Fraunhofer Institute for Physical Measurement Techniques IPM
The stationary system measures the conformity of passing trains by acquiring high-resolution 3D point clouds. The 3D image is available immediately after the train passes and can be analyzed for geometric irregularities, such as loads that violate the clearance profile, open doors, deformed containers, overriding of buffers, and loose connections between wagons.
Four scanners for one profile
Laser scanners form the core of each Sector Profile Scanner (SPS). Four scanners are needed to inspect an entire train. One pole on each side of the track carries two scanners at different heights. A rotating polygonal scanner with eight mirrors deflects the modulated laser beam onto the passing train and collects the returning light for analysis. The laser beam covers a scanning angle of 70 degrees. The measured distance values create a two-dimensional profile of the corresponding train section. The four profiles are then processed into a combined profile of the entire train. As the train moves, thousands of such profiles are measured, providing a three-dimensional image of the inspected train. The distance between profiles depends on the train’s speed and the scanning rate. A high scanning rate is crucial for achieving a good profile density for fast-moving trains.
Up to 2 million data points per second
The laser scanner can measure up to two million data points per second. Based on this extraordinarily high measurement rate and the polygon mirror design, data capture is flexible according to customers‘ need.
In addition to the standard version, Fraunhofer IPM offers a High Angular Resolution (HAR) setup that provides 1,800 data points per profile at 800 profiles per second, addressing the requirements of freight trains and moderate-speed passenger lines. Furthermore, the High Profile Density (HPD) setup is designed for use on high-speed lines. It features 900 data points per profile at 3,200 profiles per second, which results in a density of 32 profiles per meter at 360 km/h.
The optical power of the infrared laser is optimized for a measurement range of about 10 meters, allowing inspection of rolling stock even on double tracks while fully maintaining eye safety. By exploiting the advantages of the phase-shift technique, a typical accuracy of 5 mm is achieved over the full measurement range. The scanners calibrate themselves before each profile measurement. This ensures stable results over extended periods, practically independent of ambient temperature.
Reliable operation
The SPS’s design guarantees almost maintenance-free operation. The hermetic housing of the system keeps dust and humidity away from the optics and electronics. A baffle reduces stray light and pollution on the outside of the measuring window. Once the mirror stops rotating, the laser turns off, ensuring eye-safe operation at all times. The SPS is eye-safe according to IEC 60825.
Fast, accurate, and robust
With its combination of high measurement speed, accurate results, and robust design, the SPS is ideally suited for the challenging task of inspecting passing trains at full speed. This holds true even under difficult lighting and environmental conditions.