The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer...The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer needs to be precisely positioned at the center of gravity satellite,otherwise,the offset between them will bring measurement disturbance due to angular acceleration of satellite and gradient.Because of installation and measurement errors on the ground,fuel consumption during the in-flight phase and other adverse factors,the offset between the proof-mass center and the satellite center of mass is usually large enough to affect the measurement accuracy of the accelerometer,even beyond its range.Therefore,the offset needs to be measured or estimated,and then be controlled within the measurement requirement of the accelerometer by the center of mass(COM) adjustment mechanism during the life of the satellite.The estimation algorithm based on EKF,which uses the measurement of accelerometer,gyro and magnetometer,is put forward to estimate the offset,and the COM adjustment mechanism then adjusts the satellite center of mass in order to make the offset meet the requirement.With the special configuration layout,the COM adjustment mechanism driven by the stepper motors can separately regulate X,Y and Z axes.The associated simulation shows that the offset can be con-trolled better than 0.03 mm for all the axes with the method mentioned above.展开更多
The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are add...The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.展开更多
文摘The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer needs to be precisely positioned at the center of gravity satellite,otherwise,the offset between them will bring measurement disturbance due to angular acceleration of satellite and gradient.Because of installation and measurement errors on the ground,fuel consumption during the in-flight phase and other adverse factors,the offset between the proof-mass center and the satellite center of mass is usually large enough to affect the measurement accuracy of the accelerometer,even beyond its range.Therefore,the offset needs to be measured or estimated,and then be controlled within the measurement requirement of the accelerometer by the center of mass(COM) adjustment mechanism during the life of the satellite.The estimation algorithm based on EKF,which uses the measurement of accelerometer,gyro and magnetometer,is put forward to estimate the offset,and the COM adjustment mechanism then adjusts the satellite center of mass in order to make the offset meet the requirement.With the special configuration layout,the COM adjustment mechanism driven by the stepper motors can separately regulate X,Y and Z axes.The associated simulation shows that the offset can be con-trolled better than 0.03 mm for all the axes with the method mentioned above.
基金supported by the National Natural Science Foundation of China(11302010)
文摘The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.
