Game Development Reference
Table 8.7 Features of SPIDAR I and II interfaces.
900 × 600 × 600mm
300 × 300 × 300mm
Figure 8.15 INCA 6D. (Illustration: PSA, with permission)
diameter of the pulleys around which they are wound. The capacities of the SPIDAR I
and SPIDAR II interfaces are given as an example in table 8.7.
As the cables only provide a unidirectional actuation (they help to pull on the
robot gripper but not push it), it is necessary to use a minimum of m
1 cables for m
degrees of freedom. Thus, to obtain a force feedback on 3 or 6 degrees of freedom,
it is necessary to use 4 or 7 cables respectively. The actuation redundancy is used to
provide a positive voltage in all the cables at all times. On certain interfaces like the
CSHI (Cable Suspended Haptic Interface) developed in the University of Ohio, we use
a redundancy of the order of 2, with 8 cables for 6 degrees of freedom with force
feedback (Williams II, 1998). This solution is also used on INCA 6D marketed by
the Haption company (Figure 8.15).
This type of structure was used earlier on manipulator-type robots and master
arms for teleoperation like the 9 Strings 6 DOF Joystick from the University of Texas
(Agronin, 1987). Some cables are replaced with actuators on this joystick, which helps
to push on the handle instead of pulling. On a robot with 3 degrees of freedom, the