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Reference TypeConference Proceedings
Author(s)Ijspeert, A.;Nakanishi, J.;Schaal, S.
Year2001
TitleTrajectory formation for imitation with nonlinear dynamical systems
Journal/Conference/Book TitleIEEE International Conference on Intelligent Robots and Systems (IROS 2001)
Keywordsmovement primitives behaviors dynamic systems computational motor control attractor landscapes
AbstractThis article explores a new approach to learning by imitation and trajectory formation by representing movements as mixtures of nonlinear differential equations with well-defined attractor dynamics. An observed movement is approximated by finding a best fit of the mixture model to its data by a recursive least squares regression technique. In contrast to non-autonomous movement representations like splines, the resultant movement plan remains an autonomous set of nonlinear differential equations that forms a control policy which is robust to strong external perturbations and that can be modified by additional perceptual variables. This movement policy remains the same for a given target, regardless of the initial conditions, and can easily be re-used for new targets. We evaluate the trajectory formation system (TFS) in the context of a humanoid robot simulation that is part of the Virtual Trainer (VT) project, which aims at supervising rehabilitation exercises in stroke-patients. A typical rehabilitation exercise was collected with a Sarcos Sensuit, a device to record joint angular movement from human subjects, and approximated and reproduced with our imitation techniques. Our results demonstrate that multi-joint human movements can be encoded successfully, and that this system allows robust modifications of the movement policy through external variables.
Place PublishedWeilea, Hawaii, Oct.29-Nov.3
Pages752-757
Short TitleTrajectory formation for imitation with nonlinear dynamical systems
URL(s) http://www-clmc.usc.edu/publications/I/ijspeert-IROS2001.pdf

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