原理-ch19機(jī)器人及技術(shù)其應(yīng)用課件

Force

and

Tactile

SensorsYuan

Li201905221027911628@187218661Sensing

and

PerceptionThe

importance

of

tactile

sensingHow

important

is

tactile

sensing?What

is

it

useful

for?Why

does

it

remain

comparatively

undeveloped?2The

importance

of

tactile

sensing3In

Nature,

tactile

sensing

is

an

essential

survival

tool.

Even

the

simplest

creaturesare

endowed

with

large

numbers

of

mechanoreceptors

for

exploring

and

respondingto

various

stimuli.In

humans,

tactile

sensing

is

indispensable

for

three

distinct

kinds

of

activities:manipulation,

exploration,

and

response.

The

importance

of

tactile

sensing

formanipulation

is

most

evident

for

fine

motor

tasks.

When

we

are

chilled,

taskslikebuttoning

a

shirt

can

become

an

exercise

in

frustration.

The

problem

is

primarily

alackof

sensing;

our

muscles,

snug

in

our

coat

sleeves,

are

only

slightly

affected

but

ourcutaneous

mechanoreceptors

are

anesthetized

and

we

become

clumsy.

For

exploration,we

continually

assimilate

tactile

information

about

materials

and

surfaceproperties

(e.g.,

hardness,

thermal

conductivity,

friction,

roughness)

to

help

us

identifyobjects.One

reason

for

the

slow

development

of

tactile

sensing

technology

as

comparedtovision

is

that

there

is

no

tactile

analog

to

the

charge-coupled

device

(CCD)

orcomplementary

metal–oxide–semiconductor(CMOS)

optical

array.

Instead,

tactile

sensors

elicit

information

through

physicalinteraction.

They

must

be

incorporated

into

skin

surfaces

with

compliance,

to

conformlocally

to

surfaces,

and

with

adequate

friction

to

handle

objects

securely.The

importance

of

tactile

sensing419.1

Sensor

TypesThis

section

outlines

five

main

types

of

sensors1.proprioceptive52.kinematic3.force4.dynamic

tactile5.array

tactile

sensors19.1

Sensor

Types1.NormalpressurePiezoresistivearrayCapacitivearray2.

SkindeformationOpticalMagnetic3.

Dynamic

tactilesensingPiezoelectric(stress

rate)SkinaccelerationPiezoresistiveMEMS

arrayPiezoresistive(curvature)61.

Normalpressure①

Piezoresistive

arraySensor

TypesNature.

(2014)

516224.Sensors

and

Actuators

A.

(2018)

269,574.71.

Normalpressure②

Capacitive

arraySensor

TypesIEEE

ELECTRON

DEVICE

LETTERS.

(2018)

39,107681.

Normalpressure③

MEMSarraySensor

TypesPNAS.

(2005)

102,

1232393.

Dynamic

tactile

sensing①

PiezoelectricSensor

TypesWhen

some

materials

are

subjected

topressure

or

tension

along

a

certaindirection

when

deformation

occurs,

it

willcause

its

internal

positive

and

negativecharge

center

relative

transfer

andpolarization

phenomenon,

make

its

surfacecharge.

When

the

external

force

isremoved,

they

return

to

their

neutral

state.PVDFPVDF

is

anorganicpiezoelectric

material,

alsoknown

as

apiezoelectricpolymer.Such

materials

andtheir

materials

are

flexible,low

density,

low

impedanceand

high

voltage

constant1019.1.1

Proprioceptive

and

Proximity

SensingProprioceptive

sensing

refers

to

sensors

that

provide

information

about

thenet

force

or

motion

of

an

appendage,

analogous

to

receptors

that

provideinformation

in

humans

about

tendon

tensions

or

joint

movements.

Generallyspeaking

the

primary

source

for

spatial

proprioceptive

information

on

a

robotis

provided

by

joint

angle

and

force-torque

sensors.

Since

joint

angle

sensorssuch

as

potentiometers,

encoders,

and

resolvers

are

well

establishedtechnologies,

they

do

not

warrant

discussion

here.

Instead,

a

brief

reviewofproximity

sensing

via

whiskers

and

antennae

as

well

as

noncontact

proximity①

Whisker

and

Antenna

Sensors

②

Proximity1119.1.1

Proprioceptive

and

Proximity

Sensing①

Whisker

and

Antenna

Sensors②

ProximityACS

Nano.

(2017)

11,

79501219.1.2

Other

ContactSensors13Thermal

SensorsThermal

sensing

can

be

used

to

determine

the

material

composition

of

an

object

aswell

as

to

measure

surface

temperatures.

Since

most

objects

in

the

environmentareat

about

the

same

(room)

temperature,

a

temperature

sensor

that

contains

aheatsource

can

detect

the

rate

at

which

heat

is

absorbed

by

an

object.

This

providesinformation

about

the

heat

capacity

of

the

object

and

the

thermal

conductivity

of

thematerial

from

which

it

is

made,

making

it

easy,

for

example,

to

distinguish

metalsfrom

plastics.19.1.2

Other

ContactSensorsThermal

SensorsDue

to

thermal

expansion,

the

contact

of

theconductive

network

is

changed

and

the

resistancevalue

ischangedACS

Appl.

Mater

Interfaces.

(2018)

1114,

2317.19.1.2

Other

ContactSensors15Material

Composition

SensorsThere

has

been

a

little

work

on

sensors

for

materialcomposition.

In

analogy

with

the

human

sensesoftaste

and

smell,

liquid-

andvapor-phasechemicalsensors

could

potentially

determine

the

chemicalcomposition

of

a

surface.19.1.2

Other

ContactSensorsMaterial

Composition

SensorsUse

chemical

reaction,

ion

reaction

produceselectric

signalpotentially

determine

the

chemicalcomposition1619.1.4

Force

and

Load

Sensing17Actuator

EffortSensorsFor

some

actuators

such

as

electric

servomotors,

ameasure

oftheactuator

effort

can

be

obtained

directly

by

measuring

the

motorcurrent

(typically

using

a

sensing

resistor

in

series

with

the

motorandmeasuring

the

voltage

drop

across

the

sense

resistor).

However,because

motors

are

typically

connected

to

robot

limbs

via

gearboxeswith

output/input

efficiencies

of

60%

or

less,

it

is

usually

much

moreaccurate

to

measure

the

torque

at

the

output

of

the

gearbox.19.1.4

Force

and

Load

SensingForce

SensorsWhen

actuator

effort

sensors

are

not

sufficient

to

measure

the

forces

exertedby

or

on

a

robot

appendage,

discrete

force

sensors

are

typically

utilized.

Thesesensors

are

found

most

often

at

the

base

joint

or

wrist

of

a

robot,

but

could

bedistributed

throughout

the

links

of

a

robot.Miniature

fingertip

force-torque

sensor

for

a

prosthetic

hand18The

force

applied

has

sixdimensions

(X,

Y,

and

Zaxes)

and

correspondingtorque

directions19.1.4

Force

and

Load

SensingForce

SensorsPI(Polyimide)ACS

Nano.

(2018)

12,

21394619.1.4

Force

and

Load

SensingACS

Appl.

Mater.

In2t0erface19.1.5

Dynamic

Tactile

SensorsEarly

special-purpose

slip

sensors

based

on

displacement

detected

the

motion

of

amoving

element

such

as

a

roller

or

needle

in

the

gripper

surface

(e.g.,Uedaet

al.

[19.57]).

A

more

recent

approach

uses

a

thermal

sensor

and

a

heat

source:when

the

grasped

object

begins

to

slip,

the

previously

warmed

surface

under

thesensor

moves

away,

causing

a

drop

in

surface

temperature

beneath

the

sensor.

Anoncontact

optical

approach

uses

correlation

to

reveal

motion

of

the

objectsurface

[19.58].

A

number

of

researchers

have

suggested

using

conventionalarrays

for

slip

detection,

but

the

array

resolution

must

be

good

and

the

scanningrate

high

to

detect

themotion

of

object

features

soon

enough

to

prevent

droppingthe

grasped

object.2119.1.5

Dynamic

Tactile

SensorsNATURE

COMMUNICATIONS.

(2016)

7,

1122108.19.1.6

Array

SensorsArray

sensors

can

be

subdivided

into

two

primary

categories:

those

that

measurepressure

and

those

that

measure

the

deflection

of

the

sensor

skin.

Tactile

pressurearrays

are

by

far

more

common.

Pressure

arrays

tend

to

be

relatively

stiff

and

utilizea

variety

of

transduction

methods

along

with

solid

mechanics

to

calculate

contactpressure

distribution.

Skindeformations/deflectionsin

pressure

arrays

are

on

theorder

of

1–2mm.

On

the

other

hand,

skin

deflection

sensors

are

constructedina

manner

that

permits

gross

sensor

skin

deformation

during

contacts,

which

canbeadvantageous

for

grasp

stability.Contact

switch

arrays

fabricated

from

flexibleprinted

circuits.2319.1.6

Array

Sensors2419.1.6

Array

SensorsPressure

Sensing

ArraysJ.

Mater.

Chem.

C.

(2019)

7,

10225TFT

(Thin

FilmTransistor)2619.1.6

Array

SensorsMEMS

Pressure

Sensing

ArraysMicro-electromechanical

(MEMS)

technology

is

quite

attractive

for

producing

highlyintegrated

packaging

for

tactile

sensing

and

associated

interconnects

andelectronics.

Early

devices

were

produced

in

silicon

through

standard

siliconmicromachining

techniques,

including

the

silicon

micromachinedCMOS-compatible

tactile

array

capable

of

measuring

shear

and

normal

forcedeveloped

by

Kane

et

al.MEMS

force

sensor

wire-bonded

to

a

flex-circuit

and

embedded

within

a

silicone

rubberskin2719.2

Tactile

Information

Processing28For

manipulation,

we

require,

foremost,

information

about

contactlocations

and

forces

so

that

we

can

grasp

objects

securely

and

impartdesired

forces

and

motions

to

them.For

exploration,

we

are

concerned

with

obtaining

and

integratinginformation

about

the

object,

including

the

local

geometry,

hardness,friction,

texture,

thermal

conductivity,

etc.For

response,

we

are

concerned

especially

with

the

detectionofevents,

such

as

contacts

produced

by

an

external

agent,

and

inassessing

their

types

and

magnitudes.19.2

Tactile

Information

ProcessingForce

and

tactile

sensor

information

flow

and

signal

processing2919.2

Tactile

Information

Processing19.2.1

Tactile

Information

ProcessingActuator

effort

sensors

provide

information

about

the

resultantforces,

using

the

Jacobian

transpose:is.

is

an

n

×1

vector

of

external

forces

and

moments

taken

with

respect

to

acoordinate

frame

embedded

in

the

appendage；

the

Jacobian

transpose,

mapping

external

forces

and

moments

to

jointtorques；3

an

m

×

1

vector

of

joint

torques

for

a

serial

kinematic

chain

with

mdegrees

of

freedom.30If

we

consider

the

leverarm,actionof,

perpendicular

to

the

line

of19.2

Tactile

Information

Processingmultiaxis

force/torque

sensor

in

the

fingers,

as

indicated

,

or

robot

wristtoobtain

contact

forces.This

approach

has

the

advantage

of

providing

dynamic

force

signalswith

a

higher

signal-to-noise

ratio

because

they

are

not

masked

bythe

inertias

of

the

robot

arm

or

fingers

and

their

transmissions.a

contact

force,

f

,

contacting

thefingertip

surface

at

a

locationr.is

the

magnitude

of3119.2

Tactile

Information

Processing19.2.2

Solid

Mechanics

and

DeconvolutionA

basic

problem

associated

with

tactile

array

sensors

is

to

reconstruct

what

ishappening

at

the

surface

of

the

skin

from

a

finite

set

of

measurements

obtainedbeneath

the

surface.For

the

case

of

plane

strain

the

principal

stresses

in

the

(y,

z)-plane

froma

normal

unit

impulse

can

be

expressed

in

Cartesian

coordinatesasPoisson’s

ratio=0.5superpositionthe

stresses

can

be

found

by

convolution

of

the

pressure

distribution

p(y)and

the

impulse

response

Gi

(y,

z)3219.2

Tactile

Information

Processing19.2.2

Solid

Mechanics

and

DeconvolutionFor

the

case

of

elastic

plane

strain,

the

strainsare

related

to

the

stresses

byE

is

theYoung’smodulus

and

ν

is

thePoisson’s

ratiopassume

that

the

surface

pressure

distribution

canbeapproximated

by

a

finite

set

of

impulsesThe

sensor

readings

form

a

vectorThe

strain

response

can

then

bewritten

as

a

matrix

equationThe

estimated

discrete

pressure

distribution

isthen

found

by

taking

the

pseudoinverse

of

HMeasured

strain

with

assumed

5%

noise3319.2.3

Curvature

and

Shape

Information34Another

alternative

to

measuring

subsurface

strains

or

deflections

istomeasure

directly

the

local

curvature

at

each

element

of

an

array

ofsensors.

The

curvature

information

can

be

applied

directly

towardidentifying

contact

type

and

centroid

location

or

it

can

be

integratedtoobtain

the

local

shape

of

the

contact

as

with

sensors

just

describedthatmeasure

the

profile

of

a

membrane.

To

reduce

the

effects

of

noise

it

isuseful

to

assume

a

simple

model

for

the

membrane

and

use

basisfunctions

to

fit

the

curvature

data

before

integrating.19.2.4

Object

and

Surface

IdentificationThe

most

common

application

of

touch

information

has

been

in

objectrecognition

and

classification.

In

object

recognition

the

goal

is

to

identifyoneobject

from

a

set

of

known

objects

using

information

derived

from

touch.Inclassification

the

goal

is

to

categorize

objects

according

to

preselected

sensedproperties.

These

systems

are

usually

based

on

geometric

information

derivedfrom

tactile

array

or

force

sensors.

Recently

the

use

of

other

types

oftouchinformation

(e.g.,

compliance,

texture,

thermal

properties)

in

exploration

andidentification

has

received

some

attentionMany

different

features

derived

from

tactile

array

data

havebeen

used

for

model-based

recognition

and

classification.geometric

featuresholesobject

surfacesedgescornersFeature

setsgeometric

momentsLinear

transformssequences

of

surface

tangents3519.2.6

Active

Sensing

Strategies36For

dynamic

tactile

sensors

used

to

detect

such

events

as

gentle

contacts

or

slippagebetween

the

fingertips

and

an

object,

the

main

challenge

is

to

detect

the

event

inquestion

reliably,

without

false

positives.

The

dynamic

tactile

sensors

that

producelarge

signals

in

response

to

contact

events

are

also

prone

to

producing

large

signals

inresponse

to

vibrations

from

the

robot

drive

train

and

to

rapid

accelerations

of

therobot

hand.

Solutions

for

more

robustly

detecting

contact

events

include

comparingthe

signals

from

dynamic

tactile

sensors

at

and

away

from

the

contact

regions

andstatistical

pattern

recognition

methods

to

identify

the

signature

of

true

contactevents.19.3

Integration

Challengesthe

difficulty

of

connecting

to

a

large

and

diverse

array

of

tactile

sensorsthe

most

difficult

problemindexterous

hand

design

and,to

a

large

extent,

this

remainstrue

todaywireless

sensors

orbyuse

of

clever

bussingfor

power

and

signalconnections3719.4

Conclusions

and

Future

Developments38In

an

ideal

world,

one

would

incorporate

all

these

tactile

sensors

in

a

robotic

end-effectorwithout

regard

to

cost,

signal

processing

or

wiring

complexity.

Fortunately,

the

cost

andsize

of

transducers

suitable

for

tactile

sensing

are

steadily

dropping

and

the

ability

toperform

localized

processing

is

improving

with

surface

mounted

devices

on

flexiblecircuits.

In

the

near

future

it

will

be

increasingly

possible

to

fabricate

dense

arraysoftransducers

in

situ

on

contoured

surfaces,

using

material

deposition

and

laser

machiningtechniques.

In

this

way,

robots

may

finally

start

to

approach

the

tactile

sensitivityandresponsiveness

of

the

simplest

of

animals.Transparent

and

flexible

fingerprint

sensor

array

with

multiplexeddetection

of

tactile

pressure

and

skin

temperatureWe

developed

a

transparent

and

flexible,

capacitive

fingerprint

sensor

array

with

multiplexed,simultaneous

detection

of

tactile

pressure

and

finger

skin

temperature

for

mobile

smartdevices.

In

our

approach,

networks

of

hybrid

nanostructures

using

ultra-long

metal

nanofibersand

finer

nanowires

were

formed

as

transparent,

flexible

electrodes

of

a

multifunctional

sensorarray.

These

sensors

exhibited

excellent

optoelectronic

properties

and

outstanding

reliabilityagainst

mechanical

bending.

This

fingerprint

sensor

array

has

a

high

resolution

with

goodtransparency.

This

sensor

offers

a

capacitance

variation

~17

times

better

than

the

variationforthe

same

sensor

pattern

using

conventional

ITO

electrodes.

This

sensor

with

the

hybridelectrode

also

operates

at

high

frequencies

with

negligible

degradation

in

its

performanceagainst

v