Page 112 - Human Inspired Dexterity in Robotic Manipulation

110 Human Inspired Dexterity in Robotic Manipulation

Index
Middle
Ring
Little
Thumb flexion
Thumb ad/b
300
Z-direction displacement (mm) 250 –50

200
150
100 0
–200 50
–150 X-direction displacement(mm)
–100 100
–50
(A) 0 150
Y-direction displacement (mm)
280
Finger fully 300
extended Index
Middle
260 280 Ring
Little
The flexion Thumb flexion
trajectory 260 Thumb ad/b
Z-direction displacement (mm) 220 The extension Z-direction displacement (mm) 240
240
220
trajectory
200
200
180 180
Finger fully 160
flexed
160 140
10 20 30 40 50 60 70 80 –20 0 20 40 60 80 100 120
(B) X-direction displacement (mm) (C) X-direction displacement (mm)
Fig. 6.19 The trajectories of the fingertips of our biomimetic robotic hand. (A) 3D scatter
plot of fingertip trajectories. (B) The ring fingertip’s trajectories projected onto the X–Z
plane. (Note: The scatter plot is from the 20 repetitions of the full flexion and extension
motions.) (C) The trajectories of the fingertips projected onto the X–Z plane.

The difference between the flexion and extension fingertip trajectories
results from the sequential joint movements shaped by joint stiffness. As
shown in Fig. 6.14, the variable joint stiffness is regulated by the gliding
mechanism of the extensor hood and the elastic pulleys of the tendon
sheaths.
The fingertip trajectories of other digits were also recorded. Unlike the
preprogrammed inputs for the ring and little fingers, the repetitive move-
ments of the index, middle, and thumb were teleoperated by the human