Cargando…

Strategy Switching in the Stabilization of Unstable Dynamics

In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear spr...

Descripción completa

Detalles Bibliográficos
Autores principales: Zenzeri, Jacopo, De Santis, Dalia, Morasso, Pietro
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055681/
https://www.ncbi.nlm.nih.gov/pubmed/24921254
http://dx.doi.org/10.1371/journal.pone.0099087
_version_ 1782320703904677888
author Zenzeri, Jacopo
De Santis, Dalia
Morasso, Pietro
author_facet Zenzeri, Jacopo
De Santis, Dalia
Morasso, Pietro
author_sort Zenzeri, Jacopo
collection PubMed
description In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear springs, is affected by a saddle-like force-field. The non-linearity of the springs allows the users to determine size and orientation of the tool stiffness ellipse, by using different patterns of bimanual coordination: minimal stiffness occurs when the two spring terminals are aligned and stiffness size grows by stretching them apart. Tool parameters were set such that minimal stiffness is insufficient to provide stable equilibrium whereas asymptotic stability can be achieved with sufficient stretching, although at the expense of greater effort. As a consequence, tool users have two possible strategies for stabilizing the mass in different regions of the workspace: 1) high stiffness feedforward strategy, aiming at asymptotic stability and 2) low stiffness positional feedback strategy aiming at bounded stability. The tool was simulated by a bimanual haptic robot with direct torque control of the motors. In a previous study we analyzed the behavior of naïve users and we found that they spontaneously clustered into two groups of approximately equal size. In this study we trained subjects to become expert users of both strategies in a discrete reaching task. Then we tested generalization capabilities and mechanism of strategy-switching by means of stabilization tasks which consist of tracking moving targets in the workspace. The uniqueness of the experimental setup is that it addresses the general problem of strategy-switching in an unstable environment, suggesting that complex behaviors cannot be explained in terms of a global optimization criterion but rather require the ability to switch between different sub-optimal mechanisms.
format Online
Article
Text
id pubmed-4055681
institution National Center for Biotechnology Information
language English
publishDate 2014
publisher Public Library of Science
record_format MEDLINE/PubMed
spelling pubmed-40556812014-06-18 Strategy Switching in the Stabilization of Unstable Dynamics Zenzeri, Jacopo De Santis, Dalia Morasso, Pietro PLoS One Research Article In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear springs, is affected by a saddle-like force-field. The non-linearity of the springs allows the users to determine size and orientation of the tool stiffness ellipse, by using different patterns of bimanual coordination: minimal stiffness occurs when the two spring terminals are aligned and stiffness size grows by stretching them apart. Tool parameters were set such that minimal stiffness is insufficient to provide stable equilibrium whereas asymptotic stability can be achieved with sufficient stretching, although at the expense of greater effort. As a consequence, tool users have two possible strategies for stabilizing the mass in different regions of the workspace: 1) high stiffness feedforward strategy, aiming at asymptotic stability and 2) low stiffness positional feedback strategy aiming at bounded stability. The tool was simulated by a bimanual haptic robot with direct torque control of the motors. In a previous study we analyzed the behavior of naïve users and we found that they spontaneously clustered into two groups of approximately equal size. In this study we trained subjects to become expert users of both strategies in a discrete reaching task. Then we tested generalization capabilities and mechanism of strategy-switching by means of stabilization tasks which consist of tracking moving targets in the workspace. The uniqueness of the experimental setup is that it addresses the general problem of strategy-switching in an unstable environment, suggesting that complex behaviors cannot be explained in terms of a global optimization criterion but rather require the ability to switch between different sub-optimal mechanisms. Public Library of Science 2014-06-12 /pmc/articles/PMC4055681/ /pubmed/24921254 http://dx.doi.org/10.1371/journal.pone.0099087 Text en © 2014 Zenzeri et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Zenzeri, Jacopo
De Santis, Dalia
Morasso, Pietro
Strategy Switching in the Stabilization of Unstable Dynamics
title Strategy Switching in the Stabilization of Unstable Dynamics
title_full Strategy Switching in the Stabilization of Unstable Dynamics
title_fullStr Strategy Switching in the Stabilization of Unstable Dynamics
title_full_unstemmed Strategy Switching in the Stabilization of Unstable Dynamics
title_short Strategy Switching in the Stabilization of Unstable Dynamics
title_sort strategy switching in the stabilization of unstable dynamics
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055681/
https://www.ncbi.nlm.nih.gov/pubmed/24921254
http://dx.doi.org/10.1371/journal.pone.0099087
work_keys_str_mv AT zenzerijacopo strategyswitchinginthestabilizationofunstabledynamics
AT desantisdalia strategyswitchinginthestabilizationofunstabledynamics
AT morassopietro strategyswitchinginthestabilizationofunstabledynamics