tactile sensors
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Tactile sensor Tactile sensor
دهنده
ر ه
دهند
ر ه
::بيات
مرضيه
بيات
مرضيه
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INTRODUCTION
• Goal:
Measurmeant the parameters of contactbetween the sensor and an object such as
the spatial distribution of forces.
• Areas in use:
Most important of robotic sensory systems
Agriculture ,Bio medical ,…
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Different types of tactile sensorsDifferent types of tactile sensors
•• OpticalOptical
•• PiezoelectricPiezoelectric•• Strain gageStrain gage
•• ResistiveResistive•• CapacitiveCapacitive
•• MagneticMagnetic
•• UltrasonicUltrasonic
•• SAWSAW
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Optical tactile sensor Optical tactile sensor
Equipped with :Equipped with :
•• Optical wave guide plateOptical wave guide platemade of acrylicmade of acrylic
•• An array of feelers An array of feelers•• A soft rubber at the A soft rubber at the
surfacesurface
•• A light source A light source
•• A CCD camera A CCD camera
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A three_ axis optical tactile sensor A three_ axis optical tactile sensor
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T h r e e _ ax i s t a c t i l e s en s or
T h r e e _ ax i s t a
c t i l e s en s or
m o un t e d on ar o b o t m a
ni p ul a t
or
m o un t e d o
n ar o b o t m ani p ul a t or
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An image based model An image based model
diameter 2cm,length 6:2cm,
High accurately
contact localization, contact depthand curvature discrimination
Error < 0.1mm over a 4cm^2 area,
while the spatial resolution isbetter than 2mm.
Harvard University
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Piezoelectric tactile sensor Piezoelectric tactile sensor
Varies types of them use the principle of :
• change in the piezoelectric resonancefrequency of a poled ceramic with the
applied stress.
• Changes in resistance of the material
• Changes in electric charge
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A simple model A simple model
Structure & Principle:
A thin film of the piezoelectric
material covered with two
conductive layers.
Assuming uniform pressure distribution
A= the area of the contact :
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Tactile Sensor Based onTactile Sensor Based on
Piezoelectric ResonancePiezoelectric ResonancePrinciple:
The resonance frequency of theresonating material :
t = Thickness of the pizo.material.
f 0 = Natural mechanical resonancefrequency.
K = Stiffness constant of the material. p = Density of the material.
A = Constant.
F = Applied force. Hence:
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Design and Preparation
Structure:
• the PZT material thickness
1 mm ,diameter 20mmresonance frequency
~1M Hz.
Advantage:
Getting a Contour of the object.
spatial resolution:
improves by increasing the
number of array electrodes
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Ultrasonic tactile sensor Ultrasonic tactile sensor
•• A thin deformable rubber A thin deformable rubber
pad & twopad & two--dimensionaldimensionalarray of ultrasonic TX &array of ultrasonic TX &RX for measuring theRX for measuring the
thickness of the rubber.thickness of the rubber.
•• CrossCross--field switching:field switching:
using PVDF layers.using PVDF layers.•• BiBi--layer techniquelayer technique
•• CalibrationCalibration
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ResolutionResolution
256 elements256 elements
1.15x1.151.15x1.15
CounterCounter freqfreq
8080 MHzMHz
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A biosensor A biosensor AXIOM company AXIOM company
Venus HandyFrequency: 57 kHz
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dubbed Venustrondubbed Venustron
••measurementof the elasticity omeasurementof the elasticity of f skin and muscleskin and muscle•• tactile, pressure, and displacement sensor.
Medical tactile .inc (MTI)
• detection of cancer
• four times as sensitive as
human touch
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Tactile Sensor
combination of static foil sensors and
dynamic hair sensors.The analog sensors are coupled to an
8-bit controller, which uses a multiplexer
, a sample-hold circuit and analog-digital
converter for storing the latest sensor data.The controller is equipped with a CAN-bus interface
Harvard University
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T-2000
a two-dimensional array ofpressure sensing elements
The sensor elements can
be spaced as close as2 mmhigh accuracy.
ideal for tactile pplications
-0.7%/10°CBaseline Temperature Stability
0.6% RMSBias Non-Repeatability
0.3% RMSScale Factor Non-Repeatability
1.0%Non-Linearity
0.01 psi.System Resolution
5 V, 12-bit ADC Range & Resolution
2, 2.5, or 3.8 mmSpatial Resolution
20, 80, or 200 psi.Overpressure Value
3, 12, or 30 psi.Full Scale Range (FSR)
4x4, 8x8, and 16x16
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C-2000
Fingertip System
-6.6%/10°CBaseline Temperature Stability
0.4% RMSBias Non-Repeatability
0.1% RMSScale Factor Non-Repeatability
0.1%Non-Linearity
0.005 psi.System Resolution
100 psi.Overpressure Value
5-60 psi.Full Scale Range (FSR)
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