BH8-Series – User’s Manual
www.barrett.com
© 2007 Barrett Technology®, Inc.
Document: D3000, Version: AF.00
Page 64 of 82
0
5
10
15
20
25
0
10
20
30
40
50
60
70
80
Velocity (encoder counts per sample time)
F
o
rc
e
(
N
)
Figure 25 – Stalled FingerTip Force Vs. Commaneded Velocity (measured before
breakaway).
9.3.2
Spread Motion
The spreading action of fingers F1 and F2 on the BarrettHand™ increases the dexterity of the
entire unit with only one additional actuator. Optimal grasp configurations can be achieved "on-
the-fly" without costly tool changes associated with traditional grippers. In addition, the
backdrivability built into this degree of freedom causes the BarrettHand™’s grasp shape to change
in mid-grasp, creating a more stable grasp of oddly shaped target objects.
Should you wish to control the spread position of the fingers, the complete command set available
to the fingers is also available for the spread, including commands for fixed-increment motion and
move-to-position commands.
The sustainable torque that the spread fingers can exert continuously in a ‘pinch’ type grasp is
shown in Figure 26. These are found by changing the parameter FPG while keeping all other
parameters at their defaults. For a given torque setting, larger forces can be achieved by curling
F1 and/or F2 closed to the point where the contact point becomes closer to the spread axis.
