Figure 35 - Strain Gage Torque Curves
Note: In Figure 35, true SG values have been adjusted so that the no-load value corresponds to
zero torque. If the torque curve measured does not approximate the torque curve shown in Figure
35, see Section 8. The torque curves for each finger will be different due to the variations in
materials.
9.5
Forward Kinematics
The forward kinematics for the BarrettHand™ were determined using the Denavit - Hartenberg
notation described in "Introduction to Robotics, Mechanics and Control 2
nd
Edition", John J. Craig.
Each finger is considered its own manipulator and is referenced to a wrist coordinate frame in the
center of the palm. Use the forward kinematics calculated in this section to determine fingertip
position and orientation with respect to the palm.
Equation 1 is used to determine the transforms between axes
i
and
i-1
.
−
=
Τ
−
−
−
−
−
−
−
−
−
1
0
0
0
c
c
s
s
-
c
s
a
0
s
-
c
1
1
1
i
1
i
1
1
1
i
1
i
1
-
i
i
1
i
i
i
i
i
i
i
i
i
i
i
i
i
d
c
s
s
d
s
c
c
α
α
α
θ
α
θ
α
α
α
θ
α
θ
θ
θ
Equation 1 - Homogeneous Transform Between Frame {
i-1
} and {
i
}
Where:
a
i-1
= distance from z
i-1
to z
i
measured along x
i-1
α
i-1
= angle between z
i-1
to z
i
measured about x
i-1
d
i
= distance from x
i-1
to x
i
measured along z
i
θ
i
= angle between x
i-1
to x
i
measured about z
i
)
cos(
i
i
c
θ
θ
=
)
sin(
i
i
s
θ
θ
=
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