Dynamic And Integrated Control Of Vibration And Attitude For Spacecraft With High Accruracy And High Stability

It is necessary for the spacecraft to provide a working environment with high accuracy and high stability for the payload to achieve the Earth observation and space observation with high imaging quality,the intersatellite communication with the aid of the laser and so on.Therefore,an attitude control with high accuracy and high stability of spacecraft is required.However,the spacecraft would suffer vibrations generated by the external environment and its own structure when working on orbit,and which will affect the stability of attitude control.To improve the accuracy and stability of attitude control,firstly the analyis of the main disturbance sources of the spacecraft is needed,then the vibration suppression strategys should be designed according to the characteristics of the specific disturbance sources.Then the appropriate attitude control method which considering vibration suppression should also be studied at the same time.The dynamic and integrated control method of vibration and attitude for spacecraft with high accuracy and high stability requirement of is studied in this paper based on the previous researches.The specific works are as follows.Firstly,the dynamic model of the spacecraft was built according to the angular momentum theorem and the Kane equation,in which the spacecraft contains momentum exchange devices,flexible appendages and optical loads.In the model,the mass imbalance and the installation errors of the rotor of the control moment gyroscope(CMG)are considered and the CMG could be degenerate into flywheel under certain conditions.The model built in this paper has a certain generalityThen the friction and collision characteristics of the joints of the vibration isolation platform are studied since this problem is not be studied specificly before.The dynamic model of the vibration isolation platform considering the clearances of the joints is built by considering the vibration isolation struts are connected the payload platform and the base platform with spherical hinges.The simulations of vibration isolation platform with different clearance parameters are carried out,and the influences of different clearance parameters on vibration isolation performance of vibration isolation platform,as well as the influence on the stability of attitude control,are studied.The requirements for the design and processing of the vibration isolation platform in the engineering application are put forward based on the studies above and investigating the distribution of the collision points in the hinges.Then the design and analysis of 2 kinds of vibration isolation structures considering the characteristics of the attitude control actuators are proposed since the disturbance characteristics of the actuators are not fully taken into account in the traditional researches.A vibration isolation platform with negative stiffness structures is presented in the light of the the frequency of the disturbance of flywheel changes along the rotation speed of the rotor.The transmission characteristics of the vibration isolation platform with negative stiffness structures are derived,and a parameter design method is proposed based on the frequency domain analysis.On the other side,an inner vibration isolation structure for CMG is proposed in the light of the vibration isolation platform with Stewart configuration takes up a large emission volume and has some coupling channels.Then a parameter design method for the inner vibration isolation structure is proposed based on the analyze of the dynamic model and transmission characteristics of which.In order to further improve the attitude stability of optical load,an active vibration isolation method based on magnetic suspension technology for the spacecraft with flexible appendages and an integrated control strategy of vibration and attitude control are studied.Firstly,a vibration isolation strut with magnetic suspension is presented in this paper according to the basic principle of magnetic suspension.The control current for the vibration isolation strut is designed based on the analysis of the dynamic characteristics.Then the vibration isolation platform with magnetic suspension was studied which is composed by the vibration isolation strut with magnetic suspension.A parameter design method of the vibration isolation platform was proposed and the transmission characteristics of which are studied.Then the dynamics and control of the spacecraft with vibration isolation platform with magnetic suspension are studied based on the studies of the characteristics before.The vibration isolation platform is installed between the actuators and the spacecraft bus when the payload is small.To achieve the attitude control task with fast maneuver and fast stabilization of the spacecraft,the finite time control method is improved to meet the bandwidth constraint.The vibration isolation platform is installed between the payload and the spacecraft bus when the payload is large.In that case,in order to achieve high precision and high stability attitude control for spacecraft with uncertain inertia parameter of the payload,an adaptive control method is used to estimate the load inertia,and a parameter design method is proposed to ensure the stability of the control system.Finally,the vibration characteristics of the fully flexible spacecraft are analyzed and the vibration suppression strategy of which is also studied.A dynamic model with flexible spacecraft bus and flexible appendages is established by taking a large truss structure spacecraft as an example.The vibration transmission characteristics on the flexible spacecraft bus are analyzed.A vibration isolation platform is installed at each CMG installation point to achieve the high frequency vibration suppression.The transmission characteristics of the vibration isolation platform considering the installation position are analyzed.An adaptive sliding mode controller with bandwidth constraints is designed to achieve the low frequency vibration suppression.Numerical simulation proves the correctness and effectiveness of the analysis method and design method above.