Control Of Dynamic Attitude Disturbances On Spacecrafts Equipped With Robotic Systems For Orbital Maintenance
- Paper number
IAC-07-C1.8.01
- Author
Dr. Silvio Cocuzza, CISAS G. Colombo Center of Studies and Activities for Space, University of Padova, Italy
- Coauthor
Mr. Isacco Pretto, University of Padova, Italy
- Coauthor
Prof. Carlo Menon, Simon Fraser University, Canada
- Coauthor
Prof. Francesco Angrilli, University of Padova, Italy
- Year
2007
- Abstract
Space robotics currently has an important role in space operations and scientists and engineers are designing new robotic systems for space servicing missions and extra-vehicular activities. In particular, free-flying robots with extended arms have compelling applications and several prototypes have recently been developed. This paper presents the theoretical formulation and the experimental validation of an innovative algorithm for the kinematic inversion of redundant free-flying space robotic systems, which causes minimum attitude disturbances on the spacecrafts on which they are mounted. The subject is of particular interest because robotic systems used in space need to limit induced spacecraft attitude disturbances while performing manipulator manoeuvres in order to avoid communications problems. Reduced spacecraft attitude disturbances will result in a lower fuel consumption for stabilization, and therefore in an increase of the system useful life. Different authors face the problem by exploiting the minimization of spacecraft attitude disturbances as a secondary task, using the null space of the system Jacobian matrix by means of a least squares pseudoinversion. In this paper a different approach is proposed: an algorithm is developed which locally searches for the optimal solution, i.e. the minimum angular momentum on the spacecraft center of mass, during continuous end-effector path tracking. Closed loop inverse kinematics algorithms have been developed for this purpose, and singularity-robust modified forms of the pseudoinverse are proposed in order to avoid singularity problems. The proposed algorithm has been tested using a 3D free-flying robot previously tested in an ESA Parabolic Flight Campaign. In this test campaign the 3D robot has been converted in a 2D robot taking advantage of its modular structure, and it has been suspended by means of air-bearings on a granite plane. In this way it is possible to perform planar tests, which have the advantage that it is possible to simulate a microgravity environment without time constraints. The base of the robot has been fixed on ground by means of a custom designed dynamometer, which measures the forces and torques transferred to ground to be minimized. The forces and torques transferred to ground using the proposed kinematic inversion method have been compared with those relevant to a classical kinematic inversion which minimizes only the joints velocities. The forces and torques reductions obtained range from 50% to 90% depending on the end-effector trajectory, and these values have been confirmed by the experimental tests.
- Abstract document
- Manuscript document
IAC-07-C1.8.01.pdf (🔒 authorized access only).
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