Fine motion control based on constraint criteria under pre-loading configurations

This article discusses the fine motion control and extreme bounds on the maximum displacements allowed under pre-loading configurations in a robotic grasp. Fine motion is achieved by applying a preload at a contact to gain the desirable motion in a desirable direction under required sufficient contraints proposed in this paper. A particular one is the constraint of a restoring torque resulting at each contact due to the fine motion caused by the application of suitable forces through the contact. These forces are provided as preloads or the effect of preloads which can be applied through two types of pre-loading configurations, one of which is to apply a preload parallel to a contact normal and the other is through the contact normal. The article proposes mathematical models for both types of pre-loading configurations and introduces optimal preload for fine motion control in a grasped object. Examples are given in the article to support the theoretical base. Q 2000 John Wiley & Sons, Inc.