Research On Integrated Fault-tolerant Control Of Spacecraft Attitude Control System Based On Fault Estimation Method

Some countries are actively developing space,and a large number of spacecraft in orbit are provided more services for them.For example,the American Space X company is launching the "Starlink" constellation plan.After the completion of the "Starlink" constellation,it will provide full coverage,high bandwidth and low latency Internet access to the world.China is currently carrying out the "Bei Dou Navigation Satellite System" program.In 2020,China will fully build the Bei Dou navigation satellite system.Once the "Bei Dou Navigation Satellite System" is completed,it will be widely used in precision agriculture,science and technology tourism,agriculture and forestry protection and other important fields.A series of space activities have made great progress in space technology.Attitude control research of spacecraft has always been one of the hot and difficult issues in the field of space technology.The successful completion of a series of space missions of modern spacecraft is inseparable from good attitude control.As space missions become more and more complex and more difficult,this has resulted in a large number of spacecraft with advanced performance and complex structures.However,the more complex and advanced the spacecraft,the more difficult it is to ensure the reliability and safety of the attitude control system.Therefore,in order to improve the safety and reliability of the spacecraft attitude system,reduce the occurrence of space accidents,reduce unnecessary economic losses,and ensure the safety of people's lives,integrated fault estimation and fault-tolerant control technology provides a feasible solution for ensuring the safety and reliability of the spacecraft attitude control system.Based on the fault diagnosis and fault-tolerant control theory,this paper takes the rigid spacecraft attitude control system as the object,and mainly studies the integrated design of the fault estimation and fault-tolerant control of the rigid spacecraft attitude control system.On the one hand,the modern rigid spacecraft attitude control system can ensure normal work;on the other hand,if a fault occurs,the fault-tolerant controller that has been adjusted in advance is used to compensate for the fault that affects the operation of the spacecraft.The research content of this paper have the following main parts:Considering that the spacecraft with partial actuator fault,an integrated fault-tolerant control method based on the actuaor loss of effectiveness fault estimation observer is proposed.This design method have two parts.Firstly,a sliding mode fault estimation observer is established based on the sliding mode technique.Secondly,the fault estimation observer obtains the information of the actuaor loss of effectiveness factor and the integrated fault-tolerant controller to compensate for the actuator fault.In the design of the integrated fault-tolerant controller,the backstepping method and the fractional-order sliding mode technology are used to effectively ensure the spacecraft's control performance when the actuator has faults.After the theoretical proof,the digital simulations prove the accuracy of the proposed fault estimation observer to estimate the fault and the good fault tolerance of the integrated fault-tolerant controller.Aiming at the bias faults of spacecraft actuators,based on the integrated fault estimation and fault-tolerant control ideas,this paper designs a bias fault estimation observer and a integrated fault-tolerant controller to ensure the spacecraft attitude stability.The proposed bias fault estimation observer uses the adaptive method and the sliding mode technology to effectively enhance the accuracy and robustness of the system's fault estimation observer.Based on this,the previous fault estimation information is used as the input of the current integrated fault-tolerant controller.This allows the fault to be compensated in real time.Due to the combination of a fault estimation observer and a fault-tolerant controller,the advantages of the two are complementary.On the one hand,the observer provides accurate fault information to ensure that the fault-tolerant controller accurately compensates for the fault;on the other hand,the fault-tolerant controller is the guarantee of accurate fault estimation.Finally,this section gives a digital simulation and compares the simulation results of fault-tolerant controllers designed based on a fast power reaching law.The simulation comparison and digital analysis prove that the integrated fault-tolerant controller proposed in this paper has a better fault-tolerant control performance.Since the fault of the three-axis actuator of the spacecraft may be time-varying or constant,the number of occurrences is also uncertain.Therefore,the spacecraft dynamic model is affected by external disturbances,as well as the time-varying fault of multiple actuators.This section presents a actuator fault estimation observer and an integrated fault-tolerant controller.The introduction of an adaptive sliding mode term in the design of the fault estimation observer effectively suppresses the influence of disturbances on fault estimation.The designed integrated fault-tolerant controller uses the backstepping method and the fractional-order non-singular terminal sliding mode technology.By using the fault information of the fault observer to compensate the attitude system fault,the system attitude is guaranteed to be stable.Finally,through simulation verification and comparison with the guidelines of non-fractional-order fault-tolerant controllers,it is concluded that the fault-tolerant controller in this paper has a significant expected performance in the fault case of attitude system.