Vire Labs developed a train scanner for rail traffic needs

In Helsinki, next-generation laser scanners are used in the maintenance of trains. Enormous volumes of data challenge product development in an unprecedented way.

The Ilmala district of Helsinki is home to the largest rail yard in Finland. Its massive maintenance halls are used to maintain a majority of Finland’s long-distance train cars, as well as the Greater Helsinki commuter train fleet.

Train maintenance consists largely of inspection – cars are thoroughly checked, but ultimately only a few parts are replaced or repaired. Indeed, VR FleetCare, the unit responsible for train maintenance, set out to automate the inspection of trains and, in cooperation with Finnish AI and IT developer Vire Labs, created a solution that combines sensors and artificial intelligence.

The Train Scanner is a 6.6-metre-long pole at the Ilmala train yard. It contains three high-speed line cameras, a laser scanner, lights for the cameras, and Vire Labs technology.

“Sensor technology, machine vision, and artificial intelligence applications are extremely useful for inspecting rail stock”, explains Vire Labs CEO Mikko Saari.

Train speed is a challenge for reliable measurement

In principle, the idea is simple: The full length of a train is driven past the Train Scanner, allowing the sensors in the pole to measure its surface and contours. The measurement results are analysed to find deviations and other items of interest, which can be separately reported to the maintenance crew. Thus, the amount of time that would otherwise be spent on inspection can then be devoted to repairs. Ideally, artificial intelligence can also be used to recommend a solution suitable for the problems detected.

However, this simple idea is a challenge to realise. In order to maximise the utility of the Train Scanner, it must be possible for trains to drive past it at high speeds. Train Scanner’s high-speed cameras capture up to 27,000 frames per second of the side of a train, and in addition to the cameras, also LiDARs are used for the data collection.


Laser phase-shift measurement

Trains are running at high speed pose a challenge for conventional laser scanner technology but a technology called phase-shift  can significantly improve the measurement rate of a laser scanner. Instead of emitting individual laser pulses, the phase-shifting LiDAR emits continuous laser beam, and the sensor measures the phase-shift caused by the object being measured at the frequency of the laser beam reflected from a given end point. The precise contours of the fast-moving train are calculated from this phase-shift.

The problem with phase-shift laser scanners is a limited the measuring distance. Whereas a conventional pulse laser scanner is capable of measuring objects hundreds of metres away, a phase-shift laser scanner normally has a measuring distance of only a couple of metres. This is insufficient for measuring the side and roof of a train car. This was solved by using a an improved version of a phase-shift laser scanner, which has a measuring distance of nearly six metres. Installed at the top of the Train Scanner pole, this type of LiDAR is able to measure both the side and roof of a train.

The TrainScanner is assembled at Vire Labs facility in Pori, Finland
The weather-proof masts contain three Virebox.AI computers, LiDARS and other scanning devices.

Large data volume locally – efficient data transmission

The VR FleetCare Train Scanner combines a high measurement rate laser scanner with three line scan cameras, which capture tens of thousands of frames per second. Indeed, the next challenge for product development was processing the massive amount of data and sifting through it to find pertinent information – a veritable needle in the haystack.

The solution can be found in artificial intelligence and in neural networks. Each sensor is connected with a gigabit uplink to a Virebox computer developed by Vire Labs, which is designed precisely with an eye towards neural networks. The computers are enclosed in the same pole as the sensors.

The neural network is taught the correct shape and appearance of the train. The application compares the train passing by with this model and identifies potential deviations. The precision of the laser scanner and line scan cameras is even capable of detecting individual loose bolts on a train running by the Train Scanner at 100 km/h. Any foreign objects on the train roof can also be easily detected.

“LiDAR not only measures the contours of a surface, but also the intensity of the surface’s reflection. This allows us to distinguish between, for example, clean and dirty trains”, explains Vire Labs Business Development Director Ossi Porri.

When measurement readings are analysed locally, the Train Scanner is able to send out only meaningful findings, thus saving considerably on data transmission capacity. In other words, the Train Scanner does not use, for example, the PLC logic commonly found in industrial automation systems.

The Train Scanner is such a promising solution that VR FleetCare has begun selling it on the international rail market. Other types of customers can also benefit: The solution now used to measure commuter trains will, in the future, be able to measure, among other things, log loads on trucks. There are endless applications for smart sensors and advanced software!

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