How do drones fly

 

forward from BUZZ KIDS DRONES

-------The flying principle of drones

   The rotor, like the wheel, is a magical invention, which brings us more possibilities to explore the sky.
The quad-rotor UAV has been turned into an aerial camera, which satisfies many ordinary people’s imaginations about the sky.
  The reason why the rotor can fly is that the rotor provides an upward force for the load.
  People who have played with bamboo dragonfly should know that: when the hand rubs the bamboo dragonfly a rotation speed, it will generate lift force to make the bamboo dragonfly take off.

 In the same way, the multi-rotor UAV is also driven by the rotation of the motor, which causes the propeller to generate lift. For example, a four-rotor UAV, when the sum of the lift of the four propellers of the aircraft is equal to the total weight of the aircraft, the lift of the aircraft is balanced with gravity, and the aircraft can hover in the air.

  According to Newton's third law, while the rotor is rotating, it also applies a reaction force (anti-torque) to the motor at the same time, prompting the motor to rotate in the opposite direction.

  This is why helicopters now have a "small tail" that applies a force in the horizontal direction to counteract this reaction force and maintain the stability of the helicopter's fuselage.

 And back to the quadrotor, its propellers will also generate such force, so in order to prevent the plane from spinning like crazy, among the four propellers of the quadrotor, two adjacent propellers rotate in opposite directions.

   For each propeller, the speed and rotation direction are relatively independently controlled to achieve the balance and movement of the drone.

 With four flying propellers, the drone can rise, fall and hover on the vertical plane; while on the horizontal plane, the drone can not only move forward and backward, but also turn left, right or left and right. Side flight even achieves a 360° self-rotation, which is achieved by the drone's rotor control.

 【Vertical lifting】

  When the drone needs to raise its altitude, the four propellers accelerate and rotate at the same time, and the rising force increases, and the drone will rise; when the drone needs to lower its altitude, the four propellers will reduce the speed at the same time, the quadcopter will descend.

【Rotate in place】

  When the motor speeds of the four propellers of the quadcopter are the same, the anti-torque of the drone is cancelled out, and the drone will stop in the air without rotating.
  When the drone needs to rotate in place, the speed of the two clockwise rotating motors of D2 and D4 will increase, and the speed of the two counterclockwise rotating motors of D1 and D3 will decrease. Due to the influence of the reverse torque, the drone will produce reverse rotation in the clockwise direction; operate in the opposite direction to achieve clockwise rotation of the drone.

【Horizontal movement】

  Multicopters are different from the passenger planes we usually take. They do not have propellers perpendicular to the ground like passenger planes, so they cannot directly generate horizontal force to move in the horizontal direction.
  For a quadcopter, the propellers of the D3 and D4 motors will increase the speed when it needs to move in the direction of the arrow in the figure below.
  At the same time, the propellers of the D1 and D2 motors will reduce the speed. As the rear lift of the UAV is greater than the front of the aircraft, the shape of the aircraft will tilt forward.

  When the drone is tilted forward, the plan view of the inclined surface will be as shown in the figure below. At this time, the lift generated by the propeller will not only offset the gravity of the aircraft in the vertical direction, but also have a component in the horizontal direction. Force allows the drone to have a horizontal acceleration, and the aircraft can fly forward accordingly.

  On the contrary.
  When the motors D1 and D2 accelerate and the motors D3 and D4 decelerate, the drone will tilt backward and fly backward.

【Flying left and right】

  In the same way, when the propellers of the D1 and D4 motors accelerate and the propellers of the D2 and D3 motors decelerate, the drone will tilt to the left, causing the quadcopter to fly to the left;
  When the D2 and D3 motors accelerate and the D1 and D4 propeller motors decelerate, the drone tilts to the right and flies to the right.

【Summary】

  After understanding the flight principles of quadcopters, it is not difficult for us to understand why people did not use more complex fixed-wing aircraft and helicopters for aerial photography after the emergence of multi-rotor aircraft.
  The take-off and landing of a fixed-wing aircraft has very high requirements for the site, and it cannot hover, and cannot rise and fall vertically. The requirements for aerial photography are very limited.
  Although the helicopter has a heavy load and fast speed, its structure is very complicated and precise. Thousands of parts are very complicated and troublesome for individual users from the perspective of debugging and maintenance.
  Relatively speaking, the flying principle of a multi-rotor aircraft is simple, and the fuselage structure is simpler and more reliable.Users can quickly get started flying without excessive debugging and maintenance, so multi-rotor UAVs soon occupied the UAV aerial photography market.