Landing Control For Quadrotors Based On Active Disturbance Rejection Control And Visual Servo

Quadrotor has been widely used in military and civilian fields in recent years and has become a choice for ship-borne UAVs because of its simple structure,small size,light weight,the ability to take-off and landing vertically and hover.However,quadrotor has the characteristics of nonlinearity and strong coupling,and will be interfered by strong sea wind on the sea.At the same time,the ship is in a random six-degree-of-freedom motion on the sea.Therefore,it is difficult for a ship-borne quadrotor to land on the ship autonomously and the research and design of a stable,reliable and high-performance landing control system is of great significance for the application of shipborne quadrotors.The autonomous landing control system of a ship-borne quadrotor is studied in this thesis.Firstly,by analyzing the structure and flying principle of the quadrotor,the six-degree-of-freedom motion of the quadrotor is analyzed.By establishing a reasonable coordinate system and combining with Newton’s law of motion,a six-degree-of-freedom dynamic equation for quadrotor is established.At the same time,the model is simplified based on the actual situation and based on reasonable assumptions.Secondly,the sensors required for the landing control of the quadrotor,including accelerometer,gyroscope,magnetometer,ultrasonic sensor and camera,are introduced and analyzed in this thesis.Based on the Kalman filter and the extended Kalman filter,the state estimation algorithm for attitude,position,etc.are designed and implemented,which improves the accuracy of state estimation and improves the control performance of the system.Then,for the attitude control of the quadrotor,active disturbance rejection control is introduced in this thesis,which includes tracking differentiator,extended state observer and nonlinear feedback.Aiming at the problems of complicated stability analysis,difficulty in parameter tuning and complicated calculation caused by nonlinear functions in traditional nonlinear ADRC,linear ADRC is introduced and applies to the attitude control of quadrotor.The stability of the system is proved by the Lyapunov stability theory and the performance of the controller is verified by simulation and experiment.Finally,aiming at the position control of the quadrotor,a visual servo control scheme based on position and time delay compensation during the landing process is designed.Based on the minimum jerk trajectory planning,a trajectory planning method for the quadrotor landing process is designed.Aiming at the problem of uncertain delay in visual feedback,a visual sampling scheme is designed,and a delay observer is designed based on the extended state observer to compensate for the delay.The position controller is designed as a cascade PID controller,the outer loop is a position loop,and the inner loop is a speed loop.Through simulation and experiment,it is proved that the control scheme proposed in this thesis has excellent landing performance.