Inertial parameter identification of unknown object captured by a space robot

Inertial parameter identification of unknown object captured by a manipulator on a free-floating space robot is studied based on the conservation principle of linear and angular momenta. The momentum-based identification in all the published work is proposed under the assumption that the linear and angular momenta of the whole system are zero, which means the parameters can not be identified when the momenta are actually not zero. In order to resolve this problem, firstly the linear and angular momenta are expressed in the inertial frame rather than in the base body-fixed frame, so that the conservation of components of momenta is ensured. Then, by eliminating the linear and angular momenta from the momentum equations, the momentum increment equations are obtained and the inertial parameters of grasped object become the only unknown. Finally, by using three sets of measurements, the unknown inertial parameters are determined from the combined momentum increment equations. The simulation results demonstrate that the inertial parameters can be accurately identified by using this method in both cases of zero and nonzero momenta, and the problem of singular solution can also be avoided.