Fractional-Order Terminal Sliding Mode Control For Quadrotor Uav Attitude System

With its advantages of small size,strong maneuverability,easy operation,and low price,quadrotor unmanned aerial vehicle(UAV)has a good application prospect in the military,civil,and other fields.However,because the quadrotor UAV system has complex characteristics such as high nonlinearity,strong coupling,and underactuated,and is easily affected by factors such as the uncertainty of the internal parameters and external disturbances,which makes the quadrotor UAV control system has become the research focus of domestic and foreign control engineering experts.The purpose of this thesis is to design a quadrotor UAV attitude control method with strong robustness and fast convergence and to realize the precise control of the quadrotor UAV attitude system.In-depth research is mainly based on the fractional terminal sliding mode attitude control method.The work focuses on:1.The relevant properties and derivations of the fractional-order calculus defined by Riemann-Liouville are analyzed in detail,the reference coordinate system of the flight motion of the quadrotor UAV is studied,and the nonlinear dynamics model of the quadrotor UAV attitude system is established using the Newton-Euler theorem.2.A fractional-order adaptive nonsingular fast terminal sliding mode attitude control method is proposed based on the PX4 quadrotor UAV flight attitude control architecture scheme for the quadrotor UAV attitude system that is affected by the uncertainty of internal parameters of the model and the perturbation of external physical factors.The method designs an adaptive control law based on RBF neural network,adjusts the control gain online according to the time-varying disturbances,and then compensates the control system in real-time while replacing the sign function in the traditional terminal sliding mode convergence law with hyperbolic tangent function,which weakens the jitter phenomenon of the control system.The finite-time stability of the system is proved according to Lyapunov’s theorem.And the numerical simulation experiments of attitude control of the quadrotor UAV are carried out by MATLAB/Simulink to verify the effectiveness and stability of the attitude control method designed in this thesis.3.The structural composition and working principle of the AirSim hardware-inthe-loop simulation platform was studied in-depth,the attitude control method designed in this thesis was applied to the Pixhawk 4 autopilot,and a 3D virtual model of the quadrotor UAV was designed by Solid Works software to match the actual flight experiment in this thesis.The flight experiment based on this hardware-in-the-loop simulation platform is realized,the stability of the quadrotor UAV attitude control system is further analyzed,and the control performance of the control method designed in this thesis is evaluated,which reduces the experimental cost while ensuring the credibility of the experimental results.4.The overall architectural scheme of the quadrotor UAV practical flight experiment platform is proposed,based on which the selection and assembly of relevant accessories are completed,the experimental platform of quadrotor UAV practical flight with Pixhawk 4 autopilot as the core is built,and the control method proposed in this thesis is applied to Pixhawk 4 autopilot through PX4 hardware support package in MATLAB to realize the attitude tracking experiment of quadrotor UAV.