Attitude Control For Spacecraft Based On Active Disturbance Rejection Control Technique

The rotational inertias of spacecraft will be changed because of fuel consumption and large angle attitude maneuver.Meanwhile,there exists external disturbance torques.Therefore,the spacecraft attitude controller should have strong robustness in order to guarantee the spacecraft completing the regular attitude task.The objective of this dissertation is to design a robust spacecraft attitude controller based on active disturbance rejection control technique to solve this problem.The main contributes are as follows:The spacecraft attitude is described by Euler angles,and a dynamic model of spacecraft attitude is established.The dynamic model is unknown when the rotational inertias of spacecraft can not be obtained.For this case,the dynamic model of spacecraft attitude can be decoupled through regarding all dynamics and external disturbance as a total disturbance.In the decoupled model,the roll channel,pitch channel and yaw channel are independent.Thus the active disturbance rejection controller(ADRC)can be designed for these three channels,separately.Without loss of generality,this dissertation takes roll channel as an example to show the design scheme of the nonlinear active disturbance rejection controller(NLADRC)and the linear active disturbance rejection controller(LADRC).Finally,simulations are given to show that these two kinds of controllers are effective and the performances are both better than PD controller.In some cases,the nominal dynamic model of spacecraft attitude can be obtained through identifying the rotational inertias.The coupled inclusions can be regarded as the total disturbance,with model uncertainties and external disturbances.Therefore,the dynamic model of spacecraft attitude can be decoupled and the ADRC can be designed for three channels,separately.Taking roll channel as an example,we give the design methods of NLADRC and LADRC.The simulations illustrate the effectiveness of these two kinds of controllers.Compared with the NLADRC/LADRC without model information,this controller guarantees the closed-loop system satisfying the desired performance with lower extended state observer gains and lower sate feedback gains.The actuator saturation should be considered because most attitude control methods for spacecraft are in the active control way.This dissertation proposed a modified extended state observer(MLESO)adopting the idea of anti-windup compensation and a linear anti-windup active disturbance rejection controller is presented based on it.The estimation error of MLESO is firstly studied.Then an algorithm is presented to calculate the anti-windup gain.This algorithm guarantees the asymptotic stability of the closed-loop system and obtains the maximized estimate of the basin of attraction of the closed-loop system.The simulations show that the proposed linear anti-windup active disturbance rejection controller can make the spacecraft to complete the specified attitude task when actuator saturation happens during the operation.Finally,the results of the dissertation are summarized.