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Tactile Displays Kaczmarek, K.A. and Bach-Y-Rita, P. (1995), Tactile displays, in Virtual Environments and Advanced Interface Design, Barfield and Furness,

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Presentation on theme: "Tactile Displays Kaczmarek, K.A. and Bach-Y-Rita, P. (1995), Tactile displays, in Virtual Environments and Advanced Interface Design, Barfield and Furness,"— Presentation transcript:

1 Tactile Displays Kaczmarek, K.A. and Bach-Y-Rita, P. (1995), Tactile displays, in Virtual Environments and Advanced Interface Design, Barfield and Furness, pp Summarized by Geb Thomas

2 Your 2m 2 of skin n 90% hairy, 10% glabrous (hairless) n Accessible n Richly innervated n Precise discrimination n Adaptable to spatial and temporal displays

3 Covered Here n Present and potential applications n Mechanisms of normal touch perception n Technology for producing tactile displays n Practical considerations

4 Traditional displays for the blind n Braille (6-dot matrix, 2.3mm separation, 125 words*min -1 ) n Sign language: finger spelling: 6 letters* sec -1, American Sign Language: 4-5 syllables*sec -1 ) n Tadoma 3 syllables*sec -1

5 Tactile Feedback from tactile sensors n For people with poor haptic perception in their hands (Hansen’s disease, suited astronauts) n strain guages on a glove to forhead electrodes: can detect shape and texture! n Movable pins, enhanced fingerpads, tactile pads, glove-hand adhesion, removable glove fingertip n Sample task: no feedback: 92s, force feedback 63s, barehanded: 14s

6 Tactile auditory substitution n Auditory prosthesis which adjusts the perceived intensity of 16 electrodes, each corresponding to the sound intensity of a given passband in the audio spectrum. n Improve speech clarity for deaf children n Improve auditory discrimination and comprehension in older patients

7 Tactile vision substitution (TVS) n Television Camera to users skin with a vibrotactile or electrotactile stimulators array. n Stimulation intensity is controlled by grayscale n Distal attribution -- with practice, user perceives the stimulation to be in front of them

8 Tactile Reading n Optacon 6x24-row vibrating fingerpad n 90 words*min -1 exceptional 28 words*min -1 normal n Now discontinued n Significant underground calling for its resurgance

9 Static tactile displays n 64-solenoid, four level display presenting graphical information n Another model has one prime mover and many piezoelectric latches n Muscle wire display

10 Virtual tactile tablet n Fingerpad vibrotactile stimulation array on a mouse n 5x20 array of pin vibrotactors mounted directly above t-shaped mouse n Minsky’s sandpaper display

11 Human Tactile Perception n Six types of cutaneous receptors, four functions – Fast adapting, broad receptive field (FAII) -- high-frequency vibration – Fast adapting, small receptive field (FAI) -- localized movement fine form and texture – Slow adapting, large-field (SAII) -- maybe not involved in haptics – Slow adapting, small-field (SAI) -- form and roughness

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13 Measures n Smallest amount of pressure n Two-point limen (two point discrimination threshold TPDT) n Affected by location, practice, fatigue, distraction n Modeling attempts include convolving integral, low-pass filter or Gaussian blur

14 Design Criteria n Static tactile displays n Vibrotactile displays n Electrotactile displays

15 Static n High power consumption n Rapid adaptation to static stimuli n 12-20mm height to match Optacon accuracy

16 Vibrotactile n Threshold: 5 micro-m at Hz for small areas (<.05 cm 2 ) n Adaptation to strong stimuli n Full recovery requires 2 min. n 160 Hz is best n 10dB over threshold n 1 mm diameter stimulator with.5mm movement

17 Electrotactile Displays n Current through skin n Current-limited n Balanced, biphasic pulses with zero net DC current n Electrodes to produce appropriate ions (gold, platinum, silver) n Electrode size is important n Some are implantable

18 Important Issues n Pain threshold n Skin condition n Sensory adaptation n Subjective magnitude of electrotactile stimulation


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