FORCE AND POSITION CONTROL OF GRASP IN MULTIPLE ROBOTIC MECHANISMS

One of the approaches to increase the dexterity of a robot manipulatin g system is a design philosophy that consists of multiple robotic mech anisms. Applications of such a collection of manipulators can be in th e design of a dextrous end-effector, a reconfigurable fixture to locat e and grip various sized objects, or cooperative robotic arms which th rough their coordinated motions are able to accomplish a given task. A lthough the applications of such a design philosophy are endless, many problems still remain to be addressed. One of these problems is the c ontrol of the contact forces (grasping forces) between the mechanisms and the position of the grasped object. This article addresses this pr oblem. First, a model of the mechanisms in contact with the grasped ob ject is postulated; second, the problem of controlling the grasping fo rces and the position of the grasped object is formulated in the linea r multi-input/multi-output system, and, finally, a centralized optimal controller is proposed for controlling the desired variables. The res ults of this article are demonstrated using two examples. One of the m ain advantages of the proposed controller is that it also shapes the t ransient response of the grasping force, which is an important conside ration in cases when grasping fragile objects. (C) 1996 John Wiley & S ons, Inc.