Research On Mass Characteristic Estimation And Attitude Control Technology Of Variable Mass Spacecraft

With the rapid development of space technology,on-orbit missions of spacecraft become more and more complex,and the requirements for spacecraft performance and lifespan are increasingly high.On-orbit services include rendezvous and docking of spacecraft,space operation,fault maintenance,clearance of space junk.The spacecraft whose mass parameters change greatly due to the on-orbit service mission execution is called variable mass characteristic spacecraft.The parameter identification,attitude control and control allocation of variable mass spacecraft are the premise and basis of the successful completion of space on-orbit service.In this paper,the parameter identification,attitude control and control assignment of variable mass spacecraft are studied.Firstly,the mathematical description method related to spacecraft is studied.Also,the attitude dynamics,kinematics equation and disturbance torque model of spacecraft are established,which provide a theoretical basis for the follow-up study.Secondly,in view of the large variation of spacecraft mass parameters with variable mass characteristics and the difficulty of ground measurement,an independent parameter identification method based on hybrid actuator is proposed.The method is based on the independent identification of flywheel and thruster for the position of mass center and moment of inertia,which improves the identification accuracy.The hierarchical saturated PD control method based on Euler axis maneuver and the model independent attitude control method based on genetic algorithm are simulated.The results show that the attitude control method proposed in this paper can accomplish the attitude maneuver quickly with higher control accuracy.Thirdly,a model independent attitude control method based on genetic algorithm is proposed to solve the problems of large variation of mass parameters and low accuracy of attitude control.This method combines the genetic algorithm with the attitude control law to ensure the accuracy and improve the control efficiency.The simulation results of the hierarchical saturated PD control method based on Euler axis maneuver and the model independent attitude control method based on genetic algorithm are compared.The results show that the attitude control method proposed in this paper can guarantee higher control accuracy and accomplish attitude maneuver quickly.And then,in view of the issue that the combined spacecraft in the variable mass spacecraft needs to reallocate the control quantity,an optimization algorithm of the secondary allocation control allocation based on the comprehensive optimization index is proposed.This method considers the constraints of the spacecraft,constructs the optimization index and optimizes the control assignment of the spacecraft.The pseudo inverse method and the optimization algorithm based on the comprehensive optimization index are simulated.The optimization algorithm proposed in this paper considers more control constraints,helps to save more fuel,and ensures a longer life of spacecraft.Finally,a joint simulation and demonstration system is designed for variable mass spacecraft parameter identification,attitude control algorithm and control allocation optimization algorithm.The results of the simulation system are visual and easy to operate,which improves the demonstration effect of space mission verification of variable mass spacecraft.