tactile displays
DESCRIPTION
Tactile Displays. Presented By Mary Wesler Rakesh Dave. Definitions. Tactile: A sensation perceived by the sense of touch; pressure or traction exerted on the skin is perceived; sensitivity to vibration or movement to stimulation of nerves. - PowerPoint PPT PresentationTRANSCRIPT
Tactile DisplaysTactile Displays
Presented By
Mary Wesler
Rakesh Dave
Definitions
Tactile: A sensation perceived by the sense of touch; pressure or traction exerted on the skin is perceived; sensitivity to vibration or movement to stimulation of nerves.
Distal Attribution: Refers to the referencing of our perceptions to an external space beyond the limits of the sensory organs themselves (Loomis, 1992).
Definitions
Kinesthetic information: Describes relative positions and movements of body parts as well as muscular effort when touching and manipulating objects
Haptic perception involves both tactile perception through the skin and kinesthetic perception of the position and movement of the joints and muscles. E.g Cube ,through the skin of our fingers and the position of our fingers.
Advantages
Accessible, extensive in area, richly innervated and capable of precise discrimination
Does not interfere materially with other functions Number of similarities to retina Spatial+Temporal integration Visual and tactual patterns can be learned and identified
interchangeably Mach Band phenomenon demonstrable on skin(Mach's
bands, the tendency of the human eye to see bright or dark bands near the boundaries between areas of sharply differing illumination)
Functions as exteroceptor
Necessity
Tactile Cues refine and moderate manual activity
Necessary for faithful telepresence Environments where visual is less useful Some operations inherently tactile Entertainment value (Free to speculate!!!!)
Chapter Part I
Applications– Sensory substitution visual/auditory– Remote tactile sensing or feedback
Technology for production– Static– Vibratory– Electro Tactile
Uses Of Tactile Substitution
Enhancing accessibility for the blind – To enhance access to computer graphical user
interfaces – To enhance mobility in controlled environments – To allow for learning of visual concepts
Communication of visual information to the brain in situations where the visual system is already overloaded – Race car drivers – Airplane pilots – Operating rooms
Uses Of Tactile Substitution
Audio to Tactile Converters Virtual Reality Telerobotic Manipulators Prosthetic Limbs
(Courtesy Unitech Research)
Low Tech
Braille Sign Language Tadoma
Force Feed Back
Spatial information integrated with kinesthetic information received by manually scanning objects and texture information by time dependent frictional vibrations recorded by sensors. Applied to people with Hansen’s Disease and Astronauts in space
Tactile Auditory Feedback
Tacticon and AudioTact– Adjusting the perceived intensity of electrodes
based on different intensities of sound (Vocoder principle)
Tactile Visual Feedback
VideoTact– Uses 768 point array
of tactors for Image translation (capable of translating BMP or DIB format bitmaps as well as NTSC or PAL/SECAM video into an electro-tactile equivalent)
Tactile Vision Substitution
Device which converts printed matter to vibrotactile letter outlines on users finger pad. No longer in production due to high cost and low demand
Interactive Haptic Displays
Static Tactile Displays Virtual tactile tablet (finger pad mounted
on a mouse) Force Display to feel texture Electropthalm Vibrotactile forehead
display + finger display Steerable water jet display
Current Technology
Linear and Planar Graspers at MIT TOUCH Lab
Description. The Linear Grasper is now capable
of simulating fundamental mechanical properties of objects such as compliance, viscosity and mass during haptic interactions. Virtual wall and corner software algorithms were developed for the Planar Grasper, in addition to the simulation of two springs within its workspace.
Current Technology
Harvard Robotics Lab– Deformable tactile sensors.
Using this technology, deformed shape of the sensor on-line is reconstructed This sensor is currently being used in manipulation tasks and in the development of a tool for minimally invasive surgery.
Current Technology
Allows for feeling temperature at the fingertips.Used for telepresence in remote manipulators
(Courtesy C M Research Group)
Sensory Physiology
Salient Features– Skin Anatomy
• Besides fibers for pain skin has six types of receptors
Response measures of these determine the amount and type of information that can be presented and classification of these have functional roles
Sensory Physiology
Perception of non vibrating stimuli– Static force up to a minimum of 5 dynes
applied by a fine wire is detectable by human body.
( Particularly notable fact is that threshold for women is less than that for men!!!!!!!!!!!!)
Limitations
As Field of view tactually increases tactile recognition reduces when compared to visual recognition.
Salient features may be blurred by meaningless details
Distal Attribution
Telepresence - sense of being present in a remote environment
Feedback - sensory information (afference)– visual– auditory– tactile
Motor Control over the sensed environment (efference) Perceptual Model Problems
– time delays– low spatial resolution– conflicting information
Tactile Display Design Considerations
Must accommodate the unique sensory characteristics of the skin, particularly if cross-modality sensory substitution is attempted.
The perceived stimulation magnitude should closely match the same pressure stimulus on the skin.
Spatial Resolution - whole frame presentation is prohibitive tracing, slit-scan presentation, edge enhancement, and zoom features are beneficial.
Display type should match the information presentation.
Humans are resistant to change.
Static Display
Braille
Sign Language
Tadoma
Vibrotactile Display
Electrotactile DisplayTypes Chapter 9, Fig. 9-9 Surface Subdermal Percutaneous WireAdvantages to Subdermal and Wire Low JND high consistency mechanical stability no mountingSensations - tingle, itch, vibration,
buzz, touch, pressure, pinch, and sharp or burning pain
Dynamic Range
Dynamic Range
Dynamic range = threshold pain (IP)/threshold sensation (IS)
Skin - varies from 2-10 or 6-20dB– definition of pain– training– presentation of other stimuli– electrode material, size, placement, and stimulation waveform
Ear 120dB Eye 70dB
Authors’ Recommendation
Dynamic RangeProposed = Perceived Magnitude at Maximal Current (IM) without discomfort.
Note: IP = 1.3 IM
Justification: IP/IS is an electrical measure not a perception measure. Maximizing IP/IS does not guarantee a usefully strong or comfortable sensation.
Chapter 9, Fig. 9-15.
Tactile Display PrinciplesStatic Vibrotactile Electrotactile
Principles: Displaydeforms theskin exactly asthe sesor arrayis deformed bythe object
External stimulation of mostcutameous afferent nerve fibergives rise to tactile sensation
Deliver controlled information bymeans of electrical stimulation ofsmall distinct patches of skin withsurface and electrodes
Perception: Normal Touch Dependant on:Skin location – fingertips aremost sensative.Tactor sizeGap between tactorsAmplitude and frequency
Sensations - tingle, itch, vibration,buzz, touch, pressure, pinch, andsharp or burning pain
Adaptation: Rapid 7-25 min conditioningvibrotactile stimulus results infull adaptation.Full recovery in 2 min.
Varies with frequency: little at 10 Hzwithin seconds at 1000 HzBursts of stimulation reduceadaptation
Safety: Heat burnsShockSkin Irritation
Heat burnsShockStingingSkin Irritation
Comfort: Comfortable with amplitudes0.5-1 mm diameter stimulator.
Varies - stimulus adjustment andquick off ideal. Best if electrode iswet.
PowerConsumption:
Staticmechanical:1W per pixel
Varies: 250 Hz, 12.6 mm2 = 0.4mW to 138 mW sine waves atthreshold
Average 1WSubdermal 10-22W
Display Performance Criteria Minimal power consumption Maximal stimulation comfort Minimal post-stimulation skin irritation Minimal sensory adaptation Maximal information transfer measured by:
– minimal JND of the modulation parameters current, width, frequency, and number of pulses per burst
– minimal error in identifying the absolute stimulation level of a randomly stimulated electrode
– minimal error in manually tracking a randomly varying target stimulus Maximal dynamic range:
– maximal comfortable level/sensory threshold– maximal range of perceived intensities
Minimal variation of sensory threshold and maximal comfort level with precise electrode location on a given skin region
Fastest and most accurate spatial pattern recognition
Key Terms balanced-biphasic coaxial distal attribution efference copy electrotactile functionally
monophasic haptic display haptic perception just-noticeable
difference kinesthetic
perception masking
percutaneouselectrodes
sensory substitution spatial integration static tactile subdermal
electrodes tactile perception telepresence temporal integration texture vibrotactile virtual environment
REFERENCESKaczmarek, K.A. and Bach-Rita, P., (1995). Chapter 9: Tactile Displays. In Barfield and Furness, Eds. Virtual Environments and Advanced
Interface Techniques. (pp.349-401).Goodwin-Johansson, S. Palmer, D. Mancusi, J. Nawankwo, H., Wesler, M.Mc., and Marshak, W.P., (1999). Tactile interface on a mobile
computing platform. In Proceedings of the US Army Federated Laboratory Advanced and Interactive Displays Symposium. (pp. 51-55). College Park, MD: Army Research Laboratory.
Gilliland, K. and Schlegel., (1994). Tactile Stimulation of the human head for information display. In Human Factors 36(4) 700-717.Korteling, J.E. and Van Emmerik, M.L. (1998). Continuous haptic information in target tracking from moving platform. In Human Factors
40(2), 198-208Sheridan, T.B., Thompson, J.M., Hu, J.J., and Ottensmeyer, M., (1997). Haptics and supervisory control in telesurgery. In Proceedings of the
Human Factors and Ergonomics Society 41st Annual Meeting (1134-1137). Santa Monica, CA: Human Factors and Ergonomics Society.Yeh, M. and Wickens, C.D., (1999). Target cueing in augmented reality: a comparison of head mounted with hand-held displays. In
Proceedings of the Human Factors and Ergonomics Society 43rd Annual Meeting, (pp 1228-1232). Santa Monica, CA: Human Factors and Ergonomics Society.
Dow, S. Thomas, G., and Johnson, L., (1999). Signal detection performance with a haptic device. In Proceedings of the Human Factors and Ergonomics Society 43rd Annual Meeting, (pp1233-1237). Santa Monica, CA: Human Factors and Ergonomics Society.
Venkatraman, M. and Drury, C. Cross modal displays for haptic information. In Proceedings of the Human Factors and Ergonomics Society 43rd Annual Meeting, Sata Clara, CA. 1238-1242
Bullinger, H-J., Bauer, W., and Braun, M., (1997). Virtual Environments: Haptic, Kinesthetic, and Other Perceptions. In Gavriel Salvendy, Ed. Handbook of Human Factors and Ergonomics. (pp 1742-1746).
Sanders, M.S., and McCormick, E.J., (1987). Information Input: Tactile Displays. In Human Factors In Engineering Design. McGraw Hill Book Company, NY, (pp 160-167).
Sharedd Virtual Environments: with haptic and visual feedback. www.rcs.ee.washington.edu/BRL/project/shared/CyberTiuch, www.virtex.com
Bach-y-Rita, P. , Kaczmarek, KA, Tyler, ME., Garcia-Lara, J., DDS Form perception with a 49-point electrotactile stimulus array on the tongue. Center for Neuroscience and the Department of Rehabilitation Medicine, Trace R&D Center, University of Wisconsin, Madison, WI