Research On Position And Attitude Control Of Quadrotor Aircraft

The quadrotor is one of the typical aircraft that completely replaces the mechanical control with electronic control.It has the characteristics of good maneuverability,easy operation and flexible structure.The quadrotor is an under-actuated system,with many variables,strong coupling and vulnerable to external disturbances.Precise control of the quadrotor position and attitude is the basis for the quadrotor to complete flight mission.Hence,it is of great significance to investigate the position and attitude control problem of the quadrotor in depth.The main research work is as follows:Firstly,by studying the structure and control principle of quadrotor,the earth coordinate system and the body coordinate system are defined,and the rotation matrix between the two coordinate systems is presented.Then according to the position and attitude information of the quadrotor in two coordinate systems,the nonlinear models are established based on the analysis of the quadrotor's mechanics and dynamics according to the Euler-Lagrange method.Secondly,based on the dynamic model of the quadrotor,it is divided into a full actuated subsystem with two degrees of freedom and an underactuated subsystem with the remaining four degrees of freedom.The sliding mode controller based on hyperbolic tangent function is designed to realize the stable control of the position and attitude of the quadrotor.The hyperbolic tangent function replaces the traditional symbol function and can effectively reduce the chattering phenomenon in sliding mode control.Finally,a two-loop control method is proposed for the quadrotor position and attitude system.The position subsystem is an outer loop,and an adaptive sliding mode controller is designed to output the control variableU₁,the mass uncertainty and the external disturbance force are suppressed.At the same time,two intermediate command signals?_d and?_dare generated and transmitted to the inner loop attitude subsystem.The three attitude angles are tracked by an adaptive backstepping sliding mode controller.The experimental results show that the designed controller can control the position and attitude of the quadrotor.