No abstract

No abstract

This paper presents a study on the effect of design parameters of an underactuated hand on its grasp performance. Three kinds of grasp performance characteristics are considered: grasp range, grasp strength, and immobilizing grasp range. Grasp strength is defined as the stiffness of the grasp. Immobilizing grasps are those in which the object cannot be moved for a force up to a certain threshold. In general, underactuated hands cannot produce immobilizing grasps. However, we show that immobilizing grasps can be created by including joint limits in the hand design. We consider the effect of two design parameters on the grasp performance: torque ratio and finger-base distance. Results show that an optimal finger-base distance and torque ratio exists that maximizes the grasp range and grasp strength. Also, the immobilizing grasp range is increased by decreasing the finger-base distance and increasing the torque ratio and joint limits.

No abstract

In this paper, we present the derivation of the rotation matrix for an axisangle representation of rotation. The problem is of finding out the rotation matrix corresponding to the rotation of a reference frame, by a certain angle, about an arbitrary axis passing through its origin. The axis-angle representation is particularly useful in computer graphics and rigid body motion. We have used an intuitive interpretation of the rotation matrix for this derivation. The intuitive interpretation is as follows: the columns of the rotation matrix are the coordinate axes unit vectors of the rotated frame as seen from the fixed frame. This interpretation of the rotation matrix helps in quick computation of the rotation matrices required to obtain the required rotation matrix. The required rotation matrix can be computed from just two rotation matrices which are easy to find and intuitive to understand. The derivation presented in simpler to understand than presented in most books and can be grasped with minimum geometric visualization.