  Accurate information of inertial parameters is critical to motion planning
and control of space robots. Before the launch, only a rudimentary estimate of
the inertial parameters is available from experiments and computer-aided design
(CAD) models. After the launch, on-orbit operations substantially alter the
value of inertial parameters. In this work, we propose a new momentum
model-based method for identifying the minimal parameters of a space robot
while on orbit. Minimal parameters are combinations of the inertial parameters
of the links and uniquely define the momentum and dynamic models. Consequently,
they are sufficient for motion planning and control of both the satellite and
robotic arms mounted on it. The key to the proposed framework is the unique
formulation of momentum model in the linear form of minimal parameters.
Further, to estimate the minimal parameters, we propose a novel joint
trajectory planning and optimization technique based on direction combinations
of joints' velocity. The efficacy of the identification framework is
demonstrated on a 12 degrees-of-freedom, spatial, dual-arm space robot. The
methodology is developed for tree-type space robots, requires just the pose and
twist data, and scalable with increasing number of joints.
