Experimental Investigation of Mechanics in Soft-Fingered Grasping and Manipulation
This paper describes mechanical modeling of soft-fingered grasping and manipulation. Here, we used a simple hand consisting of a pair of 1-DOF rotational fingers with hemispherical soft fingertips to investigate the mechanics of soft-fingered grasping and
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Summary. This paper describes mechanical modeling of soft-fingered grasping and manipulation. Here, we used a simple hand consisting of a pair of 1-DOF rotational fingers with hemispherical soft fingertips to investigate the mechanics of soft-fingered grasping and manipulation. Based on the observations of soft-fingered grasping and manipulation, we propose a parallel distributed model with tangential deformation of hemispherical soft fingertips. We experimentally verified our proposed parallel distributed model. We then show that simulation results based on the parallel distributed model agree with the observations well.
1 Introduction and State-of-the-Art Human fingertips consist of soft tissue and this softness is one source of dexterity in grasping and manipulation of objects. The softness yields area-contact between each fingertip and an object, which allows stable grasping and manipulation. Therefore, robotics research has focused on the mechanics of soft-fingered grasping and manipulation. In this paper, we focus on a mechanical model of hemispherical soft fingertips based on observation of soft-fingered grasping and manipulation. To examine the mechanics of grasping and manipulation by soft fingertips, we used a simple hand consisting of a pair of 1-DOF rotational fingers with hemispherical soft fingertips. The deformation properties of soft fingertips may be observed clearly in such a simple hand system, which will aid in determining the mechanics of soft-fingered grasping and manipulation. Finite element (FE) analysis is often applied to study deformation of objects. Xydas and Kao reported the exact deformation shape of a hemispherical soft fingertip using FE analysis [1, 2, 3]. FE analysis can be used to simulate the process of grasping and manipulation numerically but cannot be applied to theoretical analysis of grasping and manipulation due to its complex formulation. For example, graspability of an object and stability in the dynamic manipulation process are key theoretical concepts in grasping and manipulation. FE analysis yields a procedural model of deformation. Use of the numerical procedure allows simulation of the deformation of objects but unfortunately, such procedural models cannot be applied to theoretical analysis. According to the principle of Occam’s O. Khatib, V. Kumar, and D. Rus (Eds.) Experimental Robotics, STAR 39, pp. 13–22, 2008. c Springer-Verlag Berlin Heidelberg 2008 springerlink.com
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T. Inoue and S. Hirai
razor, we should choose a simple model to analyze and explain grasping and manipulation by soft fingertips. The Hertzian contact model provides a simple closed-form description of the contact between two quadratic surfaces of elastic objects [4]. The model assumes that surfaces are open-ended, and thus the model cannot be applied to a hemispherical elastic fingertip subtended by a rigid plate. Arimoto et al. formulated dynamics in pinching by a pair of soft fingertips [5]. They applied a radially distributed deformation model of a soft fingertip to allow use of analytical mechanics theory
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