Tactile navigation system for the blind'

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Tactile navigation system for the blind.

• By
• Ahlam Chaibi Ryan Paull
  Shreedhar Kale

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Our objective

• To design and fabricate an assistive device that
  would allow the person to walk safely in the
  urban environments avoiding
• static obstacles like poles
• moving obstacles like cars and people

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TYPES OF DEVICES

• GPS (Global Positioning Feedback System)
• Electronic Compass
• Auditory trascription of image
• Objest distance deduction and tactile and/or
  auditory feedback.

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Other devices
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Market Search

• Almost 1 million Americans are blind and 3
  million are visually impaired even with the best
  correction.
• MiniGuide 300
• Mowat Sensor 775
• Polaron 870
• Sensory 6 950
• Lasercane 2500
• Sonic Pathfinder 1695
• KASPA SonicGuide 3300

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Brainstorming

• Type of feedback system to be used
• Type of sensors to be used
• Placement of the sensors on the human body
• Modification needed to suit users of different
  age and sex
• Shape of the box

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Sound Vs. Tactile Feedback

• Sound feedback causes a change or an increase in
  pitch intensity to alert the user of an object in
  their path? this might negatively affect the
  users hearing ability.
• Tactile feedback uses a variable vibration
  stepper motor to alert the user of obstacles?
  Safer in this regard.

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CyberGlove

• It features small vibrotactile stimulators on
  each finger and the palm of the CyberGlove
• Each stimulator can be individually programmed to
  vary the strength of touch sensation
• The array of stimulators can generate simple
  sensations such as pulses or sustained vibration,
  and they can be used in combination to produce
  complex tactile feedback patterns

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Sensors Location

• Sensors will be placed in direct contact with
  fingertips.
• Other options belt, wrist bands.

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Laser Vs. Ultrasonic Sensors

• Laser provides better accuracy at greater
  distances, but it covers less area in the
  immediate proximity of the user.
• Laser is also significantly more expensive than
  ultrasonic sensors.
• It can be harmful to people in case of prolonged
  use.

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Size of the device

• Instead of having different sizes, we decided to
  use a grip that would match the users
  fingertips.
• ? This will save the need to have different
  sizes of the device.
• ? It will increase the surface contact
  area of the fingertips and the tactile sensor.

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Haptics and Vision
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Information Channels in Human Hand

• Sensory
• 7 classes of mechanoreceptors.
• 2 classes of thermoreceptors.
• 4 classes of Nocioceptors.
• 3 classes of Proprioceptors.

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Sensory Receptors Properties Haptic Display
Design

• Resolution and sensitivity of the sensors.
• Temporal processing characteristics (adaptation,
  summation).
• Delays in processing the information.

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Receptors Processing Vibration
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Perception of Vibrotactile Stimuli

• The perceived intensity of the vibration is a
  function of its frequency as well as its
  amplitude.

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Acuity of the skin

• Skin movement 0.1-0.2 mm (Gould et al., 1979).
• Spatial frequency of grating Fingertip can
  distinguish 40-50Um in spatial period of
  0.7-1.0mm (Morley et al., 1983).

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The 3-D model of the device
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CAD Drawings
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DESIGN SPECIFICATIONS
Battery
Sensors
  Motors
Motor Rated 1.3VDC, 75mA running, max. WT .007
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Continued
Shell
Sensors
shell
      Microcontroller PIC16F876
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Continued
Microcontroller PIC16F876
Damping material Silicone Rubber A molding kit
made with liquid silicone rubber and a curing
agent.  
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SENSOR PLACEMENT

• FOUR SENSORS
• FRONT
• BOTTOM
• RIGHT
• LEFT

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VIBRATION MOTOR PLACEMENT

• 4 Rows
• 3 Rows corresponding to the three phalanges of
  the finger and
• 1 Row on the inside of the palm
• 4 Motors in each row corresponding to the number
  of fingers

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RIBBED SHAPE

• ADDS SURFACE AREA TO THE POINT OF CONTACT
• Placed on the inner curvature for the finger
• Placed on the outer curvature for the palm

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Tactile Directional Feedback

• Each row corresponds to one of the sensors
• The sensors located on the tips of the finger
  would be used to relay information on the left
  sensor
• The sensors located on the middle section of the
  finger would give information on the front area
• The sensors located on the bottom section of the
  finger would correspond to the right sensor
• The sensors located on the palm would transmit
  information about the ground area.

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Distance Feedback

• Each sensor in the row corresponds to a different
  distance range
• As the obstacle gets shifted into another range,
  the sensor that is vibrating changes as well.
• The sensors at the pinky would correspond to
  objects at the farthest range.
• The moving object could be detected when the
  sensors start vibrating one after the other in
  sequence
• The rate at which the sensor vibrates lets the
  user know where the object is in that range
• The vibration would increase as the distance of
  the user from the object decreases.

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Various modes of operation

• In-Out mode
• Range switcher mode
• Single direction mode

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Cost estimation
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The areas of concern/ unsurity

• Adaptability of the device in the crowded place/
  various scenario
• Accuracy of the feedback
• The unaccountable characteristics of the
  sensation of touch
• Variation of the sense of touch depending on the
  individuals age,sex and degree of dependence on
  the device

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Calendar for the future

• End of spring break A miniature working
  prototype(without the programming)
• End of March Programming that handles the
  prototype.
• Mid-April Convert the program for the controller
  and use it in the prototype.
• End April Happy ending with first prototype
  ready!