A new approach to position measurement for automation

In-Depth

New technology offers an alternative to GPS/GNSS and transponders to support container handling equipment automation and autonomous vehicles operating in terminals.

Netherlands-based BTG Positioning Systems (a sister company of BTG Electronics Design) has partnered with US-based Ground Positioning Radar (GPR) to bring a new technology for automated and autonomous equipment positioning to the container terminal market: Ground Sensing Localization (GSL).

BTG is a well-known port automation company with around 35 years of experience in developing and producing measurement systems. It is best known for its transponder-based measurement system, deployed on semi and fully automated equipment including AGVs, STS cranes, yard gantry cranes and automated straddle carriers in Europe, Asia, Australasia, the Middle East and the USA.

Mapping the terminal

Using low-frequency radar pulses that travel 2.8m deep into the ground, GSL collects data to create a detailed map of the subsurface which is stable over time.

To achieve a localised position reference, real-time data from a sensor on board the vehicle is compared to the GSL map layers. Position accuracy of +/-2cm can be achieved at all maximum speeds required on port equipment. Technically, higher speeds of up to 130km/h are possible with a position accuracy of +/-5cm.

BTG is now working to add GSL to its existing product portfolio. The company is leveraging its expertise in positioning technology, to develop vehicle-mounted sensors for different applications.

Infrastructure free positioning

In an interview with WorldCargo News, BTG CCO Daan Potters said the company is excited about the potential of GSL to address some of the key issues in positioning technology for port applications. “What sets GSL apart is its complete independence from GNSS/GPS, offering a significant advantage in today’s geopolitically sensitive world. Unlike other localisation technologies that rely on visible, above-ground reference points, often lacking in container terminals, especially along quayside where multiple vehicle movements obstruct direct line of sight, GSL requires none of these. It adeptly utilizes the subterranean landscape as its reference, overcoming line of sight barriers posed by concurrent vehicle movements,” said Potters.

It is perhaps not widely understood, but BTG’s existing transponder technology is not limited to equipment that follows a fixed travel path, like AGVs. Terminals using AGVs or automated straddle carriers – where the primary navigation system for the yard is GPS, radar or other positioning technology – also use BTG transponders at the same site for position data on the quayside underneath the STS cranes.

Transponders are old but reliable technology. They are not affected by interference from crane structures or signal disruptions from atmospheric conditions such as rain and fog. Their disadvantage is transponders have to be installed in the ground, and consideration has to be given to the construction of the terminal surface as transponders are impacted by the use of rebar reinforcing.

Potters declined to provide details, but there are terminals that have attempted to use alternative location positioning systems in an effort to avoid the fixed infrastructure of transponders, only to later install transponders to get the performance necessary to support their automation requirements.

Infrastructure free

With GSL, BTG sees a way to achieve a maintenance-free, solid-state sensor system that requires no fixed infrastructure, and has a lifespan exceeding 10 years. Furthermore, each GSL sensor operates autonomously, ensuring system or network failures do not disrupt operations.

GSL can be installed in new or retrofit applications and is ideal for free-ranging applications, where it is expected to be more cost-effective than a transponder system. Whereas a vehicle that follows a fixed path, such as an AGV, needs one transponder every eight square meters. A free-ranging vehicle like an automated straddle carrier needs one transponder per square meter.

Flexibility

In addition, GSL can support real-time positioning by continuously comparing vehicle position against the ground map. This, Potters explained, can reduce complexity compared to a navigation system that periodically checks position against a transponder reference, then relies on encoders and other systems to keep the machine on a predetermined path to the next transponder position.

Furthermore, GSL supports free-ranging navigation, so there is flexibility to change vehicle paths, including to avoid rutting and to spread the wear of heavy equipment travel on the terminal surface.

GSL also has good potential to be combined with sensor fusion kits for autonomous vehicles, including terminal tractors and other CHE. With continuous position updates, GSL can provide a local position reference. This can be combined with other sensor technologies used for collision avoidance and other aspects of autonomous vehicle systems. Other applications include driver assistance features such as auto steering for RTGs.

BTG is now working on its first-generation GSL sensors and plans to start testing these this year. Production versions are scheduled for release throughout 2025, with models tailored for precise positioning of RTGs, ARMGs, straddle carriers, AGVs, STSs, and terminal tractors.

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