Research On Nonlinear Robust Control Methods For Complex Spacecraft Oriented To Safe Flight

As one of the cutting-edge technologies developed by countries all over the world,aerospace technology plays an increasingly important role.With the continuous improvement of the spacecraft's on-orbit capability,the structural flexibility of the spacecraft is gradually increasing,and the quality of the liquid fuel carried is increased.The spacecraft model exhibits strong coupling and strong nonlinear characteristics.Secondly,during the operation of the spacecraft,due to the limitation of the actuators and the measurement components,there are multi-constraint conditions,such as attitude constraints,angular velocity constraints,and input constraints.What's more,due to the influence of unknown space environment interference and component aging,it is difficult to avoid the occurrence of faults,which will affect the spacecraft stability control.This paper analyzes and summarizes the key scientific issues of spacecraft control,and studies the safety flight control of spacecraft for the purpose of improving the safety and reliability of spacecraft operations.The main contributions of the thesis are as follows.(1)Aiming at the requirements of fast and high-precision attitude stabilization of complex spacecraft with strong coupling and nonlinear characters,the integrated design of flexible vibration suppression,liquid sloshing influence estimation and attitude controller is proposed.To suppress the flexiblevibration,a robust input shaper is designed,while the influence on the control accuracy is weakened.Secondly,the improved multivariable continuous twisting sliding mode controller is proposed,which can ensure accurate estimation and compensation of the effects of liquid sloshing and external disturbance,and guarantee the finite-time high precision attitude stabilization.(2)Aiming at the fast and stable maneuver control requirements of complex spacecraft with un-measureable angular velocity and multi-constrains,a comprehensive strategy of attitude maneuvering trajectory optimization and finite time tracking control is proposed.Considering the fast and stable requirements,the performance index and multi-constraint conditions is established to design the attitude maneuver optimization trajectory.Then,a finite-time observer is designed to obtain the angular velocity,which does not depend on the system model.Finally,based on the attitude optimization trajectory and angular velocity estimation value,an adaptive continuous multivariable twisting integral sliding mode controller is designed to realize high-precision and fast tracking of the attitude-optimized maneuvering trajectory.(3)Aiming at the fast fault-tolerant control of complex spacecraft with the sensor measurement error and actuator fault,a split-loop finite-time command filtering backstepping control strategy is proposed.Firstly,considering the measurement error and fault,the control-oriented is established.Secondly,for the attitude angle and angular velocity subsystem,the auxiliary signal and virtual controller are designed to ensure the finite time compensation of the filtering error.Finally,the fault-tolerant controller is constructed with the design of intermediate variables and the adaptive law,which can achieve the finite-time attitude control under measurement error and fault.The comprehensive stability proof is given accordingly.(4)In order to improve the flexibility and reliability of the system,the research on spacecraft formation attitude control is carried out.Aiming at the synchronous control of spacecraft distributed attitude formation under angular velocity and input constraints,a comprehensive strategy of finite-time fully distributed observer and attitude constrained synchronization controller is proposed.Through the distributed observer,the finite time estimation of the leader's attitude and angular velocity is realized.The new finite-time auxiliary system dynamic and attitude synchronization controller is designed to solve the angular velocity tracking error and control input constraints,and the finite time attitude synchronization control of spacecraft can be achieved.