Page 139 - Human Inspired Dexterity in Robotic Manipulation

136 Human Inspired Dexterity in Robotic Manipulation

7.4 VERSATILE GRASPING BY THE FLUID-FINGERTIP
EMBEDDED GRIPPER [26]

To realize versatile grasping, an underactuated soft gripper utilizing fluid fin-
gertips was developed. The target operation is to pick up an object on a table.
Assuming the final application is a shopping register task, the target objects
are daily items that can be found in supermarkets.

7.4.1 Underactuated Soft Gripper Utilizing Fluid Fingertips

Fig. 7.25 shows the developed underactuated soft gripper constructed with
two fingers, each with an underactuated joint and fluid fingertip. The key
concepts were the utilization of the combination of softness at surfaces
and joints, and the utilization of environment to minimize the number of
actuators and simplify the structure (especially for electrical components).
Several robotic hands have been developed [27] and it is from among
these that focus is set on recently developed robotic hands with softness,
which are closely related to the underactuated soft gripper. Such soft robotic
hands can be broadly divided into two types. The first type has softness at
joints, for example, snake-like gripper [22], FRH-4 hand [25], SDM hand
[28,29], Pisa-IIT Hand [30,31], SoftHand Pro-D [32], ISR-SoftHand [33],
UC-SoftHand [34], Velo Gripper [35], and adaptive prismatic gripper with
passive rotational joints [36]. The second type has softness at the surfaces,
for example, gel fingertips [8], ISR-SoftHand [33], UC-SoftHand [34],
Kanazawa hand [20], deep reef sampling gripper [37], and magnetic fields
based gripper [38]. Similar to ISR-SoftHand [33] and UC-SoftHand [34],
there are robotic hands that possess both types of softness. Using pneumatic
actuators facilitates a combination of softness types, for example, in ROBO
hand [11,12], Starfish-like hand [14], lightweight underactuated pneumatic

Rigid layer structure
Fluid fingertips
Fig. 7.25 Underactuated soft gripper utilizing the fluid fingertips and the structure of
the rigid layer inside the fluid.