A consortium in the UK has developed a positioning system for safer autonomous UAV landing on ships, writes Nick Flaherty.

The system developed by Omnisense and 42 Technology (42T) uses a ground-based ultra-wideband (UWB) positioning technology as part of the DroneHome programme supported by the European Space Agency.

The DroneHome programme is developing terrestrial radio positioning as a complementary navigation layer in GNSS-challenged environments. 42T in Cambridge, UK, designed and developed the extended-range RF hardware used in both the ground infrastructure and the airborne elements of the system.

“The architecture is that, on the landing zone, there is a set of beacons and a receiver onboard. But there are various elements controlling the timing of the beacons on the ground,” said Paul Bearpark, electronics and software group leader at 42T.

This uses off-the-shelf UWB chips from Decawave, now part of Qorvo, which transmit at a power level of -41 dBm/MHz to meet the regulations at the time, although regulations in Europe have changed recently to allow more flexibility outdoors. The concern with high-power UWB is interference with satellite systems, but there are also regulations in some countries for emergency services.

“We extended the range with a wideband low-noise amplifier, a power amplifier and the switching elements,” said Bearpark. “We had a single platform that could be used as a beacon or onboard with common hardware as a single PCB. The other thing was the selection of the antennas. On the ground, the beacons had directional antennas for more gain. This is outside the regulations, so Omnisense got a test and development licence to prove the principle.”

Boosting the signal to -20 dBm/MHz gave a range of 200 m from the landing platform, which allows the UAV to get close using inertial navigation.

The platform, possibly at sea, would rotate according to the position of the UAV so that the antenna would always be pointing at the aircraft to create a landing strip using a separate comms link.

The board, measuring 10 cm x 3 cm, is used on both the UAV and the ground antennas. The board sends chirps of information that are time-synchronised with the UAV to the onboard location system.

Omnisense had already developed the location engine as part of another project but this application needed the data transmitted more frequently. The time of arrival of the signal is coupled with the known geometry of the beacons on the platform to determine the location of the UAV.

System field trials and simulation-based analysis confirmed stable positioning within a defined envelope during GNSS-degraded operation, enabling reliable autonomous approach and landing.

“DroneHome demonstrates that terrestrial radio positioning can provide a reliable and predictable navigation layer when GNSS signals cannot be relied upon,” said Andy Thurman, CEO of Omnisense. “This is an important milestone in building more resilient autonomous systems that can maintain safe operation in real-world conditions.”

Omnisense is integrating this into next-generation navigation architectures and autonomous platforms.