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Control of grasp stability when humans lift objects with different surface curvatures
P Jenmalm1, A W Goodwin, R S Johansson
1Department of Physiology, Umeâ University, S-901 87 Umea, Sweden.
Journal of Neurophysiology
|May 30, 1998
Summary
Fingertip force control during object manipulation is minimally affected by surface curvature. While grip force regulation remains consistent across different shapes, surface curvature impacts the force needed to prevent slips.
Area of Science:
- Human motor control
- Biomechanics
- Robotics
Background:
- Previous grasp stability studies used flat surfaces.
- Real-world object manipulation involves curved surfaces.
Purpose of the Study:
- Investigate how surface curvature influences fingertip forces during lifting and holding.
- Determine the impact of varying object weights and curvatures on grip force regulation.
Main Methods:
- Subjects grasped objects with spherically curved surfaces (concave/convex) of varying radii.
- Objects had different weights (168-705g).
- Measured grip force, load force, and forces required to prevent slips.
Main Results:
- Grip force increased with object weight but was inconsistently affected by surface curvature.
- Force generation during the load phase was not influenced by curvature.
- Surface curvature affected minimum forces needed to prevent slips, with larger curvatures requiring less force.
Conclusions:
- Surface curvature has minimal influence on grip force regulation in this manipulation task.
- Moderate changes in slip force due to curvature are not fully compensated by grip force adjustments.
- Grip force safety margins against slips increase with higher curvatures.