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摘要
冲角是列车蛇形运动稳定性评价中的一关键性指标。由于列车走行步复杂、冲角值极小等原因,导致轮轨间冲角测量难度大、测量不准确等问题。本文提出一种基于激光线检测的轮轨冲角检测方法,该方法将与轮对运动方向共线的激光线照在轨面上,通过图像畸形校正、Meanshift算法平滑、Radon直线检测等算法处理分别获取轨道边缘线和激光线的位置,计算两者在图像中的夹角检测出轮轨冲角。通过仿真数据和检测结果对比表明,该方法能够实现轮轨冲角的图像检测,且原理简单可行,最后给出检测误差的修正方法,增加了检测方法的鲁棒性。该方法的提出为后续列车运行的稳定性和安全性评价奠定了基础。
Abstract
Attack angle is a key index to evaluate the stability of snakelike motion in the train. Due to the complexity of the running train and the small angle of attack, it is difficult to measure the angle between the wheel and rail. This paper presents a method for attack angle detection based on the laser line and the direction of motion as collinear wheel on the rail surface. The laser line and orbital edge line were obtained by image correction, Meanshift smoothing, and Radon line detection, and then the angle was calculated in the image. Comparison between simulation data and test results shows that the method can realize the detection of attack angle and it is simple and feasible at the same time. Finally, the correction method of the detection error is given, which increases the stability of the detection method. This method may lay the foundation for the evaluation of stability and safety of train operation.
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Key words:
- attack angle /
- snake motion /
- image detection /
- laser line
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Overview
In the locomotive operation, because of the hunting motion caused by pure conical tread, a lateral force and complex creep force between the wheel and rail will emerge and result in attack angle between the wheel and rail when crossing a curve line. Although the attack angle is microscopic, it affects the wheel/rail contact loss and vehicle safety seriously and attack angle is a key index to evaluate the stability of snakelike motion in the train. Monitoring and analyzing the wheel/rail contact condition and the change of attack angle in the locomotive operation play a significant role in the stability and safety of vehicle operation. Due to the complexity of the running train and the small angle of attack, it is difficult to measure the angle between the wheel and rail. A method for combining the on-board camera with the laser line is presented to complete the image acquisition and detect the attack angle based on the laser line and the direction of motion as collinear wheel on the rail surface. The laser line and orbital edge line are obtained by some algorithms such as image pre-processing algorithm, image correction, Meanshift smoothing, and Radon line detection. The angle between the laser line and orbital edge in the image can be got through a series of image processing algorithms, which can reflect the attack angle in the running of locomotive. Radon detection algorithm is used to detect the relative position between laser line and rail edge line, and different conditions of undershooting changes are compared by simulation. The comparison between simulation data and experimental data shows that the method can simply realize the detection of attack angle and it is feasible enough. The results of detection illustrate that the change of attack angle is between 0.355 and -0.72 degrees, and the maximum error is 0.091 degrees. Finally, the correction method of the detection error and measurement accuracy analysis is given, which increases the stability of the detection method and demonstrates that it can meet the demand in engineering applications. It costs about 500 ms when the system completes primary detection of attack angle, which indicates that the detection speed is fast enough, and it can meet the detection requirements in engineering applications. However, some factors such as illumination and external vibration still need to be further studied to emphasize the robustness of the system. This method lays a foundation for further monitoring the condition of train operation and improving the safety mechanism of train.
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表 1 检测结果及误差分析.
Table 1. Test result and error analysis.
Group number Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7 Group 8 Fit-slope 1/k 0.0121 0.0092 0.0103 0.0084 0.0106 0.0073 0.0152 0.0062 Left lateral coordinate 165 156 264 182 167 187 159 153 Attack angle/β 0.693 0.749 0.527 0.481 0.607 0.418 0.871 0.355 Test table settings 0.72 0.84 0.55 0.45 0.65 0.40 0.85 0.40 Absolute errors 0.027 -0.091 -0.023 0.031 0.043 0.018 -0.021 -0.055 Average error -0.016 表 2 9组检测和实际数据.
Table 2. Nine group test and actual data.
No. (△ui, △vi) 1/tanα Detect distance/mm Actual distance/mm 1 (3, 265) 0.0113 102.4 103.00 2 (3, 275) 0.0109 103.7 103.00 3 (3, 269) 0.0111 102.7 103.00 4 (4, 402) 0.0099 163.5 163.00 5 (4, 396) 0.0101 162.8 163.00 6 (4, 406) 0.0098 164.1 163.00 7 (5, 466) 0.0107 195.9 196.00 8 (5, 471) 0.0106 196.6 196.00 9 (5, 475) 0.0105 197.1 196.00 -
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