Performance Oriented Robust Adaptive Control Of Quadrotors

Quadrotors has been widely used in military and civil fields due to the low cost,flexible operation,easy maintenance and strong adaptability to the environment.However,the characteristics of underactuation,nonlinearity and strong coupling in the quadrotor bring great challenges to its controller design.On the basis of studying the control algorithms for the quadrotor,this thesis further considers swarm control and fault-tolerant control of quadrotors.The main research contents are given as follows:Firstly,based on the established nonlinear mathematical models of two common configurations of the quadrotor,a robust adaptive controller is designed to deal with model uncertainties and external disturbances to achieve the control objective.An immersion and invariance(I&I)adaptive controller is designed for the position loop to ensure excellent steady-state accuracy of the system and improve the transient performance as well;a controller based on a disturbance observer(DO)is designed for the attitude loop to compensate for unknown disturbances,and an adaptive bounding law is used to attenuate the error between the nominal model parameters and the actual model parameters to realize the attitude stabilization.Numerical simulation and experimental results are given to show the effectiveness of the proposed control algorithm.Secondly,considering the situation of a quadrotor flying in a specific wind disturbance environment,the Dryden wind disturbance model is established.Based on the principle of adaptive internal model,the error system of each subsystem is obtained.I&I adaptive laws are developed to compensate the unknown parameters both in the system and the disturbance,and a robust adaptive controller based on internal model principle is designed by combining the dynamic surface control(DSC)method,which makes the closed-loop system robust to both model uncertainties and external disturbances.Stability analysis,numerical simulation and experimental results illustrate the satisfying performance of the designed control algorithm.Thirdly,the designed robust adaptive controller based on internal model principle is extended to the swarm system which composed of multiple disturbed and uncertain quadrotors.Based on the knowledge of algebraic graph theory,directed graph is used to describe the topological structure of the system.Considering the fact that not all the subsystems can obtain the reference trajectory of the swarm,those subsystems without the reference information can estimate it online by adaptation laws.Based on the position consensus error,a distributed robust adaptive internal model swarm controller is designed,and the consensus of the swarm system is ensured by stability analysis.Numerical simulation and experiments results verify the trajectory tracking ability of the controlled swarm system.Finally,considering the quadrotor system with uncertain actuators,the actuator fault model of loss of effectiveness(LOE)is established.For attitude subsystem and altitude subsystem,fault-tolerant controllers based on classical adaptive method and I&I adaptive method are designed,respectively.For horizontal subsystem,controller with integral feedback is designed to ensure excellent tracking performance.Theoretical analysis and stability proof show the asymptotic stability of attitude subsystem and altitude subsystem,as well as the boundedness of tracking error of horizontal subsystem.Numerical simulation and experimental results show that the designed adaptive compensation control algorithm can ensure excellent system control performance.