1. The flight principle of the drone

The multi-rotor drone is driven by the rotation of the motor, causing the propeller to generate lift. For example, a quadrotor drone, when the sum of the lifts 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.While the rotor is rotating, it also applies a reaction force to the motor to cause the motor to rotate in the opposite direction. The propeller on the quadrotor also produces such a force, so in order to avoid the crazy spin of the aircraft, the two propellers of the quadrotor rotate in opposite directions.The front, rear, left and right rotation of a multi-axis aircraft is also achieved by the speed control of multiple propellers:(1)Drone vertical lifting when the airplane needs to raise the altitude, the four propellers accelerate at the same time, the lift increases, and the airplane rises. When the aircraft needs to reduce the height, the four propellers will reduce the speed at the same time, and the aircraft will drop.
(2)Drone in situ rotation when the speed of each motor of the drone is the same, the counter torque of the aircraft is canceled and no rotation occurs.
When the aircraft is to be rotated in situ, the two clockwise rotating motors in the opposite direction increase in speed, and the other two counterclockwise rotations decrease in speed. Due to the anti-torque effect, the aircraft rotates counterclockwise.
(3)Horizontal movement when the drone needs to advance, the motor propeller will increase the speed on the same line (not diagonally to the straight line), while the other two motor propellers reduce the speed. Since the lift at the rear of the aircraft is greater than the front of the aircraft, the attitude of the aircraft will tilt forward. At this time, the lift generated by the propeller has a component in the horizontal direction in addition to offsetting the gravity of the aircraft in the vertical direction. This component gives the aircraft a horizontal acceleration and the aircraft can fly forward.

2. Several major systems of drones

(1)Flight control system：The Flight Control System can be regarded as the brain of the drone. Whether the aircraft is hovering or flying, and in which direction it is flying is commanded by the flight control.
How does the flight control control the aircraft to maintain its posture? This is because the flight control contains the “cerebellum”, that is, there are several sensors. The basic flight control includes the following sensors:GPS: used to obtain the latitude and longitude information of the aircraft and determine its own position;
Barometer: used to measure the current atmospheric pressure and obtain the altitude information of the aircraft;
IMU: The inertial measurement unit consists of a three-axis accelerometer and a three-axis gyroscope to measure the angular velocity and acceleration of the aircraft in three-dimensional space and to calculate the attitude of the object;
Compass: used to distinguish the orientation of the aircraft in the world coordinate system, that is, to link the east, south, west, and north with the front, back, left, and right of the aircraft.(2)Remote control system：The remote control system includes a remote control for the ground and a receiving module for the aircraft.
In addition to the four channels of pitch, roll, yaw, and throttle, it also includes functions such as switching flight mode, controlling gimbal rotation and controlling camera photography. These commands are transmitted to the aircraft by wireless signals through the transmitting system of the remote control, and the receiving modules of the aircraft receive signals. The current mainstream radio signals are 2.4G signals.(3)power system：The power system includes the electronic governor ESC, motor, blade, and power battery of the drone.ESC: Converts the DC power provided by the power battery into three AC powers that can directly drive the motor. After the ESC receives the flight control command, it controls the motor speed to achieve the change in the inclination of the aircraft.
Motor: At present, the mainstream motor is a brushless motor. The function of the motor is to rotate and drive the rotation of the propeller to provide lift.
Paddle: The blade is fixed on the motor shaft and rotates with the rotation of the motor to bring a lift to the drone for flight.
Power battery: The aerial drone currently uses lithium polymer as the power, and several pieces of batteries are connected in series to provide power for flight.(4)Graphic transmission system：The image seen on the plane is transmitted to the screen in front of the user. In addition to the picture, the picture transmission also transmits the flight data of the aircraft.
Therefore, the user can see the real-time image and altitude and speed information of the aircraft on the display screen and the APP. The picture transmission usually uses the 5.8G, 2.4G frequency band.
The commonly used pictures are transmitted by analog pictures and digital pictures. At present, the advantages of high quality and long transmission distance in digital aerial drones are more popular among consumers.(5)Gimbal: The Gimbal acquires data from a three-axis accelerometer and a three-axis gyroscope, calculates the tilt angle, and reverses the position to maintain the level of the camera picture.
The three-axis gimbal can eliminate the jitter in all directions. For this reason, there are three motors on the gimbal. If the airplane is tilted to the right, the pan-tilt is tilted to the left and is relatively horizontal with the ground, thus achieving picture stabilization.(6)Aerial camera：Some aerial drones include cameras, while others require GoPro or other cameras. The dedicated aerial camera is basically the same as the ordinary camera, except that the Aerial photography is generally far away from the camera, and has a large object distance and a large depth of field. In addition, the aerial camera uses a wide-angle, fixed-focus lens.