14 MECHATRONICS

SiGNAL NIPULATION AND

E It has hwo cqual reststos as a voltage divider, that is, R,-8 RThe output of the CONVERSioN 145
cicut with a
positive feedback t

s h A T B. ASchmit trgger Ouput oncillates in a sy eeles choalit trigier eie npur otfers alitional suise
colessly dhae lo RC beTwork fendhack, which resulls in the conveniOnof a bistable tnulti-v ieve a
ceR Ouipit signal
imanity
to a stable mult-vbrator
hyste erosie APPLICATIONS
TriangularwaVe generation (chackAiakan ocao c tor
Shctation of MORE OP AMP
t as sbown in Eigs a) andt (6|, nrespoctively
a
triangular avelon
wavef
entioned applications, 0p Amps
t aforement arE also used in frectilien, ero creaing deocun
t ro ee-to-voltage andl
voltage-locunntcomvercn.eic. 1 aE G cd n De o n g
ncr dade
1Cs are lkstod in Appendix C

ymangilar e Sone op-anp

U1 Precdsion Rectifers

An Op Anp can wotk n aupet b e Or a

prectsio rectiier, u shirwnt in Fig 40a)
Tnang Dp

b)
Oa nanguwave geneabon 0
Tangular wive output

42.16 Comparator as Null and Zero Crossing Detectors

A relcrence voltage anl an unanow vollage are applicd lo
P non-IVCTting and
imverting terimal ot a

e
tviy.
olage, that
he ull
,
detector cin
The statis of the unknown a Ciher be a positive of
Hg40 (a Preciion recter (bi Atetnate half-wave recthe
rctence
eacen input vottagts, the
reierence tnput is known. The ce
Aa

ae uretnent f the input voltage difference multiplied by thegain

gain (hefthe
(G)ofth 9 Amps as Super Diodes or Precision Nectifers
Glef 10 output is zcro. Let us
say that the votage limit isS V wih a pait appledvoltage
a. herlird
appliod input voltage is negative, the diode has negalivepeth s t r c
a
t e n c e of 5 uV e
in case of a
zero croisine d
aetorm takes piace, as the output of theparat check the time at which a change in polarity of h Nlpait curent ot the
c n .de cnducts so that the Cp A
changes ts
poianty he
comparator outpuits that point of time when the AC wavefom W h e ppu e feedback effect
hat 15, Jow, lor a
n g p , feor positive pulse of the wavcform an
ncgatlve pulsc ot he wavelon
the v
The thrrhold voltaae alnot cqual to the notmal a
2ero. It is A put becomes
i s circait is not used because if its input becones even s W Oe Ane
Selection ofr tomporro
an le applied voltage, leading to sataration
ae
hiod Thenefin, an

AN g pocitbcations, but they consurne more O f the saturntion to function again.

1his WAY,
powir. 1HcncE
consumption, for e O e application and features sich high specd and o A
as l e circuit used,
is as shown in Fig 440O)
ATion oscaliatoe, siach as an A Cfeaing a hig-spcet clock signal oy ng
i

nps as Alternate Half-wave

nstor ogic efL) whose speed ranp M Rectine than OV, and the oupr is
z e 0 becaue ,
virtall

ce atcs de to the hysteresis ca

Lae1D, is off and D, is on for an input of more

d, tar is
nd, that l, 10 clurrenit hows a
a
he pat sigal: This noise signal reules in un
anpiy

c a s e of rising as well as falling voltaves, Therefoee les than zero.

Howrva,
te opul
y s l c m i s . if exit, an external fysteresis
D, becomes on and D, off if the iaput is

cincuit iv seieed i e e thie oroblem oof the inout

 SiGNAL MANIPULATION
186 MECHATRONICS AND CONVERSION 1
U6 Woltage-t0-requency (onvert
432 Peak Detectos etiws
previous circuit results in a peak delec Citu useful for coverting, an output voltage sijgnal
441. The cireait capacikr aintats t a frequency outpuit signal, ax sbown in
level of the sipual. The swich is used to reset the detiectied level.of the o this circuit, capacitor C is chariged and discharged
1 the charging voltage o1 o
gnal
RappenA Mhen
red tocharge a

433 Voltage-to-current Comverters appicd.

he
ampa o outpul voltage
e

d voltage is ot the oupt voltage ts

Sone transdicers produce ONutputs n teritis of veltage, bowever, it is
Fig 441 Peak detector Saod, but the frequetcy eQuput, voltag
rejuired to be coeverted 1o curent An Op Amp can produce outputs oertional to Chanu 445
shown in
Fig
in terms of curet for agiven input voluge
5
As
SEn
een from Fg 442 as
saueform is

curent , towing throngh lod resor oow Fig 445 p

U hequent0-rotage converters

comverter
w Le show a teguy econverter (vC),
where
Figure 4,46 ef Which ma lepending on the applied voltage sijgnal
and e sae cureit pasies t p h A, 1oo dr outpul of
the
cotnpai tching, say from
to -ve swilching, and
+ve

topucrcy charge the capacitor depends on the inpt votage s

apacilor 0

Therefers, 433) ig442 otage to-curent

converter thisway, the e i r e e
verts the frequency ofvoltage 0A voge proportionl
to the

Hee, Bhe output current is

proportional fo A mes the
Og
4.3.4 Carent to-voltage Canverters
Capiciir voltags
An09 Ap Can output voltage for agven input current, as shown in Fig 4.43.
wich
r c r o e , te oupur votage ts given by the
Cwnpa churgng
otlowing rela
9-446 equencyto-votage comerter

Thas, the output

voltage is proportional to the Curment
p A an pe c o act as a
44 AMPLIFIER ERRORS i h n ne
voltage-controlled current onder to hting
back Therefoe
anve
in
Fig. 4.43 Current-to
e oued volape souroe. Similarly, it acts as a voltage a Op Amp crcuits,the open- whichis known as a closed-loap u
Dge soueapd
cunienlcontfrolled curTenl source loo.
uablerange, t is lowered w tint amplificr and a non-mvertmg
Abasic feedback circu
term
3.3 Phase Shirters
(0 to 360) these circuits does not incluoe
he
the
ufrequency
aOO 0r
mesignals a
de ofei etam angle for G GcL
Posot ofa a nverting amplitier,
avefom.
lt is used in measme
t o allow the
required signal level
agc and a
amplifier, Ga1+Ga
O cT 1heie require phasie micasurement or laanoe-inverting
applicatiotis Figure 444 sbow a phase shifer circuit As hete tor Gez
(Cosed oep)
heets the

alfready discussed. gain a grven by the following Gd Ge is the closed-loop gal

froquency
untl the
lne

equation Howev offers no change with

Hg444 Op Armp as phase shite e So OL (open loop) in the anplifier s B000 P

where 2 and 24 are the

input and feedback impedances, respectively. similar to R, and R, in Op Amp wcben
ets ca eder ko the onine reioucer in the cumpanion
 MECHATRONICS
4.5 SIGNAL FILTERING
In Chapter 2, we have studied about the changes in the physical parameters pertaining
t
yatem composed of senisors and trasducets, 1heC eanges tm e punneters are
normally comachie
fom
anniroaces
electricalnoise
signalin the
usingouiputtranulucer,
a
but the conversion of one ofcnergy parameter to
clectrical signal. On the other hand, there exists the possibility of in
of
emons in the transducer output signal, which affect the measurement of the actual value due to introducs
thee
n wheh it operating such as tenperature, pressure, clectric field, vibration, dast, and ma
Therefore, the transducer output clectncal signal ts passcd througn a n e t ) to remove the
unwand
ntroduced during convesion Thus,
htering the process is of removing a certain band of
frequen
a sijgnal (transducer output signal) and allowing transmission of other signals
Th for
amplification
filter is determined by the number of reactive
components (L and CO used in the filter design The orl
The frequency range
of a signal that is allowed by a filier is known as pass band, and that
allowed is known as stop band. Signal
froquency range outside the pss and stop bands is known as t which is
off frequency
Pass band Itis the range of frequencies allowed to pass through with minimum attenuation (c-3 d
Cut-off frequency This is the
frequency at which the
output wavetorm of the pass band
Stop band tis the end
drops to-3
of the response
4.5.1 Quality factor (0)
The quality factor
(Q) of a tuned ampliher represents its hgure ot merit. tis equal to the ratio of its
centre frequency to its bundwidth.
The characteristics of an ideal
amplitier are determined by the
geome
ci
quality factor (Q) The quality factor 1s gven by the following equation:

Quality factor= BW
(4359
where BW is the
frequency bandwidth and , is the frequency
Basic Filter Types
There are generally thwo types of filters:
analog filters pas flter High-pas fler
that filter analog signals and digital filters that filter
discrete or digital signals. These filterS are further
Pas Siop band
divided into active and
passive filters; bused on their SuopPhus ban
characteristics, these can be classitied as folows
4.47) Highest trogucia Lowesd Iegky
Low-pass filter ftallows all frequencies from 0
to some highiest
up ala d-slop thltet Band-pass
frequency Gu) to be transmitted.
High-pass filter tallows all froquencies from some Pas Sto Pass
lowest
frequenicy 00) value up to infinity to
pass.
Band-pass hiter lt
allows all frequcncies that are p
fregung
specthed wThin certain range of
frequencies, that is, la-hi=
Band of

Ua toJa) to pass. characternsno

Fig. 4,47 Types of fiters as per their

Band-stop hiter t allows all frequencies
implies that it stops the specihed band of except aparticular band, that
ansmitted.
is,
sh
frequencies U
 SIGNAL MANIPULATION AND CONVERSION 169
Filters are also classified based on their frequency range of
operation with RLC components :

high
frequency filters (1 MHz) and low-frequency filters (1-1 MHz)

Passive Filters
Filters constitute passive elements and use external power supply with active such as
components transistors
and Op Amps. Passive tilters are built using resistors, capacitors, and inductor
inductors 1s to oppose hign-frequency signals and allow low-
components. The use of

frequency signals, wereas that ot capacitors is for exactly the

opposite purpose. An RLC Circut is suitable for the minimization
of signal distortion using a high-quality factor inductor in series
with a resistor tor nilters under 1KHZ
applications
Low-pass filters This type ot tilter is shown in Fig 4.48(a). It
allows curent to pasS through an inductor
capacitor via ground.
or a
The fhilter 1s featured to attenuate
low-frequency signals by a small
value, as compared to high-trequency signals the
in
trequency
range ot 0 to pass band. They are used as signal-conditioning8
as most ot signals being transmitted
Components, the informationis also
of low trequency. A noise
are
or
introduced at a high
signal
theretore. a low-pass filter is used to block it off.
requency
Hgh-pass ilters Frgure 44806) shows a high-pass filter It is used
Hg4.48 (a) Low pass fhiter
to attenuate high-frequency signals as compared to low-frequency
(6) High-pass hilter
signals. A pass band of all frequencies from some specified value up
to intinity 1s
permitted to pass through this hlter
such niters, resistors along with inductors and capacitors are used w
n
Eet the time constant of the filter circuit.
to

filters Figure 4.49 shows band-pass filter This type of

Dand-pass
niter allows all the
a

frequencies of the signal within a specified band to be

a

transnitted, as stated previousiy Giround

Fig. 4.49 Band-pass fhiter
Band-stop filters This type of a filter stops all frequencies within a
r c u l a r band y D from being transmitied. Figure 0 shows a passive o w-

banid-stop filter.
Passive filters affect the performance of a filter due to the flow of current

gh passIve elements such as R, L, and C

pplications of Passive Filters The following are some applications of
passive fhlters:
used to nlter out high-pitch sound noise of g.4.30 Band-stop passive
-pass ilters are hlter
speikers, subwoofers, broadcast,
ctc.

. Harmonics present in radio signal transmitters arc filtered through low-pass filters to reduce the
etfect of interference from another signal. Low-pass filters are used in digital-to-analog (DAJ signal

conversioni to reconstruct continuous signals trom sanpledlowsignals

cut-off frequency range. It suitable for
Incaseof DC, ahigh-pass filter offers zcro gain withina
called a De blocking hlteE
is

biocking DC signals, and hence

7 MECHATRONICS
SiGNAL ANPULATIOR AND CONvERSION
Actve Foites
cicet sct 9 p
sons, and requt
and require ters A band-pans fhller creed by
tomhing shighip
Acte titers censist of active colemal povs bown in F g 4550), 1he oulput fespesw for a firnt-onder ci

le A d
Lm-pafliers
ke a perfect

s 0 Howeveapracthical filier circuit has a resporse of 20 m/

squar
Bandpaaslter trequency h h h
Len-pas
FE nir circuit In case ofa secondtucr cis gie and Co
Sor a sige dor to the ideal situation by offering a cul-aff at 40 dB/dec
We
AS3aL wi rogone i Fig 45261, Her, vofagr pain s below Su (Cut-off freque w
tonulae
The atematon tacor and cul an f m y
S
g

36

ww Fig. 4.53 a) First-order high pas fite D Second-order hegh pn n

30 dnibecae
tic

Tiae (
(h
fimy
Fig 4.51 lal Fest-order low-pass hter (bj Hespone ot first-order nite
9 e pb
DjOutputPEspoeOeopu

w sadcak
w

nd arder iowe pass fiter b) Response of second-order n

(a) Band-pass fiter lb Bunopaa
Cua-off frequecy fa.C 4
Fig455
as her sing
igh-pas filters outpuf voage demne the value ef Ru
Aample 414 A ensor

hetr inpul and Fgn4$3ajand

outpul relate
(b) show afirst-order and
second-arder hup
a
r tbe suppliod trgucny
tage, he c e a t i o n factir danl c freguency areandgiven by theyJolow0 K
(b). res andi7
o
o
The cut-ofH frequency
Atesal tcot 4el
(43

Cut-off frsqucy
RC -2i142x 50 =J14 oad
 SiGNAL MANIPULATION AND
172 MECHATRONICS CONvERSIGN
alher is designed with
eng changnd o a tes cmee freqey
ime cean 09ss l aty Chang ain (0) or banua , The values o c g a e s from o M will be p

tonmu
t m e c a s t a t of c e p t s gm dhe ota
44)

Example 4 S D e e bn %A), tor the tilher cinuitw h e e

narrew-tan e y
d 1o attemulite snge
Podcea
Salin Dhe ciit and femt a gvn.a f l o 1300 Hz Most or
ng N
Caef y l w pau thA2RG 331425x10' 01x10 x 10'-5i8SHe t s and wuf-A-W
Atier
Caef fngumy ef b 2x3147
2x1142 x10x10 x02x10 79.6H circuit with low 3 a
o
0 can be increascd by intertacinev
sbow n .57a)nd ().
lower with the filler, as
The ooch 1re o
p p e s p I voltage is s9 VDetermmine the value of the 443) Fpisy
2xRC
ed
Anech hiter 1s g 457 a arrowband pans he

F-2-2-7 b Output
) ispone
design the saoe-bund-pas Siher ibown
oge G10.000 termine thee values of compconients RR and , 1o

457T0) The fiter is operating for a centre freqguency H,

sach
www ain A s e that all capacitor used im
the circuts have cqtual valus
10
13.312
arrww-band-pans ern has p
of a lier Is Ued for hitcring a
specifhc cetilhe
ftoque ae of4coai14xiirx001uFx12
multiple feedback syitem wih a sin
nt
Cieneraly,i uency of applicatiom ouaie f
2nCa0o 2314xitrx001ua w100-12

2x3.14%1Hzx1l2x100-12
38147kE
w Band widh-fa-h. 14%00tuF Tkitr
7 with a humiting
d ot t e y y 3
De
an outpul olage
Athemocoupic produces
Seladim
the citcait, C-0.094 uE freqaensy/
d Fr
EKat23.14 x500 hed with 3 4 kkG reuo
mor, hat t, (A23 c e
pe,

9456 a
umo band pass fiter bi
OutputPespoa NO 0,094 uF capacituns are connecico sod in e

To und the u o a t o n s of active filters Active filter curcus ids etc A chanoel sclec
s d m tbe cincuat, the
following cquations hi z ) for modens in audio s lcpditioning compone tio
(441 s %
GHz-rangs (2-9 GHz)band-pus stion system c
Anps, filter, and ADCs are require r furthet processng
aducers and sends them to a compuiet
 SIGHAL MANPULAT AND cONVERSION
73
do not u he p Amp. These vulag
453 Comparison of Actie and PassiveHes diodes
Thewe diod
aec see lied so a fne
mli
to prolect continuas cuet valura
I5 Oue to
Active he 1T Aeoe under control oonditiots such as thor
a,pund ,
L. t i e mm p s c t mes p A n p s and traraisor dition 5 sed due toecesiv
C Surt-o
shurt-circuo
touching of conducions Heat, geme
dA
so
s
dt , foliowed by
toilow
ala -PrmP

hgh pain the time. / the current,erelstance, and i the eto

pr a
het/poc,
This condition s cauu
dact isa Ground t on d u paocoming
on
ha e alo
t a c t with the object, he/she grts electncal sbockas
an utput loading
censideratioe d condition This conditon arises dae to placing to0 a h Sd on he n fro
Atve fitets do sot use inductors jam in machine, poor s CE w e h resalts m deteniontien a f wire imialatin,

M
s
costie than
u m a e ala
a
passive ilier moloe trasformer follow ed by overheating. and short circut
large cument
10 kis sable su banie i
Acurrent-carrying Syem pa, ner a he soure af oute, eus
BUFFER IC
0 p Anp hutier circat (IC) s used for the transfcr of
volitage from one circr
P
c a coupics two circuins, similar toa
tallic conductor When &current abovea specified value fdows through it, its wire prt meled
d i cireuit is disconnected. In this manoet, a device is protected from the stresa of exc
v g cureet nce
used t any arther component requirement This JCn he fise is melted, a new wire is placed to allew current so pass for the operation of the devioe. Uer pes
5-18V. Tbe
e oftz Bt aninnm voltage level ot 18 V and
voltage supply o rangE e tectablie tuse
inpul-outpul relaton t gven by
theolow ua Circit breaker ltis used for heavy loads h senses the maxim or minimuam valr of te c u t and t n
ich that gain 1 he rcuit above or under the set vaue It operates on45
thermal or mapetc acta A

hie
wns on thermal principle, a shown in Fig
whee curTent passes fhrough
cacesstve reiay cont, 1, sets the suthcae cpy
haget,
47 CIRCUIT PROTECTION c D so as to disconncct the circuit as SnoWR

9A
a T r prutecthon gainst tene

0Sbo cicat,
common die nd high
g s of maden On A e ha
c o s t ef roductioe in som
p e c d of operation, dynamic
E However, lled

protectis i y ICh wley

tequire fcuts Ha458 Op-Amp protection cl

prolceng d er
fe
pu kermimai, as shown M FE
Hg 439
currernt sensing t m e t a i
p

ver-
 12MECHATRONICS SIGNAL MANPULATION AND
CONVERSION 177
47.2 Resettabie Fuse
dgital cire with
e rom gde ture coeftsc power circuit Couplinjg of a circuit can be dons 2 aprudect the
e l o s the current to Bow even after the curres
mens in oul denending upON the reuuite , tor exanpie, a cnsciti
gie
evels with increases in resistnce, so ai lo peodect the circut unl fuse 1s tripped. However, theTe s
gal
n
transmissio, but o to pO n tranmision.
and reception ota s i g l P p i c a t o n i motor
Fjgures 4620)
peed
and (D)
meaurem
mit of cutremit fow above whach the ccatt trppe Abpicarectabie fuse and its characteristics are s ment. pect
.ia aN ( , rep oncettis fise tmelts, it trin
able Fase
hi PTC H allw the eeenected oouinnent to oneate evceta te Furnber
During the tripped stale, a resettable fusc lienits the curent to its leakage current vae in the rm eminal
of mA h
eher featurcs ofa 9EaptcT 2

Citond
fose matial
g462 (a optical ouping diode (D Motor shaft speed imeasurenent

alre ecussed in Chapter 3, transmt tignal

Cue cinat bieakincP AnO M circuits hut not for high powcer ine. It be used feor
diital can
analog as
tl ar digital signaltransmission over single o r multi-chatnel appitcaion

Coupng
ion
g461 la| iesettable tuse (bi Characteristies N e a l number of primary
d seccomdary tums It is used De-to-DC convertennpu
4.7.3 Thermal Dissipathon
nd digital and analog circunt coupine
cift 1s Enpiemented through a heal sink, a metallhc
pint cone Crcus, ghetc coupling15 as0
)AC 3
acfhi in the transicr ef mechanical porwer
d
urrent produc edece when a put Tto ot
trgue
DeaT pat
iei rc
d ccut
cotponent, by increasnu the 2.14.7)
E s aho uiod in place of a transfoiner for coupling
component Acoppier-aluminium-zinc plate is used as a heat sink. Aprinted
UD coppe-plaled holes to alow geater area to he
exposed in air. This allowk
Cpc c a l magnetic coaping crcut 1or, trals
traeston
coulig of
e c e from bcating o w in F1g 4.63
Hg. 4.63 Magnetic
n e r e n c e s between p DIGITAL-TO-ANALOG
and
output-side voltage and cuzent levels h ANALOG-TO-DIGlTAL AND
e c c E , he mote the heat produco
CONVEBE ALONVERSION:
wEASTON ERUCESSES
4.7.4 Motor/Circuit Isolation Schemes enAP
and Cla
o votve anaiog-to-dgal

o peo hecancal et r
s ad froma col toalog (DYA)
work, such as stirming, motoring, farning. tractiomin
oR Cun, and power ratings, which are atways higher ailowing sectiona, the comporncots and devices irvolved in anlo ioved in these cothesio
SputctE cotrol system along with its suppen r e dealt with briefty for ubdersal
angng r o m nA to nnA with a n cte and at a very low current t
pulses. n

e at a lugh voltige level, safe oneratin stem Sample and-hold Devcs

gnals ino a
traof c to maintain it for
troi the I c e is uscd to Capture AEYL d vot a const
OE c couging 15
reqaireil the captured volase
hod device locks or freezes
 GNAL MANIPULATION AND CONVERSIiON
178 MECHATRONICS

operations are performed by

certain
period of tine.
In prachical dat opaa Anakigime
upickCh, peak de
Sungle anit, called a sanple-alnt-0l
an
ev elcctons,ad ADC
a d DAC devices

Operation
yby the controller to
re .0)
sboas an S / circLA Sanpe
coa35sue the
coatrouc o

ciose the
or (EET) fast switch, it allows an analog sinal to
witch. 0h c hoach the output of the batter artplbet H d track

na its voltage due to its stored churje. This capacitor is thus charged by its own
well as hy the leakage curent Charging and discharging of capacitor make it volatile within a D
hold tim
Figues 46b) and te) sheow he anpic o e timie atis in these
figures shows the sanpling tume d u r a t h Ihs ime s 0etecu y u e t e constant ot the RC circuit

Aperture me hetwen hokl and

Lero-or HOId
n an Alxhe device pertoms sampng quanttation and cDding or cncoding, However, a DAC performs

deseding ot diga words itple vale of he gnal acte-ne 1om,tojlowed by the comversicn cf Fig 4.64 a) 5/H circut tbj Sampied gnal ia SH input-output sgnal

n esafnple unt
hold (ZOH) of DAC Figure 4 644c) shows a tynical Pseoence ntod h d
c o c a the
49 DIGITAL-T0-ANALOG CONVERSION
analog sgal costier than a
DA
than an ADCAh AD, De tmore compiet, s sloW responane and
ADAC13 simpier
UN ceact
wich 91 Basc Elements of DAG

Cis used to obtain analog values

fot a
ga a8
leck iagrath o a
Apl worid. gure
red to he mpic ce
al

Z0H unit,
T
o g c eo
o3a
an Syi
DAC, which consists ot a decoder,

A Logie CKT
Holbing Aal

Hold
bocK g r a n o r e k
uncbor

g.0 into a Dumber

of anpude-tu

Smple S&H oup g purpose is to decode the appliod

digital word
pecifted sanpling
Thia component cxtrapolates an anaog efetce
retice
voltage or cument our
This
1s uscd fo control the sn o the applied digital 0 the
et
p u t ferrminals
of the testslor ne witch, it closes the s
a n b e r Appears at
the
SO s hinary '0' ooenect
t h c reference voltage, Howevet, ap

nc (0 network
DACx
192 ladder
Types of DACS witr PACs and R-3R
 GNAL
1 MECHATRONICS
MANPULATION AND CONVERSION
mplementetion af 4-bit Weighted-register DACs
n a c is shosn in Fig 4.66, The output ot the
neta B90cmed by the
of m-bit binary nework containing parallel resistor branches fomga W
Wghied fOstom

wwT
4D, npaln weighd

D
4

Groend s ial values or,

Fig. 4.66 Fourbit weighted-register OMC

The restslor the iea

gica
in DE8 b as e of4 he
output of the
vem by aie
tolewiE
voltage is

es
4 444)
MSB
he values of a
w w ww
The valaes of the sumening resitors of theO
connected thnough an clectroic switch to the (referenoe voltage) or so ground, When abinarv1 ig 4.67 aR-2 1adder rnetwork DAC b tquvälent circut for 100 dgtd ingut
t ot te c h , it closes the rwisch to cocnect with the respective weig
the agiat nput b gpren in
E o e r hanad, a Denay epmects fhe respectve weighiod resistp 1 p 0D, , the equivalent circuit conependng 1o
TOund. Ashe operatiod aunplahcr ofets a
bagh gain, 1nput mpchdchoe a
VETy o, 0 that tae volge a eresoee, the Tesitance w u d s the np dfA hode be R

001,
1Dy are gro wo ien wile as folloE
0 MSB fu
sa
n
(e,test
wlches to ground, and the last switch to ie 1

he outpot of a DAC Armpliher generates oscillations and spikes in the transient output 1heret,
e in a DAC to eliuminate these
2R-28 M ne
spikes
he swilchot the LSf branch twdching of 0100-D,DD D, bit D,D,D, artpond levE,
ix contnected to d the other three ewilches to the grounl, cof
24, bat the iqpt volage
it

oa digital word
of Col, outpul volaae is
tbe grven as foldow
Bi 2 , and the sotal equivalent resistance again
V x-SVx(4k2)/20k0)-IV erclee, R-38 4
Since aod 6
iniput 0010 inpul and 0001, output isalog Values ae
y,for digital
en that connecting to other higher suhseqient bits will result m outputs of
8N Jor the binary codo values of O10, 0100, and 1o00,
respoctvely e law o
of the oitput volage ievesph
8-2R Ladder DACS s p
15 the sih

u
C ven by the following epresso
a y eo valies of siators R and 2 connected in a ladder tashion such that its so
a t rence ee towarts (2) terinating teststor (left drgital input) trom any no
Nolc that the
407a equrvalent trestslanice atany level always ts
s2 MECHATRONIOS siONAL WA NIPULATION AND
CONVERSION 1
O in general focm, for w-bit DAC, 1tis pven by the folowing expression essive approimation

reratios (singie Pe
r eal
fmp ADC

ler on
The digital input applied to the DAC is generaled by the microprocessor On coipletion Parallel ty
fADC 15 ctu
anaiog val, he tntetpal latc holkds thas
va
the pext
Analog data ate
ready. An ENARt
E a l ADCs are availas on
nven, cost acccy, and
made1iGHIC9 by
the mhicrnprocesor l b he data AEr getung the analog voltage output, the F
, he ENABLE
y o h d f 1al
scale (1S}
cant bit
g n becomes Lw0 1, tne
c
1SB, that
ifthe veference vellage is 10,for a DA u ges at bits
D, D,D, ADCS
D, are5V 2.5 25,nd s W, respectvely, tot a HiGNO)
value 81 Sucesswe ADproximaton

pprosimatio Ppe e deteminatin of the weght of

F i e 4.69). In this oetbod, an
unAD
mple 4.19 the dgalhina-coel p , n s
oqutvalient analog
t pat o r i n e weieht of the hie e e
Soii The sch a MSB and l
shant brach uft c o t i e l e d o bie reterence
r eoied and anothcr weighit of a smaller valoe is placed irhe ohieet is o l l beae
vollage, so thut the m
R weight, thut is, objectweigt, anodhier wright of a maler vaiue b added to the weight
iready present and dhe measurernent ss carried out 1he renoval of the t t wght s kno EEO

owever, placing p c e e kn a SET)

Simiarhy, if the weipht of an unknown ooject u t e tan t p
Hete, , and 4 k
wiR

15x4iax s20 i0-15v e donieted within eetified a

efer efer to the word lengih of ADC This will be made cleur hy the folkrw iag sectom of
4.10 ANALOGT0- DIGITAL ONVERSION A N OrDOess

g gnal continuous analor al (v

D Wsally perfoms the operations in tr foll to the dipa
mpde The blick dagra an Fig 468 shows its funictioning and is discussnd in the cn
Dipital ale
a a o g gnal hatntaned at fiaed periodic intervals heoretically, the holdag isqualt
t , e AD cpnvesion time a Dot zero, lo reduce the etfect of sigal, varjataa
nalg dig
e i e util the conversion is completed set ligaal "
The funct

a l Mgnal ootpu
al
Qua
uar Lacoer ck, a comparalor, DMC,
a na

Dglla eure 40 shows that an SAA

o the ADC are et zer
o
tu
ller: At the start of the conversion, all the ots
e MsB is then set 1o T (he
bit (MSB A
Rig 4.58 Functional biock.diagram a e with the analog input. lfthe input i greaice e n tarnod on anil coarod
representation of AD

p u o ah AD 15 usualy at analog t u t h e d an, otherwise, t Net fo 0 2

d the &
signal of a voltage, which ts
quantie
o i c e is purtitioncd nto 2 discrete
rang h e n a status line tndiçates thal t e
c
e , fibcr of bits tn ihe output signal sbould be increased at
e
hat bs
1o havca OR
e t s l o n tim
the cost of bomples knou
EEon ot an AD0 ms depends
depemdis on
o0 e a
the.conserion ine
clcui a alable,
aaiion,
and the mast oomonly used ADC: are as
fou huen 100
 S1GNAL MANIPULATION ANO CONVERSION 1
MECHAIRDNIC

Find the digital value for an S 4bLDC, if e

he tee irsndueer log output volags fnd to t
i f tet t u
5y
J27Ma rereoce voltage of
SA C
diy an ao Set D-1, thereforr, output 2V-25
ar weknsow 3.2172.5; thereforE, D 1ocepe 2.5 V
Sap O SeD1:therefore, ouput5523325
we k12178,75, therefovr, set D=0(rject15
2a293.125W
Gagr ll SetD, hereoupu
3,125 Vi
erial thigital
Cenparing, we know ett, set D 1 o e p t
217

theretore, outputUl25*52x2N2*2)-34375V

Coparg 343153theteotetD-o
(Thandt)
o d t a l coversion

Example 4
Os moerving e itart ef cevesien (C)counand, e SA ccareu to 0 and its MSB s set to 1
Saluun An 8tADKquryalcnvacs
ae copered dcompund o et () or rehet 10) based o the
follow
The mbil.sucene pprostot AD pec o
g bubsection Cpare
Dpertien D, D, D, D,D, D D, D
, Reset 2,5
bit S/A Analog to digitaf (amversion D Set1900000 et 125 9375
d
aalog m al tor quvaient digstal yalue, to find the m-bit digital value fir
gvtt ataleg voltage , use he Salowing
2D. Set 0.625 do D, Set 00110010P D, Set 0.97725
sleps doD, Set 00110000F D Se 0,9375 do D, Set ot00
sMep 1 widey2al npar W he gen analog vollage , se or MSBof Lheteit, tMM
A W p t plal wO 00110
MSB
,
E
9 for

4.11 SENSOR AND ACTUATOR INTERFACE

u r , oe hy i add this valuc to the previous set of
valucs to
compare wth the Frvs
g lge duing sep1he MsH is set to 1, comipuare with more sensos
to make any thehoic
ape eeh
that
e the bt nght t MSBoderwise. set the bit rightr tvnes of transducers have been discussed, alog w
so SMSH 0. Add this tesulk to the prevjo result, and
Ma hsical parameter(s) o be heasure
Sep 1, reach a coltolie
uch
a
MS a t to 0,cempire dnlywid 1f set the bit right to ignal This transducer signal
electrical has to

therwiae, set he bit rit to MSB C

NS E n a b l e logic controlier,
wich
te a A rio
AC are 01 'or 00 1or the previos ransducer Output clecthcal signa p with ADNT 1Oo get the digital cutput for
gFurther, dieide Vby
r
2 e previous sct ot valcoy plihcation, manpu
and
mal sinal conditioning is co
rh the gren ng t
valueCmparc with with
f the previous resaft is 11', conpl i n this chapter, with passrve c
O
ro a 01,rcomparewithif the result "00.
terfsce with sensors and tra nction as Pet
an
tbc ghe e
is
If this added ve
Similarly, actuators are the final conirol dvCe p iinelemented in an analog
nb i t "1'se
et
Nw dgital
0
als
.
b,en, Set
F01, 110or tóe Jor prevous set t, and 011, Oulput sugual, whicth is etrolir digital output i o a
ument; thereiore, it is turthT
T e actstor to act pon acsordingy n

ep4 a DAC with required signal comito

Kepeat the peicess of with signal-conditiotng a
divsdg, alding
a
1unl al pbit wonds an led Thi ting the next bit 1 for or discasd inCh Befr to Table 43 for a list of ens0r e i c e s is illustratied in
uge with g co
all net bi i
rhe calcalaed dital qualent numerical digital rditioning devices An example of interfacng Attain
pa
ns thal there is no neod
o the piven analog voltage at any g 471ta)
to
proceed turihet.
 S1ONAL MANIPULATION AND CONVERSIOH
ECHAAONis

Wheststone bridge ca
bridge cireut. Wben there isno
Wheattnne Do in, be
nd wih a
uput Ro
An pu h e hdg
A eonsted as shrwn in t o tor
gmal amplik.
erting and to av
t
a u p u t is gran ty R(R
Bob - V Anied beile
-mujge ouput

noitioningd
o o n g oevices

Tabie 43 Lto enr ou

ngai S k n rmguired

Circut paratcier imt Cand iheir

dvideLmite bna c g r e n t level chn
sgracondiuoning devices for
strain measument
Fig. 471 a) intertacinpo
pu ties, IAs mable gain
b Using 0p Amp for bridge output ampihcaton
gal . d
PROJEGTDEVELOPMENT HELP
los5hers5ters specifcally desined to s
jocton ofS0-60 Hz n o n e

aders unt thscp M

ust e
mrted eto dgal
LincariatiR CITet eane these controilert understand only
ADC a r i o u s types of design probiems digtal sigal The selecsion af anoranulcg odgal
Analos
the level of working of analog computen coersicn i o
Dpa Sudents have understood how a trans
neifier elipeer, clamper, comveriet, nput, Jolowt
ioveher chugo a eo duee e in Sten 3 of proiect developnent help wth the bed o
nie wvefies diode, SeRTRIC, DIAC, ete)

Su an Modests
measutement and thus in control action, This signa, utable harchw
as per the requiremen is thern Ted to anoence P

1 Polld u rial and for spkpurpo raorid implementaticm equires anaog

Pallel a erial USARE, LAR
S a l o pamlel fam Wto m comparison with another signal foe sigrali for an Cs0
achievethat d
making certain decihion through arithnetic
Tunctons

o addition, Subtraction9 e cured in 123 csesof pr

ntegration, and e i e dewlooment help to get the co
Sengle gecime Moreover, if the output of a trarsducer is expressed in pam
erms of curent or frequency,.tcan be c o n v e t R
ur ofdevices
iCe versa. Lust orica t o W i e d o n
nd fiscussed previously and ther yaue e
tetin Steo 1of project Appendis a n S a

atelchange in strain giugr develcpment help, the signal requres to be fed into laoe coverters anid vice
Tolier uch as A
edversa ADCs DACS ett
eoiel

SUMMARY

Bridee s o nhalances OpAmps are

the
ba 9 o Op
.Chanter
htended to mathermatically manipulate hi
O c Amp. comp npiter Ihe

471
 S1GNAL MANIPULATION AND CONVERsiON 199
input sign
he A Cueno nd a
voltaoes Cunentvolluge co Hend-pas fller frqas
invertig
wN 9
NdKating con M oget
output 21 Name hand pss ler
wth or
pled
signal
e l y
used f volitag
n g op Rhering is an important signal-c l e i oTactorA
h o u f am
ovide
gnals e I AcvE 2 Nchar sa d e
de
A wnmng pas of top ban
dpAnp s use ta PPications A low-t
,
Nctve g - p a iner

2DAcvrir
a aher aterbaon es Ahigh-pass fiter allows si eny to
Dhee hemate s9uare. and requency to pas5 A biand-pass flter o
Pe eoectively Peeg range of freo
pass
Cur-off freqa 2RG
Anitegal Op Amp is uned
afeeet pes af input na computer
one using an ADC Therefore an arve dg
GLOSSARY
untnic ind econential p Amps ar uedanalog transducer signmal into a digital sior

osps the logarthc and expon smia,work on analog signals s

from
gong o
s d pu com
Active hiter t r hih fucianalhascamgarwdto
sU
nbe i t n innut an analog signal using a DaAC T wer cource for thelr furictioning low freqiuency signais A pats band of al The
hA oltage tsl ue Convertsa digital signai into an analog signal all the p pa
Band-pass fiter This type of a hiter allows
frequencies of a s1gnal a p ecifhed bavd to be
Ama ofes output in terms of

rane ntegration of input voltage sigral with.qain in tem

KEY FORMULAE Band-stop hite of RAC and R
S0 D of d
ed to determine the level
L0yAmpo vellag a hage (higher or kower by ormpai
polwity 9
p Anp da
tor apifier pain G voltage l e y
tage amplifer ts cmbinabom

0 co ampifiesconnected in senp
2Vand P Eapuncntial amplifier output: ,RI 9 our-slag
term oe ol indvidual gais
1. Logarnthmic arnplther: Difference
o l t a e i t h aain in teems of Rand R

Differentiator It offers output in tems of dittere Narrow band pass ts

1 d eauatió
erental ja1
rling amplier gai tiaton of input voltage signals, with gain im e c for
g a i Amp put
DNson
ap eed in Non-inverting ampliher tu N
in phs M g
i ddiference of log A and log # vignas polarity 1DC or
Ape G
Mubstage amplitier gain U Exponential amplifier t offers output
in terms o

reject iter
nd
Thste

1. Saming impiier ponential functions of input voitage eaparticular reqaency. say 700r 1200
ERkgwaR,thet G R ain in tems of RUR) and ,diode turatn a single freguenc
requency-to-votage co wich Past band s fe-34B
15, Vollageto-current converter comparator oupas patt
DSetator iber ga dina o n the applied voltage rtesContan
pase
e e n e n t s and

G Passive t e r
e
igral frequency for switching purpoe
 ECHATRONIS
SiGNAL MANIPULATION AND CONVERSi0
h bufer an
Durer amp
utput vollaje
tenal pewer
54y iD
winga high wavefo y pl mpetatie of a
nin and Op Attpk DWt pal OpAmp p r voltage
niphitir hi
eung
adivk a An Op A tare charactn as yllags m
Aelaxation orca et 9ven t voltage W f as On Amp 420 Me
rangular wp s
o b Ampcanbe 9 Nanie
ve output for Amp is ised for lincaruing ihe seno emplifer
d a nave output for a
output signal by a circuit
capacitor C h y 421 What he portancr af
ter a t e innit g a n odally gg and tt Wy de we ue a hiph-perfomance lDAC
do yos unoelanu oy quanzation?
woltage follower a used o
7na oa9
12 What
anpling tate and
413 Dere a33 Wneithe stros t are ned ao comvent an ana
i a l adiaital tianal
EXERCISES 14 What ceree 424 Draw and cplais the.churacteridka

16 Wrise a short note o differenOe anpltncs

4I6 Why is pomt X(ie, pot i betieenA,
and d
(d) hone of these
(c) Highpas bltes
Ecoding 46 Without
Saglir od heidc a
nepitrve teedback, an
Op Amp a
tis the
sugtiea 45 Drs and eplain the
functi of a -
olage gain o r u ot erns 4-bit ADC
2 which of te followin 5 tiparator
p u n g timea b) buffe Numerical r o 0 F e m s
Deeder 47 What is the final gaitr of a multi-stage amalie ot an 0p Ainp is 30 AIta and
closod-lp g
erne the ow 1he operating frequency banw idth
es: 6Mie)
u 9 Easach slas is J00 k z F m the m c s i a t outpur voage of le

(6 DHtcrence ot gaits at cach stage perating frequency of an amplther

a S-10 Mnt A Jew ate of opening arnpliher to
DE
o
-0 MHE d) None of the these J An 0p Anp s diesigncd ustng an iveting eC
+.8 Which device is tnvolved in the process t a N nHin 1e vain forla)
o t a g E of Op Amp
ADCT
F
applhed lo the inverting terminal of the OPAinpshow
put is
ak speE lo aput DAC volage is gvn by the
(0) o
Fiddhe ouut wvefori of the Op Aunp ( Ctgut
phaie W
A sv
of pha )CChanges
V

No ctecl w
pu vor, be
d espect -15
al in po oupt OD
410 C
A W
(a) cloie-ode rejection ratio Fig 4721
f phae
couo-mode rejechon rate 5 D w the output waveform of ihe Op Amp shown an PiE IS
l h (a) and (6) ( d ) none of t e

eview Questions to 300 ka fron 25 32

9n
changed
upply beig 1 Y

phe pplctions ef an43 Draw the

Ans Waveonu.n
42 Wlat is de
diffen equrva
pNtcl OpAnpd e a l and hat are thelimitathons O
d #g.47218
a 45 wha is t
product
192 MECHATRONICS I n t e g r a t i o n

terminals
ter oof the op
mvertnE

A
input
is given
to the

circuit
dere
4.6 A
square
wave

output
wiave
for
the
[Ans: Ourput wavefom
D e t e r m i n e
the is
0 J

1
V Ovapa hang
Input squarewae

Fig.4
4.73

) for a non-inven m
output voltage Me
value of the ampliied. to the amplifier is - 1
4.7 Find the
and the sensor output
volftage fed
as input 120uV,
R-20k2,
1o Dring e Output to a usable
sensOr

gives an output voltage of 20 pv. of the amplifier

vollagr e
output voltage
e
overall
Calculate the
stage amplifier is uscd.
R, 3Rk£2.
R-Rk R,=2RkN, and the inverting
terminals of a
amplifier circuit (reder
summing amplifier
are applied to
49 Iftwo input signals are
0my and 5 0 mV and
when the inputs
4.12),find the valuc of output
and R- 120 k2. for the filter u
filter shown in
Fig. 4.35(a) eircuit

4.10 Determine the bandwidth of the band-pass 0.6 juF

12 k£2, C, -0.2 juF, and C
areR,2 kA, R,
=

Ans:f-397.8 Hz. J422.1 H2, bandwidth frequney rag

4.11 An inductive transducer produces an output voltage with humtning sound of froguy

Determine the valuc of capacitance C tor a notch niter wim resistance 9K20 eliminae ti

Ans: C
4.12
signal,
1f the digital binary-coded input word to a DAC 1S 1001, find its cquivalent analog valar is te
shown in Fig. 4.66 for given values ot R=25 kE and R 1 kE2 if P 5

B
D

sv Ew
2 k

Fig.4.74
413 Find the digital valuc for an S/A4-bit ADC, if test transducer
1S2.15 Vat analog outpul voag
a reference voltage of 5 V.
4.14 Find the value of
output voltage V, of the circuit in Fig. 4.74 da

Answers to
Multiple-choice Questions
41(d) 42 (o) 43 (b) 44(0) 45 () 4.6 lu) 49(a) 4
471c)
71e)48 (a)
586
Computer Numerical 18
Control and Robotics

LEARNING OBJECTIVES
Studly of mechatronics makes students understand to understand the following:
its application in the field of computer aided manu-
facturing (CAM), computer numerical control (CNC) .Functions of CNC and its operations
machines, robotics, and industrial automation. It is be- .
Components of CNC machining
cause of the fact that they are capable of performing .Functions of robots and their operations
a job intelligently. With knowledge of all components .Standard laws and terminology of robots
of mechatronics, students can easily understand the
.Classification ofrobots
function and operation of CNC machines and robot-
ics. The concept of CNC and robotics discussed in this .Components ofrobotic systems
chapter will help students design an automated ro . Robotic arm positioning concepts
botic and CNC system for a three-dimensional oper Robotic arm path planning
ation. After reading this chapter, students will be able Computer control ofrobot paths

INTRODUCTION
A numerical control (NC) machine is a semi-automated or fully automated robotic system with limited
features of structure and intelligence. Numerical control is an automated process of cutting. drilling. milling.
etc. using various types of machine tools that are operated with precise control of programmed commands
encoded on a storage medium. Conventional manual control systems use handheld tools such as wheels or
levers, or mechanically automated vice cams alone. However, with the advances in semiconductor controllers
such as computers, operations of NC mills (machines) are controlled through a computer, and henee these
are named as CNC systems. CNC systems are now Uscd for the purposes of face milling. shoulder milling
tapping, drilling, and turning along three axes (x, Y, and 2) along with one or more rotational axes. Many
companies such as GE, Fanuc, Allen-Bradley, Okuma, and Bendix are producing such CNC controllers
Robotic svstems, which can think, act, and behave like human beings, were developed to help and
at level to enhance the effectiveness of the system or process
cooperate with human manpower every
With further advances, the interference of human operators was eliminated by the use of robotic sysiems
apartfrom CNC activities in variousindustries. Robots were supposed to replace someofthe human activities,
such as walking, talking, transporting, guarding, teucnng nd many more. A robotie system is featured
to hehave like human beings;, however, its intellgence ievel is deternined by the ability of the integrated
to execute a decision accordingly.
software and hardware robot are given in Table I8
differences bet ween a CNC and
Some ofthe basic discussecu along with CNC, which is als0
fundamentals o1 rObotics are a robotie
In this chanter,
with limited features.
678 MECHATRONICS

robots
Table 18.1 Difference between CNC and

CNC Robot
four DOFs. However, most
A CNC machine offers a fewer number of degrees A robotic system offers minimum
more than six DOFs.
of freedom (DOFs) as compared with robots. It of the robots are designed to exhibit
generally provides three or four DOFs
A CNC machine, in order to impart motion in The programming language of robots has an entirely different
on the involvement of vectors.
different directions, uses the most common language structure depending
languages known as G and M codes.
Generally. CNC machine program codes are Old robots have been programmed manually for movement
robots are
entered through a keyboard. in steps per requirement, but new-generation
or as

capable of training themselves like human beings as they

learn new activity with trial and error
grow with age. They can
to help the robot in
process. However, a trainer is required
learning to correct errors.
The inherent structure of a CNC machine is quite Structures of robots are better in assembling parts and related
functions.
good for fabrication, cutting, milling etc. of a
Workpiece due to its robustness to withstand a large
amount force
With the improved version of CNC machine tool The limitation of handling large amount of force by a robot is
a

technologies, it is possible to perform tasks likeea improved through stronger and more rigid structures, in order
robot to produce complicated parts.
A CNC machine tool is considered as a factotum A robot offers less precision as compared to a CNC machine
of precision in the area of manufacturing and while handling a large amount of loads. However, the use of
ndustrial applications. robots in CNC machining is economical also.

ACNC 5ystem with robots can operate in diverse Robots are featured to provide faster, fexible, robust, and
manufacturing and production processes. reliable operations as compared to industrial CNC machines

18.1 CONVENTIONAL MILLING MACHINES

Architectures of conventional vertical and horizontal milling machine are shown in Figs 18.1 and 18.2,
respectively. These methods are used manually through electrical motor drives.
Conventional NC machines also operate through manual switching to carry out a particular job such as
cutting, drilling, and so on. A switch-based manually operated NC machine is shown in Fig. 18.3.

Cutter
Job

Worktable
Cutting Spindle
tool
Job

Workiable Base
Bae

Fig. 18.1 Conventional Fig.18.2 Horizontal Fig. 18.3 Switch-controlled

vertical mifling milling manual NC machine
 COMPUTER NUMERICAL CONTROL AND ROBOTICS
679

18.2 NUMERICAL CONTROL MACHINES

CNC method
NC method is
is automated system that
an
operates machine tools as per the code of letters
s . numbers, and specifi
numbers, specnc cnaracters to
(e.g., G and M
codes), produce a desired piece of work using the
numerical inputdata are fed into a machine in program input. The
the form
tis called a CNC part program. Later, this program isoftranslated
a program produce
to a part of the work. This data
into the
nnropriate electrical signal output to run the servo or stepper motor used machine code program, followed
in the CNC system at the desired
esired direction to achieve the
ed and in the desi desired
P e e d

product.
183 FEATURES OF CNC MACHINERY
ACNC machine is capable of moVing a tool as well as
Amachine tool can operate along one to five axes
worktable/workpiece as per the design of the machine.
as per the code entered. A
with a machine control unit (MCU) whose complex CNC machine is featured
purpose is to manage all operations entered in the
However, movement of a tool program.
or
workpiece is
controlled by a servo or stepper (based on
selection) motor
that acts as an actuator. Any change from the desired value
of output results in an error with
measured feedback value provided by the sensor/transducer. The selection or respect to the
through tool magazines automatically. changing of a tool is performed

18.4 COMPONENTS OF CNC MACHINESs

A CNC machining system is composed of six major components:
Input devices These include keyboard, mouse, RS-232, Ethernet, etc.
Machine tools Generally, CNC machines are used for cutting, surface
smoothing, and other lathe operations
and hence require cutting. milling, and plotting motion tools.
Driving system to impart motion in order to impart motion, non-servo, DC/AC servo, linear, and stepper
motors are used.
Feedback transducers In order to control a machine continuously, feedback on its velocity and
position
is required. For position feedback, potentiometers, strain gauges, and angular encoder transducers are
For velocity, tachogenerators are used.
used
Controller as MCU A microcontroller of PLC-based controller can be used.

Display unit It can be an LCD, a printer, etc. Moreover, an advanced display system is featured with
a graphic display of simulation of the tool patn as per the part program input, which helps in confirming
in advance. before actual machining is impiementea, to output a desired workpiece. It also helos in the

maintenance and installation work of a CNC system in terms of machine parameters, logic diagram of the
error massages, diagnostic data,
programmer controller,
Display unit
etc.
the brain of a CNC
unit It is basically
Machine control data processing unit MCU Head
units, namely,
It consists of two DPU CLU Work picce
system.
loop unit (CLU).
and control
(DPU) as hardware parts
components
are
treated
Working table-
These 18.4.
shown in Fig.
as
CNC system, with three-axis servo drive Base
CNC system
A typical 18.5,
is
shown in Fig. Fig. 18.4 Typical CNC system
control
680 MECHATRONICS

Y-axis control
Servo/StepperDisplay
motor
Circuit

Spindle hecad
My

Servo/stepper
Working table motor

M,
Servo/Stepper X-axis control
motor
Z-axis control

Z-axis Intelligent X-axis

control controller control
circuit (computer) circuit

Spindle X
speed control
circuit
Z

Fig.18.5 Three-axis CNC control system

CNC tool movement control Generally, two types of motion or position control system are available to
direct the tool in a predefined motion or path. They are known as point-to-point and continuous path control
systems for tool movement, as shown in Figs 18.6 and 18.7, respectively. An advance CNC machine is
equipped with 100 or more tools for milling, drilling., tapping, boring, face milling, cutting, etc. These tools
are selected automatically by this automated machine.

Wire
M

Tool PO
Workpiece P I
Tool
P5
P4 P3 P2
Workpiece
Working table
Working table

Fig. 18.6 Point-to-point Fig. 18.7 Continuous path tool

movement control system movement control system

18.5 WORKING OF CNC MACHINES

A CNC machine is controlled by G and M codes (instructions with numbers). The number values and

coordinates are entered within a specified format. Each number ofa code represents a particular type o
 COMPUTER NUMERICAL CONTROL AND ROBOTICS 681

ration on a given piece of work. These codes

operath

ed to write a CAD program by the user.

are

he G and M codes, once entered, automatically

The

erate the
g e n e r
respective machine codes for
cution. A typical automated CNC machine is

shown in Fig. 18.8.

18.6 AXIS OF MOTION IN CNC

A CNC machine can offer three linear, such as
X.Y. and Z, and three rotational axes of motion.
These together form the degree-of-freedom
(DOF) coordinate system. In CNC, operations
are performed in various dimensional systems, as Fig. 18.8 Automated CNC machine
discussed in the following subsections:
Incremental systems n this method of control, a reference of measurement is taken from the preceding
point, as shown in Fig. 18.9. Therefore, an error at any stage results in a cumulative error.
Absolute systems In this method of control, a reference of measurement is taken from the origin of the
coordinate, as shown in Fig. 18.10. Therefore, all control commands are written with the reference to the
origin.

18 mm
20 mm 77 mm

59 mm
39 mm- 39 mmH

-XTTTITTT TTT X -XTTT

18
38 mm|
mm mm
36 mm'

56 mm

92 mm

Incremental coordinate Fig. 18.10 Absolute coordinate

Fig. 18.9

18.7 APPLICATIONS OF CNC MACHINES

CNC machines are used mostly for metal shaping by cuting. drilling, urning. grndng, centring. pressine
ng.
punching, surface machining, etc. Most industries use automated C'NC nachines tor assembling tiny ssmall
also used for desi
repeated operations. It
is
tools, by
and large components through sophisticated where a possibilty ot error
exists. Other
applicati
complicated contours, jigs and fixtures, and costly parts
(E:DM), laser cutting, waler-jet cutting. and indiscs
involve wire cutting, electrical-discharge machining
robots.
682 MECHATRONICS

18.8 ROBOTICS
A robot is mechatronic sysiem that is capable of performing the assigned work in the same manner
a
as
human beings. A robot is also known as an industrial robot, a robotic man1pulator, or a robotic arm
depending
upon applications.

18.8.1 Evolution of Robots

The term 'robot' was first time used by the Czech playwTight Karel Capek from the Czech word in place of
forced labour called serf.
He defined robot as 'a
reprogrammable. multifunctional manipulator designed to move material.
tools, or specialized devices through various programmed motions for the parts
tasks performance of variety of a

18.8.2 Definitions
With the evolution of robotics, the
definition of robot has changed from time to time. Depending on the
advances in technoiogies, and the
sensory capabilities and intelligence level of robots. robotics has been
defined in several ways, some of which are
as follows:
1. Robotics is an
interdisciplinary
area of
engineering
engineering; computer science; and several other comprising
mechanical, electrical. and electronic
2. It is the science of disciplines.
designing and developing robots that are useful for real-life
manufacturing and non-manufacturing sectors in an automated manner. applications of
3. It is a
knowledge-based art that presents the knowhow of designing.
in human endeavours. developing, and applying robots
International Standards Organization or /S0 definitions
These definitions were
adopted by the ISO and have been agreed upon by
An industrial robot is an
automatic, servo-controlled, freely
mostof the users and manufactures:
with several areas for the programmable,
handling of workpieces, tools or special devices. Variablymultipurpose manipulator.
make the execution of a
multiplicity
of tasks programmed operations
possible'.
Robotic Industries Association
These definitions
(Formerly, Robot Institute of America) Definitions
were adopted by the Robotic
Industries Association
1. An industrial robot is (RIA)
reprogrammable multifunctional manipulator designed to move material,
a

tools specialized devices

or
through
various parts
programmed motions for the pertormanee of a variety
tasks. of
2. It is automatic machine that
an
performs functions ascribed to humans or a machine in the form of a
human being.
3. It is asoftware-controllable machine that uses sensors and transducers to
effectors with the gude one or more end
help of programmed motions in a workpiece for manipulating physical
4. It is a number of objects.
rigid links connected through different types of joints that are controlled and
by a computer to perform the assigned task. monitored

18.8.3 Types of Motions of Robots

A robot acquire
can
any combination of six basic motions DOFs.
or
They are
explained as follows:
 COMPUTER NUMERICAL CONTROL AND ROBOTICcs 683
errical motion An arm of a robotic manipulator is capable of moving up and down in the vertical
direction
ith
with the help of a shoulder swivel. It is
possible either by turning towards the horizontal axis or by
vertically.
sliding
Radial motion This type of motion is achieved due to in and out movements of the
enerally occurs in case of elbow or manipulating arm. It
gene
leg extension or drawing back activities.
Rotational motion The angular movement is either clockwise or anticlockwise about an axis. It is generally
about the axis
ab that is vertical to the
manipulator
arm with the help of an arm sweep.
Pitch motion This motion
enables up and down movement of the wrist. It
motion and it is known as wrist bend, involves angular or rotational
Roll motion This is
rotational motion that enables
a
movement of the wrist, known as wrist swivel.
Yaw This enables the wrist to move in the
Thus, a robot can offer motions right or left direction, which is known as wrist
(DOFs) in terms of horizontal movement, yaw.
movement, vertical arm movement, rotary wrist rotary movement, radial arm
movement, wrist bend, and wrist sweep.
18.9 FUNCTIONS OF ROBOTS
A robotic system performs its task in three
Fig 18.11, where the robotic functions are stages,
as shown in
Fig. 18.11. This can be understood from
classified into three areas.
Sound Vision Stages of functions of robot

Proximity Environment Sending environment Controller decision

Performing task
through sensors and making based on
transducers input from sensors through end
and transducers effectors
(actuators)
Color Touch Stage 1
Stage 2
Obstacle Stage 3

Fig. 18.11 Function of robot

Stage 1 The task of this
stage is to sense the outside world environment
as vision, obstacles, sound, colours, touch, using sensors and transducers
and proximity to feedback such
motion or path. information in order to modify the
Stage 2 Controller decision is taken based the information obtained from
on
the sensors and
via interfacing outside world devices and control schemes transducer
ers,
to send usea w n or without a
servo
mechanism, in onder
signals to the actuator or the final control element sucn as
based on information received from the outside world
tor
arives, or
storage of program(s) and data
patn pianning along with speed,
time, ete. accurateh
Stage 3 This stage involves performance of the assigned task as per the command
given by the
controller
Suitable manipulating arm with a specified coordinate system, so as to reach all definodpO ihlrllet A
and a suitable gripper that can fit to the workpiece geomery
tot d g . 8 used to tinally implement tho
decision of the controller.

18.10 GOVERNING LAWS OF ROBOTICS

tatd
Sir Issac Asimo gave three 'laws of robotics for its development, eroth law' was
added h him
eroth law A robot must not injure humanity or, through inaclion, allow
humanity to cama ...
am.
684 MECHATRONICS

First law Arobot must not harm a human being or, through inaction, allow one to come to harm unlessthis
would violate a higher-order law
Second law A robot must always obey human beings unless it is in conflict with a higher-order law
Third law A robot
must protect its own existence unless that is in confict with a higher-orderlaw
18.11 ROBOTIC TERMINOLOGIES
Some important terms frequently used in the study of robotic systems are discussed in the following sections:
Links A link is basically a solid structure of an arm used in the robotic
system.
Joints A joint is a moving coupling between links. It
may be one of the following types:
Rotary Such joints are moving under the control of electric motors with a chain/belt'gear
system.
transmission
Linear Such joints have linear movement
provided by hydraulic cylinders and levers. In a prismatíc system.
slider joints with links supported by a linear slider
bearing are used to achieve a linear motion. This type of
motion can be actuated by ball screws and motors or
cylinders.
Degrees of freedom In a robotic system, every joint of the robot requires a certain DOF in terms of
rotary, or other types of actuators. A robotic system may have five or six DOFs.
slider,
six DOFs has the capability to reach
However, a robot with
every position and orientation in a three-dimensional
space. Typical
three, four, and six DOFs in translational and rotational motions for a three-dimensional space are shown in
Figs 18.12(a)Hc).
Z-axis Z-axis Z-axis
Rotational/Angular
Linear/Traslational Linear/Traslational
motion motion Linear/Traslational
6-degree freedommotion
Translation 3-degree freedom

Y-axis Translato
4-degree freedom

Y-axis
ranslation Y-axis
Linear/Translational Linear/Translational Linear/Translational
motion motion motion

X-axis
Rotational/Angular
X-axis X-axis

Fig.18.12 Degrees of freedom (a) Three DOFs (b) Four DOFs (c) Six DOFs degree

Orientation axes A robotic system describes its orientation axes in terms of rolls, pitches, and yaws. as
shown in Fig. 18.13.

Top or left Top or left

Pitch
Yaw Yaw
LRoll Forward
Clockwise right Right
movement
Roll
Bottom or left Bottom or nght
(a) (b) (c)

Fig.18.13 Three-dimensional movement/orientation (a) Pitch (b) Yaw (c) Yaw and Pitch
 COMPUTER NUMERICAL CONTROL AND R0BOTICS 685
Dasition axes 1hese describe the various positions
TCP (tooi center point
ofthe
tool in a
three-dimensional space, regardless of
orientation.

Link

Tool centre point or TCP It is used to hold something

Joints
ilable on the robot or on the tool,
and is availal
as shown in
Fig. 18.14.

Work envelope (workspace) It is the

geometrical
houndary of positions in space that a robot can reach, as Fixed

shown in Fig. 18.15. It can be fixed or variable,

depending on the design. Fig.18.14 Tool centre point

Speed It represents the maximum speed of TCP or

joint(s) that can be achieved. Workspace
Joint
Payload It represents the maximum mass that a Object
robot can handle without failure; else, there is a loss of L i n k job)
accuracy, leading to an error. Gripper

Settling time It is the time required by a robot to move

away from the final destination. This arises because of Working envelope
the fact that a robot moves faster while at start and as Fixed
it approaches the target destination, its speed becomes
slow so as to reach the target smoothly without
jerk.

18.12 CLASSIFICATION OF ROBOTS Fig. 18.15 Workspace/Work envelope

Robotic systems are discussed based on four types of classifications, namely, basic, standard, broad, and
general classifications, as shown in Fig. 18.16.

Robot
classification

Basic General Broad Standard

classification classification classification
classification

Stationary Movable
robot robot
General Special Programmablel Intelligent Tcle-operated Mechanical Control
purpose Reprogrammable robot robot
purpose configuration applieation
robot robot
robot

Servo Non-servo-
controlled
Servo- Non-serv0- Sensory Cartesian Cylindrical Spherical Jointed an controlled
robot conliguration contiguration
controlled controlled coordinate
Revolute
robot robot configuration contiguration
18.16 Classification of robots
Fig.
 686 MECHATRONICS

18.12.1 Basic Classification

Robots are classified into the following two categories:
Mobile robots This type of robot is featured with the
capacity to move within a specified workspace. They
are suitable for cleaning nuclear waste, accident areas, manufacturing industry, etc.

Stationary robots These are featured with robotic arms to perform the tasks while robot remains fixed at
one place.

18.12.2 General Classifncation

Under this category, robots are either general-purpose- or special-purpose-type robots.
General-purpose Robots
These robots
produced in mass because they are designed and developed to perform common tasks
are
such spraying, painting, picking, placing, welding, and a variety of jobs. Such robots
as
end effectors or fingers to be attached require suitable
according to the requirement or task to be handled. They are easily
available and cheaper.
General-purpose robots, based on their complexity and sophistication, are further classified as non-servo-
controlled, servo-controlled, and sensory types.
Non-servo-controlled robots These robots are designed for
simple and limited sequence control operations.
The movement of arms are controlled by an open-loop system on each axis from one end
point to another, as
shown in Fig. 18.17. That means points between two ends are not defined; only
point-to-point control for end
points are defined. However, how an arm reaches these end points is not of concern.

Controller
command signal

Robot Solenoid To arm/Wrist

controller valve Actuator
positioning
Non-servo-controlled
arm/wrist manipulator
Sensor
feedback End position
sensing by
limit switch

Fig.18.17 Non-servo-controlled robotic system

However, in case of control along a trajectory such as a circle, a spiral, an arbitrary curve, or a combined
trajectory, all points falling between the start and end points must be defined in advance, that is, should be
predetermined.
Servo-controlled robotsThese types of robots use various types of sensors and transducers to estimate
the internal manipulator state by measuring physical parameter(s) values such as state, acceleration., force,
location, position, velocity, and torque, as per the requirements. Suitable corections are applied to states that
deviate from the predetemined operational parameters set by the control program, to reduce the deviation to
zero from the order of 0.1 to I mm. Figure 18.18 shows a servo-controlled robotic system.
 COMPUTER NUMERICAL CONTROL AND ROBOTICS 687

Input signal
fnom contmller

Servo-controlled To arm/Wrist
Actuator
valve positioning
Servo signal Servo-controlled
amplitier am/wrist manipulator

Sensor
feedback Sensor for
detecting
position

Fig. 18.18 Servo-controlled robotic system

These robots are capable of liting high-capacity variable spccd loads like the human arms. It can
calculations
also find the shortest path between two points with prescribed constraints
by performing
automatically.
These robots use two types of sensorS; one type is used for internal position or location
Sensory robots
via external The other type
of components based on information gathered from the outside world
sensors.

inductive magnetic sensors, force

incudes various external sensors such as CCTV cameras. pressure sensors,
finders that are used for gathering information from
and torque sensors, and laser and IR sensors for range
the internal control of sensors by establishing
the environment: and it plays an important role in determining
environmental information to determine the location of the parts. Sensory
a relationship with the gathered
tasks:
robots are capable of performing the following
and situations of
their computer programs as per the changing requirements
They can change or modity as small as eight DOFs, which
sensors. Such robots with arms can otfer
the environment through information
object(s) individually or from a cluster objects comfortably.
of
help in identifying. picking. placing the language of human voice. The robotic vision is
suitable for
These robots are capable of understanding
at a high speed. The concept of pattern recognition
identifying, sorting, and collecting objects automatically and adapting to the suitable operating
for selecting different ypes of object(s)
also implemented functions of sensors, such as proximity sensing
and tactile sensing.
action. The
software algorithms for
of a robot is controlled by electrie and hydraulie
help
of
identify certain type objects.
Movement
ofjoints
drives. DC servo motors or DC stepper motors. However
of robotic manipulators uses
Motion manipulation robots.
motor drives in these
with high loads requires
high-speed manipulation

Special-purpose Robots i sa
and develope
to neet the requirenment ofa specitie nanure. Being designed
These robots are designed or development. Robots are neither produced in
robot takes a lot
ol time manutacturing
tor
its

shecific task, a market. Hence, their cost is

high.
available in the
m a s s nor easily
produced
for aa specifie purpose with a limited range of DOFs of manipulators,
designed and The sotware program of robot
They are or
pneumatically. a or
controlled hydraulically
are
arns
to pertorm the assigned task, is copied in its memory. These tves af
ucatial movements
carrying ou a n d l i n e of small.
smal and large objects, weldng. pnting, material casting. components
handling of
used in
robots are

assembling, etc.
 688 MECHATRONICS

18.12.3 Broad Classification

Robots are also broadly classificd in the following three classes:
Programmable/reprogrammable robots These robots are programmed and controlled by a computer for
iheir control. Such robots are first traincd belore perfoming a task. They arc capable of performing a task, in
the field of assembling of components. welding. painting. loading and unloading of objects, machine tools,
and all structured operations. by exccuting the operation repeatedly.
Tele-operated (man-in-the-loop) robots These arc is basically human-controlled robots. They are different
from fully machine-controlled robots. Here, a human operator is taken into the loop depending upon situations
where it is difficult to predict the motion and handling neds. Accordingly, the detailed information gathered
on the situation helps the operator to program or train the robot for its control action. They are generally used
in hazardous situations. The control action is featured with a servo-driven master slave feedback manipulator
system. Moreover. sometimes, a vehicle-mounted, heavy-duty. multi-axis power manipulator is used for
performing tasks in a hazardous zone according per the control commands of the human operator. It is capable
of controlling the manipulation of slave arms at a hazardous place safcly, through viewing the situation in a
closed-circuit camera or a television as per the decision of the master controller.
Intelligent robots These robots are similar to sensory robots featured with advance state-of-the-art and
artificial machine intelligence. Moreover, they can perceive neuro-muscular communication and coordination.
similar to human beings. They are used for exploring environmental conditions and their evaluation in
real time for decision making regarding the movement of a manipulator, depending on the sensor input
information.
Such robots are capable of taking decisions and implementation for movement on floors, climbing slopes,
and removing obstacles. They are available with high power-to-weight ratios in a compact assembly featured
with sophisticated sensor instrumentation and power supplies.

18.12.4 Standard Classification

This classification is based on physical as well as mental approach for the implementation of robotie funetions.
Eagleburger classified standard robots into two eategories: one based on mechanical econfiguration and other
based on the control method applied.
1. Under the classification based on mechanical configuration, various types of joints and links that
constitute the physical structure of a robot affecting their input-output relationship are considered.
2. Most robots available in the market can be grouped into four basic configurations, namely. Cartesian
coordinate, cylindrical, spherical, and jointed-arm (revolute/articulated) configurations.

Mechanical Configuration
Various types of mechanical configuration robots are discussed in the following sections:
Cartesian (rectilinear/gantry) coordinate configuration A Cartesian (rectilinear) robot has the
simplest configuration; it is also known as a gantry robot. This configuration of robots offers three mutually
perpendicular axes (X, Y, and Z) for lincar movements and is described by either a rectangular or a cubical
workspace volume, as shown in Fig. 18.19. It has no angular mover ent of links.
Cartesian robols are of two types: First, a cantilevered C'artesian configuration offers a limited range of
movement for its extension from the
support lrame. Itis less rigid in nature and works in a smallerrestricted
workspace as compared to thers. It has better repeatability and accuracy as comparcd to others like SCARA.
It can casily be programmed due to its inherent
natural coordinale systems.
 COMPUTER NUMERICAL CONTROL AND ROBOTICS 689
Sccond. gantry style Cartestan
which is used for precise movement of
contiguration, 17axis
heavy loads, Linear
more rigid in nature and mstalled on
the ceiling. motion
and thus covers less weorkspace volume.

Clindrical configuration Cylindrical configura-

ton robots otler two linear and one
angular move-
ments in such fashion that its workspace is
a
described Grnper
hy a Cvlindrical coordinate. It has one Iinear Linear
vertieal column
for movement of a robot arni on one side of the ro-
bot, which is capable of moving down the
eolumn, as Rectangular/Cuhical
shown in Fig. 18.20. Other two linear workspace
are also capable of angular movement
moving arms
simultaneous- -axis
Y-axis
. The angular rotation by 360° 18 not possible due to Linear
motion
Linear
hydraulic. electrical, or pneumatic connections. How- motuon

ever, it detines the minimum and maximum

move
ments of mechanical links in the overall Fig.18.19 Cartesian coordinate robots
cylindrical
volume or work envelope.
Spherical (polar) contiguration This configuration offers two angular and one linear
in a spherical workspace volume, as shown in movement of links
Fig. 18.21. It has a telescopie arm about a pivoted horizontal
axis and another that rotates about a vertical axis. It offers less
arm
workspace for movement of mechanical
andor actuator connections than the
cylindrical configuration.
Z-axis Linear

Z-axis: angular
TLinea
motion
Spheneal
i ylindrical wrna
Linear Angular workspace
motion motion Y-ANIS
Cylindrical
workspace Lincar -a Lanear

Lad Angular
Anpular
XaNiN

robots
18.20 Cylindrical contiguration Fig. 18.21 Spherical conhguration robots
Fig.
aute/articulate)
ar
connguraon A JoInted armm pe obot
capable of nork ina
Is
Adone linear movements through jonnts ant ams, as
Ls and rotatory joints, Can be
uNC as shoulder, am, and show
n in Fig
wrist ivints. These 18.22
OCS
types of jointed arm con
three diflerent
of joimted am
configuTtons, naneiy. paure
ah.
available in pthetical,
cal, and cylindrical. parallelogram spheri-
spher
690 MECHATRONICS

axis
SCARA lt is an abbreviated form ofselective
Angular
compliance assenmbly robot arm (SCARA) motion

It is a special class of jointed cylindrical

manipuiators. It be used like shoulder

can

and elbow with vertical rotational axes for

rapidand smooth movement. It is suitable for
o Y-axis
Angular
motion

aranging component assemblies for inserting axis

objects into holes. SCARA ofiers highly stif Angular
movement vertically and laterally, which helps motion

in inserting a component into a process or

system
Fig. 18.22 Articulated configuration robot

Control Classification Robotic arm

Based on the control configuration, a robot per-

Fecdback
forms its control either in an open-loop orin mechanism Output
a closed-loop scheme. Further, implementation
Sensor angle
of a robotic system can be described by control Closed loop
configurations, such as servo-controlled and robotic system

non-servo-controlled configurations, as shown Processor

Robot
(robot controller) Input angle
in Fig. 18.23. Linear as well as angular move-
ments are controlled using these techniques si-
multaneously. Fig. 18.23 Simple closed-loop-controlled robot
Servo-controlled robots Robots using servo control nmechanism may either follow a continuous path or
perform a point-to-point movement.
Point-to-point or PTP robots In this type of robotic system, software programs, for controlling the
movement of each arm and joint from a reference starting point to an end or final point, are stored in the
memory. These robots are used for repeated works such as welding of a job piece, pick-and-place work, and
So on

Continuous Path or CP robots This type of a robot has the capability to cover a continuous path consisting
of various path nodes. Information on each node, in terms of its position and velocity, is stored in the memory
and is continuously monitored through a feedback mechanism to control related links and joints of the
robot. The program requires inputs for the nodes on the continuous path of the robot. The motion cyeles are
continuously and closely monitored for a smooth motion of the robot on the path. These types of robots are
used in contour tracing. path finding, spray painting, are welding, etc.
Non-servo-controlled (limited sequence) robots They are controlled by setting the limit switches(s) for
the movement of each joint that mechanically stops at the point of target, rather than using sottware control.
Software programs are written for the mechanical set-up involving proper positioning of the moving armms
and joints along with the sequence of events; however, the endstop is implenented mechanieally. Theretore,
they are known as limited-sequence robots. They are used as end-point robots,. pick-and-place robots, or
bang-bang robots.

18.13 FEATURES OF ROBOTS

Some advantages and disadvantages of using a robotie system are explained in the following subsections:
 COMPUTER NUMERICAL CONTROL AND ROBOTICS 691

A robot cannot take jobs other

Limitations
than when programmed in danger or emergencies. It is a costly
air to install a robotic system for production. Replacement of human workers develops resentment in them.
Segtures
Features
Arobot, as an intelligent machine, has been proved to be highly beneficial to industrial and other

cations, such as for

performing repetitive tasks precisely and accurately to deliver quality products,
arying out monotonous Jobs, increasing eficiency leading to in enhanced production, reducing faults and
accidents, reducing wastage of raw materials and thefts, reducing labour deployment and related problems,
and performing economic and safe operations even in hazardous areas.

Head
18.14 COMPONENTS OF ROBOTIC SYSTEMS
Neck
0 Eye ball

The major components of a robotic system that help Shoulder

in generating various types of motions are structures, Chest
volume
sensors and transducers, controllers, actuators and Upper armm
Spinal
transmitters, manipulator arms, and end-of-arm column

tooling (EOAT)/end effectors. The details of these -Chest wall mass

components are explained in the following sections. Lower arm
Hand

18.14.1 Structures Abdominal mass

The structure of a human robotic system in the form

of a mechanical model is shown in Fig. 18.24, where M-D-S
each MDS block represents mass (M), damper (D), M: Mass. D: Damper. S: Spring
and spring (S) systems and joints with rectangles
and diamonds, respectively. However, the electro-
Legs Joint (S)
mechanical model of the system is added
with
clectrical motors and electronic components along
Fig. 18.24 Mechanical robotic model
With a controller such as a computer.
An electro-nmechanical model of a robotic arm may consist ofsix Steppers operating under the master and

slave mechanism with PID controllers, as shown m Fig I8. Waist, shoulder, elbow, wrist roll axis, wrist
controlled by Mj, M2, M3, M,, Ms, and M.. resnbcti sl
molors
Pitch axis, and wrist yaw axis are

Slaves

Driver (DCDAStepper
Master circuit notor 1 0Joint
DC2
M- )Joint 2
Robot
controller
-DCa M Joint
(compuler)
DC4 M Joint4
M )Joint 5
Driver Stepper
circut Joint 6
PID
ontrollers/

Electro-mechanical motion control of rotbatic

18.25 arm
Fig.
692 MECHATRONICS

18.14.2 Sensors and Transducers

Their purpose is to collect information from outside world environment and provide feedback to the controller
devices so that the manipulating robotic armm and end effectors such as grippers can take further actions or
revise them. Sensors and transducers are broadly classified into contact and non-contact types.

Contact-type Sensors
These sensors and transducers collect information from the environment, when it comes into contact with the
discussed as follows:
parameter measureand(s). Some of them are
Tactile sensors When a tactile sensor comes in contact with an object, it generates an electrical analog or a

digital signal, and sends it to the microcontroller/microprocessor controller.

Microswitches Electrical signals can also be generated with the help of microswitches.
Strain gauges Mechanical pressure applied to a strain gauge causes a change in resistances, which is
detected with the help of a bridge circuit as a proportional change in the bridge output voltage.
Piezoelectric transducers An electrical potential is created when a piezoelectric crystal material is subjected

to pressure.
Other contact-type robotic transducer sensors are force sensors, temperature sensors, torque sensors,
touch sensors, and position sensors.

Non-contact-type Sensors
These sensors are limited by their range; however, these are capable of sensing the physical parameter(s)
remotely and producing an electrical signal.
In order to detect various physical parameter(s) such as proximity of an object, displacement, speed,
distance, image, etc., transducers are available. These transducers work on one of the principles such as

change in magnetic fields, infrared and ultraviolet light, X-rays, electrical fields, ultrasonic sound waves, or

electromagnetic waves.
Various types ofsensors and transducers are discussed in detail in Chapter2.

18.14.3 Controllers
The role of a controller in a robotic system is to receive the sensor and transducer input signals for the purpose
of determining the values of parameter(s) under measurement, such as distance, image, speed, and light,
followed by the desired control action. This measured value is compared with a set or desired values, in order
to make a decision. Thus, a decision(s) is implemented through actuators in terms of action to minimize the
error or act as directed by the controller. A controller may be a microprocessor, microcontroller, or PLC-based
system. The details of various types of controllers are discussed in Chapters 7, 8, and 9 (microprocessors,
microcontrollers, and PLCs, respectively).

18.14.4 Actuators and Transmission

Movement in a robotic system can be induced using various types of actuators depending upon the problem
to be handled and robot design. Gienerally, a robotic arm can provide the desired type of motion with its
payload. Accordingly, a suitable drive system is selected, which is capable of providing power to drive tne
systems under control. Robots generally use one of the following three different types of power drives:
Pneumatie drives Generally, compressed air pressure is used as the
moving agent in a pneumatic a
system for robotic arm movement. A pneumatic drive acts like a linear actuator with either single- or doudie
 cOMPUTER NUMERICAL CONTROL AND ROBOTICS 693
d y i e r s lt can also be used
for rotary actuators through vane
n S I . tast, and eliable. but it can motors. A pneumatic actuator
Y only handle less payloads and it offers a delayed
ATt t iS Suitable response
tor non-serno robots. Pneumatic actuators have been discussed in detail in

Hvdraui drives ln this

dive system, the
hydraulic (uid oi)
NVnE Agent that causs the robotie arm to move with thepressure ereated by an electric motor pump
nar S roay
aiator assemblies. A help of a double-acting piston cylinder for
hydraulie drive system is capable
of oftering higher payloads
N paeumane dnve systems. but it is not as accurate
S Dave been iisussad in detail
in Chapter 13.
as
pneumatic and electric drives. Hydraulic
Electrical drives ln comparison with
array and reliability with a wide pneumatic and hydraulic drives. electrical drives offer high degree
range of payload capacities at a
iei mOTUT dnves used in robots are DC servo motors. brushless DC
competitive cost. Some important
electrical drive actuators have been discussed in reversible12.AC servo motors.
segper motOrS. ete. Details of motors,

Chapter
Tramsmission
order toransmit power berween
actuators and robotic
mechanical) ransmission joints of mechanical
linkages, a suitable power
arrangement is required. This is because of the
1. The acTuator ourput power is not suitable to
drive the robotic
following
facts:
Exmple: The spead of an electrical DC motor drive linkage directly.
is. say, 2000
at a slower
spead. say 40 rpm. That means 200 rpm is rpm, which is used to drive the robot
of a suitable eficient required to be converted to 40 rpm with the
gear system. which can reduce the help
The output of the actuator is speed by 1 5.
different from the required motion of robotic joints.
Example: The output of an electrical drive
is rotary motion. but
linear motion: in this case. the the robotic
rotary motion has to be converted to a joint may require a
mechanism. Similarly, in case the output of a linear motion
hydraulie drive is linear. but the robotic using a suitable
rotary motion. then the joint requires a
3. The size and load of
linear-to-rotary-motion
conversion mechanism is
used.
actuators. being large, cause
problems in
Erample: order to impart motion from an actuator, whichlocating
In
is
the actuator at the
joint
distances. suitable linkage or gear train is heavy and large in size, to
required. large

18.14.5 End-of-arm Tooling/End Effectors

The final end of a robotic arm is called a robot end
etteetor. it nay be
am tool, which is fitted on the
robotic wrist of the basically a gripper or ths ond af a
adaptable to operations; however, the role of end cttectors is quitemanipulating
àm.. A robotie
manipulator is tlevible and
speciie in nature. A
to Derform
Various types of activities; therefore, the design ot an end ettector robot is dasi
determined by the activities to be performed. tooling and or erinner i
is
Example: A gripper designed to put a bolt cannot be
used as simple pickine tost.C
a

welding of

Classification of E0AT
EOAT is classified as grippers and tools.
Grippers A gripper is available in multiple, single, internal, or external type. Vari
used for designing a gripper; however, seven important gripping methods ofmethods.
are
widely used for the
purpose
694 MECHATRONICS

of gripping a body. They are grasping hooking, scooping, infiating around, magnetic attraction, vacuum
attraction, and sticking.
Tools Atool can be of compliant, contact, or non-contact type.
Manipulator arm This component is the most important part of a robot, which requires certain moving
mechanical structure in order to facilitate am movement within the work cnvelope. It is designed to take
maximum possible load while maintaining the precision of speed for repeated applications. A robotic arm can
have independent movements in two to three axes, called two or three DOFs.
A robotic manipulator arm is designed and developed with several separate links to form a chain. One end
of a robotic am is mounted on a fixed or movable base. The free end is fitted with an end effector, a gripper,
or a tool holder to hold a drill bit, welding torch, welding or hammering tool, etc.
A six-DOF robot uses the first three links of the manipulator that form the architecture, which helps to
desired position by the end effector within the working environment (volume). The remaining t
links form the wrist of the manipulator, which helps to determine the orientation of the manipulator end point
function.
Most robotic joints use a pair of one-DOF revolute pair (R) and one-DOF prismatic pair (P) for robotic
arm manipulators.

18.15 ROBOTIC ARM POSITIONING CONCEPTS

Accurate positioning of a robotic arm is subject to many factors related to sensors, actuators, control circuits
for measurement, and feedback control mechanis1ns used in the system. Some of the important points include
resolution, spatial resolution, electromechanical control resolution, control resolution, repeatability, accuracy
etc.

18.16 SOURCES OF ERRORS

In order to have a high-precision control of a robotic system, accuracy in calibration, kinematics, and
repeatability must be ensured. Other related parameters such as resolution, kinematic modelling errors, and
random errors must also be taken care of.

18.17 ROBOTIC ARM PATH PLANNING

In order to plan the path of a robot, the related parameters such as slew motion. joint interpolated motion,
and straight-line motion should be calculated and modelled to a defined
implement usinglike technique PlD
18.18 METHODS FOR JOINT-SPACE TRAJECTORY GENERATION
Accurate placement of a robotic arm is also important. It considers joint velocity and jerk calculation using
important analysis tools for controlling joint angles. There are two methods forjoint-space trajectory generation,
namely, third-order polynomial and fifth-order polynomial, which are expressed mathematically as follows:
1 ) = at + br + c; ) = ar t bf + cr' +d

They can be simulated using MATLAB.

*students can refer to the online resources on the companion website for more details
 COMPUTER NUMERICAL CONTRoL AND ROBOTICS 695

18.19 COMPUTER CONTROL OF ROBOT PATHS

It uses ineremental interpolation in path planning. It look-up table that has already been described
uses a
before the movement of the robot takes place. The real-time look-up table helps in path
ISe of all values available in the planning through the
However, an advanced, online
trajectory table.
path planner controller gets look-up values in the
trajectory table at a
predetermined time. These values are set at an appropriate time by the controller for
This technique is used to update the implementation.
current values based on the errors
produced by the planned and actual paths.
18.20 ADVANTAGES AND DISADVANTAGES OF ROBOTS
There number of
are a
advantages
of using robots. Some of them
1. A robot is suitable for
are as follows:
2. It does not get
performing
repetitive work.
exhausted, and so can work round the clock to increase productivity, thus offering
higher eficiency.
3. It has predefined area of
a
work; thus, there are fewer chances of accidents.
4. It measures and controls its
work accurately; thus, raw material
5. It is less dependent on workers wastage and thefts are minimized.
and hence reduces
6. It offers
worker-related problems.
long-term economic benefits.
7. It is capable of
performing in places where a human operator cannot, such as in
8. The operating functions are hazardous areas.
The
implemented more precisely and
accurately than by a human operator.
disadvantages of a robot are as follows:
1. In order to operate a
robot, people should be trained.
2. A large amount of
money requires to be invested for operating a robotic
3. It is dangerous to function.
operate a robot beyond the workspace. There may be conflicts
and robots regarding taking decisions. between human beings

PROJECT DEVELOPMENT HELP

In order to design and develop a CNC and robotic also need to be
system, calculation for various types of load(s) must
determined. The calculation for
the signal
conditioning
be done as per the requirement and environmental need to be made to drivecomponents and devices
the transducer
condition. the controller as well as signal to
the controller to the
Based on the calculated data, suitable specifications drive. motor
for motor drive need be determined, which can meet A suitable software
program needs to be written
the above requirement. as per interface circuit for
measurement and control
Similarly, suitable transducers with specifications applications as per the processor used.

SUMMARY

machines A CNC system is a

CNC system controls the operation of
A
and tools by direct insertion
of numerical data that operates on computer-controlled
a
stored
NC
system
device such as a
The
keyboard. the NC function.
Thus,
program to
perform
input it
through an
order to produce a part,
are
microcomputer that acts as
requires a mini- or
numerical data, in
system.
a
controller in the a
entered in the part program. CNC
696 MECHATRONICS

A CNC system is a reprogrammable system that which function in the closed-loop feedback
offers higher degree of flexibility and computational control mode, which makes it intelligent through
capability as compared to an NC system for cutting, measurement, comparison, and control.
milling, surface finishing, grinding, etc. .A robot can be classifhed based on the types of
A CNC system operates a number of machines by a geometries, end effectors, or grippers, and the
common computer through a direct connection in types of control used in the robot.
real time. Robots are availablein four possible geometric
.CNC offers precise positioning and repeatability of configurations. These are Cartesian, cylindrical,
machine tools; however, errors are introduced due spherical, and articulated configurations.
to friction, known as the stick-slip phenomenon. The flexibility of a robot is determined by the
A robot is a reprogrammable machine that offers number of axes and DOFs of a robot. The axes of
higher degrees of freedom (DOFs) than a CNC motion also play an important role in the position
system. Thus, a robot has several independent DOFs and orientation of the grippers.
in order to communicate with other devices in its A robot works on a workpiece through an end
environment. effector(s), which is attached to the wrist of the robot.
The main components of a robotic system are Robots have a large number of applicatiorns in
transducers, actuators (which may be mechanical, the area of processing, material handling, parts
electrical, pneumatic, or hydraulic) and controllers assembly, parts inspection, safety, etc.

KEY FORMULAE

P
1. Deflection due to payload =
ôp =3EI arm due to gravity is given as: 8, = PPw
3EI' 8Er
2
G
3.
8EI
The deflection produced due to the combined effect
4.
K
of the payload and robotic link mass on the robotic 5 Angular movement= 6=(0 +6,+ 0,)

GLOSSARY

Cartesian (rectilinear/gantry) coordinate configura- Machine control unit (MCU) It is basically the brain
tion A Cartesian (rectilinear) robot has the simplest ofa CNC system and controls the CNC with the helpof
configuration; it is also known as a gantry robot. a data processing unit (DPU) and a control loop unit
Cylindrical configuration Cylindrical configuration (CLU).
robots offer two linear and one angular movements in Mobile robot This type of robot is featured with the
such a fashion that their workspace is described by a capacity to move within a specifhed workspace.
cylindrical coordinate. Numerical control machine A computer numerical
Degrees of freedom Ina robotic system, every joint control (CNC) machine is an automated system that
of the robot requiresa certain degree of freedom in operates machine tools as per the code of letters, such
terms of slider, rotary, or other type of actuator. as G and M codes.
Instruction block (code sequence format) An in- Sensory robot This robot uses two types of sensors;
struction block or a code sequence format is com- one of them is for internal position or location of
posed of various codes in order to implement by the components based on information gathered from
MCU as per the code entered in the instruction
block. outside world via external sensors.
 COMPUTER NUMERICAL CONTROL AND
ROBOTIcS 697

tionary robot It is featured with robotic arms to

omthe
perforn the tasks while the robot remains fully machine-controlled robots.
fixed at one
Tool centre
centre point (TCP) It isis used to
place to hold
and is available something
Tele-oper. erated (man-in-the-loop) robot It is basi-
on the robot or on the tool.
cally human-controlled robot. It is different Work envelope (workspace) Itit is the the
boundary of positions in space that a robotgeometrical
from
can reach.

EXERCISES
Multiple-choice Questions
18.1 Which information signal is received
controller from robot sensors? by a robot (d) All of these.
(a) Pressure 18.7 Which of the
(b) Feedback
(c) Signal following pointsis correct with
(d) Output respect to absolute tool
positioning of a CNC
18.2 Which robot with its own system?
independently on other robots'computer
computer?
works
(a) Dimensioning mistake of an individual
(a) Android
point does not affect the remaining
(b) Insect robot
dimensions.
(c) Automated guided vehicle (b) Movement of each tool is
(d) Autonomous robot measured with
18.3 Which respect to a fixed point or
origin.
of the following dimensions is (c) Errors
with spherical coordinates, in
associated
order to
are
(d) All of these.
checked easily.
the define
position of a point? 18.8 Which of the
(a) One dimension following points is correct for a
(6) Two dimensions point-to-point NC movement system?
(c) Three dimensions (a) It allows controlled
tool movement
an axis at a
time. along
(d) Four dimensions
18.4 What is the (b) This operation is
name of the region over which a
implemented
location for a two-axis
at a fixed
robot arm coordinate
accomplishes its tasks? (c) This enables machine and tool position.
(a) Coordinate geometry (c) Reference movement
frame control in all
(6) Reference axis (d) Work envelope planes regularly.
18.5 What is the name of the (d) None of these.
coordinate in which a 18.9 Which of the
robot arnm is able to move
along three straight following points is corect for a
contour or continuous
independent perpendicular axes? path system?
(a) Revolute geometry (a) It allows tool movement control
axis at a time. along one
(b) Spherical coordinate geometry
(c) Cartesian coordinate geometry (b) It allows machine and tool
control in all planes movement
(d) Cylindrical coordinate geometry regularly.
8.6 Which of the (c) It does not require a
specitie path
following points is correct with movement from one
tor tasl
respect to incremental tool positioning of a point to the nert
(d) None of these
CNC system?
18,10 In which mode, coordnates
(a) Each tool movement is
performed with enterng into a

respect to the last tool position. program are speciied relattne to the
zero point? program
(b) Each tool movement is measured from a
(a) C'anned eyele mnode
fixed point (origin).
(b) lneremental mode
(c) Each tool movement is measures from a
(c) Absolute mode
Tero point.
(d) Rapid mode
 698 MECHATRONICS

Review Questions
18.1 What are the advantages of NCmilling machines 18.17 Classify robots based on their working volurme
over conventional miling machines? 18.18 Write down the general classification of robots.
18.2 Why are numerical control machincs so popular? 18.19 Explain the broad classification of robotic
18.3 What are the features of CNC machinery? systems
18.4 What are the components of a CNC machine? 18.20 What arethe components of a robotic system?
Explain in brief. Explain each in brief.
18.5 What are the roles of machine control unit 18.21 Write the types of sensors that are used in a
(MCU)? Explain. robotic system. Explain them
18.6 What are the types of CNC tool movement 18.22 State the types of actuators that are used in a
control systems? Explain. robotic system. Explain them.
18.7 Draw and explain the process of a point-to-point 18.23 What is the role of end of arm tooling (EOATy
movement control system. end effectors? Explain.
18.8 Draw and explain the process of a continuous 18.24 Write the factors involved in the design of a
path tool movement control system. robotic arm. Explain them their effects.
18.9 What are the types of CNC axis of motion? 18.25 Explain the forward transformation method for
Explain in brief. gripper position determination.
18.10 What are the methods of CNC machine 18.26 Explain the backward (inverse) transformation
programming? method.
18.11 What are advantages of computer-aided part 18.27 Write the concepts involved in robotic am
programming using a CAD database over "M' positioning. Brief them.
and 'G'codes based the part programming method? 18.28 Write the factors involved in robotic arm path
18.12 What are the applications of a CNC machine? planning. Explain them.
18.13 Define a robotic system and explain the functions 18.29 Write the methods for joint-space trajectory
of a robot. generation.
18.14 What are the types
ofmotions
associated with a 18.30 Explain the computer control of robotpaths
robot? Explain in brief. 18.31 What are the possible sources of errors
18.15 What are the governing laws ofrobots?
Explain introduced in a robotic system?
in brief. 18.32 What are the advantages and disadvantages of
18.16 Write important robotic terminologies. robots?

Answers to Multiple-choice Questions

18.1 (b) 18.2 (d) 18.3 (c) 18.4 d) 18.5 (c) 18.6 (a) 18.7 (d) 18.8 (b) 18.9 (b) 18.10 (c)