Research On All-attitude Modeling And Sliding Mode Control Of Quadrotor

Rotor aircraft has advantages such as vertical take-off and landing and hovering.Compared with the fixed wing aircraft,rotor aircraft is easier to perform in complex areas of disaster relief and target monitoring.Quadrotor is simple-structure,strong-maneuverability,and has been widely applied in military,civilian areas.The Characteristics of nonlinear,under-actuation and strong-coupling of quadrotor have brought great challenges to the design of controller,making it an effective verification platform of complex control algorithm.Therefore,the quadtotor caused extensive concern of the domestic and foreign scientific research institutes.It now has become the focus of the experts and scholars,and has high engineering significance and academic value.Traditionally,the model of quadrotor is linearized near attitude of hovering,and then controller based on classical control algorithms is designed to this approximate model.This paper embarks from the six-degree-free model without singular of quadtotor and sliding mode variable structure control(SMVSC)is introduced to deal with the control problem of quadrotor nonlinear model in large dip angles.Different SMVSC law is designed through the research of reaching law in SMVSC.Finally,fuzzy control is introduced to the exponential reaching law,solving the drawback of fixed-parameter.A new controller base on this reaching law is given to accelerate the reaching speed and suppress fluttering.Firstly,a detailed analysis of the mechanical structure and working principle of quadrotor is conducted.Quaternion without gimble lock is taken to establish the six-degree-free nonlinear and all-attitude model.System state space equations are given and it suggests that the model is under-actuated nonlinear and strong coupling.Secondly,in order to control of the attitude of quadrotor,research about SMVSC is conducted.Controllers based on reaching law such as uniform reaching law,exponential reaching law and power reaching law is designed.Simulation shows the effectiveness and improvement suggestions are given.Thirdly,as the conventional reaching law parameters are fixed,approach velocity can't give consideration to problems of buffeting.By using the method of fuzzy control,a variable exponent reaching law is designed.Simulation shows controllers with this reaching low can both improve the approaching speed and reduce the buffeting.Finally,on the basis of control algorithm,the quadrotor platform is built.Hardware circuit is designed with a high-performance microcontroller and nine-axis digital motion processor.Software is completed by implementing the algorithm of controller and attitude-solver.A complete physical platform is shown at the end of the article.