Dynamic Deflection of a Railroad Sleeper from the Coupled Measurements of Acceleration and Strain

• Main Authors: Sung-Ho Joh, Katherine Magno, Sung Ho Hwang
• Format: Article
• Language: English
• Published: MDPI AG 2018-07-01
• Series: Sensors
• Subjects: deflection; railroad sleeper; structural health monitoring; ballast track; computer vision
• Online Access: http://www.mdpi.com/1424-8220/18/7/2182

Dynamic deflection of a railroad sleeper works as an indicator of ballast stiffness, reflecting the health conditions of a ballast track. However, difficulty exists in measuring dynamic deflection of a railroad sleeper by conventional deflection transducers such as a linear variable differential transformer (LVDT) or a potentiometer. This is because a fixed reference point is unattainable due to ground vibrations during train passage. In this paper, a patented signal processing technique for evaluation of pseudo-deflection is presented to recover dynamic deflection of a railroad sleeper using a coupled measurement of acceleration and strain at the concrete sleeper. The presented technique combines high-frequency deflections calculated from double integration of acceleration and low-frequency deflections determined from strains. Validity of the combined deflections was shown by the deflections measured with a camera target on a concrete sleeper, captured by a high-resolution DSLR camera with superb video capturing features and processed by computer vision techniques, such as Canny edge detection and Blob analysis.