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A Computational Model of Arm Trajectory Modification Using Dynamic Movement Primitives

2007

Conference Paper

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Several scientists used a double-step target-displacement protocol to investigate how an unexpected upcoming new target modifies ongoing discrete movements. Interesting observations are the initial direction of the movement, the spatial path of the movement to the second target, and the amplification of the speed in the second movement. Experimental data show that the above properties are influenced by the movement reaction time and the interstimulus interval between the onset of the first and second target. Hypotheses in the literature concerning the interpretation of the observed data include a) the second movement is superimposed on the first movement (Henis and Flash, 1995), b) the first movement is aborted and the second movement is planned to smoothly connect the current state of the arm with the new target (Hoff and Arbib, 1992), c) the second movement is initiated by a new control signal that replaces the first movement's control signal, but does not take the state of the system into account (Flanagan et al., 1993), and (d) the second movement is initiated by a new goal command, but the control structure stays unchanged, and feed-back from the current state is taken into account (Hoff and Arbib, 1993). We investigate target switching from the viewpoint of Dynamic Movement Primitives (DMPs). DMPs are trajectory planning units that are formalized as stable nonlinear attractor systems (Ijspeert et al., 2002). They are a useful framework for biological motor control as they are highly flexible in creating complex rhythmic and discrete behaviors that can quickly adapt to the inevitable perturbations of dynamically changing, stochastic environments. In this model, target switching is accomplished simply by updating the target input to the discrete movement primitive for reaching. The reaching trajectory in this model can be straight or take any other route; in contrast, the Hoff and Arbib (1993) model is restricted to straight reaching movement plans. In the present study, we use DMPs to reproduce in simulation a large number of target-switching experimental data from the literature and to show that online correction and the observed target switching phenomena can be accomplished by changing the goal state of an on-going DMP, without the need to switch to different movement primitives or to re-plan the movement. :

Author(s): Mohajerian, P and Hoffmann, H. and Mistry, M. and Schaal, S.
Book Title: Abstracts of the 37st Meeting of the Society of Neuroscience
Year: 2007

Department(s): Autonomous Motion
Bibtex Type: Conference Paper (inproceedings)

Address: San Diego, CA, Nov 3-7
Cross Ref: p10143
Note: clmc

Links: PDF

BibTex

@inproceedings{sfn2007c,
  title = {A Computational Model of Arm Trajectory Modification Using Dynamic Movement Primitives},
  author = {Mohajerian, P and Hoffmann, H. and Mistry, M. and Schaal, S.},
  booktitle = {Abstracts of the 37st Meeting of the Society of Neuroscience},
  address = {San Diego, CA, Nov 3-7},
  year = {2007},
  note = {clmc},
  crossref = {p10143}
}