I agree. If she could bring a demonstration with her, so much the better.
Do you want to invite her Curtis, or shall I? Or, Tim, do you want the
On Oct 4, 8:52am, "Lloyd G. Rasmussen" wrote:
} Subject: EE Times, more tactile virtual reality
} This looks almost interesting enough that we might want to invite them to
} the R&D committee meeting. Or maybe they need to tour the IBTC.
} Haptics lab aims for good VR vibes
} By R. Colin Johnson
} EE Times
} (10/02/00, 4:56 p.m. EST)
} BALTIMORE _ While most virtual-reality engineering focuses on accurately
} the visual elements of experience, Allison Okamura's new Haptic Exploration
} Lab at
} Johns Hopkins University focuses instead on the sensation of touch.
} "The sense of touch is a key mechanism used by humans to learn about their
} said Okamura. "The same should be true in VR, but today designers are
} heavily on visual presentation. My lab will instead explore means for
} both tactile perception through the skin and kinematic perception through
} the position
} and movement of the joints and muscles."
} Perception, as opposed to sensation, holds the key to Okamura's refinement
} of VR
} accuracy, since sensations can conflict even in real life, whereas
} perceptions reflect
} a decision to "trust" an interpretation of sensations. For instance, a
} pencil in
} a glass of water appears to be broken because the visual sensation shifts
} where it emerges from the water.
} Humans "perceive" the pencil as straight, however, because they can verify
} by touching
} the pencil that it remains unbroken where it emerges from the water, even
} visual sensations suggest that it is broken. Primates, especially humans,
} use touch
} as their "perception verifier," but most lower animals follow their nose _
} for instance,
} a dog would verify that the pencil remains unbroken by smelling it.
} Unfortunately, the ability to verify conflicting sensations and conjure an
} internal perception is almost entirely missing in current VR environments.
} Even sophisticated
} electronic gloves only track the position of the hands for display in VR.
} "We want to characterize materials in the real world, so that we may then
} mimic the
} necessary sensations in VR that will allow people to accurately perceive
} said Okamura.
} She will present her preliminary results and future research directions in
} at the American Society of Mechanical Engineers' Dynamic Systems and
} Control Conference.
} There she will describe a method of accurately mimicking the vibrational
} of wood, aluminum and rubber.
} "Today, even if you bump into a wall in VR, it just tells you that an
} obstacle exists.
} But in real life, when you bump into something, you use the resulting
} sensation to perceive the wall as made of a certain type of material," said
} Everyone admits that rapping on a wall is the best way to tell if its made
} of wood
} or just has an imitation wood grain veneer. However, no one has
} characterized the
} "output" vibrations of materials as a result of an "input" rap of the
} knuckles. Therefore,
} there are no existing models to reproduce those vibrations in VR.
} "There are all kinds of physical models available to accurately represent
} the 3-D
} geometry of objects _ how things look from different angles _ but there are
} no models
} available to represent the vibrational signatures of materials," said Okamura.
} Consequently, Okamura cut through the theoretical logjam by skipping the
} model for
} now, settling instead for recording the vibrations of real materials from
} and then playing back the recording into a haptic display. Using real human
} to experience the recorded vibration sensations, Okamura was able to
} accurately induce
} the perceptions of wood, aluminum and rubber.
} "We allowed the test subjects to select the best parameters for our
} vibrational recordings
} by comparing them with vibrations from real materials," said Okamura.
} Subjects used a tethered stylus (from San Jose-based Immersion Corp.) to
} "tap" on
} real wood, aluminum and rubber blocks for direct sequential comparisons
} with nine
} different parameter sets of the real recordings. The parameters of the
} were variables such as a multiplier for amplitude of the vibration waveform
} to the impact velocity of the stylus. Other parameters besides the
} slope included the decay rate and frequency parameters of the recordings.
} All test
} subjects were able to exceed 80 percent accuracy in identifying virtual
} of wood, aluminum and rubber after about 15 minutes of parameter selection.
} Tele-operated medical surgery is one area where the new virtual reality
} system could
} find an immediate application. "There are many tactile problems to be
} solved for
} tele-operated surgery. For instance, when you put a needle through the skin
} it is
} hard to avoid overshoot; you have to compress the skin to get the needle
} but once it's through you have to back off the pressure in just the right
} to end up with the needle at the right depth," said Okamura.
} Solving the needle insertion problem, however, would involve characterizing
} the soft
} tissues of the human body _ a difficult task that illustrates how far
} haptics research
} needs to travel from characterizing the simple vibrational characteristics
} of wood,
} aluminum and rubber. Consequently, for the foreseeable future, Okamura's
} lab will
} perform basic research into what she calls "dexterous manipulation."
} Ultimately, multiple robotic fingers will cooperate to grasp, manipulate
} and explore
} the world, for the same reason that humans verify conflicting visual
} "You have to work backward from the object to the actuators that will
} it when formulating a dextrous manipulation problem for a robot," said
} Okamura. In
} doing so, a system of equations can be built that describes the
} robot-object system
} in terms of shared characteristics, such as points of contact, finger-arm
} compatible with object geometry, and kinematic bounds such as how much
} pressure can
} be applied when picking up an egg.
} The first step in dexterous manipulation is usually to calculate backward
} from the
} desired pressure on the object, to the fingertip forces to be employed by
} the robot.
} >From there things get complicated, since accuracy in anthropomorphic
} robotic hands
} involves rolling and sliding them against the object as it is manipulated.
} take as input the location, texture and relative velocities of object and
} and output parameterized velocities to describe the motions of the contact
} over the fingertip and object surfaces.
} While other labs have explored most of these dexterous manipulation
} problems, Okamura
} believes her effort will have unique aspects that pull together diverse
} resources to solve the problem. Automated grasping and motion planning, for
} 3-D manipulation
} of realistic virtual materials with rolling and sliding, will be the
} ultimate goal
} of the lab. Today such calculations must be done offline, but Okamura
} believes that
} better algorithms can soon solve the problem.
} All material on this site Copyright c 2000 CMP Media Inc. All rights reserved.
} Lloyd Rasmussen, Senior Staff Engineer
} National Library Service f/t Blind and Physically Handicapped
} Library of Congress (202) 707-0535 <email@example.com>
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>-- End of excerpt from "Lloyd G. Rasmussen"
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