Static Analysis of Indeterminate Contact Forces in Robotic Grasping and Manipulation

In this paper, indeterminate contact forces in robotic grasping and manipulation are investigated. Previous studies by Omata et al. showed that static friction forces in power grasps were constrained by rigid-body contact kinematics. The set of possible contact forces can be calculated using the constraint on static friction. However, their formulation generates paradoxical results on contact forces in some cases. In this paper, we study this problem and propose a modified method to calculate the set of possible contact forces, which can be applied to not only power grasps but also other robotic manipulation. The method excludes the above-mentioned paradoxical results successfully. In addition, a sufficient condition to reduce the computation for the method is derived.