Volume 19 Issue 09 - Publications Date: 1 September 2000
Multiple Center of Mass Space Images of Single Objects and Their Impact on Path Planning
W.R. Doggett System Integration Branch, NASA Langley Research Center, W.C. Messner Department of Mechanical Engineering, Carnegie Mellon University and J-N. Juang Structural Dynamics Branch, NASA Langley Research Center
The center of mass space is a convenient space for planning motions that minimize reaction forces at the manipulator's base or optimize the stability of a mechanism. A unique problem associated with path planning in the center of mass space is the potential existence of multiple center of mass images for a single Cartesian obstacle, since a single center of mass location can correspond to multiple manipulator joint configurations. The existence of multiple images results in a need to either maintain multiple center of mass obstacle maps or to update obstacle locations when the manipulator passes through a singularity, such as when it moves from an elbow-up to an elbow-down configuration. To illustrate the concepts presented in this paper, a path is planned for an example task requiring motion through multiple center of mass space maps. The object of the path-planning algorithm is to locate the path with a bang-bang acceleration profile that minimizes the manipulator's base reactions in the presence of a single Cartesian obstacle. To simplify the presentation, only nonredundant manipulators are considered and joint nonlinearities are neglected.
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