Game Development Reference
In-Depth Information
Table 8.5 Features of Force Dimension interfaces
3DOF Delta
6DOF Delta
Omega
TTravel
360 × 360 × 300mm
360 × 360 × 300mm
160 × 160 × 120mm
RTravel
-
40 × 40 × 40
-
T Resolution
< 0.03mm
< 0.03mm
< 0.009mm
R Resolution
-
< 0.04
-
Peak force
20N
20N
12N
Continuous force
20N
20N 0.2Nm
12N
Friction
-
-
-
Stiffness
14.5N/mm
14.5N/mm
14.5N/mm
Apparent inertia
-
-
-
Other force-feedback interfaces use a parallel mixed structure. The most known
is the Haptic Master developed in the University of Tsukuba in Japan and marketed
by the Nissho Electronics company. This interface consists of three sub-structures
with 6 degrees of freedom connecting the fixed base to the platform operated by the
user. Each branch is made up of a serial parallelogram with a pivot linkage for the
translations and a ball joint for the rotations. The first three articulations are motorised.
We thus have a total of 9 motors, which helps to restrict the singularities that may
occur on this type of robot. The force capacity is quite high (12N and 0.56N
m
continuously, 21N in peak) thanks to the use of gear reducers that are more compact
than the capstan reducers for an identical amplification of force. On the other hand,
the friction is higher (1N) and the stiffness is relatively low (0.29N/mm).
Haption also markets a haptic interface with 3 parallel branches, the Virtuose 6D
Desktop, whose design comes from the works of the CEA LIST (Gosselin et al., 2005c).
Its work space is a sphere with diameter 120mm. Unlike Haptic Master, it only has
two motors per sub-structure. Its force capacity is from 7 to 10N. Three of the motors
are fixed while the others are close to the base, which helps to minimise the apparent
mass.
The use of capstan reducers helps to minimise friction as well.
Finally, the sub-structures point towards the interior, which provides a more
compact design (Figure 8.11).
Another solution for obtaining a force feedback on 6 degrees of freedom was
used on the Tsukuba Pen developed in the beginning of the 90's in the University
of Tsukuba in Japan (Iwata, 1993) (Figure 8.12). This interface consists of two sub-
structures connected to the pen held by the user, by a dial from one side and a ball joint
from the other. As for the pen, it is made up of two interconnected parts connected by
a helical linkage. The sub-structures each integrate three motors, which helps to fully
control the position of the two ends of the pen in space.
We obtain a movement of translation by moving them in the same direction. We
obtain a movement of rotation by moving them in an opposite direction (on the axis
of the pen, the helical linkage helps to transform the extending/shortening movement
of the pen in rotation). Mechanically, this interface is relatively simple. Moreover, all
the motors are placed near the base, which helps to have a very low apparent inertia.
Finally, it is more compact for an equivalent work space than the interfaces with
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