Page 11 - Human Inspired Dexterity in Robotic Manipulation

Background: Dexterity in Robotic Manipulation by Imitating Human Beings 5

x
m€¼ kx d _x + f : (1.3)
If letting f be the input, Eq. (1.3) can be formulated as the form of state
equation as follows.

_ x 0 1 x 0
¼ + f (1.4)
€ x k=m d=m _ x 1=m

1.2.3 Mechanical Impedance

The concept of mechanical impedance came from the concept of electrical
impedance and represents the dynamics of the system by the model of mass,
damper, and spring (1.3). If changing Eq. (1.3) as a form of the relationship
between force (left side) and motion (right side), the mechanical impedance
can be represented by Eq. (1.5). For more details, please see robotic text
books such as [2].

x
f ¼ m€+ d _x + kx (1.5)

1.2.4 Fundamental Grasping Style
There are several grasping styles, but the most popular and fundamental ones
are precision grasp and power grasp, as illustrated in Fig. 1.2. For the pre-
cision grasp, only fingertip areas are utilized for grasping, and the mobility
of objects is good. An in-hand manipulation can be then realized for this
style. For the power grasp, the object is enveloped by several parts of a hand,
and the motion of the object is restrained. However, the graspable weight is
big, and uncertain disturbances can be easily balanced. For more details,
please see text books such as [3].

Fig. 1.2 Fundamental grasping style; (A) precision grasp and (B) power grasp.