Research On Trajectory Tracking And Formation Control Of Quadrotor UAVs Under Different Contraints

The special physical structure of the quadrotor UAV determines that it has the characteristics of underactuated,nonlinear,strong coupling,etc.,and it is affected by internal parameter changes,external uncertainty disturbance,communication limitations,and obstacles in the application environment.As a result,the nonlinear control methods commonly used in the control field are not suitable for the quadrotor UAV system,which brings more challenges to its control.With increasingly complex working environments and operational requirements,the control requirements of quadrotor UAV in all walks of life are constantly improving.Therefore,the trajectory tracking control and formation control of quadrotor UAV system under external disturbance,parameter uncertainty,communication limitations,and collision avoidance constraints are deeply studied in this dissertation.The main research contents are as follows:(1)The trajectory tracking and formation control problems of quadrotor UAV systems are studied under the conditions of wind disturbance and some unmeasured states.A robust backstepping sliding mode output feedback controller with low computation cost and high performance is proposed by combining extended state observer(ESO)and third-order differentiator.Firstly,four basic wind field models are combined to simulate the effect of actual wind disturbance on the system.Secondly,the ESO is designed using only the quadrotor UAV position and attitude information to estimate unmeasured states and wind disturbance online.Finally,a third-order differentiator is introduced to obtain the derivatives of the desired attitude angle and the virtual control law,which relaxes the condition of continuous differentiability of the desired attitude angle,and avoids the problem of“differential explosion”.The simulation results show that the controller can not only achieve good control performance but also improve the robustness of the system.(2)The leader-following formation control problem of quadrotor UAV system under communication limitations and wind disturbance is studied.Firstly,based on undirected topology and follower state information,a distributed estimator with finite time convergence is designed to estimate the leader state,which transforms the formation control problem of quadrotor UAV into trajectory tracking control problem.Secondly,to reduce the influence of wind disturbance on system performance,a finite time disturbance observer is designed to quickly estimate wind disturbance.Finally,the quadrotor UAV system is decomposed into two subsystems with different time scales by using the singular perturbation theory to reduce the difficulty of system controller design.On this basis,an integral sliding mode controller with strong robustness and high control accuracy is proposed to realize leader-following formation control of multi-quadrotor UAV system.(3)The leader-follower formation control problem of quadrotor UAV systems with directed topology and combined disturbance is studied.Firstly,a novel distributed estimator is proposed to solve the problem of unknown leader state in unidirectional information flow and reduce the requirement of system communication.Secondly,the adaptive estimation law designed by tracking error and its derivative is used to estimate the combined disturbance,which has low calculation cost and high estimation accuracy.Finally,fractional-order terms are introduced into the sliding surface to increase the freedom of parameter adjustment and improve the flexibility of controller design.Based on the above,a fractional-order adaptive non-singular fast terminal sliding mode controller is designed to realize leader-follower formation control of quadrotor UAV system,and Lyapunov stability theory is used to prove that the closed-loop system error converges in a finite time.(4)The collision-free coordination trajectory tracking control problem of uncertain multi-quadrotor UAV system is studied.Firstly,the collision avoidance potential function constructed by the relative position and velocity information is introduced into the tracking error,and a bounded control input is designed to realize the collision-free tracking control of multi-quadrotor UAV.Secondly,to reduce the computational cost of the controller,a single-layer neural network is used to approximate the optimal value function and avoid solving the nonlinear Hamilton-Jacobi-Isaacs(HJI)equation.On this basis,an H_∞optimal controller is designed based on approximate dynamic programming(ADP)framework and two-person zero-sum differential game theory to realize collision-free coordinated trajectory tracking control of multi-quadrotor UAVs.(5)The problem of fixed-time optimal trajectory tracking control for multi-quadrotor UAVs with combined disturbance and collision avoidance constraints is studied.Firstly,according to the collision avoidance potential function,a bounded control input is designed to realize the collision avoidance tracking control target of multi-quadrotor UAVs.Secondly,the auxiliary function and a new inverse optimal control form are constructed in the design process of the adaptive neural inverse optimal controller to avoid solving the HJI equation and singular problems.The fixed-time optimal tracking control of multi-quadrotor UAVs is realized.Finally,the stability and fixed-time convergence of the system are proved by using the double Lyapunov function.