Trajectory Tracking And Autonomous Landing Control Of Quadrotor

The quadrotor is the simplest type of rotorcraft unmanned aerial vehicle(UAV),due to the advantages of vertical take-off and landing(VTOL),operating easily,flying in narrow space etc.It is getting more and more extensive application in military investigation,police riot control,agricultural and forestry inspection,mass entertainment and many other scenes.The demand for its autonomy,rapidity,safety and accuracy is more and more urgent,and requirement is stricter and stricter.Since the quadrotor is an nonlinear system,which is underactuated,strong coupling and sensitivity to disturbance,there are some difficulties in the design of the controller.In the general mission,the autonomous flight of the quadrotor can be divided into two main stages: autonomous trajectory tracking and autonomous landing.The former requires that it be able to fly in accordance with the reference trajectory,while the latter has a higher demand for its safety.Therefore studying trajectory tracking and autonomous landing of quadrotor is very significant.The main research contents in this paper include the following aspects:Based on the analysis of the structure and flight principle of quadrotor,a six-degree-of-freedom dynamic equations of translational and rotational of quadrotor are established by choosing the appropriate earth coordinate frame and body fixed frame.In order to solve the problem of underactuated and strong coupling,the virtual controllor is designed to deal with the model,which lays the foundation for the design for the subsequent controller design.Aiming at the trajectory tracking control problem of quadrotor,two problems are mainly considered.On the one hand,considering the practical constraints of the linear velocity of the quadrotor can not be directly measured,a finite time observer based on the finite time control theory is proposed to estimate the linear velocity accurately.Furthermore,the finite time controllers of position loop and attitude loop are designed.On the other hand,taking into account the quadrotor is susceptible to wind gust during flying,a disturbance observer is used to estimate the influence of wind,and an adaptive controller considering the disturbance of 2D wind field is proposed to ensure that the quadrotor has higher tracking accuracy and flight save under the 2D wind field.Aiming at the autonomous landing control problem of quadrotor,two cases are considered according to whether the obstacle topography is known in advance.Considering landing on a fixed platform problem,in which the obstacle information is already known,an Gauss form potential function is constructed by using quadrotor position and obstacle position,an autonomous obstacle avoidance landing controller based on potential function is designed.Furthermore,in order to overcome the shortcomings of the Gaussian form potential function in describing the obstacles,the cylindrical potential function is proposed,and a time-varying sliding mode is proposed by using the potential function gradient,then an autonomous obstacle avoidance landing sliding mode controller is designed.Considering landing on a fixed or mobile platform problem,which considering the obstacle information is unknown,in order to obtain the obstacle information during landing,a kind of distance sensor installation method is designed to detect the azimuth and relative distance of the obstacle.By using the relative distance to construct the cylindrical potential function,an autonomous obstacle landing controller is designed.Furthermore,in order to solve the ‘deadlock' problem of potential function,the autonomous obstacle avoidance control method based on impedance control is designed by using impedance control theory.The validity of all controllers proposed in this paper are all verified through numerical simulations.