Three-dimensional kinematic analysis of influence of hand orientation and joint limits on the control of arm postures and movements |
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Authors: | Xuguang Wang |
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Institution: | INRETS – LBMC, 25 avenue Fran?ois Mitterrand, Case 24, 69675 Bron, France, FR
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Abstract: | The problems related to kinematic redundancy in both task and joint space were investigated for arm prehension movements
in this paper. After a detailed analysis of kinematic redundancy of the arm, it is shown that the redundancy problem is ill
posed only for the control of hand orientation. An experiment was then designed to investigate the influence of hand orientation
on the control of arm movements. Since movements must be made within the limits of the joints, the influence of these limits
was also analyzed quantitatively. The results of the experiment confirm that the increase of movement time because of the
change of object orientation is due to the lengthening of the deceleration phase disproportionately to the rest of the movement.
The variation of hand path due to the change of object orientation was observed as being surprisingly small for some subjects
as opposed to the large range of object orientation, implying that hand path and hand orientation could be controlled separately,
thus simplifying the computational problem of inverse kinematics. Moreover, the observations from the present experiment strongly
suggest that a functional segmentation of the proximal and distal joints exists and that the control of wrist motion is dissociated
from the rest of joint motions. The contribution of each joint in the control of arm movements could be determined through
the principle of minimum energy and minimum discomfort under the constraints of the joint limits. A simplified inverse kinematics
model was tested. It shows that these hypotheses can be easily implemented in a geometric algorithm and be used to predict
arm prehension postures reasonably well under the constraints of joint limits.
Received: 6 August 1998 / Accepted in revised form: 16 December 1998 |
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