Research On Quadcopter U’s Finite-ime Trajectory Tracking Control

With small size,light weight and the capability of stable hovering and flexible flight,the quadcopter UAV has great application potential in national defense and national economy.Trajectory tracking is a basic control problem for quadcopter.However,most traditional quadcopter UAV control methods can only guarantee asymptotic convergence,that is,it takes infinite time for the real trajectory of the quadcopter to converge to the desired trajectory,which may not meet the trajectory tracking task requirements in some practical applications.Therefore,in order to improve the transient performance and disturbance-resistence and ensure fast convergence of the quadcopter trajectory tracking control,this thesis focuses on the finite-time trajectory tracking control of the quadcopter UAV.The main contents are as follows:First of all,the flying principle of the quadcopter UAV is introduced,and the mathematical equations for the translation and rotation of the quadcopter UAV are given.Then,considering the underactuation and strong coupling characteristics of the quadcopter UAV,a nested dual-loop control scheme is adopted to simplify the controller design,of which the outer loop is a position control loop and the inner loop is an attitude control loop.Secondly,the finite-time trajectory tracking control of a quadcopter UAV based on homogeneity is studied.A finite-time disturbance observer is designed to eliminate the influence of the disturbance on the system,and a finite-time position and attitude controller design scheme is proposed based on the homogeneous system theory.Based on the homogeneous system theory and Lyapunov’s stability theorem,the finite-time convergence characteristics of the designed scheme are analyzed theoretically.At the same time,the numerical simulation results verify the theoretical results.Thirdly,the fixed-time trajectory tracking control of a quadcopter based on terminal sliding mode control is studied.In view of that traditional terminal sliding mode control faces with singularity problem,existing non-singular terminal sliding mode control is either not able to estimate convergence time,or high in computational complexity and conservative in estimated time,and finited-time control mthod is more limited than fixedtime control in terms of convergence time,the design scheme of a novel non-singular sliding mode surface is proposed.Then based on the newly designed sliding mode surface,and a fixed-time disturbance observer,a non-singular fixed-time trajectory tracking controller for a quadcopter is proposed,and an estimate of the upper bound of the convergence time is given.Numerical simulation results prove the fixed-time stability of the closed-loop system and its superiority over other fixed-time control algorithms.Finally,an experimental platform of flight control based on the Crazyflie 2.0 quadcopter UAV is set up,and the experimental results of the finite-time control method of the quadcopter UAV are given.