Unleashing the power of automation

A digital signalling solution is helping metro operators run more trains on networks and may contribute to increased use of autonomous trains.

A digital signalling solution that helps metro operators run more trains on networks.

That attractive proposition is how Thales has pitched its SelTrac G8 product, the newest generation of Thales CBTC solution.

The technology behind this is called Communications Based Train Control, or CBTC.

SelTrac is natively driverless, but it can still be used with an attendant or driver.

“Customers who deploy SelTrac™ G8 can benefit from a lifelong innovation insertion, which is enabled through the new digital architecture,” said Nuno Guerra, Thales ground transportation systems and secure communication and information systems.

“The new generation also provides extensive services to operate and maintain the systems more efficiently.

“The beauty of it, it is also autonomy ready.” Guerra said a key aspect of SelTrac™ G8 was its compatibility with Thales’ NGPS (Next-Generation Positioning System), an autonomous train position system that underwent a proof-of-concept with MTA New York City Transit. Instead of conventional odometers and tags, NGPS uses inertial navigation, radar and radio ranging sensors or GPS. These features are combined with a 3D reference map to determine precise train position.

“In the future, LIDAR (light detection and ranging) and high-definition video cameras will provide additional data to enable capabilities such as obstacle detection,” Guerra said.

“The diversity of sensor types deployed in the autonomous positioning system contributes to resilience in two ways.

“First, it means there is no single point of failure. If information from one sensor group is temporarily unavailable, the remaining two provide sufficient data to position the train reliably.”

If sensors at one end of the train fail, then the system can seamlessly use sensor information from the other end of the train.

“Second, sensor diversity reduces the uncertainty associated with using a single sensor technology: using three different types of sensor ensures that positioning computations are safe,” Guerra said.

Underpinning everything are sensor fusion algorithms that evaluate and combine data from all three sensor groups to provide an accurate real-time train position. Sensor data also will be compared with static datasets from the reference map to further increase certainty.

For example, data from the IMU devices is continuously referenced to a 3D digital route map which incorporates data about track curvature and gradients along the line. Matching the curvature detected by the IMU with the curvature on the map is one way the position of the train can be checked
and recalibrated.

Guerra said there were three important new features in SelTrac™ G8. The first was new digital architecture.

“This is based on common hardware platforms and is designed to be upgraded easily, including our new object controller or Remote IO to reduce the amount of wayside equipment required,” he said.

“Secondly, we have our suite of enhanced services, to support operators to achieve maximum availability. Thirdly, and last but not least, SelTrac™G8 is autonomy ready.”

Permanently upgradeable

Guerra said the beauty of SelTrac™ G8 was that it was permanently upgradeable. New functions can be added easily by upgrading software.

“We call this ‘innovation insertion’,” Guerra said. “SelTrac™ G8 also features advanced diagnostic and health monitoring tools, easing maintenance and boosting reliability. In addition to this, our customers benefit from a significant reduction in wayside equipment, so installation and maintenance costs are lower.”

SelTrac™ G8 can support almost any type of radio communications, including LTE.

“Thanks to our onboard communications gateway, you can switch between multiple radio technologies, so your train always stays connected,” Guerra said.

Thales successfully demonstrated its next-generation positioning system in a nine-month pilot project on the New York City Subway.

The new positioning system was fully integrated on four trains on the Flushing (7) Line, which already operates using communications-based train control (CBTC). Each of the four trains was fitted with ultra-wideband (UWB) radio, radar and inertial measurement units. The project yielded strong results and underlines the way that advanced train positioning technology can dramatically accelerate the deployment of CBTC signalling.

“Additional benefits of the new positioning system include greater reliability thanks to increased redundancy, improved train positioning accuracy and ease of installation.

“The project also shows the potential for next-generation positioning technology to integrate seamlessly with existing CBTC systems,” Guerra said.

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