A SPACE MANIPULATOR WITH INERTIALLY FIXED BASE

At the heart of the Canadian contribution to Space Station "Freedom" are two manipulator systems: The Space Station Remote Manipulator System and the Special Purpose Dexterous Manipulator. The payload handling performance requirements for these manipulators are specified assuming an inertially fixed operating base, which is equivalent to assuming an infinitely large Space Station. This paper examines the reasons for, and the effects of this seemingly unrealistic assumption which has been the subject of considerable debate within the Space Station "Freedom"F'rogram. It is demonstrated that this assumption represents a worst case with respect to key parameters of the actual on-orbit manipulator performance. It is further shown why this assumption does not affect the manipulator control system design. Interaction effects between the Space Station attitude control system and the manipulators are included in the discussion and it is shown that in certain respects the "fixed base assumption" is also a worst case assumption for the interactions of manipulators and the Space Station attitude control system.