How does drones work?

July 9, 2021

Introduction of Drone

Drones have evolved over the years and become perfect flying machines. Drones are also referred to as UAV Unmanned Aerial vehicles. It is an aircraft without an onboard pilot. A drone is typically made of lightweight, composite materials, to reduce weight and increase maneuverability during flight. Did you have questions about how it flies without a pilot? Why are drones designed the way they are today? Why are they so efficient at moving so swiftly? You will get all the answers here. In this article, I will explain to you the drone’s design and its different types. Drone’s motion and more. Let's travel into a design journey starting with a simple drone and moving on to the most modern drone.

Fig:1 Components of drone

Drone Designs

Here I will explain different types of drone designs.

1)Single propeller design(single rotor)

Here is the simplest drone design: a single propeller design. You can see in Fig:2 below One-propeller drones providing enough lift force to keep the drone hovering in the air, but there is no way to control this drone. All it can do is go vertical and come down. Another issue is that this drone’s body will keep rotating opposite to the propeller, which is a consequence of Newton's third law of motion.

Fig:2 Single propeller drone

You can see here in this figure the motor’s stator supplies the necessary torque to the rotor part. According to the third law, this means that the rotor should give an equal amount of torque back on the stator. As the stator is fixed to the drone body, this reaction torque is applied on the drone body as well(Fig:3).

Fig:3 This reaction torque gives the drone a crazy undesirable spin

2)Two propeller design(two-rotor)

So why not use two propellers? This is certainly a possibility, and a company called Zero Zero Robotics has made a serious attempt to develop such a drone. You can see in Fig:4A below the fewer the number of propellers, the less energy the drone will consume, and the longer it can stay in the air. But the main issue is that manipulating the drone to fly at high speeds and take sharp, quick turns requires a higher degree of control accuracy and stability. Let’s hope that with the advancements in control algorithms, two-propeller drones will achieve good stability one day.

Moreover as shown here the blades of a two-propeller drone rotate in the opposite direction. This way, the motor’s reaction torque caused due to Newton's third law gets canceled and the undesirable body spin can be avoided(Fig:4B)

Fig:4A Power consumption comparison of two and four propeller
Fig:4B Two propellers rotate in the opposite direction

3)Three propeller design

Three-propeller designs are very rarely used. The main issue with these types of drones is the motor’s reaction torque and gyroscopic precision. These issues cannot be canceled out and create unnecessary complications in the design and algorithms. I have shown an illustration of this in the Fig:5 below.

Fig:5 Three propeller drone

4)Four propeller design(quadcopters)

In the next variation, you can see in Fig:6 below four-propeller drones or quadcopters usually have an H shape or an X shape.

Fig:6 Four propeller drone

Axis rotation of the drone

Here are some movements of drones, I have explained below.

1)Pitch motion

Now let me summarise this for you. I have a drone and I want to move the drone forward. then I will slow down the front propeller speed while the rear propellers speed up. This will cause pitch motion(Fig:7A). Now, let’s make all the force values the same by making the propeller speeds the same. Here suppose I have balanced the vertical component of the resultant propeller forces with the weight of the drone. Even after this, there is an unbalanced horizontal force, which will make the drone move forward(7B).

Fig:7A Pitch motion
Fig:7B Forward motion

2)Roll motion

A similar technique is used to enforce a drone’s roll movement. Put simply, this movement is carried out by creating an imbalanced lift force in the left and right pairs of propellers.

Fig:8 Drone’s roll movement

3)Yaw Motion

Here you can see A quadcopter’s yaw motion is achieved uniquely. At the beginning of this Article, we discussed the motor’s reaction torque and its effect on the drone. To avoid such undesirable spin, in quadcopter drones one diagonal pair is spun opposite to the other pair(Fig:9A). This technique cancels the reaction torque completely.

However, if you want to yaw the drone or spin it, all you have to do is make sure that these reaction torques are not getting canceled, which you can easily achieve by reducing the speed of the one diagonal pair. The reaction torque is proportional to the propeller speed. Eventually, a net reaction torque will occur, and the drone can achieve the yaw motion(Fig:9B).

Fig:9A To avoid undesirable spin in quadcopter drones,
one diagonal pair is spun opposite to the other pair
Fig:9B Here reducing the speed of the one diagonal pair

Obviously, the quadcopter drones are the most stable. With the ability to move at high speeds and take sharp turns swiftly, they are used in almost every industry. Now let’s see some advantages of drones below.

Advantages of drone

1)Affordable Cost-Saving Technology.

2)Quality of aerial imaging.

3)Easy to deploy and control.

4)In-depth and detailed terrane mapping.

5)Flexibility for quick inspection.

6)Reach hazardous area.

That’s all about drones. I hope you now have a good understanding of Drones. If you want to know more about drones, you can check this link. Here I have explained in detail about their main components, sensors, Kalman filter, and much more.

Other more articles:

How does a Helicopter fly?

How does an Airfoil generate Lift?



B.Tech in Electronics & Telecommunication Engineering. Currently, he is working at Lesics Engineers Pvt.Ltd as a Product Developer and Visual Educator. His areas of interest are Embedded Systems, IoT, and Printed Circuit Board (PCB) Designing. To know more about the author check this link. To know more about the author check this link