1. Structure?

? The rotors are symmetrically distributed in the front, back, left and right directions of the aircraft, and the four rotors are in the same height plane, and the structures and radii of the four rotors are the same. Four motors are symmetrically installed at the bracket end of the aircraft, and the flight control computer and external equipment are placed in the middle space of the bracket. Is the structure as shown in the figure? 1. 1.

principle of operation

? Four-rotor aircraft can change the rotor speed by adjusting the speed of four motors to realize the change of lift, so as to control the attitude and position of the aircraft. The quadrotor aircraft is a six-degree-of-freedom vertical elevator, but it has only four input forces and six state outputs at the same time, so it is also an underactuated system.

? The motor of a quadrotor? 1 and motor? 3 when rotating counterclockwise, the motor? 2 and the motor? 4 rotates clockwise, so when the plane flies in balance, the gyro effect and aerodynamic moment effect are offset.

? In the picture above, the motor? 1 and motor? 3 counterclockwise rotation, motor? 2 and the motor? 4 Rotate clockwise, and specify along? The forward motion of the X axis is called forward motion, and the arrow above the rotor motion plane indicates that the motor speed increases, while the arrow below indicates that the motor speed decreases.

(1) Vertical motion: When the output power of four motors increases at the same time, the total pulling force increases with the increase of rotor speed. When the total tension is enough to overcome the weight of the whole aircraft, the quadrotor aircraft will rise vertically from the ground; On the contrary, the output power of the four motors decreases at the same time, and the quadrotor aircraft descends vertically until it lands in balance, reaching? Vertical motion of z axis. When the external disturbance is zero and the lift generated by the rotor is equal to its own weight, the aircraft will remain hovering.

(2) Pitching motion: In Figure (b), the motor? 1 speed rise, motor? 3? Motor speed decreases (the change amount should be equal), motor? 2. Motor? 4? The speed remains the same. Due to the rotor 1? The lift is rising. What about the rotor? 3? Lift drops, and the moment turns the fuselage? y？ The shaft rotates, too, when the motor? 1? The speed of the motor decreases. 3. The fuselage rotates in the other direction around the Y axis to realize the pitching motion of the aircraft.

(3) Rolling motion: follow the figure? b？ The principle is the same, in the picture? c？ Change the motor? 2 and the motor? 4 speed, keep motor 1 and motor? 3. Can the fuselage be wound? x？ The rotation of the shaft (forward and backward) realizes the rolling motion of the aircraft.

(4) Yawing motion: During the rotor rotation, due to the action of air resistance, a reaction torque opposite to the rotation direction will be formed. In order to overcome the influence of reaction moment, two of the four rotors can rotate forward and two can rotate backward, and each rotor on the diagonal rotates in the same direction. The magnitude of the reaction torque is related to the rotor speed. When the four motors rotate at the same speed, the reaction moments generated by the four rotors are balanced with each other, and the quadrotor aircraft does not rotate. When the rotating speeds of the four motors are not exactly the same, the unbalanced reaction torque will cause the quadrotor aircraft to rotate. In the photo? In d, when the motor? 1 and motor? 3? Speed up, motor? 2? What about the motor? 4? When the rotor speed drops. 1 and the reaction moment of rotor 3 to the fuselage is greater than that of rotor 2 and rotor 4 to the fuselage, so the fuselage is wound under the action of excess reaction moment. Z-axis rotation realizes the yaw motion, steering and motor of the aircraft? 1, motor 3 is in the opposite direction.

(5) Forward and backward movement: In order to realize the forward, backward, left and right movement of the plane in the horizontal plane, a certain force must be exerted on the plane. In the photo? In e, add a motor? 3 speed, increase tension, and reduce the motor accordingly? 1 speed, so that the tension is reduced, while keeping the speed of the other two motors unchanged, the reaction torque should still be balanced. According to the picture? B's theory, the plane tilts to a certain extent, so that the rotor pull produces a horizontal component, so that the forward flight movement of the plane can be realized. Flying backward is just the opposite of flying forward. (in the picture? b？ Figure? In c language, the aircraft will produce pitch and roll motion and along? Horizontal movement of x and y axes. )

(6) Tending to exercise: in the picture? f？ Because the structure is symmetrical, the working principle of oblique flight is exactly the same as that of forward and backward flight.