Civil Engineering Reference
In-Depth Information
PIP joint
L
2
L
3
L
2
−
(L
1
/2)
L
2
−
(L
1
/2)
q
2
L
3
−
L
2
+(L
1
/2)
L
1
/2
D
2
D
3
DIP joint
q
´
L
1
/2
q
3
MP joint
L
1
R
D
1
L
1
/2
FIGURE 45.12
Schematic diagram of Grip I. (Reproduced from Kong, Y. K. (2001)
Ph.D Dissertation.
Pennsylvania State University. With permission.).
(L
3
2
L
2
þ
L
1
/
2). The bisector of the MP angle creates another right triangle:
2(R
þ
D3)
u
3
¼
2 tan
1
(45
:
33)
2L
3
2L
2
þ
L
1
where: u
0
3
is the MP joint angle.
In the case of Grip II (see Figure 45.13), the second contact point is assumed to divide the medial
phalanx into two equal lengths (L
2
/
2). The perpendicular bisector of the medial phalanx forms two iden-
tical right triangles, yielding equal DIP and PIP joint angles (u
0
1
and u
0
2
):
u
1
¼
u
2
¼
2 tan
1
½
2(R
þ
D
2
)
=
L
2
(45
:
34)
The third contact point divides the proximal phalange into two unequal lengths. One is L
2
/
2 while the
2. The MP joint angle (u
0
3
) can then be estimated as:
other is L
3
2
L
2
/
2 tan
1
2(R
þ
D
3
)
u
3
¼
(45
:
35)
2L
3
L
2
Based on this biomechanical hand model, tendon forces for each finger and in total were calculated for
both types of grip and for 11 cylindrical handles with diameters ranging from 10 to 60 mm. For Grip I,
tendon force were minimized at 30-35, 38-43, 40-45, and 25-30 mm for index, middle, ring, and little
fingers, respectively. The total of tendon force for all fingers was minimized for an approximately 40 mm
cylindrical handle (see Figure 45.14). As the size of the handle deviated above or below 40 mm, the total
tendon forces increased.
For Grip II, tendon force were minimized at 23-28, 28-33, 28-33, and 20-25 mm for index, middle,
ring, and little fingers, respectively. The total of tendon force for all fingers was minimized for an approxi-
mately 28 mm cylindrical handle (see Figure 45.15). The combined results for each type of grip are
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