tactile sensors

8/18/2019 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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