Flight Control Method Design Of Quadrotor System

Quadrotor,as a popular type of UAV, is a kind of Vertical Take-Off and Landing(VTOL) vehicle which could be launched from anyplace and hover above and target.In comparison with classical helicopters conventionally equipped with a main rotor and a tail rotor, quadrotors with higher versatility and manoeuvrability, larger payload capacity and lower cost possess a simpler structure to carry out various types of tasks such as military application, rescue, near-area surveillance and so on. Quadrotor is an under-actuated system with the features of nonlinearity, multivariable and strong coupling, which attracts a large number of researchers. This paper concentrates on the nonlinear model and flight control of a quadrotor, and the main research contents and research results are as follows:Firstly, we give detailed review about research status, applications, main technology and development prospects of quad rotors.Then, an introduction about how quadrotors wok is presented. We establish the airframe and the ground coordinate subsystem describing the flight movements of the quadrotor aircraft,and give the coordinate transformation matrix between the two coordinate systems. Under a series of reasonable assumptions, a simple version of dynamical system based on Newton-Euler formalism is derived. For easy control of the flight, four virtual control variable is introduced which makes the quad-rotor model decoupled to four separate loops.What’s more, we divide the whole system into two subsystems:attitude subsystem and position subsystem. For attitude subsystem is independent of position subsystem, different control algorithms including PID control, Backstepping control and Sliding Mode control based on Backstepping are applied to attitude subsystem. The performance and effectiveness of the proposed controller are tested in a simulation study in Matlab Simulink.Finally, after the combination of the attitude controller and position controller in the form of internal and external loops, the overall system controllers are designed:A desired three position information and yaw angle information are supposed to be the input of the entire system. According to the difference between the current quadrotor position and the desired position, the position controller generates the desired Euler angles. Subsequently, Euler angular controller uses the information provided by position controller to calculate the desired angular velocity. Then, the angular velocity controller calculates the actual control inputs. The output vector is then fed back into the controllers. Last but not least, PID control and Sliding Mode control based on backstepping algorithm are applied to the control of whole system, which are verified in Simulink simulation.