Research On Practical Finite Time Attitude Control Of Quadrotor Unmanned Aerial Vehicles

With the development of microcomputer,sensors and various communication technologies,the quadrotor UAV(Unmanned Aerial Vehicle)has been applied in various fields because of its simple structure and flexible operation which has extensive application prospect.The control system of the quadrotor UAV is generally divided into position system and attitude system.Compared with the position system,the analysis and design of the attitude system is more complex,and the control performance is also higher.In order to improve the dynamic and steady performance of UAV attitude system,many scholars at home and abroad have done a lot of research on attitude control of quadrotor UAV and aircraft by using various nonlinear control methods.Compared with the traditional linear control method,the finite-time control technology has the characteristics of fast convergence and better disturbance rejection ability.Therefore,this paper designs the attitude control system of the quadrotor UAV from the finite time control technology.On the other hand,in order to design a globally stable attitude controller,the unit quaternion is used instead of the traditional Euler Angle to represent the attitude dynamics of the UAV.The contents of this paper are summarized as follows:(1)For the attitude control problems of the quadrotor UAV with actuator input saturation,failure and external uncertain disturbance,a finite-time attitude controller is designed by using terminal sliding mode technology and adaptive control algorithm.Firstly,a dynamic model based on error is derived from the dynamic model of the UAV,and the finite time control of the UAV attitude is realized by combining the characteristics of simple design and good robustness of the terminal sliding mode and the adaptive control algorithm.The simulation results show that the attitude error can be convergent to the neighborhood near the equilibrium point in a finite time.(2)Aiming at the problems such as the model parameters of the quadrotor UAV cannot be accurately modeled and unknown external disturbances exist,a finite-time attitude tracking controller is designed by combining the finite-time control technology and disturbance observer technology.In the process of designing the controller,the uncertainty of system model parameters and the unknown external disturbance are regarded as the total disturbance of the system,and the disturbance is estimated by the design observer.In order to improve the convergence rate of error and the convergence performance of finite time,the double power reaching law is used.The simulation results show that the control method can achieve finite time state tracking.(3)For the attitude tracking problem of UAV with output constraints,a finite time control method based on state constraints is proposed.Based on the existing quaternion attitude model,the system is transformed into a new system with output constraint parameters,and the attitude tracking problem is transformed into the problem of determining the system’s boundedness.Then,the dynamic surface technique and finite time control technique are used to design the final controller.The simulation results show that the state constraints of the system are within a given constraint boundary.