Experimental investigation of effect of fingertip stiffness on resistible force in grasping

Fujihira, Yoshinori; Harada, Kensuke; Tsuji, Tokuo; Watanabe, Toru

doi:10.1109/icra.2015.7139797

Cited by 15 publications

(8 citation statements)

References 20 publications

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“…15. These results correspond to our previous results, which showed that stiffer fingertips have a higher resistible force (frictional force) [11], [12].…”

Section: B Results and Discussionsupporting

confidence: 81%

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Bent Sheet Grasping Stability for Sheet Manipulation

Fujihira

Nishimura

Watanabe

2016

IEEE Robot. Autom. Lett.

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Abstract-In this study, we focused on sheet manipulation with robotic hands. This manipulation involves grasping the sides of the sheet and utilizing the convex area resulting from bending the sheet. This sheet manipulation requires the development of a model of a bent sheet grasped with fingertips. We investigated the relationship between the grasping force and bending of the sheet and developed a bent sheet model. We also performed experiments on the sheet grasping stability with a focus on the resistible force, which is defined as the maximum external force at which a fingertip can maintain contact when applying an external force. The main findings and contributions are as follows: 1) After the sheet buckles, the grasping force only increases slightly even if the fingertip pressure is increased.2) The range of the applicable grasping forces depends on the stiffness of the fingertips. Stiffer fingertips cannot provide a small grasping force but can resist large external forces. Softer fingertips can provide a small grasping force but cannot resist large external forces. 3) A grasping strategy for sheet manipulation is presented that is based on controlling the stiffness of the fingertips.

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“…15. These results correspond to our previous results, which showed that stiffer fingertips have a higher resistible force (frictional force) [11], [12].…”

Section: B Results and Discussionsupporting

confidence: 81%

“…Watanabe et al [10], [11], [12] investigated the effects of fingertip stiffness on the grasping stability by performing experiments. These studies focused on the contact between rigid objects and soft fingers.…”

Section: A Related Workmentioning

confidence: 99%

Bent Sheet Grasping Stability for Sheet Manipulation

Fujihira

Nishimura

Watanabe

2016

IEEE Robot. Autom. Lett.

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“…These four parts are connected with a fitting. The silicone part played a key role acting as a spring, and was made of silicone: KE-1308 and hardener (volume: 6 %): CAT1300L-3 (Shin-etsu Silicone, see [22], [23] for details on the stiffness information; Fig. 17 (a) shows the material information for the relationship between the load and displacement).…”

Section: Structure and Principlementioning

confidence: 99%

Stiffness Measurement System Using Endoscopes With a Visualization Method

et al. 2016

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Abstract-A novel stiffness-sensing system was developed that works by attaching the proposed sensing part to endoscopes or cameras. The system provides a method to investigate the stiffness of tissues or objects in deep areas that can only be observed with endoscopes in order to detect abnormalities. The system is an extension of our previous force sensing system that utilized a force visualization mechanism. The force is visualized at the sensing part, and can be measured as visual information via endoscopes or cameras. The sensing part also has a limiting structure used as a threshold for the applied force. By measuring the force at the limitation, the stiffness can be measured. The limitation point is detected by the brightness changes of the captured images. The developed sensing part has the advantages of having no electronic components, being disposable, simple, easy to sterilize, MRIcompatible, and low-cost. Image processing methods for realizing the mechanism are also proposed. The system was experimentally validated.

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“…In other words, the pushing distance/force at the danger area starting point is the guaranteed maximum (grasping) force that can avoid fracture. In addition, a phase change from Phase 1 to Phase 2 indicated an alteration in the tofu (it became hard), and there have been reports that a harder contact area can produce larger frictional forces when contacting soft materials [18,19]. Therefore, easier grasping can be expected compared to previous phases.…”

Section: Danger Area Starting Point For Avoiding Fracture and Delmentioning

confidence: 99%

Identification of danger state for grasping delicate tofu with fingertips containing viscoelastic fluid

Adachi

Fujihira

Watanabe

2015

2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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Abstract-In this study, we experimentally investigated the process leading to fracture in tofu grasping by deformable fingertips filled with a fluid. In our previous papers [1, 2], we developed deformable fingertips using a rubber bag filled with a viscoelastic fluid, and presented a strategy for delicate tofu grasping without any advance knowledge about fracture. However, the predication point was close to fracture, and the prediction was then still a gamble. In order to realize fracture prediction at an earlier stage, we examined the process leading to fracture when pushing tofu by the deformable fingertips. The stiffness of the fingertips can be controlled with the pressure of the fluid inside the fingertips. The pushing force and fluid pressure were examined for different levels of stiffness of the fingertips. The main findings and contributions are as follows. 1) The convergence of the ratio of the contact force to fluid pressure gives an indication of dent occurrence. This convergence could be seen when fingertip rubber bag was not filled (low stiffness). 2) It was easier for a dent to occur when the fingertip rubber bag was not filled than when it was filled (high stiffness). 3) Changes in the rate of increase of the fluid pressure as the tofu was pushed were repeatedly observed. We defined this as a phase change and present a method for detecting such changes. The phase change points were detected by comparing the fitting accuracies of different approximation models. 4) The last and second to the last phase changes before fracture were detected by detecting the first phase change (after the convergence of the rate of the contact force to fluid pressure if the fingertip bag was not completely filled). The detected points can be regarded as alert points indicating a fracture risk that is not close to the fracture point.

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Experimental investigation of effect of fingertip stiffness on resistible force in grasping

Cited by 15 publications

References 20 publications

Bent Sheet Grasping Stability for Sheet Manipulation

Bent Sheet Grasping Stability for Sheet Manipulation

Stiffness Measurement System Using Endoscopes With a Visualization Method

Identification of danger state for grasping delicate tofu with fingertips containing viscoelastic fluid

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