Game Development Reference
Figure 8.17 Wearable Master. (Illustration: University of Tsukuba, with permission)
internal reaction force feedback interfaces. Generally, the base is fixed on the body of
the user. This kind is referred to as portable interfaces. Exoskeletons are also included
in this category, even if some of them need to be fixed to a frame, as they are too
heavy to be portable. These interfaces provide great freedom of movement, however
their drawbacks include the weight of the mechanism that is non-compensable and the
overall dimensions around the body.
There are also other specific problems that occur on this type of interfaces:
The mobility of the base on the portable interfaces requires using a 6D tracker to
measure its position and orientation in space (optical, magnetic, ultrasound, etc.
trackers) which increases the cost and complexity of the system;
Generally as the force feedback is not taken by a fixed base, we cannot block the
user against the environment, which is not very realistic;
On the portable interfaces, any force at the level of the robot gripper is accompa-
nied by a parasite force exerted by the base of the robot on another part of the
body (the force chain closes on the user's body), which can disturb his perception;
Most of the internal reaction force feedback interfaces include body segments.
Under these conditions, the questions regarding safety arise in a particularly critical
manner because the user cannot easily free himself of the system.
These constraints partly explain the low development of portable interfaces. Today,
most of them still remain laboratory prototypes. In this document, they are classified
based on their structure which depends on the type of force feedback and its location.
184.108.40.206 Generic portable interfaces
This type of interface can use a serial architecture like the Wearable Master developed
in the University of Tsukuba in Japan (Figure 8.17). This interface with 3 degrees of