Research On Quadrotor Control Technology Based On Disturbance Suppression

At present,quadrotors are becoming more and more popular in the military and civilian fields.However,due to their susceptibility to external interference and uncertain factors in their own systems during flight,the research on the disturbance suppression of quadrotors is of great significance.For one thing,the quadrotor is an under-driven system,and its six degrees of freedom cannot obtain input excitation.For another thing,the quadrotor is also a non-linear,multivariable,strongly coupled and uncertain system.The research on the quadrotor controller makes a big difference.Sliding mode control is widely used in the field of nonlinearity.By designing a sliding mode surface,the error will eventually converge to zero,which is very popular in disturbance rejection.Nevertheless,there is a chattering phenomenon in the slip mode control,so it needs to be shivering.The extended state observer is the core component of the active disturbance rejection control technology.The uncertainty of the system itself and the external interference are estimated as a total disturbance,and the control algorithm is combined to realize the compensation for the disturbance.Aiming at the problem of quadrotor disturbance rejection,this thesis designs a sliding mode controller on the basis of the extended state observer to control the attitude and position tracking of the quadrotor.Analyzing the high-order observer and the disturbance-based observer,merging advantages of the both,a high-order extended state observer in view of the disturbance model is proposed to accurately estimate the composite disturbance and improve the control accuracy of the system.The main research contents of this thesis are as follows.(1)In the light of the characteristics of multi-variable,non-linear and system existence model uncertainty of the quadrotor,this thesis makes use of the extended state observer to estimate the interference,and the sliding mode variable structure as its control algorithm to process the system.In attitude control,a second-order fast terminal sliding mode control algorithm with integral sliding mode surface on account of the extended state observer is proposed in this thesis,which makes the state error converge in a finite time.The function of the extended state observer is to estimate the disturbance,combine with the sliding mode controller to compensate for the disturbance,weaken the chattering phenomenon,and improve the control accuracy.(2)For the position tracking control of the quadrotor,by decoupling the mathematical model,the system is divided into a fully actuated subsystem and an underactuated subsystem.The under-drive subsystem contains matching interference and non-matching disturbance,and applies different expansions.The state observer estimates different disturbances,improves the traditional observer design based on the system model,and simplifies the design of the controller.For the fully actuated system,a nonlinear back-step high-order sliding mode controller is designed,and the super spiral sliding mode algorithm function is used as the virtual control law to find the real control law and realize the tracking of the expected value.(3)Aiming at the traditional extended state observer,this thesis finds out its shortcomings in practical application through theoretical analysis,and then analyzes the high-order extended state observer and the extended state observer based on the disturbance model.Combining advantages of the both,a high-order extended state observer on the strength of the disturbance model is proposed,which can accurately estimate constant,slope,and time-varying disturbances.