Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
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Development of Variable Stiffness Soft Robot Hand for Improving Gripping Performance

그리핑 성능 향상을 위한 가변강성 소프트 로봇 핸드 개발

  • Ham, KiBeom (School of Mechanical Engineering, SunMoon University) ;
  • Jeon, JongKyun (School of Mechanical Engineering, SunMoon University) ;
  • Park, Yong-Jai (Department of Mechatronics Engineering, Kangwon National University)
  • 함기범 (선문대학교 기계공학과) ;
  • 전종균 (선문대학교 기계공학과) ;
  • 박용재 (강원대학교 메카트로닉스공학과)
  • Received : 2018.09.17
  • Accepted : 2018.12.07
  • Published : 2018.12.31
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Abstract

Various types of robotic arms are being used for industrial purposes, particularly with the small production of multi-products, and the importance of the gripper, which can be used in industrial fields, is increasing. This study evaluated a variable stiffness mechanism gripper that can change the stiffness using the nonlinearity of a flexible material. A prototype of the gripper was fabricated and examined to confirm the change in stiffness. The previous gripper was unable to grip objects in some situations with three variable stiffness mechanism. In addition, these mechanisms were not balanced and rarely rotated when the object was gripped. Therefore, a new type of gripper was needed to solve this problem. Inspired by the movements of the human palm and Venus Flytrap, a new type of a variable stiffness soft robot hand was designed. The possibility of grasping could be increased by interlocking the palm folding mechanism by pulling the tendon attached to the variable stiffness mechanism. The soft robotic hand was used to grasp objects of various shapes and weights more stably than the previous variable stiffness mechanism gripper. This new variable stiffness soft robot hand can be used selectively depending on the application and environment to be used.

산업용으로 다양한 형태의 로봇팔이 사용되고 있으며, 특히, 다품종 소량생산으로 생산방식의 변화가 이루어지면서 산업현장에서 다양하게 사용이 가능한 그리퍼에 대한 중요성이 높아지고 있다. 이러한 중요성에 기반을 두어 본 연구진은 기존에 연성재질의 비선형성을 이용하여 강성을 변화시킬 수 있는 가변강성 메커니즘 그리퍼를 연구하였다. 시제품을 제작하고 실험을 통해 강성의 변화와 그 유용성을 확인하였다. 그러나 세 개의 가변강성 메커니즘을 배치하여 그리퍼를 설계 및 제작함으로써 물체를 파지하는 상황에 따라 파지를 제대로 하지 못하는 현상이 발생하였다. 또한, 그리퍼 간의 균형이 맞지 않아 물체 파지 시에 파지할 물체가 회전하면서 미끄러지는 경우가 드물게 발생하는 문제가 있었다. 이러한 문제점을 보완하기 위하여 새로운 형태의 그리퍼가 필요하게 되었다. 새로운 형태의 그리퍼를 설계하기 위하여 생체모사기술을 적용하였다. 사람의 손바닥과 파리지옥의 움직임을 통해 영감을 얻어 새롭게 가변강성 소프트 로봇 핸드를 설계하였다. 손바닥이 접히는 메커니즘을 가변강성 그리퍼에 장착된 텐던을 당기는 것과 연동하여 파지 성능을 높일 수 있었다. 가변강성 메커니즘에 파리지옥과 손바닥 형태의 메커니즘을 결합하여 파지 안전성을 높인 소프트 로봇 핸드는 기존의 가변강성 메커니즘 그리퍼보다 다양한 형태와 무게를 가진 물체를 안정적으로 파지하였다.

Keywords

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Fig. 1. Concept of a variable stiffness mechanism. The state can be changed by pulling the tendon[8-9].

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Fig. 2. Palm shape and its role

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Fig. 3. Example of flytrap

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Fig. 4. Proposed gripping mechanism

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Fig. 5. CAD model of soft robotic hand with Variable stiffness mechanism

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Fig. 6. Prototype of soft robotic hand with variable stiffness mechanism

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Fig. 7. Gripping motion of the soft robotic hand

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Fig. 8. Gripping test (a) previous soft gripper, (b)proposed soft robotic hand

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Fig. 9. Gripping shape comparison between the previous soft gripper and the proposed soft robotic hand

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Fig. 10. Gripping test at 500 g

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Fig. 11. Gripping test at 1000 g, and 1800 g

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Fig. 12. Maximum weight gripping test: the moment when the maximum weight is exceeded and the object can not be caught

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Fig. 13. Gripping test with different shapes (a)-(c) sphere, cylinder, rectangular cuboid with previous gripping mechanism respectively, (d)-(f) sphere, cylinder, rectangular cuboid with soft robot hand respectively

Table 1. Weight change for gripping experiment

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Table 2. Maximum gripping weight

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Table 3. Geometric parameters of each sample

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