Disturbance Rejection And Tracking Control For Quadrotor UVAs Based On Equivalent-Input-Disturbance Approach

Quadrotor unmanned aerial vehicle(QUAV)has four cross-coupled propellers.This special mechanical structure enables it many distinct abilities such as perform vertical take-off and landing(VTOL),hovering,and cruising.Relying on those abilities,QUAVs are used to accomplish some practical missions,and thus they are widely used and studied in the world.The control of QUAVs is the key to accomplish missions.Thus,the research on the control scheme of QUAVs has important scientific research value and engineering application prospect.Although a QUAV has simple structure,its control is not easy.And many difficulties have to be overcome for the well control of QUAVs.For example,its mathematical model is a nonlinear,strongly coupledsystem and has uncertainties;a QUAV suffers various disturbances(such as pressure change,temperature change,and wind change)in the fight environment;a QUVA system has four control inputs and six control outputs,which means that it is an under-actuated system.In conclusion,a QUAV system is an under-actuated nonlinear multiple-inputs multiple-outputs(MIMO)system.This dissertation focuses on three typical problems in the control of QUAVs:fixed-point tracking control,waypoint-tracking control,and trajectory-tracking control.Considering the influences of nonlinearities,uncertainties,and underactuation,this dissertation puts forward three control methods to improve the robustness and accuracy of the controller,and dynamic and steady-state performance of the system.The contributions of this dissertation are as follows:(1)This dissertation presents a SMO-EID-based control method to suppress the exogenous disturbances in the fixed-point tracking control.A quadrotor dynamic model is divided into two subsystems: fully-actuated and under-actuated.For the fully-actuated one,strict linearization and PID control are used to achieve the control target.For the under-actuated one,approximate linearization and SMO-EID approach are used to achieve the control target.Liapunov theorem is used to derive the stability conditions based on the concept of the GUUB(globally uniformly ultimately bounded).Simulations and comparisons demonstrate the effectiveness of our method.(2)Considering the influences of model uncertainties and unknown external disturbances,this dissertation presents a PID-EID-based control method to achieve the waypoint-tracking control and disturbance rejection.Strict linearization is used to linearize a QUAV system.The value for the control of position is obtained using the control-input-transformation algorithm.Four EID estimators,two PI controllers,and two PD controllers are designed to reject disturbances and track the desired waypoints.Simulations and comparisons demonstrate the effectiveness of PID-EID method in thewaypoint-tracking control.(3)Considering the influences of parameter uncertainties and unknown external disturbances,this dissertation presents an improved-EID-based(IEID)approach to achieving the trajectory-tracking control of a QUAV.Compared with the conventional EID method,the IEID method has better disturbance-rejection performance,and the stability domain of the IEID-based control system is larger.The influences of the filter in the EID approach on its disturbance-rejection performance is discussed And then he configuration of the IEID estimator is given and its advantages are analyzed.Next,the configuration of the IEID-based control system is given.Finally,simulations and comparisons demonstrate the effectiveness of IEID-based control method in the control of trajectory tracking.