Design And Realization Of 2D Laser Distance Sensor Used In Wheel Tread Measurement

With the fast development of Chinese railway in recent years, the traffic safety of trains is paid more and more attention. Wheel-set is the critical part of railway trains, and wheel tread, as the rolling contact part between the wheel and rail, has a significant effect when trains are in operation. Monitoring and measuring the dimension parameters of wheel tread is very important. For the purpose of measuring the wheel tread dimension parameters quickly, a 2D laser distance sensor based on laser triangulation is designed and developed in this paper.Firstly, after the investigation of domestic and overseas distance measuring techniques, and combining with the non-contact measuring requirement, the laser triangulation method is adopted in this paper. The overall scheme of the sensor is designed, including the sensor configuration, hardware processing circuit and the overall data processing flow. According to the processing circuit scheme, circuit modules, including power supply, FPGA and DSP peripheral and configuration circuits, communication interface and SDRAM memory expansion, are designed and debugged.Then the laser line pattern image is grabbed and processed by FPGA and DSP. In FPGA, the image data of 2D laser line pattern is grabbed and stored in SDRAM memories, and other logic functions are also implemented, such as decoding the DSP command, controlling the SDRAM and switching the buses. In DSP, the original image is processed in different aspects, such as rectifying the geometric distortion, threshold processing and extracting the centerline of the laser line by centroid method.Finally, the system parameters of the sensor are calibrated by the least square method, and a Matlab GUI interface is design to control the sensor, to read and display or to store data from the sensor. The experiments are performed to measure the wheel tread standard component, and the measured data is analyzed. The experiment results demonstrate that the sensor can work at reliable measuring precision and speed.