Slowly, but surely, drones are becoming widely accessible and the number of their applications is rising by the minute. They’re used in military, photography and aerial mapping, Amazon uses them for package delivery and they are also used for recording events (sports, celebrations, festivals, etc.). We can see them soaring up in the sky on daily basis. You should know that all unmanned aerial vehicles (UAVs) are considered as drones. They come in all shapes and sizes, and they’re equipped with various types of wings, rotors, engines, batteries, sensors, mounts, etc. They are developing quickly, getting easier to control during flight and landing and, in general, becoming safer. All of that makes them an expensive toy that gives you a wide range of possibilities and an eye in the sky! Some of them can be acquired at a lofty price of tens of thousands of dollars! It makes us wonder, how do they work, what makes them as costly as a new BMW?
Structure and Overview
Every drone has four main parts: its body, a battery or an engine, rotors or wings, and the electronics that are essential for control and the autopilot.
When someone says ‘drone’ you probably envision a multi-rotor kind, most commonly the one with four rotors – the quadcopter. It’s the most popular one because its multiple rotors make it easy for the drone to stabilize itself and it’s also easier to control. However, its rotors use a lot of power, which requires a large and heavy battery. Because of that, the structure has to be extremely lightweight, and new, light and durable materials have to be used (such as carbon fiber composite materials). To keep themselves stabilized they need to change the engine power quickly, which makes the gas engines unsuitable – they use the electric engines only. All of this means: more energy consumption, more weight and less flight time.
Some of the other commonly used drones are single-rotor, fixed-wing and hybrids.
Single-rotor drones are like helicopters, and fixed-winged ones are aerodynamically shaped to resemble planes. Both of these have less power consumption, which gives them more flight time (and they can use gas engines), but they’re also very difficult to control, and previous training is required. Also, because of the helicopter’s large and sharp blades, it can be extremely dangerous if it hits someone! It’s enough to say that some fatalities have been registered. The blades need to be large and sharp because they need to generate the force equal to the force generated by multi-rotor drones.
Hybrids are still in development. They’re a combination of multi-rotor and fixed-wing drones. The idea is to maintain the ease of control, while making the UAV more energy efficient. The most famous example is Amazon’s delivery drone.
Stabilization and Sensors
It’s not easy to master navigating a flying device. Imagine if you also had to fly it in a way that prevents it from losing stability and falling! Drones have a built-in autopilot system that keeps it stable during flight. This system is composed of various sensors and a software that uses the data from those sensors to calculate the optimal performance parameters for the electric engines. The usual sensors used in drones are gyroscopes, accelerometers, compasses, barometers (pressure sensors), altimeters and airspeed sensors (the Pitot tube).
A gyroscope is a device that maintains one of its axis vertical, no matter how the drone is oriented in space. Gyroscopes are usually a part of accelerometers (these components have become so small and cheap, that it makes no sense to manufacture them as separately). The main task of an accelerometer is to measure acceleration in three defined directions, but all sorts of information can be derived from acceleration – like shocks, sudden drops or halts, which also involve crashes, etc. By using a gyroscope, an accelerometer and a compass, the drone always ‘knows’ its orientation and how much it tilted relative to its horizontal and vertical axes.
Altimeters are used to register if the drone is flying too low (some UAVs have a built in stabilization and/or safety landing procedures in that case). Also altimeters are used when you want your drone to hover – they keep them on that exact height you wanted. Of course, a GPS system is also needed for hovering. Some of the drones that have a GPS system also have the option to remember the coordinates of the place from which they took off – so they can come back in case of some unexpected malfunction.
All of these sensors are essential in flight control and the software that operates with the information obtained from sensors is complex and there’s always room for its advancement. Just think about how easy it is for us to loose balance, how often we trip and fall, just while walking. And keep in mind that our body is stabilized by our brain which is working mostly unconsciously like an autopilot, and the human brain is supposed to be the most advanced and evolved part of any operating system in nature. So, compare our ‘autopilot’ with the one that’s supposed to stabilize your drone during flight, and you’ll grasp the importance of programs that help you fly your drone.
Drone controllers have become some serious gadgets. They only resemble the controllers of our childhood! They’re equipped with joysticks and antennas , but they also have LCD screens and various buttons and switches, including the ones for taking shots with you camera or recording a video. Also, you can communicate with your drone using your smart phone or tablet. Drones are receiving their instructions through radio waves and the frequency of those waves is usually 2.4 GHz, because Wi-Fi signal can also be transmitted like that. Drones have microcontrollers that use the information obtained through radio waves, and control the electric engines to execute the commands. If you have an LCD screen on your controller, you can see what the drone sees from above, because the drone is also transmitting data to your controller, not just vice versa.
Flying and Landing
In order to fly, a drone has to overcome the force of gravity that’s keeping it on the ground. The gravitational force is proportional to the mass of the drone. Hence, it’s extremely important to make it as light as possible – in that way it uses less power. Another way to make it more energy efficient is to design the most aerodynamic shape, which will create less drag.
When the thrust force created by rotors overcomes the gravity and drag, it’s flying!
One of the advantages of a multi-rotor device is that it can hover, which makes it perfect for photography and filming. Many breathtaking pictures of splendid landscapes or cityscapes we see nowadays have been made by drones!
Another advantage of quadcopters and similar drones is that they can take off and land vertically. Thus, these difficult parts of the flight have been made incredibly simple.
On the other hand, along with all of their advantages, single-wing and single-rotor drones have a huge disadvantage of being extremely hard to control. Some of the single-wing drones can be launched by throwing (with your hands), but most of them need some kind of a launching device or a runway that can be assembled and disassembled quickly. Similarly, a single rotor drone is apt to turn over and fall, if the person that’s controlling it didn’t have some previous training and practice. Helicopters are a lot more complex than plains, when it comes to turning and tilting.
Drones that land vertically usually have a built-in program that takes over while landing. This is necessary because they have to land very slowly. If they dropped quickly, they would create a pressure difference that would push them uncontrollably in the direction of the ground. All of those specific occurrences that are related to fluid motion are not very familiar to us. But don’t worry! That’s why autopilot exists and why drones have huge and robust programs – so you don’t have to go through an Aviation Academy to fly your drone!
To sum everything up: drones are controlled by people thanks to various kinds of controllers, including phones and tablets, which transmit the data through radio waves. They are powered by batteries or gas engines, and they can fly successfully when the generated force overcomes the gravity and drag.The drone stabilizes itself thanks to various sensors and complex programs. Next time you fly your drone or use it to make cool shots, be sure to appreciate the fine engineering that stands behind all that! With all their complexity and hard work put in their design, they’re becoming a symbol of modern technology.