Game Development Reference
Figure 8.23 Force feedback Orthosis. (Illustration: CEA-LIST, with permission)
helps to naturally integrate the actuator following a direction perpendicular to the
motorised axes. This characteristic is particularly interesting in the case of an orthosis
because it helps to integrate the actuation unit in line with the segments (Figure 8.23).
In addition, this technology helps to obtain a high force capacity while remaining
mechanically reversible (low friction). Under these conditions, it is possible to use
relatively light actuators that can be arranged in the segments and it is not necessary
to use transmissions, which simplifies the machine.
The performance obtained is summarised in table 8.9. Two different force capacity
versions have been dimensioned. It is possible to pass very easily from one to the other
by changing the nuts of the jack reducers.
The main defect of these interfaces is that their operation is related to the adapta-
tion of the robot to the anatomical characteristics of the user, as the articulation axes
of the robot and the user must coincide. In order to avoid this problem, it is necessary
to design redundant systems that can be reconfigured according to the user like the
Wearable Robotic Arm developed by Nano Bio Robotics Lab of the Korea Institute of
Science and Technology (Jeong et al., 2000).
There are several other exoskeletons that use pneumatic actuators or artificial
muscles like the Pneumatic Haptic Interface developed in the Systems Laboratory of
the Southern Methodist University in Texas (Hurmuzlu et al., 1998).
The force feedback interfaces make it possible for a user to feel the presence of objects
and the result of the actions that he carries out in a virtual environment. The incredible