Research On Fault Tolerant Control Of Satellite Attitude System

The satellite attitude system is the most important part of the whole satellitesystem, its security and reliability is the most essential problem to be consideredwhen designing the control system. In order to realize the controllability of reactionwheels appears to be complete failure, this paper uses three orthogonal and oneoblique installed reaction flywheels as the actuator of the zero momentumsatellites, and uses the integrity control theory of the passive fault tolerantcontrol method to solve the actuator complete failure problem. Thus the main jobof this paper is as following:Firstly, the modle of the attitude contrlo sysytem with actuator failure faultsis obtained. The Euler-angle descripted attitude kinematics model of satellite isdeveloped by using Euler-Newton method， according to the transformationrelation between each coordinate, the attitude dynamic model of the satellitesystem is obtained, and put stress on the attitude kinematics model of satellitewith reaction flywheels. In addition, this paper also studied several commonforms and its mathematical model of the actuator fault, and established themathematical model of satellite attitude control system with actuator failurefaults.Secondly，according to the researched fault type, the appropriate controlleris designed for the satellite attitude system with the fault type:①According tothe actuator complete failure and constant value deviation failure fault, based onthe Riccati equations and LMI, the state feedback fault tolerant controller withcertain stability margin and great disturbance attenuation characteristic isobtained;②According to the actuator complete failure, based on the directadaptive method, a integrity and disturbance attenuation fault tolerant controlleris obtained, it has no need to solve specific parameters, and can make the closed-loop control system stable under any initial value;③According to the actuatorcomplete failure, based on the linear matrix inequality, a guaranteed performance,integrity, H_∞state feedback controller is designed for the actuator failuresatellite attitude systems.④Furthermore, the conclusion that the design controllercan be applied to more kinds of actuator failure forms can be drawn，the inference and its proof is given.Thirdly, a digital simulate on the actuator failure satellite systems is given todemonstrate the effectiveness of the design control method, the analysis andcomparing of the results of the research is also given. Using the LMI tool boxand the Simulink tool of the Matlab simulation software, the model of satelliteattitude control system with actuator failure is built, and the results is given thatthe simulation on the actuator failure satellite systems demonstrates theeffectiveness of the designed fault tolerant method. Furthermore, the comparingof the three fault tolerant control method on the performance and effect is given,which will provide background for their using.