How does a drone move?

While drones are the result of complex mechanics, some users often ask themselves the question about this mechanics. What makes drones fly? If I want to make my drone myself, what are the physical principles I need to apply so that it can take off? Today’s article will introduce you to how our mechanical companions are designed to fly them.

Basic Principle

The basic principle of the quadcopter drone is that the rotation of the propellers allows the drone to rise in the air and maintain itself in the air thanks to the lifting force.

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In the image presented, different parts of the drone are distinguished: A rotors rotate clockwise while B rotors rotate counterclockwise. This results in a “zero torque effect” that is, the forces rotating the drone to the left are compensated by those that make it turn to the right. With each rotor connected to its own individual motor, they can rotate independently at different speeds as needed.

What movements can a drone perform?

The drone is an extremely agile machine that can go in eight different directions: forward, backward, left, right and diagonally (Front Left, Front Right, Rear-Left, Rear Right); not to mention the heights. The movements he will perform will be made via the speed of the different rotors. Thus we distinguish 4 different types of movements:

  • Gas or Throttle: This movement is done by increasing the speed of the four rotors to go up or down to descend.
  • Pitch or Pitch (forward or backward): this movement is done by increasing the speed A and B rotors from Behind and decreasing that of Front rotors, so the drone will move forward. To make it back, we will increase the speed of the Front rotors and decrease that of the behind rotors.
  • Roll or Roll (fly left or right): same principle as for the Pitch but with the rotors on the sides. Thus, we increase the speed of the left rotors and decreases that of the right rotors to go to the right and vice versa.
  • Yaw or Yaw (circular flight): here we will decrease the speed of the B rotors and increase the speed of rotors A to make the drone fly circular clockwise and do the opposite if we wish to fly the other direction.

What are the forces that act on the drone?

The Larousse defines a force as “a concept that translates quantitatively the interactions between objects and to explain their deformations or changes in their movements”.

Thus there are four forces that interact with the drone and without which it cannot fly:

  • The drag that corresponds to the force that is opposed to the movement
  • The lift that corresponds to the force that pushes the drone upwards
  • The traction that corresponds to the force that moves the drone forward
  • The gravity that corresponds to the force that draws the drone to the ground

In order for the drone to take off, the propeller power (lift) must be at a minimum capable of lifting the weight of the aircraft. Similarly, it will be remembered that in the static position the Trail and the Traction balance between them. It is thanks to the impact , i.e. the degree of inclination of the gear, that the drone will move.

Another physical element to consider is the Stall Speed , which is the minimum speed below which the drone will not be able to hold in the air.

The shape of the propeller according to Newton

Newton’s third law explains that “The action is always equal to the reaction, that is, the actions of two bodies on each other are always equal and of opposite meaning.” This law makes it possible to explain the curvature of the propellers of a drone.

As shown in the diagram below, the curving of the moving propellers will create a vertical force going to the ground, and according to Newton’s law, an equal force going upwards will be generated. It is this force that will allow the drone to take off.

What happens when my is flying drone?

So when the drone takes off, the lift is greater than gravity. The Propeller speed is therefore large enough to ensure that the drone does not stall.

When the drone is in balance in the air, the lift force and the force of gravity are equivalent. To move it forward, simply tilt the drone, so change the angle of incidence, so that it goes in the desired direction. For this, some rotors need to decrease their speed of rotation, depending on the direction you want to take as seen above. However, this loss of speed must be compensated by the other rotors in order to allow the drone to maintain the same altitude.

A drone “as a couple”

An important point regarding the drone is the torque effect . If all the rotors rotated in the same direction, the drone would continuously rotate on itself. On a helicopter, the torque effect produced by the main propeller is compensated by the propeller that is placed on its tail and which produces an “anti-torque” effect. On the drone, the torque effect produced by the hourly rotation of two rotors is compensated by the counterclockwise rotation of the other two rotors. Thus, it is possible by decreasing the speed of the rotors on the same axis and increasing that of the rotors of the opposite axis to play on the torque effect and make the drone rotate on itself.

The following video details the points discussed earlier: can’t be loaded because JavaScript is disabled: Quadcopter Dynamics ( Finding

You now know the different physical forces and phenomena that occur during the flight of your drone. The technologies that are now installed on drones manage to take into account some of the effects of these forces in order to make their influence almost zero on steering. However, this technological leap has a consequence: it increases the weight of the drone, which increases the power needed to fly it and thus reduces the flight time.