Research On Flight Control Method For Quadrotor UAV

In recent years, the applications of quadrotor UAVs have gotten great expansion, especially military and civilian aspects, quadrotor UAVs have been utilized to effectively carry out a wide range of missions, besides, their commercial trend is also highlighted. This paper mainly studies the flight control methods for the quadrotor, different control methods have been proposed in allusion to the existing problem of the flight control of quadrotor UAVs.The dynamical mathematical model of quadrotor UAVs has the characteristics,which are underactuated, high-coupling and nonlinear, those lead to increasing the difficulty of controller design. In order to perform the position and attitude tracking control of the quadrotor perfectly, simultaneously, decrease the stability time and acquire the precise coefficients of the sliding mode switching surface, the model of the quadrotor is divided into two subsystems, i.e., a fully actuated subsystem and an underactuated subsystem. The main contents are as follows:Firstly, the controller for the fully actuated subsystem is designed by adopting a novel robust terminal sliding mode control algorithm, which is utilized to guarantee the subsystem state variables quickly converge to their desired values, decreasing the stability time of the quadrotor, and the subsystem state variables are acted as time invariants in the underactuated subsystem, so the highly-coupling problem is improved; the controller of the underactuated subsystem is designed via using a sliding mode control, which can guarantee the subsystem state variables converge to their desired values in finite time, thus, on the whole, the position and attitude tracking control of the quadrotor are obtained. In addition, the effectiveness and robustness of the proposed control method are demonstrated by the simulation results.Secondly, the controllers for the fully actuated subsystem and the underactuated subsystem are designed via adopting second order sliding mode control. Considering that the coefficients of the sliding mode switching surface are nonlinear, however, in the most of existing literatures and research efforts, the coefficients of the sliding mode switching surface are taken as special values and given directly in the simulations, the condition of Hurwitz stability is used to calculate the coefficients and obtain the precise coefficients finally in this paper. Then, in order to control the quadrotor with control input saturation effectively, a second order sliding modecontrol method based on control input saturation is utilized in this paper. Besides, the effectiveness and robustness of the two proposed control methods are also verified by the simulation results.Thirdly, the Optimal Kalman Filtering algorithm for estimating the two subsystems state variables is adopted. Considering that the process white noise and measurement white noise are possible, the dynamical mathematical model is changed by the discretization and linearization based on the extrapolation method in this paper, the Optimal Kalman Filtering algorithm is used to estimate the state variables, the simulation results verify the filter algorithm has the ability of decreasing the disturbances of the process and measurement white noises.