Dissecting Drone Technology (Part 1)
About Cobus Heukelman
Part 1 of 3 where Symmetry Electronics Applications Engineer Cobus Heukelman dissects all the systems in a drone
Why are drones so fascinating to technology aficionados? Well for starters they’re just plain awesome. Then there’s the fact that they allow us to solve everyday problems in the most high-tech, complicated ways possible. You may ask how that’s practical, but that’s like asking a 10-year old boy if his nuclear powered car really needs a rocket booster strapped to the roof . . . yes, obviously. However, just because something is complicated doesn’t mean it’s not efficient, and that’s where drones make sense in business. Let’s say you’re filming a movie scene that requires a breathtaking aerial shot. Now the simplest solution is to tell your cameraman to get in a plane and start filming, but what if he could do it without you having to rent a plane and pay for the services of a pilot? Suddenly a high-tech drone doesn’t sound so silly anymore.
Figure 1: The commercial/civilian sector does not currently have the lion’s share of the drone market, but this sector is anticipated to have compound annual growth rate of 19% between 2015 and 2020.
According to the Business Insider Drones report, worldwide drone sales (both civilian and military) are projected to exceed $12 billion in 2021 [1]. As shown in Figure 1 the largest portion of the drone market belongs to the military, but the commercial/civilian market is set to have the highest growth with a compound annual growth rate of 19% between 2015 and 2020 [1].
With the increases in computational power, improved energy efficiency in electronics, and the growth of the IoT industry in recent years we have seen great advances in consumer and enterprise drones. At this year’s CES there were drones as far as the eye could see. The Phantom 4 from DJI offers 4K video recording and the ambitious Ehang Drone Copter wants to be your flying Uber.
Figure 2: DJI Phantom 4 [Courtesy http://www.dji.com/product/phantom-4]
Figure 3: Ehang Drone Copter
Image from: https://www.lily.camera
Traditionally drones have been quite tricky to fly, but companies like DJI and Lily Robotics have come up with artificial intelligence that allow a drone to follow the user. The Lily Camera drone wants to make action videos a breeze. Although this drone isn’t in production quite yet, the concept is that you just toss it into the air, and that would start the video. You can then ski down that slope, knowing that your trusty drone is filming.
For a drone to fly around your neighborhood, it needs multiple systems working in harmony. First, it needs a flight system to keep it upright and to ensure that each electric motor provides enough thrust for the drone to move in the desired direction. Second, it requires a communication system so that the user can tell the drone where to go. Modern drones also have video systems so that the user can control the drone without directly looking at it. To avoid crashes it may need some more sensors and a collision avoidance system. Finally, if you want the drone to be autonomous then it will need a navigation system to plan its route. Even if you’re not designing a drone, your product may still need one of these technologies. Grab your scalpel and forceps; next we’re going to dissect a few of these systems.
Communication System
The communication system is responsible for sending the user’s commands to the drone, and reporting the drone’s state back to the user. If it cannot send commands to the drone quickly enough, the user will experience lag and be unable to control the drone. While the lag and throughput of the communication system are important, it should also be power efficient. Drones use a lot of power to stay in the air so every watt is precious. One last thing to consider is the range of the communication, does the drone need to have a range of 10m, 100m or 1000m?
For simple short-range drones up to 100m, Bluetooth Smart is an attractive technology. It features extremely low power consumption, but the low throughput means that streaming video is out of the question. Symmetry offers many options for Bluetooth Smart modules such as the Silicon Labs BGM111 and BGM113 modules, which make integration a breeze. You can start your design with a module, and when production volumes increase you can take advantage of using the Blue Gecko Bluetooth Smart SoC directly, without having to change your firmware. Nordic also offers Bluetooth Smart SoCs such as the nRF51822, which is now available as a thin WL-CSP variant measuring only 3.83 x 3.83 x 0.35mm and the nRF52832 which supports Bluetooth Smart, Ant and proprietary 2.4GHz protocols with data rates up to 2Mbps.
For longer ranges a module that operates in a lower frequency band, such as the 868MHz or 915MHz bands can be used. The Multitech MultiConnect mDot module offers a range of up to 10 miles in the open and 1 to 3 miles through buildings. The price of extra range is a lower throughput, so these modules give a maximum data rate of 300Kbps. This would be ideal for a surveillance drone, which does not communicate constantly. Another scenario where this technology can be useful is for retrieval of a drone that has crashed or is out of power. The low power consumption and long range of these modules means that a lost drone can send its GPS coordinates to the user on an almost empty battery.
Most of the consumer drones today use WiFi for all communication including streaming video. That’s because it’s easy to connect to existing devices such as smartphones and tablets, and it supports high data throughput needed for video. The Silicon Labs WGM110 module is great for easy incorporation of WiFi. It measures only 14.4 x 21.0 x 2.0mm and can provide data rates of 72.2Mbps.