A soft-surfaced fingertip of a robot hand is deformable and can grasp an object of complicated form rather easily, since the contact area can be enlarged by surface deformation in response to the object form. Soft-surfaced fingertips are very effective in grasping soft objects; even tofu can be grasped. Generally, however, the surface friction of soft material is high, which makes releasing more difficult. It is also difficult to release objects to desired positions, especially in cases where the working space is narrow.
A group led by Prof. Tetsuyou Watanabe at Kanazawa University has been conducting research on control technology for grasping objects by the fingertips of robot hands. In the present study, the group aimed to develop a friction control system. The group used the soft fingertips of a robot hand for grasping objects; releasing was accomplished by applying (injecting) a lubricant. In this study, absolute ethanol (>99.5%) was employed as lubricant, since ethanol is chemically safe and easy to dry and since its surface tension is low.
Rubber - Film - Sides - Fingertip - Foundation
A nitrile rubber film was bonded to the sides of the fingertip foundation to create a space for filling with chain saw oil to make a "fluid fingertip." Then a silicone "texture"*1) was bonded to coat the rubber film; the material of the "texture" was a silicone sealant with slits, whose interval was 1.5 mm, perpendicular to the load direction. The slits were introduced for a large friction under a water-wet condition and for lubricant spreading. With this fluid fingertip, objects of various materials used for kitchen utensils were grasped and it was verified that, upon applying the lubricant, the friction was indeed reduced . The friction was reduced under both dry and wet conditions, whereas such a lubricating effect was not observed under...
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