抄録
This paper shows that a minimum d.o.f. robotic hand with two fingers is able to achieve the secure grasping of an object according to the local minimum of elastic potential energy (LMEE) . First, we derive an elastic force and an elastic potential energy equations due to deformation of soft fingers, which can be calculated into straightforward equations in an analytical way. These formulae lead to the fact that the potential energy of a soft fingertip is a function of two variables, and has a local minimum through the elastic rolling of a contacting object. Second, we formulate four geometric constraints in the grasping motion of a rigid object by means of two degrees of freedom robotic hand that has two rotational joints. Third, we define a basic motion that includes a translational and a rolling motions when two fingers rotate by infinitesimal angle, and propose a quasi-static manipulation and its algorithm by using the LMEE of soft fingers with the geometric constraints. In this theory, we define an energy function that includes the LMEE algorithm. By solving that function we simulate the path of the center of gravity and the change of orientation of the grasped object, and compare those values with measurements actually obtained from a CCD camera equipped above the manipulated object. Finally, we confirm the effectiveness of the quasi-static manipulation theory based on the LMEE algorithm from experiments.
