title: A computer algorithm for representing spatial-temporal structure of human motion and a motion generalization method.
abstract: Inspired by the generalized motor program (GMP) theory, this study presents a symbolic motion structure representation (SMSR) algorithm that identifies a basic spatial-temporal structure of a human motion. The algorithm resolves each joint angle-time trajectory of a multi-joint motion into a sequence of elemental motion segments and labels each motion segment with a symbol representing its shape ("U": monotonically increasing; "D": monotonically decreasing; "S": stationary). By concatenating symbols according to their order in time, the spatial-temporal structure of a joint angle-time trajectory is represented as a symbolic string. The structure of a multi-joint motion is then represented as a set of symbolic strings. A sample motion, whose structure is identified by the SMSR algorithm, can be generalized to produce an infinite number of similar motion variants. To generate a variant of a sample motion, segment boundary points of the sample motion are first relocated to new locations in the angle-time space, and then individual motion segments of the original joint angle trajectories are shifted and proportionally rescaled to fit the new segment boundary points. This motion generalization method provides a basis for developing GMP-based motion simulation models, and exploring ideas and hypotheses related to the GMP theory through simulation. As an application of the motion generalization method, a motion modification (MoM) algorithm is presented, which adapts existing reach motions for new target locations. Some examples generated by the MoM algorithm are illustrated.
authors.affiliation: Department of Mechanical, Industrial, and Nuclear Engineering, University of Cincinnati, University and Campus Drive-626 Rhodes Hall, Cincinnati, OH 45221-0072, USA. woojin.park@uc.edu
authors.forename: Woojin
authors.initials: W
authors.lastname: Park
authors.forename: Don B
authors.initials: DB
authors.lastname: Chaffin
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Martin
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Faraway
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006801:Humans; D007596:Joints / Q000502:physiology; D008954:Models, Biological; D009048:Motor Skills / Q000502:physiology; D009068:Movement / Q000502:physiology*