full Paper - Nguyen Dang Binh

LDOF#
HDOF#
VHDOF#
Complexity
Classification
Joystick Like
One Point Attachment
Task Replica
Multi-Point Attach
Wearable Interfaces
Functional
Classification
Figure 1: HI Classifications
field of haptic interfaces. Only recently some simple force
feedback joysticks have been introduced in the game and entertainment
market due to the reduction of costs of the technology.
Safety is the primary rule to follow when producing a
robot which interacts with human. Even if the user drives
the interface not properly, the haptic interface shall always
be safe for the operator. This should be done by providing a
careful design which is not only robust, but also capable of
detecting that the interface is properly working and to provide
emergency buttons for making the system unoffensive.
Most of the existing haptic interface have been designed
for a standard user, but, just like dresses, they should be designed
on the size of the user they are dedicated for. In wearable
haptic interfaces such as arm exoskeleton and gloves
mechanism should be present for sizing correctly on the user.
Sizeability should be pursued whenever it does not complicate
too much the mechanical design.
Easiness is the interface property of being driven by commands
which are intuitive or easy to be learned by the operator.
Easy interface requires load learning times and offer a
better presence sense since they does not compel the operator
to work in an unnatural manner.
3. Classification of the haptics
A first classification for the haptic interfaces was presented
by Vincent Hayward in. The Hayward classification distinguishes
haptics interfaces on the basis of the design complexity
in terms of Degree of Freedom of the interface. He
defined three big classes:
¯ Low DOF Devices (LDOF#);
¯ High DOF Devices (HDOF#);
¯ Very High DOF Devices (VHDOF#);
A Low DOF Devices is an interface which presents few
degree of freedom. The LDOF# does not attempt to address
c­ The Eurographics Association 2005.
Massimo Bergamasco / Haptic Interfaces
7
Figure 2: A 3DOF (LDOF# Joystick) designed at PERCRO
the literal emulation of a task or of a sensation which would
occur during some kind of virtual experience.
It has been found that for example 2 or 3 controlled
mechanical freedoms could provide the operator with a
sufficient impressive information capable or realizing a
“metaphor” sufficiently suggestive for leading to an high
level of usefulness. The combined use of several LDOF#
tools can lead to a richer set of metaphors.
The figure 2 represents the case of a simple three DOFs
joystick interface realized at PERCRO laboratory. The interface
possesses XYZ rotational DOF and can exert force
feedback along these axes. It has been conceived for desktop
operation such as “Virtual Prototyping”, testing and access
for disabled patient.
High DOF Devices attempt to recreate the task force information
as they were produced inside the environments.
Under this category we find all devices which have been designed
around an hand-held manipulandum and applying arbitrary
forces and torques. In fact, in this case the interface
should be designed with at least 6 DOFs for allowing to the
user a complete freedom of operation. The HDOF# have at
least 6 DOFs.
Figure 3 is a 6DOF Joystick. Using such a Joystick, which
has been designed for a 400mm-edge cubic workspace,
the user has the possibility of feeling forces inside the
workspace with an high degree of fidelity. The adoption
of the parallel kinematics structure helps to improve forces
and backdriveability while preserving all required degrees of
motion.
Very High DOF devices are those interfaces whose number
of DOFs is greater than six. VHDOF# interfaces are
generally used for realizing extremely complex interactions.
The motivation for such a type of interfaces can be found in
the application which presents a complex kinematical structure
or in contextes which require the presence of many
haptic feedbacks. The PERCRO Hand EXOS and the Arm
EXOSkeletons represented in figure 4 are an example of