Visual landing system of UAV based on ADRC

The fixed-point landing technology of multi-rotor aircraft is an indispensable step to realize fully autonomous flight. Most of the aircraft in the horizontal positioning relies on visual guidance, and PID control is generally used in height control, but it is difficult to resist the interference of the aircraft at low altitude spoiler. The Active Disturbance Rejection Controller(ADRC) designed in this paper can compensate the unknown disturbance independently of the exact model of the system, and effectively overcome the above problems. By detecting the target circle, the displacement vector from the center of the image to the center of the circle can be calculated, and then output the horizontal control amount to realize the horizontal alignment of the aircraft. Simultaneously, the landing height of the aircraft is controlled by using the auto-disturbance rejection controller. The experimental results show that the proposed algorithm can eliminate all kinds of spoiler disturbances at low altitude by feedforward compensation, and make the four — rotor aircraft landing in the target area quickly, steadily and accurately.