Online detection system for wheel-set size of rail vehicle based on 2D laser displacement sensors

The real-time detection of wheel-set size, the most significant technical parameter during vehicle operation, has important implications for ensuring the safety of wheel running. Based on laser ranging, an online detection system of the wheel size installed below the track is developed. Eight two-dimensional (2D) laser displacement sensors are applied to detect the wheel-set size including wheel flange and tread profile. A digital I/O card is utilized to generate synchronous signals which guarantee simultaneous working of all sensors. Least square based curve fitting and pick-up algorithm of tread feature-points are used to process the measured data and calculate the flange width, flange height and wheel diameter. The experimental results show that the online detection system of wheel-set size can realize the non-contact, dynamic and real-time measurement of wheel-set parameters. When train running speed is under 5 km/h and sampling frequency is 30 Hz, the detection accuracy of flange width and height is ±0.2 mm and the detection accuracy of wheel diameter is ±0.5 mm, which can meet the requirements of maintenance operation.