Micro-Epsilon - Integrated measurement for railway wagons and other applications

Micro-Epsilon is a medium-sized family-owned company that is at the forefront of measurement technology. micro-Epsilon's product portfolio includes sensors for displacement and distance measurement, infrared temperature measurement and colour detection, as well as systems for dimensional measurement and defect detection. micro-Epsilon's areas of application are: integrated measurement of railway wagons, the inspection, maintenance and repair of tyres and brakes, inspection of tracks and rails, etc.


Application areas
I. Integrated measurement of railway wagons
1）Measurement of tilt angle of passenger trains
Inductive EDS displacement sensors are integrated in high-speed trains to determine the tilt angle of the car body required for steering. This data is passed on to the control units in the following vehicles, which tilt the coach body accordingly to compensate for the resulting lateral acceleration. The bus body of the vehicle is tilted towards the inside of the bend with the aid of hydraulic cylinders. The degree of tilt is controlled by the induSENSOR EDS sensors, which reduces the effect of lateral acceleration on passengers.


2) Train vibration measurement
Wear and tear on the wheel pairs and bogies can make natural vibrations perceptible in the passenger area. Acceleration sensors from Micro-Epsilon are used to record these vibrations, detecting vibrations at various points in railcars, locomotives and wagons. These high-precision measurements are used to compensate for the vibrations.

3) Automatic check of stuck brakes
In order to test the braking systems of wagons and railcars, test benches are used to install infrared pyrometers or thermal imagers. These temperature measuring devices detect passing trains and make lateral measurements of the braking system. Due to friction, the jammed brakes generate high temperatures, which are detected by the infrared temperature sensors. The non-contact temperature measurement automatically identifies railcars and wagons whose brakes are stuck and marks them for repair.



Tyre and brake inspection
1. Wheel pair ellipticity inspection
Axle measuring machines are used to check the ovalness or diameter of wheels, bearings and gears. These are equipped with four light-controlled laser micrometers that measure on the rotating axle. Thanks to their high precision, the ovalness or diameter can be determined very precisely. As the measuring distance is variable, the micrometers can also be used for large object diameters.

2. Measuring the profile of wheel tyres on the test stand
Rail vehicles suffer from wheel wear due to high mileage, which affects safety and running characteristics and incurs high maintenance costs. micro-Epsilon's laser sensors are integrated into the test bed of the track bed and are used to preventively check the profile set of the entire train. The sensors are mounted in three tubs which are embedded in the roadbed, one behind the other, at right angles to the direction of travel. Two optoNCDT laser distance sensors are located in each tub 1 and 3 to determine the wheel diameter and the position of the wheel tyres. Tub 2 contains the scanCONTROL laser profile sensor for measuring the wheel profile. The sensor measures through a groove halfway down the wheel tyre track. Maintenance dates for re-profiling are determined from the profile data.

3. Optical measurement of drive shafts, brake discs and wheel tyres
The tread of wheel tyres is subjected to significant loads, so wheel brake discs are inspected regularly. This is the only way to determine the condition of the components, to detect defects and to take timely repair action. Wheel sets are first tested on a measuring machine with a Micro-Epsilon optical sensor. The rotating wheel sets are measured with laser distance sensors to determine axial and radial runout. A laser profile scanner also detects the complete profile at selected measuring points.




III. Care and maintenance
1. Monitoring the lathe
The laser triangulation sensor monitors the distance to the rotating wheel tyre as it is rotated. This means that ablation is detected with high precision. The high-performance sensor detects the dimensional accuracy of the wheel tyre at high speed and with micron-level accuracy. In addition, the laser distance sensor monitors the position of the wheel tyre during the automatic clamping process.


2. Detection of the lifting height of the lifting platform
During repair and maintenance, it is often necessary to lift entire trains. A synchronised heavy-duty lifting system is used for this purpose. To synchronise the lifting heights of individual columns, optoNCDT ILR laser time-of-flight sensors are used. They measure the vertical distance from the support arm to the ground and thus determine the lifting height. Their modern interface concept, combined with high precision, enables the synchronised tuning of the lifting units.


In addition, further optoNCDT ILR time-of-flight sensors measure the entry of the train into the maintenance hall in order to park the train in the correct position. Due to the large measuring range of the sensor, the entry is detected and recorded at an early stage.

3. Inspection of combustion chambers of internal combustion locomotives
The inspection of internal combustion locomotives requires regular inspection and documentation of the combustion chamber. Inadequate quality checks or faults, such as defective valve seats or running surfaces, can lead to serious faulty engines and therefore locomotive failure. Inspections are usually carried out in a confined space with no direct power connection. For this purpose, Eltrotec video borescopes are used. These video borescopes are lightweight, mobile and work independently of the power supply. The robust probes are available in different lengths and designs and can examine even limited spaces. Images and movies are stored on an SD memory card.




IV. Inspection of rails and rails
1. Rail wear and gauge measurement
To inspect the rails, Micro-Epsilon uses a measuring vehicle containing six ScanCONTROL laser profile scanners. These scanners can inspect the profile of the rails from below, above and to the side. The large measuring range of the scanners allows many parameters to be recorded in a single measurement. The width of the guideway and the height of the guideway on both sides can be determined simultaneously and evaluated directly in the sensor. The scanner works reliably under changing environmental conditions and provides accurate measurement results despite variations in the surface (e.g. due to dust or light).

2. Overhead line diameter inspection
Particularly in the case of high-speed trains, the preventive inspection of overhead lines is very important in order to ensure line accessibility. Light-controlled laser micrometers are used for reliable diameter testing. These devices are mounted on maintenance locomotives and guided through the frame on the overhead line during the journey. The high precision of the micrometers enables wear measurements with high accuracy.

3、Track position error measurement
In railway transport, the construction and modification of track sections is subject to increasing demands. A perfect track geometry is essential, especially for high-speed lines. To ensure this, tamping machines are used, which compact the ballast lying under the sleepers, give the track the necessary grip and avoid positional errors. In order to assess the exact position of the track, precise information is needed about the state and position of the track before the track tamper. Two INC5701 inclination sensors from Micro-Epsilon record the lateral and longitudinal inclination angles in the mobile measuring device and transmit this information to the tamper travelling behind. This makes the precise position of the track possible.