full Paper - Nguyen Dang Binh

most 1. The applications of this interface can be the field
of Teleoperation (deming, manipulation of toxic or radioactive
materials, inspection of dangerous zones, maintenance
of satellite or space stations) or in the field of Virtual Reality
(virtual prototyping, medicine and rehabilitation, ergonomic
assessment, art and cultural heritage [17] e [18]).
3.2. Hand-Exoskeleton Haptic Interface
The Pure-Form Hand-Exoskeleton [19] (PFHE) is a portable
Haptic Interface designed to exert forces of arbitrary direction
and amplitude on the index and thumb fingertips
Figure 6: The L-Exos and Hand Exos integrated configuration
This interface has been conceived as a modular system, so
that it can be used either independently fixed on a desktop or
mounted and totally supported on the terminal link of the
arm exoskeleton (figure 6). Assembling these sub-systems,
it is possible to achieve a better HI that combines the greater
workspace of the arm exoskeleton with higher degree of manipulation
provided by the PFHE. The PFHE was used to
simulate the contact with virtual surfaces, while exploring
virtual sculptures in the Museum of Pure Form [20]. The final
version of the device is composed of two serial limbs,
each one with three actuated degrees of freedom. The last
actuated links of the two limbs are connected to the respective
end-effector (a thimble) by means of a gimbal, which
allows the mechanism to reach the user’s fingertip with any
c­ The Eurographics Association 2005.
Massimo Bergamasco / Haptic Interfaces, Design considerations
28
orientation. The PFHE is actuated by 6 ironless DC motors
(three for each one of the two limb) sensorized with highresolution
encoders. A bilateral tendon transmission system
with steel cables driven by idle pulleys is used to convert
the torque of the motors into the force applied at the endeffector.
This solution, joined with the choice of high- performance
materials, such as carbon-fibers composite materials
and the aeronautic aluminum, has allowed to reduce the
total weight of the interface and, in particular, of the moving
parts (about 206g per limb). In this way it has been possible
to reduce the perceived inertia by the user, increasing the
transparency during the free exploration of the virtual environment
and maintaining good levels of stiffness and dynamic
performances. The main performances of the device
are listed below:
¯ Minimum continuous force at the end- effector in the
worst configuration: 3N;
¯ Maximum peak force at the end-effector auto-limited at
15N in all the workspace;
¯ Minimum stiffness at the end-effector guaranteed in the
worst configuration: 5N/mm;
¯ Flexion-extension angular excursion allowed to the wrist:
+/- 45ˇr.
4. Conclusion and Acknowledgement
Six new types of haptic devices have been shown. Each of
them presents innovative aspects in terms of functionalities,
performances, operability and design. A summary of the device
performances can be found in table 1. A comparison
with existing device has also been provided in the same table.
The work of design of these devices has been carried
out within the EU project TREMOR, PUREFORM, GRAB
while the current application development is supported by
the IT project VICOM and the EU NOE Enactive. The authors
are grateful to National and European governments
whose grants constituted a valid cofinancing of the presented
research. The authors also thank the partnership of the mentioned
project that provided a valid support in the functionality
definition and/or system assessment.
where:
1. Haptic Pen;
2. Haptic Desktop;
3. 3DofJoy;
4. GRAB;
5. L-Exos;
6. Hand-Exoskeleton Haptic Interface;
7. DELTA;
8. PHANTOM 1.5.
5. References
[1]. Hayward, V.; Astley, O.R. Performance measures for
hap-tic interfaces, RoboticsResearch: The 7th International
Symposium, 1996.