| Quad-rotor Unmanned Aerial Vehicle has the characteristics of flexibility,efficiency and convenience,and is widely used in transportation,construction,disaster prevention and rescue,channel patrol and other fields.The four-rotor UAV has weak anti-disturbances ability and is extremely vulnerable to the influence of external environment,which increases its control difficulty.Therefore,a robust and reliable control method is particularly important.This paper focuses on the attitude control of the four-rotor UAV.The observer and controller are combined to achieve accurate and fast tracking of its attitude angle in a limited time in the presence of one or more disturbances.The effectiveness of the proposed calculation method is verified by software and hardware simulation.Its main work is summarized as follows:(1)For the attitude control system of four-rotor UAV with unmodeled dynamics and environmental disturbances(generally assuming known disturbance derivative bound),a finite-time extended state observer(FTESO)is designed to estimate the lumped unknowns composed of unmodeled dynamics and environmental disturbance,and a complementary sliding mode controller(CSMC)based on unknown compensation is designed using the estimated values to achieve accurate trajectory tracking.The stability of the system is proved by using Lyapunov theory,and a model-free finite-time control scheme is established.Finally,the effectiveness of the algorithm is verified by numerical simulation.(2)Unlike the previous section where the disturbance derivative bound is known,in this section,when the disturbance derivative bound is unknown,an adaptive sliding mode disturbance observer(ASMDO)is designed to quickly estimate the disturbance,and a non-singular terminal sliding mode controller(NTSMC)based on disturbance compensation is designed using the estimated value to realize fast and accurate trajectory tracking.Then,it is proved that the estimation error of disturbance and the track tracking error of four-rotor UAV can be stable in a limited time.Finally,the effectiveness of the algorithm is verified by hardware-in-the-loop simulation.(3)A dual observer is designed for the attitude control system of a four-rotor UAV with complex nonlinear disturbance and some known information disturbance.First,the extended state observer(ESO)is used to estimate the complex nonlinear differentiable disturbance.Secondly,the exogenous system model is used to describe some known information disturbance,and the disturbance observer(DO)is used to estimate it.Then,a sliding mode controller(SMC)based on double disturbance compensation is designed by using the estimated values of the two observers to realize the attitude control.Lyapunov theory is used to prove the stability of the system and realize the composite anti-disturbance of the attitude system.Finally,the designed double observer and controller are verified by simulation experiments. |
