Considering quadrotor is an underactuated

strong coupling

nonlinear system

in order to achieve purpose of quick

accurate and stable control of quadrotor

backstepping method is proposed to solve the nonlinear problem of the quadrotor. Meanwhile

overall control of quadrotor is divided into inner loop and outer loop subsystem. The first step is establishing the dynamics and kinematics equations of the quadrotor

and simplify the mathematical model. Backstepping method is used to solve control law. In view of the couple relationships

the backstepping method is applied to the inner loop for attitude control;the PID method is used in the outer loop for position control. Set up system modeles

the control system is simulated on Matlab/simulink platform. The simulation results show that the controls of attitude and position gain good results under small attitude angles or hovering conditions. The validity of controllers designed and math model is proved by simulations.