Research On Attitude Control For Low Velocity Quadrotor Aircraft

The low velocity quadrotor aircraft is a kind of six degrees of freedom non-coaxial aircraft,with the nonlinearity,the strong coupling and multivariable characteristics,and the actual flight control system will be affected by a variety of physical effects and the interference of the external environment,so it is very difficult to design the controller.However,in military and civilian fields greatly need rotorcraft to deal with difficult problems that manpower cannot solve,especially quadrotor aircraft,which can realize things like real-time reconnaissance and surveillance of the battlefield,searching and rescuing after the major natural disasters.In order to make its flight quality maintain fast and stable level under various interference,and ensure normal use under various extreme circumstances,the attitude control is an important guarantee for actual flight vehicle,meanwhile,rotor aircraft as a research platform shows the feasibility in attitude detection,nonlinear systems and intelligent systems control,thus has a significant research value.Therefore it is worthwhile to make an research on the attitude control of the quadrotor.This article is focused on construction of the quadrotor model,analysis and design attitude controller,the main research work are summarized in following aspects:(1)Based on a survey of the research situation at home and abroad and related technologies,analysing the characteristics of quadrotor and the force states of system and building the non-linear system model.(2)To simplify the model of quadrotor,details on the application of the principle of Linear Quadratic Regulator(LQR)to design the attitude controller,then through the system simulation model to verify the feasibility of the proposed controller.Nevertheless,the inaccurate of the simplified model cause the overshoot of the attitude angle,considering the actual flight process may induce the body out of balance,it is necessary to improve the controller.(3)Aiming at the nonlinear model of quadrotor,to design an active disturbance rejection attitude controller(ADRC)is proposed.The simulation results indicate that the proposed control scheme can achieve the decoupling control effectively and can overcome the interference obviously,then the Lyapunov is used to test the stability of the proposed control system.(4)The linear active disturbance rejection attitude controller(LADRC)is proposed in order to solve the problem that ADRC has too many parameters and is difficult to tune.The linear extended state observer(LESO)is redesigned using the information extracted from the model.The total disturbances can be traced and estimated in real-time,and estimated value of disturbances is compensated on-line by the proposed controller.The simulation reveal that the attitude controller has stronger robustness.The stability of the closed system in frequencydomain is also analyzed.Finally,in order to prove the effectiveness and practicability of the proposed attitude controller,the hardware-in-the-loop platform of the quadrotor is presented for attitude control experiment.The experiment show that the control effect of the proposed LADRC are better than LQR and ADRC,which can effectively reduce the overshoot of the attitude angle and the tracking error,and keep the system still maintain a better stability in case of unknown disturbance.