On-orbit cooperating space robotic servicers handling a passive object

A planning and control methodology is developed for manipulating passive objects by cooperating orbital free-flying servicers in zero gravity. Both on-off base thrusters and manipulator continuous forces are used in handling on-orbit passive objects and eliminating the effects of on-off control. For two different contact types, the system dynamics are presented. Using a two-layer optimization process, a planning strategy for the trajectory tracking motion of a passive object, including optimal end-effector contact point selection, is developed. A model-based controller adapted to the special characteristics of the system, such as the unilateral constraints and the on-off thrusting, is presented and its response is discussed, for both contact cases. The manipulation strategy is illustrated using a three-dimensional task. For the cases studied, the system performance exhibits desirable response characteristics, such as remarkable positioning accuracy and reduced thruster fuel consumption.