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Published on: December 15, 2010
Task-dependent viscoelasticity of human multijoint arm and its spatial characteristics for interaction with
1NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, Kanagawa, 243-0198, Japan.
Summary
Human arm stiffness can be adjusted by changing joint stiffness, altering hand stiffness ellipse shape and orientation. This control is crucial for interacting with objects and stabilizing movement.
Area of Science:
- Biomechanics
- Human motor control
- Robotics
Background:
- Human arm viscoelasticity is vital for posture, movement, and object interaction.
- Hand stiffness ellipses characterize arm viscoelasticity, influenced by posture.
- Limited understanding exists on joint stiffness changes and their impact on hand stiffness ellipses.
Purpose of the Study:
- Investigate dexterous control mechanisms of the human multijoint arm.
- Analyze viscoelastic properties, controllability, and spatial characteristics.
- Examine effects of cocontractions and force interactions in a horizontal plane.
Main Methods:
- Studied human multijoint arm viscoelasticity during cocontractions and force regulation tasks.
- Varied cocontraction ratios between shoulder and elbow joints.
- Analyzed force interactions in different directions and amplitudes.
Main Results:
- Altered cocontraction ratios changed stiffness ellipse shape and orientation, particularly at proximal hand positions.
- Single-joint stiffness correlated with own joint torque; cross-joint stiffness correlated with elbow torque.
- Viscosity-torque relationships showed similar tendencies.
- Stiffness ellipse characteristics varied during force regulation tasks due to joint stiffness changes.
Conclusions:
- Humans can modify hand stiffness directional characteristics by adjusting joint stiffness.
- This joint stiffness modulation enables diverse object interactions.
- Proximal posture allows significant changes in ellipse characteristics, suggesting a control mechanism.
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