Measurement framework of partial cage quality

When an object is caged by a set of fingers, it cannot move arbitrarily far from the caging fingers regardless of what possible rigid motion it takes. Although this condition makes caging an attractive choice for nonprehensile manipulation, it could be too restrictive than necessary in many real cases. This is because some object motions rarely occur in reality. Therefore, some non-caging formations of fingers that only allow these escape motions can still effectively be deployed in many caging tasks. This paper proposes a simple framework for measuring the quality of non-caging formation. The framework takes geometrical information of partial cage as inputs and estimates the order of input´s quality which is determined by the effort needed to make an object escape from partial cage. Results from preliminary experiments are presented to help support the proposal of the framework.