Issue 40 Unmanned Systems Technology October/November 2021 ANYbotics ANYmal D l AI systems focus l Aquatic Drones Phoenix 5 l Space vehicles insight l Sky Eye Rapier X-25 l FlyingBasket FB3 l GCS focus l AUVSI Xponential 2021

Platform one Researchers at the University of California, Berkeley, have developed a system of airborne robots that can replenish batteries in mid-air to achieve flight times that are impossible for normal UAVs (writes Nick Flaherty). The team has developed a ‘flying battery’, essentially a small UAV with a secondary battery pack. It can be used to recharge another UAV in flight, called the primary UAV, using four spring-loaded contacts for the charging and some simple control logic. Charging is completed before the secondary cell is disconnected. Using multiple flying batteries, the flight time of the primary UAV is extended from 12 minutes to 56. Another, more radical approach is to discard the battery as it is discharged, solving the problem of carrying a depleted battery’s dead mass. A multi-stage multi- rotor uses separate battery cells and jettisons a cell when it is depleted. The cell falls to the ground safely using a parachute for retrieval. This approach gives twice the flight time than using one pack with the same number of cells. The team, at the university’s Hiperlab, is also working on algorithms that allow a UAV to adapt its flight configuration in-flight to continuously maximise efficiency. This is especially useful for systems carrying payloads whose characteristics (size, shape, mass) vary from one flight to the next. The mechanical design of the vehicle is crucial for the power consumption. The researchers found that tilting the vehicle’s propellers away from the common thrust direction can lead to improvements in the total power consumed. This is because the vehicle gains control about its yaw axis, leading to less energy having to be spent to reject disturbances. All these factors are combined to boost the flight time of a UAV system. In-flight recharging UAV Airborne vehicles The ‘flying battery’ has been shown to extend UAV flight times for 12 minutes to 56 ENABLING TECHNOLOGY EVERYWHERE Harwin’s connector products are proven to perform in extreme conditions, with shock, vibration and temperature range rigorously tested. Micro connectors start at 1.25mm pitch delivering 2A per contact, up to 8.5mm and 60A - we cover a wide range of applications for when SWaP matters most. With our quality, service, support, and highly reliable products, you can depend on Harwin. harwin.com Engineer to Engineer – Harwin won’t let you down. Scan here for more Connect with confidence Connectors shown actual size Harwin UAV Unmanned Systems Oct 21.indd 1 01/10/2021 11:26