Application of multibody dynamics to on-orbit manipulator simulations

This paper discuses a generic multibody dynamics formulation and associated computer algorithm that addresses the variety of manipulator simulation requirements for engineering analysis, procedures development, and crew familiarization/training at the NASA Johnson Space Center (JSC). The formulation is based on body to body relationships with no concept of branched tree topologies. This important notion results in a single recursion pass to construct a system level mass matrix as opposed to the traditional inbound/outbound passes required by the other recursive methods. Moreover, the formulation can be augmented to account for closed loop topologies. The base body of the structure can be fixed or free; each subsequent body, if any, is attached to its parent body via any combination of rotational or translational degrees of freedom (DOFs). Furthermore, each body in the multibody system can be defined as rigid or flexible. The algorithm is designed to partition the data variables and associated computations for multi-frequency or multi-process computation. The resulting algorithm requires approximately one third the computations (in terms of additions and multiplications) of techniques previously used at the NASA JSC.