Authors: This paper presents the analysis and validation of a Least Squares based Inverse Kinematics solution for the control of the reaction torque transferred to the floating base of a redundant space manipulator. The solution, which is suitable for real-time implementation and can be extended in order to take into account the joint angle, velocity and acceleration limits, has been recently developed and experimentally validated by the authors in the case of a fixed-based planar manipulator. In this study, the solution is validated in the case of a planar three degrees of freedom free-floating manipulator by using a software simulator. Moreover, the operations of a free-floating robot and of a fixed-based robot are compared in different ways. First, the possibility to use fixed-based kinematic and dynamic models in order to reduce the computations necessary for the proposed solution is investigated. In particular, a limit base/arm mass ratio is derived, for which the approximated model can be favourably used, taking into account the requirements on base attitude pointing accuracy and end-effector trajectory accuracy. Then, the requirements on the maximum joint variables of a free-floating and of a fixed-based robot are compared for a given task. Higher joint angles, velocities and accelerations are expected with respect to a fixed-based robot that performs the same task, due to the base rotation displacements. This effect can be limited thanks to the proposed torque minimization solution, since motions can be studied in which a fixed base orientation is maintained, if sufficient redundant degrees of freedom are present. Finally, the study of the workspace in which a zero reaction torque can be obtained is performed for different base/arm mass ratios, both taking into account the physical joint limits or not. Cocuzza; Pretto; Debei
Journal: 2009
Conference: 60th International Astronautical Congress 2009, IAC 2009
