Single-Motor Robotic Gripper With Three Functional Modes for Grasping in Confined Spaces

This study proposes a novel robotic gripper driven by a single motor. The main task is to pick up objects in confined spaces. For this purpose, the developed gripper has three operating modes: grasping, finger-bending, and pull-in modes. Using these three modes, the developed gripper can rotate and translate a grasped object, i.e., can perform in-hand manipulation. This in-hand manipulation is effective for grasping in extremely confined spaces, such as the inside of a box in a shelf, to avoid interference between the grasped object and obstacles. To achieve the three modes using a single motor, the developed gripper is equipped with two novel self-motion switching mechanisms. These mechanisms switch their motions automatically when the motion being generated is prevented. An analysis of the mechanism and control methodology used to achieve the desired behavior are presented. Furthermore, the validity of the analysis and methodology are experimentally demonstrated. The gripper performance is also evaluated through the grasping tests.

I. Introduction

This study presents a novel robotic gripper that can achieve three functional modes using a single motor. The developed gripper is shown in Fig. 1(a). The three motion modes of the gripper are as follows: 1)

Grasping mode: closing and opening the fingers to grasp and release an object.

2)

Finger-bending mode: bending the finger to rotate the fingertip to rotate a grasped object.

3)

Pull-in mode: translating a grasped object.

Fig. 1.

Developed gripper. (a) Gripper operation. (b) Representative target task. (c) Grasping operation in the confined spaces.