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Research Papers

A Constant-Force Compliant Gripper for Handling Objects of Various Sizes

[+] Author and Article Information
Jung-Yuan Wang

Department of Mechanical Engineering,
National Cheng Kung University,
No. 1, University Road,
Tainan City 70101, Taiwan
e-mail: jungyuanwang@gmail.com

Chao-Chieh Lan

Department of Mechanical Engineering,
National Cheng Kung University,
No. 1, University Road,
Tainan City 70101, Taiwan
e-mail: cclan@mail.ncku.edu.tw

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received July 16, 2013; final manuscript received March 19, 2014; published online April 28, 2014. Assoc. Editor: Oscar Altuzarra.

J. Mech. Des 136(7), 071008 (Apr 28, 2014) (10 pages) Paper No: MD-13-1311; doi: 10.1115/1.4027285 History: Received July 16, 2013; Revised March 19, 2014

This paper presents the design, simulation, and testing of a compliant gripper that can provide a constant gripping force to handle objects of various sizes. Maintaining a proper gripping force is challenging when manipulating delicate objects with uncertain sizes and stiffnesses. To avoid damage and provide a stable grip of an object, force feedback is often required so that the gripping force can be directly or indirectly regulated. Without using additional sensors and control, the proposed gripper passively maintains a constant prespecified contact force between fingertip and object. The gripper is designed to have a constant input force generated by a constant-force mechanism (CFM). Transmitted through a statically balanced (SB) mechanism, a constant gripping force is obtained at the fingertip. After a formulation to find the optimal gripper configuration, the design is verified through comparison with simulation results. Finally, a prototype of the constant-force gripper is demonstrated. The novel gripper is expected to serve as a reliable alternative for object manipulation.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

(a) A rigid-body gripper and (b) a compliant gripper

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Fig. 2

(a) fiδi curves of a rigid-body gripper, (b) fiδi curves of a compliant gripper, and (c) δyδi curve of a gripper

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Fig. 3

fiδi curves of an SB gripper

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Fig. 4

fyδy curves of (a) a compliant gripper and (b) an SB gripper

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Fig. 5

fiδc curve of a CFM

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Fig. 6

(a) Schematic of a CF gripper and (b) fiδc curves for different gripping range δy

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Fig. 7

Schematic of the SB gripper

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Fig. 8

Schematic of the CF gripper

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Fig. 9

(a) Optimal initial shape, (b) preloaded shape with δi = 0, and (c) preloaded shape with δi = Δp

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Fig. 10

fiδi curves of the optimized gripper

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Fig. 11

fyδy curves of the optimized gripper

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Fig. 12

Initial shape of an unbalanced gripper

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Fig. 13

fiδi curves of an unbalanced gripper

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Fig. 14

fyδy curves of an unbalanced gripper

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Fig. 15

Optimal initial shape (upper bounds relaxed)

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Fig. 16

fyδy curves of the optimized gripper (upper bound relaxed)

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Fig. 17

CFM model (four layers)

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Fig. 18

fiδc curves of the CFM

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Fig. 19

Solid model of the CF gripper

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Fig. 20

CF gripper at fully opened and fully closed positions

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Fig. 21

FEM results of the fyδy curves

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Fig. 22

FEM results of the fiδc curves (eight layers, δy = 1.2, 6.0, and 10.8 mm from left to right)

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Fig. 23

Effect of deviation of contact point location on the fyδy curves

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Fig. 24

CF gripper with two sets of four-bars

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Fig. 25

The CF gripper gripping (a) a rigid object and (b) a soft object

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Fig. 26

fiδc curves using different boundary conditions (δy = 1.2, 6.0, and 10.8 mm from left to right)

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Fig. 27

Experimental setup

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Fig. 28

CF gripper prototype

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Fig. 29

Experimental fiδc curves of the CFM

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Fig. 30

Experimental fiδi curves of the SB gripper

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Fig. 31

Experimental fiδc curves of the CF gripper (eight layers, δy = 1.2, 6.0, and 9.6 mm from left to right)

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Fig. 32

CF gripper experimental result

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