A new method for online identification of the center of mass of spacecraft using multiple accelerometers

The online estimation of the center of mass plays an important role in the attitude and orbit control law design for spacecrafts with significantly time-varying masses. A new method is proposed to estimate the center of mass of a spacecraft by using six accelerometers and three gyros. The six accelerometers are used to measure the accelerations of six different points in three directions, and the three gyros are used to get the angular velocity of the spacecraft. By combining the acceleration and the angular velocity, the angular acceleration can be obtained directly instead of differentiating the angular velocity. In this way, the differential error can be avoided and thus the center of mass estimation precision can be increased. Besides, the requirement on the measurement precisions of gyros and accelerometers can be relaxed. Two configuration modes of the six accelerometers on three directions, 2-2-2 and 3-2-1 are discussed, and based on that the simulation results are generated and evaluated in terms of the root of mean square error of the center of mass estimation. When the measurement precision of accelerometer is higher than 10-5g, the results have shown that the root of mean square error of the estimated center of mass is less than 10mm given the location error and the angular misalignment of accelerometers are less than 5mm and 0.5°, respectively.