Mathematical Model for Measuring Geometric Parameters on a Train Wheel Profile

摘要

The measuring system is based on the principle of stereovision measurement. The linear laser light is projected onto the trackside of the wheel and a planar curve with the 3-D profile information is produced. The image of the curve is acquired with CCD cameras. The coordinate transforming relationship between the image coordinates and the corresponding world coordinates is mainly introduced. One of the key problems is the calibration of CCD camera. The reference object for calibration is a steel board with three triangular columns. After the precise measurement by three- coordinate measuring machine, we can get the 3-D coordinate data of the characteristic points, and then the corresponding image coordinates are easily confirmed. So we can get the coordinate transforming relationship between the image coordinates and the corresponding world coordinates for determining geometric parameters of the measured train wheel.