Force Distribution in Multiple Whole-Limb Manipulation

This paper deals with robotic systems composed of multiple actuated limbs (such as arms, fingers, or legs) cooperating in the mampulation of an object. The problem of decomposing the system of contact forces exerted between the robot limbs and the object, in order to apply a desired resultant force on the object (and/or to resist to external disturbances) is studied. Enveloping (or “whole-limb”) manipulation operations that exploit any part of the limbs to contact the object are considered. The peculiarity of such systems is that contacts occurring on links with limited mobility (such as the inner links of a robot arm or hand), and even on fixed links (a robot chest or palm), are possible. Among the many consequences of this characteristic, the one studied in this paper is that only some of the internal grasping forces may be actively controlled to increase grasp stability.