Force and Tactile Feedback
Authors: Corde Lane and Jerry Smith
The sense of touch is one of the most powerful learning tools that
humans have. Whenever someone discovers something new, instinctively
they want to hold it, poke at it, touch and feel it. Since, so much
can be conveyed by the haptic senses, integrating them into a virtual
environment would yield great rewards. However, the difficulty is
great in dealing with the complex problems of creating such stimuli.
Therefore no generic output tool exists that can be integrated easily
into a virtual environment. Therefore the prototypes that do exist
are used only in specific functions.
The most common force feedback technique uses movable platforms. In
many video game arcades there are games where one drives a vehicle
like a motorcycle. The player sits on a seat and as they control the
motorcycle, the seat reacts to give the rider a feeling of actually
being on a motorbike. The seat will vibrate and move to one side as
the player maneuvers around a curve. Although interesting, players
rarely find this convincing.
Disney's Star Tours or the locally known attraction Days of Thunder at
King's Dominion are simulated rides that use motion platforms to
enhance visual cues of movement. These attractions strap people to a
motion platform. A large screen depicts an action, like flying on an
airplane or riding a speeding car. The motion platform actually moves
to create an illusion of accelerating or turning. These simulation
rides are engaging; however they are not interactive. The audience is
just along for the ride.
The military uses motion platforms in their expensive flight
simulators. Along with recreations of the control panels and high
definition visual displays these simulators provide an interactive and
engaging training program.
Force Feedback Devices
There are few commercially available force feedback output devices.
This is due to the complexity of delivering force feedback. Since
research in this area is not as intensive as with visual or auditory,
there are few commercially available interfaces.
Portable Dextrous Master
The Portable Dextrous Master (PDM) is a force feedback system for
delicate hand motions. It is design to be used with the VPL
DataGlove. The DataGlove detects finger movement to the computer
which then sends signals to the PDM which, in turn, supplies force
feedback in the thumb, forfinger, and middle finger through
piston-like cylinders mounted on ball joints. The entire unit
attaches to the palm of the DataGlove.
The University of North Carolina (UNC) modified a mechanical
controller for a robotic arm previously used in radioactive material
handling. Motors were added to the Argonne remote manipulator (ARM).
The motors would be activated by the virtual environment to create
forces on the controller. UNC used this in their GROPE-III system to
help chemist "feel" the attractive and resistive forces of molecules
reacting and bonding to each other. The chemist could use the forces
and torques to learn how to make new chemical compounds.
PER Force Handcontroller (Cybernet Systems)
The PER Force Handcontroller supplies six-degree-of-freedom force
feedback much like the ARM (see GROPE-III). It is a hand feedback
system that mounts to a desk or other flat surface. The operator may
then grab a handle grip to use the system. Its main advantage over
the ARM is its light weight and small size.
FRHC (University of Maryland)
A force reflective hand controller (FRHC) is being developed to
control a robot arm. When the robot arm picks up an object or pushes
something, those forces and torques are felt by the operator. The
operator can now tell how much strain is placed on the robot's motors,
gears, and structure. Also this controller gives the operator a
partial sense of touch that the robot would have.
Exoskeleton (University of Utah)
At the University of Utah, an operator can strap their arm into a
large 50 pound exoskeleton developed to deliver force feedback. The
operator's arm and hand can move in 10 different ways at the same
time. The computer constantly changes the force output of the motors
and hydraulic actuators on the exoskeleton so that it can feel
essentially weightless. However, when the operator touches something,
the virtual forces become actual forces felt through the exoskeleton.
They could feel the increasing resistance of compressing a virtual
spring or their arm would stop hard when it reached a virtual wall.
Tactile Feedback Devices
TeleTact Glove (UK's Advanced Robotics Research Center and Airmuscle)
TeleTact offers force feedback and tactile feedback by using small
airbags inside the lining of the TeleTact Glove. When worn, the user
can feel the size, shape, and some texture of a virtual or remote
object because the airbags quickly fill and deflate to provide touch
sensation to the hand.
Begej Glove Controller (Begej Corp.)
The Begej Glove provides advanced tactile and force feedback to three
fingers of the hand. It provides force feedback using and exoskeleton
mechanism that provides the necessary resistance to movement. For
tactile feedback, the Begej Glove uses what Begej Corporation calls
taxels, arrays of small tactile display elements positioned an the
pads of the fingers. The Begej Glove is currently still in research
and is not commercially available.
TiNi Alloy Tactile Feedback System
Using shape-memory alloys, or memory metals, the TiNi Alloy TFS
provides temperature tactile feedback. This feedback is displayed by
heating the appropriate memory metal element positioned on the hand
(probably in a glove). This product is still in research and is not
Sandpaper System (MIT)
The Sandpaper System is a mouse like device that provides tactile
sensations through the mouse by changing the bottom of the "mouse's"
surface depending on the virtual surface it is passing over. This
product is still in research and is not commercially available.
How To Get Involved
Learning about the sensors, electronics, and mechanics, can come from
a variety of classes and work areas. Therefore education areas
include how the human body reacts to forces, classes in biomechanics
provide this knowledge.
Remis, S. J.; Nelson, D. K. "Force-Reflecting Interfaces to
Telemanipulators Testing System (FITTS", Interim User's Guide; Interim
rept. Jan 89- Dec 90.
Srinivassem, M. "Design Requirements for Force Reflecting Master
Controllers", MIT, Cambridge, MA, 1992.
Human Interface Technology Laboratory