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Many devices have been developed in the last 30 years in order to address
the somatic senses of the human operator, but only few have become widely
available. The most probable reason for that is that the devices are either
not very useful or really expensive (from US $10,000 up to more than US
$1,000,000). By ``devices for tactile/haptic output'' we mean devices that
have been especially designed for this purpose. In some sense, a standard
keyboard and mouse do also provide some kind of haptic feedback, namely the
socalled breakaway force when a key or button, respectively, has
been pressed. Although this is important as tests have proven to increase
the input rate in the case of a keyboard, we do not consider these devices
within this section.
Devices with tactile, haptic, or force output address the somatic senses of
the user (see 2.1.4 ). This can be done by the following
methods (taken from [309]):
- Pneumatic stimulation
- This can be achieved by air jets, air pockets,
or air rings. Problems arise due to muscular fatigue and the pressure or
squeezing effect which means that the ability to sense is temporarily
disabled. Another drawback of pneumatic devices is its low bandwidth.
- Vibrotactile stimulation
- Vibrations can either be generated by blunt
pins, voice coils, or piezoelectric crystals. These devices seem to be
the best ones to address somatic senses because they can be build very
small and lightweight and can achieve a high bandwidth.
- Electrotactile stimulation
- Small electrodes are attached to the
user's fingers and provide electrical pulses. First results are
promising, but further investigation is needed in this area.
- Functional neuromuscular stimulation (FMS)
- In this
approach, the stimulation is provided directly to the neuromuscular
system of the operator. Although very interesting, this method is
definitely not appropriate for the standard user.
Other methods do not address the somatic senses directly. For example, a
force-reflecting joystick can be equipped with motors that apply forces in
any of two directions. The same method is used for the Exoskeleton. In the
following paragraphs, mainly devices with indirect stimulation methods will
be described.
Nearly all devices with tactile output have been either developed for
graphical or robotic applications
. Many
different design principles have been investigated, but the optimal
solution has not been found yet. Most probably, the increasing number and
popularity of Virtual Reality systems will push the development of force
feedback devices to a new dimension. In the following, the most popular
devices will be reviewed very briefly in chronological order:
- The Ultimate Display (1965)
- Ivan Sutherland described his vision of
an ``ultimate display'' in order to reflect the internal world of the
machine as close as possible. He proposed to develop a force reflecting
joystick [334].
- GROPE (1967 -- 1988)
- In the project GROPE, several ``haptic
displays'' for scientific visualization have been developed in different
stages of the project [48]. Starting in 1967, a 2D device for
continuous force feedback (similar to an X/Y-plotter) has been developed.
In the next stage (1976), a 6D device was used in combination with stereo
glasses for operations in 3D space. The device was a kind of master
manipulator with force feedback. In the third (and last) phase of GROPE
which started in the late 1980s, the hardware has been improved, but the
principle layout of the system was not changed. The results in the domain
of molecular engineering seem to be very promising, i.e. the
performance has been increased significantly by the use of haptic
feedback.
- Joystring (1986)
- A very special design of a 6D
manipulator with force feedback has been realized independently by
Agronin [4] and Staudhamer (mentioned in [103], further
developed by Feldman). A T-shaped grip is installed inside a box with
three strings on each of its three ends
. In Agronin's version, the strings' tension is controlled
by three linear motors, whereas the second one uses servo motors. No
results have been published.
- The Exoskeleton (1988)
- For telerobotic applications, different
skeletons which have to be mounted on the operators arm have been built
at the JPL [150], the EXOS company [87], and the
University of Utah (in [269]). The systems are used as a kind
of master-slave combination, and forces are applied by motors at the
joints. Unfortunately, these devices are usually very heavy, therefore
they can also be used in special applications. EXOS, Inc. has developed a
``light'' version for the NASA, but this system does not have any force
feedback.
- The Compact Master Manipulator (1990)
- The master manipulator that is
presented in [148] is based on flight simulator technique. All
three translational and rotational axis can be controlled and are
equipped with force feedback. Additionally, the thumb, the indexfinger,
and the other three fingers control a grip which also applies forces to
the user, thus yielding a 9-DOF device with force feedback.
Unfortunately, the paper only covers the design of the manipulator but
does not contain any results.
- A 3D Joystick with Force Feedback (1991)
- A joystick for positioning
tasks in 3D space has been developed by Lauffs [174]. The 3 axis
of the stick can be controlled independently, but rotations are not
possible. Force feedback has been realized by the use of a pneumatic
system, which is very robust but too slow for most applications.
- A Force Feedback Device for 2D Positioning Tasks (1991)
- A device
that is very similar to the one developed in GROPE I (see above) has
been realized by Fukui and Shimojo [111]. Instead of a knob,
the X/Y-recorder is moved with the finger tip. The resulting force will
be calculated and sent to the application, and if a collision is
detected, one or both axis will be blocked. This device has been
developed for contour tracking operations, its advantage is its almost
friction and mass free operation.
- PUSH (1991)
- In [131], a Pneumatic Universal
Servo Handcontroller is described. It has been developed for the
control of industrial robots. By using cardan joints and an orthogonal
coordinate system which is placed in the operator's hand, all axis can be
controlled independently. The device, which is rather large, can apply
forces by pneumatic cylinders. As the 3D joystick described above, it is
very slow.
- Teletact (1991)
- A data glove with tactile feedback
has been developed by Stone [326] and is used for outputs to the
user, whereas a second data glove is used for inputs to the computer. The
input glove is equipped with 20 pressure sensors, and the output glove
with 20 air pads, controlled by 20 pneumatic pumps. The major drawback of
this system is the very low resolution, additionally a force feedback is
missing completely. The next generation, Teletact-II, has been equipped
with 30 air pads and is available on the market now.
- Force Dials (1992)
- A dial with force feedback has been realized by
computer scientists and chemists for simple molecular modeling
tasks [127]. The force is controlled by a motor. The main
advantage of this device is its low price and its robustness but due to
its simplicity it will not be very useful for a multimodal system.
- Multimodal Mouse with Tactile and Force Feedback (1993)
-
In [6], an interesting approach to equip a standard input
device with output capabilities has been described. A common mouse has
been equipped with an electro magnet and a small pin in its left button.
This idea is especially appealing because it is cheap and easy to
realize. First results are very promising and have shown that the
performance in positioning tasks can be increased with this kind of
feedback by about 10%.
- PHANToM (1993)
- In his master thesis, Massie developed a 3D input
device which can be operated by the finger
tip [214]
. It realizes only
translational axis, but it has many advantages compared to other devices,
like low friction, low mass, and minimized unbalanced weight. Therefore,
even stiffness and textures can be experienced.
- A 2D Precision Joystick with Force Feedback (1994)
- Sutherland's
basic idea has been realized by researchers at the University of New
Brunswick [10]. The joystick has been made very small in
order to achieve a very high precision in its control. Results have shown
that the accuracy in a contour modification task can be increased (44%),
but the time will increase (64%), too.
Next: Bi- and Multimodal
Up: Computer Output Media
Previous: Hardware platforms
Esprit Project 8579/MIAMI (Schomaker et al., '95)
Thu May 18 16:00:17 MET DST 1995