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- Title
Attractor and Lyapunov Models for Reach and Grasp Movements with Application to Robot-assisted Therapy.
- Authors
Guastello, Stephen J.; Nathan, Dominic E.; Johnson, Michelle J.
- Abstract
The principles of attractors and Lyapunov exponents were used to develop a reaching-to-grasp model for use in a robotic therapy system for stroke patients. Previously known models for these movements, the fifth order minimum jerk and the seventh order polynomial, do not account for the change in grasp aperture of the hand The Lyapunov model was tested with reaching-to-grasp movements performed by five neurologically intact subjects and produced an average R2 = .97 over 15 replications for 41 different task events, reflecting a notable advantage over the fifth order (average R2 = .58) and seventh order (average R2 = .67) models. A similar level of success was obtained for the Lyapunov model that was specific to grasp aperture. The results indicated that intentional movements can be accurately characterized as attractor trajectories, and as functions of position along two Cartesian coordinates rather than as functions of time. The Lyapunov exponent model requires fewer parameters and provides an efficient platform for real-time implementation.
- Subjects
LYAPUNOV exponents; DIFFERENTIAL equations; ATTRACTORS (Mathematics); DIFFERENTIABLE dynamical systems; ROBOTS
- Publication
Nonlinear Dynamics, Psychology & Life Sciences, 2009, Vol 13, Issue 1, p99
- ISSN
1090-0578
- Publication type
Article