2006 Volume 42 Issue 2 Pages 98-104
This paper deals with the path planning of human digits in grasping a cylindrical object with the thumb and index finger. The digit of thumb approached to the cylindrical object along to a tangential line with respect to the lateral of the object. The trajectory of the thumb from initial position to the target could be divided into three patterns, a convex, double convexes, and non-convex type line. These distinctive patterns could be approximately expressed by the Three-order Bezier curve. In the grasping process, the contacted position of the two digits with the lateral of the cylindrical object changes according to the relative target position to the trunk. With reference to the hand posture, grasping motion was performed without bending the wrist region. Therefore, the grasped parts of the cylindrical object depended on the upper limb posture. Considering the obtained characteristics, the approximated model based on the upper limb posture was constructed. As a result, it was confirmed that the suggested model could adequately estimate the contacted position of the thumb with the lateral of the cylindrical object.
