Control Of Quadrotor Based On Extended State Observer

With the development of battery technology and flight control technology,a quadrotor has been rapidly developed.Due to the advantages of small size,simple operation,high reliability,and convenience,a quadrotor has been widely used in many fields such as load transportation,urban monitor-ing,environmental monitoring,and precision agriculture,and has very important civilian and military value.A quadrotor is a nonlinear,strongly coupled,underactuated complex system.In practice,there are often unknown external disturbances,model uncertainty,unmeasured states,input saturation,and other problems in the quadrotor system,which will affect the actual flight effect,so these problems need to be taken into account in the process of controller design.The objective of this paper is to design a robust nonlinear controller to realize position tracking control and attitude tracking control of a quadrotor.The main work of this paper is as follows:1.Considering unknown external disturbances and model uncertainties in attitude tracking of the quadrotor,a backstepping sliding mode control method based on the TVESO has been proposed in this paper.Firstly,the mathematical model of the attitude system of the quadrotor is introduced.Secondly,the TVESO is used to observe unmeasured states and the ”lump disturbance”,and to overcome the ”differential peak” phenomenon which often appears in the traditional LESO,and it is proved that the observation errors of the observer are bounded.Then a novel controller combining the TVESO and sliding mode control to control attitude of the quadrotor.In addition,the designed controller can ensure that all signals of closed-loop system are bounded.Finally,the effectiveness and superiority of the proposed controller are verified by numerical simulation.2.Aiming at unknown external disturbances,model uncertainties,unknown velocity and unknown angular velocity in trajectory tracking of the quadrotor,a nonlinear controller based on the TETESO and nonlinear differentiator has been proposed.Firstly,to facilitate the controller design,the quadrotor system is divided into position subsystem and attitude subsystem,which are converted into the original cascaded dynamic system.Secondly,based on ensuring the basic performance of the LESO,the TETESO can reduce the communication resources between sensor and observer,and effectively avoid Zeno behavior.The nonlinear differentiator can avoid the complexity of direct derivations of desired position signals and desired attitude signals.The proposed nonlinear controller can ensure the quadrotor tracks the desired trajectory.3.To solve the problems of unknown external disturbances,model uncertainties,control input saturation,and measurement noise,a novel robust backstepping controller synthesized by the ILESO,auxiliary dynamic system,and sliding mode differentiator is proposed in this paper.The ILESO is used to observe unmeasured states and ”lump disturbance” of the quadrotor and deal with the measurement noise problem.The auxiliary dynamic system can solve the input saturation problem of the quadrotor.The sliding mode differentiator solves the ”differential explosion” problem in the traditional backstepping controller.The proposed robust backstepping controller can make the quadrotor track the desired attitudes,and the stability of the closed-loop system is proved by using the Lyapunov stability theory.