Research On Attitude Control Of Quadrotor

Quadrotor is a special type of rotorcraft. Its four-propeller drive structure is widely adopted in micro-Unmanned Aerial Vehicles. The properties of nonlinearity, strong coupling and sensitivity to outside interference make it more difficult to the system controller design.Since there is a strong coupling between attitude control and altitude control of the four rotor aircraft, if spacecraft attitude can be precisely controlled then its altitude control would be relative easier. This thesis mainly focus on the model analysis, controller design, simulation and experiments for quadrotor’s attitude control.(1)The linear and nonlinear models are established based on the analysis of the quadrotor’s mechanics and dynamics. The simplified linear model is derived according to the law of rigid body’s fixed-axis rotation, which omits the uncertainty caused by the relative motion between coordinate systems around fixed point. So after the detailed torque analysis of the quadrotor’s fixed-point rotation as a rigid body, this thesis further studies the nonlinear differential equation model with the Euler dynamic equation.(2) Design and simulations of three types of attitude controllers are presented based on the obtained quadrotor models. Linear quadratic regulator is designed based on quadrotor’s linear model. Backstepping controller is deduced by the reverse recursive construction of Lyapunov function, while the sliding mode controller is designed to ensure the system state variables to slide along the pre-set sliding surface according to the sliding mode variable structure principle. Simulation results certify that above control methods can keep the quadrotor stabilization while hovering. Detailed analysis among these metods is also presented with comparation of their control performances.(3) Finally, LQR controller and Backstepping controller are implemented to the quadrotor experimental platform. After a comprehensive comparison and analysis of the experimental results, by augmenting the Backstepping controller with an integral element, the Integral Backstepping controller is proposed as the attitude controller of the quadrotor experimental platform. Experiments show that the Integral Backstepping controller can effectively reduce the overshoot and oscillation volume of each control channel, eliminate Backstepping controller’s static error, and show better dynamic performance.