Page 120 - Human Inspired Dexterity in Robotic Manipulation

118 Human Inspired Dexterity in Robotic Manipulation

Fig. 7.3 Fingertip and control unit [2].

layer in the design of BioTac is used for sensing force, vibration, and heat.
Therefore, the features of soft grasping, such as adaptation to object shape,
are weak. From the moment Simoga and Goldenberg pointed out the
effectiveness of soft fingertips [8], many soft fingertip schemes have been
developed. However, these fingertips, except that of BioTac’s, were con-
structed using deformable skin and air [9–17] or power [18–20]. As a result,
all of them lost the important features for delicate grasping, such as uniform
contact pressure.

7.2.2 Stiffness of Fluid Fingertip
The softness of the fluid fingertip has other benefits besides those mentioned
previously. One of these is local compliance, in which fingertip stiffness
increases with the increase in fingertip deformation resulting from contact.
To observe it, a compression test was conducted using the experimental
setup shown in Fig. 7.4. The fluid fingertip was fixed and then pushed by
a flat plate attached to a force gauge (IMADA DS2-50N). In the initial state,
when there was yet no contact pressure between the plate and silicon

Dd
Force

0.00 N

Fingertip
Flat plate Force gauge
Fig. 7.4 Experimental setup for compression test to observe fingertip stiffness [2].