Modeling And Control For Spacecraft With Liquid Slosh And Flexible Structure

With the development of national security technology,the aerospace industry has developed rapidly and the space missions have become more and more complex.In order to complete the space missions,more structures have been adopted to the spacecraft,such as flexible appendages and liquid storage chamber,these structures not only change the control mode but also makes the control problem more complicated.In addition,as is known to all,the control torque produced by the actuator is usually not infinite for the practical applications,which will no doubt cause the control saturation problems and lead substantial degradation to the system.Although series of controllers to effectively handle the control saturation have been developed,hardly any study discussed the control algorithm for spacecraft with flexible structure and liquid sloshing(SFL)under control saturation and thus cannot meet the demands of future aerospace task.Based on the above reasons and in order to meet the needs of national defense and cater to the development trend of the future spacecraft,this paper has made the following research on the SFL:Firstly,according to the conservation law of momentum and the equivalent mechanics,the flexibility vibration and liquid sloshing for the SFL have been analyzed respectively.Then,based on the moment balance principle,the control-oriented dynamic model of the SFL is established.What's more,due to the introduction of flexibility vibration and liquid sloshing,the control-oriented SFL model is more complex and coupled.Thus,the type-2 adaptive fuzzy disturbance observer is designed to estimate the lumped uncertainty,which is caused not only by the inertia uncertainty and the external disturbance,but also by the liquid sloshing and flexible structure vibration.At the same time,a terminal sliding mode controller(TSMC)is designed.The proposed TSMC could achieve better control performance than the traditional sliding mode control,such as reducing the chattering and accelerating the convergence speed.The numerical simulations are presented to demonstrate the effectiveness and advantages of the proposed method.Then,considering the limited input,the overall model of the SFL is rewritten,and by introducing a dummy variable,the system perturbance caused by the input limitation can be converted into a part of the lumped uncertainty.Then,using the control method of the previous chapter,the new system can be controlled with a high accuracy and a rapid speed.In addition,the control method which combine the adaptive control and the sliding mode control is considered and the control effect is simulated and verified by the MATLAB.The simulation results show that this method could ensure the convergence speed and the control accuracy,that provides a new approach available for the control of SFL under control constraint.Finally,this paper considers the interference caused by flexible vibration,the longterm and high frequency vibration of flexible attachment would not only affect the control of the SFL but also damage the equipment.Thus,in this paper the active vibration suppression is studied.It focuses on both of the theoretical research and the application of positive position feedback(PPF)in suppression of flexible vibration.The effectiveness is certified by the simulation results,and thus provides a theoretical basis for the further research of the SFL.