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首页> 外文会议>Annual Symposium on Quantitative Nondestructive Evaluation; 19980719-24; Snowbird,UT(US) >REAL-TIME PROCESSING OF CONTINUOUS DOPPLER SIGNALS FOR HIGH-SPEED MONITORING OF RAIL TRACKS
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REAL-TIME PROCESSING OF CONTINUOUS DOPPLER SIGNALS FOR HIGH-SPEED MONITORING OF RAIL TRACKS

机译：连续多普勒信号的实时处理，用于铁路轨迹的高速监控

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摘要

A novel concept based on the Doppler effect was introduced for continuous monitoring of rail defects at high speed. This approach exploits the relative motion between the propagating ultrasound and the rail defect. It was shown from the feasibility tests that low frequency air-coupled transducers can be effectively used for detecting rail surface defects, thereby eliminating contact between the transducers and rail surface. The feasibility of this technique was experimentally studied and verified in a laboratory setting. In a test conducted using a rotating disk with a notch on the periphery, the Doppler effect was clearly observed. The continuous wave ultrasonic signals are reflected from the surface notch, resulting in Doppler shift in the as-obtained waveform. Due to the narrow bandwidth of the signal, the magnitude of the shifted frequency was clearly pronounced in the frequency spectrum. The shift was experimentally detected in the frequency domain using the Short-Time Fourier Tranform and peak-detecting the transformed signals. It is believed from this feasibility test that CW Doppler can be used as an effective means of high-speed rail monitoring, particularly for detecting surface defects and broken rails. For the future work, a criterion to set a threshold magnitude of the peak-dected STFT should be established. Once the threshold is determined, the system can be designed to issue an alarm when the peak magnitude exceeds the threshold value. This condition may indicate any surface anomalies and thus can be used as a criterion for the alarm. More importantly, further investigation is necessary for monitoring internal defects which may also seriously affect the rail integrity.
机译：引入了一种基于多普勒效应的新颖概念，用于高速连续监测钢轨缺陷。这种方法利用了正在传播的超声波和钢轨缺陷之间的相对运动。从可行性测试中可以看出，低频空气耦合传感器可以有效地用于检测轨道表面缺陷，从而消除传感器与轨道表面之间的接触。该技术的可行性在实验室环境中进行了实验研究和验证。在使用旋转盘在其外周上具有凹口的测试中，清楚地观察到了多普勒效应。连续波超声波信号从表面凹口反射，导致所获得的波形发生多普勒频移。由于信号的带宽较窄，因此在频谱中显然可以明显看出移频的幅度。使用短时傅立叶变换并峰值检测变换后的信号，在频域中通过实验检测了频移。从该可行性测试中可以相信，CW多普勒可以用作高速铁路监控的有效手段，特别是用于检测表面缺陷和断裂的铁路。对于将来的工作，应该建立一个标准来设置峰值检测STFT的阈值幅度。确定阈值后，可以将系统设计为在峰值幅度超过阈值时发出警报。这种情况可能表明存在任何表面异常，因此可以用作警报的标准。更重要的是，有必要进一步调查以监视可能严重影响轨道完整性的内部缺陷。

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