A Hybrid Gripper With Soft Material and Rigid Structures

Abstract

Various robotic grippers have been developed over the past several decades for robotic manipulators. Especially, the soft grippers based on the soft pneumatic actuator (SPA) have been studied actively, since it offers more pliable bending motion, inherent compliance, and a simple morphological structure. However, few studies have focused on simultaneously improving the fingertip force and actuation speed within the specified design parameters. In this study, we developed a hybrid gripper that incorporates both soft and rigid components to improve the fingertip force and actuation speed simultaneously based on three design principles: first, the degree of bending is proportional to the ratio of the rigid structure; second, a concave chamber design is preferred for large longitudinal strain; and third, a round shape between soft and rigid materials increases the fingertip force. The suggested principles were verified using the finite element methods. The improved performance of the hybrid gripper was verified experimentally and compared with the performance of a conventional SPAs. The ability of the hybrid gripper to grasp different objects was evaluated and was applied in a teleoperated system. Index Terms-Soft material robotics, grippers and other endeffectors, flexible robots. I. INTRODUCTION R ECENTLY, the limitations of rigid gripper due to the necessity of additional linkages, complicated controls, and so on, have been overcome by the soft gripper [1]. Especially, the soft grippers based on soft pneumatic actuators (SPAs), which offer better compliance, and a higher degree of freedom than the rigid robot, have been actively developed [2]-[9]. Due to the inherent compliance of soft materials, complicated controls and additional structures are not needed with soft grippers, as the proper selection of materials of various stiffness allows for simple control. Furthermore, soft grippers with SPAs are constructed from low-cost and readily-available elastomers.

Design and Optimize of a Novel Segmented Soft Pneumatic Actuator

“…Table I shows a comparison of the maximum working pressure, bending angle and output force of our new segmented actuator with other soft pneumatic actuators. In table I, capacity of the traditional segmented actuators [18,20], the hybrid structured actuator [30] and the fiber reinforced soft actuator is compared with our new segmented actuator. These five actuators have similar structure parameters and material parameters.…”

A Sensorized Hybrid Gripper to Evaluate a Grasping Quality Based on a Largest Minimum Wrench

“…R ECENTLY, soft pneumatic grippers (SPGs), which offer a more compliant bending motion than rigid robots owing to their simple morphological structure and higher degree of freedom, have been actively developed [1]- [3]. Moreover, to enhance their grasping performance such as actuation speed and finger force, soft pneumatic actuators (SPAs) have been developed in many ways [1]- [5]. Different chamber shapes, such as the fast pneumatic network (PneuNet), have been investigated for improved actuation speed [6].…”

“…Different chamber shapes, such as the fast pneumatic network (PneuNet), have been investigated for improved actuation speed [6]. Additionally, SPAs have also been reinforced by fiber, fabric, and integration with rigid and soft materials to realize enhanced fingertip forces [1]- [5].…”

“…1. The hybrid gripper [5], which was previously developed for improved grasping abilities such as actuation speed and fingertip force or torque, was sensorized by embedding a soft force sensors and a bending sensor. The grasping quality was calculated by the force closure, which indicates how well the grasp can resist the external force or torque before it fails to grasp [18], [19].…”

Customization Methodology for Conformable Grasping Posture of Soft Grippers by Stiffness Patterning

“…For example, variable stiffness structures (Amend et al, 2012 ; Cheng et al, 2016 ; Wei et al, 2016 ; Al Abeach et al, 2017 ; Fei et al, 2018 ) and friction pads (Zhou et al, 2017 ; Glick et al, 2018 ) were integrated into soft fingers; novel materials such as edible gelatin (Shintake et al, 2017 ), self-healing materials (Cheng et al, 2014 ; Terryn et al, 2015 , 2017 ), and 3D printable materials (MacCurdy et al, 2016 ; Mutlu et al, 2017 ; Hu et al, 2018 ) were used to fabricate soft fingers. Also, some studies developed new designs of air chamber sections by employing modular approaches or exploiting multiple materials (Milana et al, 2018 ; Zhang et al, 2018 ; Park et al, 2019 ).…”