Deliveries from an unmanned aerial vehicle (UAV), or drone, have launched in some cities, and it won’t be long before drone drop-offs will be a regular occurrence. However, a number of power supply issues must be addressed first to make sure a UAV will hold charge long enough to fly to and from drop-off locations with additional payload.

In order to make deliveries efficient, drones would need to be charged between deliveries without any considerable delay. At this time, most UAVs need to be manually connected to a power source in order to charge, or the UAV’s battery pack has to be manually replaced. To address this, researchers from the University of Glasgow have created a wireless power transfer system for drones.

“Normally, UAVs are capable of uninterruptedly running for 20-60 minutes,” said researcher Hadi Heidari. “As soon as you add a payload to the UAV this time drops. We wanted to address this longevity by offering wireless power transfer stations, allowing drones to charge autonomously at different locations.”

This wireless power transfer station could be positioned at multiple locations, bypassing the need for a UAV to visit a particular location to charge, and increasing the radius of operation.

Figure 1: Wireless power transfer station for UAV systems

This proposed charging station utilizes inductive coupling to power the drone. This technique works by inducing a voltage in a transmitter coil placed on the charging pad, which generates a magnetic field to induce a voltage in a receiver coil on the drone to wirelessly charge it.

The closer the drone is to the charging pad, the greater the voltage and charge that can be generated. The researchers found that a distance of 12cm or less is ideal to charge the drone’s battery. When the primary coils on the pad and the receiving coils on the drone are separated beyond this distance, the charging will stop.

Figure 2: Distance vs. output voltage

In order to ensure the proper transmission of energy and the stability of the electromagnetic field, there must be no metal in the vertical space of the receiving coil. To accommodate this, the researchers extended the receiving coil away from the body of the drone.

By 3D printing the drone, the researchers were able to fully seal the battery and electrical components, limiting the impact of weather on the device. This allows the drone to fly in harsher conditions and environments, including forests, factories and farmland, where particles and dust in the air would typically impact drone performance.

This proposed solution may greatly reduce the cost of labor and will bring drones closer to being able to deliver in cities, as remote charging sites will increase the efficiency and travel distance of the devices. The researchers see this wireless charging technology being used for a range of applications, including autonomous cars, wearables and implantable devices. Following this initial research, the team is now involved in a number of projects to bring this technology to medical devices.

For more information on wireless charging, visit the IEEE Xplore Digital Library.