracy of profiling the geometry structure. An engine cylinder head blank is then scanned using the designed system. The three-dimensional data are analyzed by reverse engineering software and the profile is reconstructed well.