Opposition Space as a Structuring Concept for the Analysis of Skilled Hand Movements

Iberall, Thea; Bingham, Geoff P.; Arbib, Michael A.

doi:10.1007/978-3-642-71476-4_12

Cited by 160 publications

(95 citation statements)

References 15 publications

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“…Finger positions appear to be normally computed so as to ensure a stable grasp, a necessary precondition for transport and manipulation. Indeed, an opposition axis which does not pass through the center of gravity of the object will reveal itself inadequate because the object will slip and fall (Iberall et al 1986). When the proposed axis was offset from center in our study, it made it more likely that the computation of opposition forces prior to the grasp became more difficult and required a longer time.…”

Section: Discussionmentioning

confidence: 82%

“…During a real grasp, the final finger position defines an opposition axis (or an opposition space if more than two fingers are involved) through which opposite forces operate on the object (Napier 1955;Iberall et al 1986). Obviously, the orientation of this axis is constrained by the biomechanics of the arm, in such a way that certain orientations will be systematically avoided in order to prevent end-position discomfort or even failure of the grasp (Stelmach et al 1994).…”

Section: Discussionmentioning

confidence: 99%

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Orientation of the opposition axis in mentally simulated grasping

Frak

Paulignan

Jeannerod

2001

Experimental Brain Research

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Abstract. Five normal subjects were tested in a simulated grasping task. A cylindrical container filled with water was placed on the center of a horizontal monitor screen. Subjects used a precision grip formed by the thumb and index finger of their right hand. After a preliminary run during which the container was present, it was replaced by an image of the upper surface of the cylinder appearing on the horizontal computer screen on which the real cylinder was placed during the preliminary run. In each trial the image was marked with two contact points which defined an opposition axis in various orientations with respect to the frontal plane. The subjects' task consisted, once shown a stimulus, of judging as quickly as possible whether the previously experienced action of grasping the container full of water and pouring the water out would be easy, difficult or impossible with the fingers placed according to the opposition axis indicated on the circle. Response times were found to be longer for the grasps judged to be more difficult due to the orientation and position of the opposition axis. In a control experiment, three subjects actually performed the grasps with different orientations and positions of the opposition axis. The effects of these parameters on response time followed the same trends as during simulated movements. This result shows that simulated hand movements take into account the same biomechanical limitations as actually performed movements.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Orientation of the opposition axis in mentally simulated grasping

Frak

Paulignan

Jeannerod

2001

Experimental Brain Research

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“…Opposition primitives. Images taken from [15] Another way of looking at hand function computationally, is through the Opposition Space theory proposed by Iberall and Arbib [15], to explain the prehensile capabilities of the hand in a task or goal directed manner. In this theory, hand function is seen as the principal motive that drives all prehensile posturing, and the hand´s ability to engage oppositional forces are seen as a functional basis.…”

Section: B Opposition Spacementioning

confidence: 99%

“…The precise manner in which they are combined determines the quality of the opposition space and the mix of force, motion and sensory ability that can be delivered. For a detailed explanation of opposition primitives and their properties, refer [15]. To arrive at a particular set of parameters, we must identify the oppositions that are present in a demonstrated grasp and describe the virtual fingers that form them.…”

Section: Palmmentioning

confidence: 99%

“…This is a known fixed configuration of the hand, which captures the intention of a particular opposition type and which serves as a starting point for hand closure, in order to arrive at a final grasp manifesting that opposition. Working from this assumption, the oppositions detected in a demonstrated grasp, are the outcome of their respective opposition pre-shapes being mixed together by the closure of their respective grasping patches along their respective opposition vectors (the process referred to as encloseschemas in [15]). The closure of the hand to form the final shape always operates under the basic functional intention determined by the set of pre-shapes from which it originated, and hence it is sufficient to examine these, instead of the final grasp.…”

Section: ) Virtualfinger1 -Based On the Demonstrated Graspmentioning

confidence: 99%

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On the representation of anthropomorphic robot hands: Shape versus function

Souza¹,

Bernardino²,

Santos-Victor³

et al. 2012

2012 12th IEEE-RAS International Conference on Humanoid Robots (Humanoids 2012)

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Abstract-We address the problem of representations for anthropomorphic robot hands and their suitability for use in methods for learning or control. We approach hand configuration from the perspective of ultimate hand function and propose 2 parameterizations based on the ability of the hand to engage oppositional forces. These parameters can be extracted from grasp examples making them suitable for use in practical learning-from-demonstration frameworks. We propose a qualitative method to span hand functional space in a principled manner. This is used to construct a grasp set for evaluation and a qualitative baseline metric derived from human experience. Our results from human grasp data show that hand representations based on shape are not able to disambiguate hand-function. However, those based on handopposition primitives result in the widest separations among grasps that have radically different functions and can even clearly separate grasps whose functions overlap a great degree. We trust that these "functional parameterizations" can bridge the contrasting goals of task-oriented robotic grasping, that of controlling a dexterous robot hand to manifest hand-shape but with the ability to exercise specific hand-function.

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2 Does Torque Minimization Yield a Stable Human Grasp?

Baud-Bovy

Prattichizzo

Brogi

Springer Tracts in Advanced Robotics

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Abstract. In this paper, we present a study of the human grasp conducted with a mathematical formalism that has been developed in robotics during the last two decades. The main objective of this study is to assess the extent to which the structure of the hand is adapted to its grasping function by identify the conditions under which a model minimizing energy expenditure predicts a stable grasp. The idea is that the human hand, as the result of evolutionary pressure, must be designed in such a way that it can grasp objects with minimum effort. To test this hyptohesis, we defined a cost function minimizing the weighted norm of the joint torque vector of a simple biomechanical model of the hand. The contact forces predicted by the model are then compared to the ones observed in a experimental study of the human tripod grasp. The results indicate that this cost function can predict a stable grasp when the external force is zero. A possible interpretation of this result is that the external force represents an unknown that cannot be taken into account by an evolutionary process."The coordination of a movement is the process of mastering redundant degrees of freedom of the moving organ, in other words its conversion to a controllable system" (Bernstein, [6], p. 127).

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Opposition Space as a Structuring Concept for the Analysis of Skilled Hand Movements

Cited by 160 publications

References 15 publications

Orientation of the opposition axis in mentally simulated grasping

Orientation of the opposition axis in mentally simulated grasping

On the representation of anthropomorphic robot hands: Shape versus function

2 Does Torque Minimization Yield a Stable Human Grasp?

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