Abstract:
This thesis is concerned with a freeflyer robotic spacecraft for in-orbit satellite
servicing employing a dedicated attitude control system, ATLAS (Advanced
TeLerobotic Actuation System). It adopts a unique control system design to alleviate
the reaction coupling between the spacecraft mounting and the manipulator such that
control of both the spacecraft attitude and manipulator kinematics may be effected in
real-time using present-day space-rated electronics. It has been found that very few
additional computations are required to compensate the coupling problem over
standard terrestrial resolved motion robot control algorithms and standard spacecraft
attitude control techniques. A mathematical proof of the concept is outlined. The
technique is also extended for dual-arm operation. Two manipulator arms are
necessary for EVA-equivalence to afford maximum flexibility. Mutual collision
possibilities will be eliminated by incorporating a modified Zambesi bridge via interrupt
software whereby each manipulator is restricted to operations within its own quadrant.
This eases the computational burden of monitoring arm-to-arm collisions in the open
chain mode with little loss of flexibility. Closed chain mode is shown to be similar to
the open chain mode but with the addition of certain kinematic and force constraints.
Each arm must be capable of operating independently or cooperatively, necessitating a
hierarachical control architecture which is compatible with the NASREM control
architecture. Given that the single arm freeflyer is the baseline of this thesis and that
dual arm configurations are merely extensions of this, a simulation program of the
techniques outlined has been constructed to output some of the parameters o f interest.
Consideration is also given to the possible commercial impact of such a system.
