Unmanned Systems Technology 025 | iXblue DriX I Maintenance I UGVs I IDEX 2019 I Planck Aero Shearwater I Sky Power hybrid system I Delph Dynamics RH4 I GCSs I StreetDrone Twizy I Oceanology Americas 2019

55 The marker has a chequerboard pattern of light and dark colours that can be printed on virtually anything. It is typically printed on a thin piece of aluminium that can be deployed quickly in the back of a truck or on a boat. The size of the marker depends on factors such as the size of the UAV and the landing platform, and the required range of detection. The larger the marker, the longer the range of detection. For a pick-up truck travelling off road, for example, the UAV would typically be up to 10 m away, so the marker is well under a square metre. Planck has a version that allows a 1 m target to be detected from 70-80 m away. The UAV has to know the pattern on the marker, as the detection is tightly coupled to the aircraft’s controls, so understanding the size of the target on initial detection is really important. This also helps prevent any potential ‘bad actors’ from duplicating it – there is a lot of information encoded in the marker but generating the size from the encoding itself has some limitation, so the company says it’s better to have operators enter that size themselves. The data on the marker contributes to the error-correction algorithms running on the UAV to improve the accuracy of the landing. “The UAV knows which QR code it wants to land on, then it locks on and starts its descent, with frequent checks – there are multiple levels of checks,” says Twining. Timing is essential for planning the approach and touchdown, and there are multiple failsafe modes to ensure a safe landing. That means the UAV will not land if conditions are not right and if a number of condition are not met at the same time. The UAV’s response would then vary depending on the situation – it could hover in place and wait, or ascend away from the platform and restart the process. There is always the ability for the human operator to abort the landing as well. Avionics The sensors on the UAV are tightly coupled to the Planck controller, which is based around the TX2 module from Nvidia. This board is linked to a camera module, typically a 4K resolution 1080p camera sensor with a MIPI-standard interface. There are several suppliers of such modules, but tight integration between the controller and the camera is required to ensure that the camera is properly calibrated and that the board interfaces correctly with the autopilot via a simple serial interface. The connection is usually via the NAVlink protocol to a common Planck Aero Shearwater | Digest The reason we focus on vision is that it is the most reliable and robust approach, but has the smallest impact on the system Unmanned Systems Technology | April/May 2019 The Shearwater’s automatic landing system is relatively simple, being based on a single optical camera For landing, the system locks on to a QR code-like marker on the boat or truck