Large-scale flexible spacecraft mass properties determination using torque-generating control

Abstract

It is necessary to determine the mass properties of an on-orbit large-scale flexible spacecraft in order to achieve high-precision attitude control. The mass properties of the spacecraft include the inertia, the center of mass, and the mass. Research in this area had been mostly focused on rigid spacecrafts. The coupling between the rigid body of the spacecraft and the large flexible appendages on it, however, could have significant effect on the mass properties determination. This article proposes a momentum conservation–based determination method that takes into consideration the rigid–flexible coupling factors of large-scale flexible spacecrafts. First, a control method is designed to ensure that the spacecraft stays motionless after the motivation incurred for mass properties determination. Second, an inertia matrix determination method is developed using a Kalman filter, in which the coupling factors are added in the amendment procedure. Third, the Kalman filter with input is applied in the determination of the center of mass: on the one hand, this method can use one the accelerometer placed at the flexible appendages, if the deformation can be measured; on the other side, the method can use three accelerometers placed at three orthogonal points of the rigid part of the spacecraft, when the deformation cannot be measured. Finally, the mass can be gained by estimating the center of mass twice. Simulations were carried out on a large-scale rigid–flexible coupling spacecraft. The results demonstrated that the determination errors in all cases are less than 10%, which meet the engineering requirements.

Integrated control scheme for a large membrane diffractive space telescope

“…Two particularly influential components of the disturbances are high-frequency disturbances generated by the attitude actuators (such as flywheels 5 and Control Moment Gyroscopes, 6 CMGs) and low-frequency disturbances generated by the flexible appendages. 7 Also, the system in Figure 1 will be very flexible, 8 thus unwanted relative motion between the primary lens and the receiving imager will be present. The control system for this kind of spacecraft should be designed dedicatedly.…”