Compliant grasping force modeling for handling of live objects

Models quasi-statically the force acting on an object by a rotating flexible finger. As compared to fingers with multiple active joints, flexible fingers have many potential advantages; specifically, they are lightweight and have no relative individual moving parts in each of the fingers. Their ability to accommodate a limited range of varying sizes, shapes, and the natural reactions of some objects (without the need of a feedback mechanism such as a visual servo) makes a system using flexible fingers an attractive candidate for use as a grasper in a high-speed production setting. The advantages of flexible fingers are seldom exploited for grasping, however, because of complicated analyses involved in their design. The paper offers two methods to determine contact points/forces. The first analytical model, based on the Frisch-Fay (1962) flexible bar theory, provides an approximate closed-form solution for determining the contact points and forces. The second method using FEM predicts the stress distribution around the contact area. Both methods of predicting the contact forces have been verified experimentally. The effects of parameter variations are presented. Our results demonstrate that the model could be used as a practical means to measure the contact force between the finger and the live object.