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Soft Gripper using Variable Stiffness Mechanism and Its Application

  • KiBeom Ham
  • Jiho Han
  • Yong-Jai Park
Regular Paper
  • 197 Downloads

Abstract

Soft robots have advantages such as low weight and compact size compared to rigid robots. Variable stiffness is one of the key methods of improving the performance of a soft robot. The soft gripper grasps objects of various shapes or sizes based on the variable stiffness. In a previous study, we validated the variable stiffness mechanism where flexible and rigid segments were connected alternately in series. This paper presents a soft variable stiffness gripper that can be used to control the stiffness by pulling tendons. The soft gripper has three variable stiffness structures acting as fingers and the stiffness can be controlled using two motors by winding tendons. To understand the tendency of the stiffness variation and determine the design parameters, a compliant mechanism was developed using a pseudo-rigid-body model (PRBM). The experimental results show that the difference between the lowest and highest stiffness values of the fabricated variable stiffness gripper was 5.6 times the original. Similarly, the difference in the gripping weight was 19 times. Using the experimental results, the variable stiffness gripper can be designed and manufactured based on the required stiffness and used to grip various types of objects.

Keywords

Variable stiffness Adaptable structure Adjustable mechanism Soft robotics Gripper 

Nomenclature

E

Young’s Modulus

G

Shear Modulus

I

second moment of inertia

S

shape factor

R

radius of cylinder

l

compressed length

lf

length of flexible segment

lR

length of rigid segment

Li

length of ith segment

γb

characteristic radius factor due to bending force

γm

characteristic radius factor due to moment

Ki

pseudo torsional spring constant of ith flexible segment

Cθb

parametric angle coefficient by bending force

Cθm

parametric angle coefficient by moment

(EI)’

effective bending stiffness of bonded cylindrical layer

θi

deflection angle of ith flexible segment

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Copyright information

© Korean Society for Precision Engineering and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Mechanical EngineeringSunmoon UniversityChungcheongnam-doRepublic of Korea

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