The Study On 3D Measurement Of The Outer Diameter Of Train's Wheel Set

Train's wheel set is one of the most important interchangeable components in the vehicle, and plays key role in the safety of railway transportation. But in our country ,the wheels are still measured by handiwork, that is low efficiency. In developed countries such as Japan, USA, advanced research has been done and many new technologies and equipments have been developed leading high efficiency and economics. With the development of industrial control technology and the open of market, the application of computer control technology and information technology in railway transportation meets the great chance.This paper introduces a method for wheels measurement based on the technology of CCD image processing and 3D measurement base on line structured light, and the correspond software is done.The theory of 3D measurement base on line structured light is simple, the structure is easy to actualize, and the precision is high, so it plays a important role in the field of vision measurement. The system consists of laser, CCD camera, computer and some software, it can get the world 3D coordinates of the section of the line structured light on the object, processing such as measurement can be executed using these coordinates.This paper consists of two important parts: the calibration of CCD camera and the processing of light section.The calibration of CCD camera is base on Tsai arithmetic. Those parameters can be got using the image coordinates of coplanar characteristic points and the corresponding world coordinates, and then the transform relation between world coordinates and image coordinates can be established. In this paper the characteristic points are got from the corners from coplanar square by Harris arithmetic, and on that base sub pixel image coordinates can be got by using advanced arithmetic.The processing of the section of light is the basement for the calibration of the plane of line structured light and the application for future. The processing includes some image processing arithmetic such as binarization, filtering and thinning. The coplanar board is located at different position, and each corresponding section of the light can be got by the CCD camera, then the image coordinates of these sections can be computed using some arithmetic and the world coordinates can be got by the transform relation which is established from the calibration of CCD camera, so finally the function of the plane of line structured light can be got by fitting those world coordinates.Each corresponding world coordinates of the points in the section of light can be computed by simultaneous equations system of the transform relation between world coordinates and image coordinates and function of the plane of line structured light.