Dcservo Motor 150404122524 Conversion Gate01

8/20/2019 Dcservo Motor 150404122524 Conversion Gate01

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D C

S E R V O -

M O T O R

Guided by:

Prof. .I.PATEL


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First, What is the meaning of servo?

In modern usage the term servo or servo-

mechanism is restricted to a feedback contro systemin !hich the controed variabe is mechanica"osition or time derivatives of "osition such asveocity and acceeration.

A servo is a device# eectrica# mechanica oreectro mechanica# that u"on recei"t of a stimuus orin"ut# !i em"oy feedback for veocity and$or"osition contro# creating a cosed oo".

A feedback system is a contro system !hich tendsto maintain a "rescribed reationshi" bet!een acontroed %uantity and a reference %uantity bycom"aring their functions and using the di&erence asa means of contro.


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Eectrica feedback contro systems rey mainy on

eectrica energy for o"eration. Im"ortantcharacteristics usuay re%uired for such a controare '(fast res"onse# )(high accuracy#*(unattended contro and +(remote o"eration.

The essentia for such a contro are '(an errordetecting device# )(an am"i,er and *(errorcorrecting device# as iustrated in foo!ing ,gure.

Continued


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Continued

Each eements serves a functiona "ur"osein matching the reguated or controed%uantity to the reference %uantity.

The error-detecting device determines!hen the reguated %uantity is di&erent from

the reference %uantity.It then sends out an error signa to the

am"i,er !hich in turn su""ies "o!er to theerror correcting device.

ith this "o!er the error correcting devicechanges the reguated %uantity so that itmatches the reference in"ut.

The cosed oo" at feedback controsystem is sho!n in ,gure.


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Servo-motor: signa# a$ru"t#% and a!!e#erate the #oad&ui!'#% are !a##ed the servo-motors( A servo-motor is motor !hich is a "art of

servomechanism. It is ty"icay "aired !ithsome ty"e of encoder to "rovide "ositioningand s"eed feedback and some errorcorrecting device !hich actuates the su""y

signa. The fundamenta# !hara!teristi!s to besought in any servo-motors '(The motor out"ut tor%ue shoud be

"ro"ortiona the votage a""ied to it. )( The direction of the tor%ue deveo"ed bythe servo-

motor shoud be de"end u"on the


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Continued There are mainy t!o ty"es of servo-motors#

'(A /ervo-motor )(0 /ervo-motor

A servo-motors are generay "referred foro!-"o!er use. And for high-"o!er use 0servo-motors are "referred because theyo"erate more e1cienty than com"arabe to

A servo-motors


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DC Servo-motor:

2nike arge industria motors# dc servomotorsare not used for continuous energy conversion.

The basic o"erating "rinci"e is same as othereectromagnetic motors.

0esign# construction and mode of o"erationare di&erent. The rotors of this kind of motor

are designed !ith ong rotor engths andsmaer diameters. They have arge si3e thanthat of conventiona motors of same "o!erratings.

There are various ty"es of dc servomotors!hich are '(/eries motors# )(/"it seriesmotors# *(/hunt contro motor 4 +(Permanentmagnet shunt motor.


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Series motors: The series motor has ahigh starting tor%ue and dra!s arge

current ./"eed reguation of this kind ofmotor is "oor . 5eversa can be obtained byreversing the "oarity of ,ed votage !iths"it series ,ed !inding 6i.e. one !inding for

direction of rotation(. This method reducesmotor e1ciency to some e7tent .

S"#it series motors: /"it series motorare the dc series motor !ith s"it-,ed rated

!ith some fractiona kio!att . This ty"e ofmotor can o"erate as a se"aratey e7cited,ed-controed motor. The armature issu""ied !ith a constant current source. /"it

series motor has a ty"ica tor%ue-s"eed


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Shunt !ontro# motor: 0 shunt ty"eservomotor is not di&erent from any other dc

shunt motor. It has t!o se"arate !indings:,ed !indings "aced on stator and armature!inding "aced on the rotor of the machine.9oth !indings are connected to a dc su""y

source. In a conventiona dc shunt motor#the t!o !indings are connected in "araeacross the dc su""y. In case of aservomotor# the !indings are su""ied !ith

se"arate dc source. )ermanent magnet shunt motor: Permanent magnet shunt motor is a ,7ede7citation motor !here the ,ed is actuay

su""ied by a "ermanent magnet.


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Constru!tion:

It has construction as same as dc motor. It is

consist of stator and rotor and controing"arts.

It has feedback generator for generatingfeedback for controing the s"eed 4 tor%ue.

It has t!o "orts one for dc su""y and otherfor controed dc su""y.


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Constru!tion:


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In 0 o"eration# servomotors are usuay

res"onds to error signa abru"ty andacceerate the oad %uicky. A 0 servo motoris actuay an assemby of four se"aratecom"onents# namey:

'. 0 motor). Gear assemby*. Position-sensing device+. ontro circuit.

r'ing "rin!i"#e of DC servomotor:


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The motors !hich are utii3ed as 0

servo motors# generay have se"arate0 source for ,ed !inding andarmature !inding.

The contro can be archived either bycontroing the ,ed current or armaturecurrent. ied contro has some s"eci,cadvantages over armature contro and

on the other hand armature contro hasaso some s"eci,c advantages over ,edcontro. hich ty"e of contro shoud be a""ied

to the 0 servo motor# is being decided

Continued


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Continued

In case of ,ed controed dc motor# the ,ed ise7cited by the am"i,ed error signa mentioned

earier. The armature !inding is energi3ed froma constant current source. Tor%ue deveo"ed is"ro"ortiona to ,ed current 6I;( u" to

saturation eve.

This method is a""ied in sma servomotors. Ithas onger time constant o!ing to highyinductive ,ed circuit so dynamic res"onse isso!er than armature controed dc motor.

9ut in armature controed dc motor# the motorarmature is energi3ed by am"i,ed error signaand ,ed is su""ied from a constant currentsource.


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The ,gure beo! iustrates the schematic diagramfor a ,ed controed 0 servo motor. In thisarrangement the ,ed of 0 motor is e7cited be theam"i,ed error signa and armature !inding is

energi3ed by a constant current source. The ,ed is controed beo! the knee "oint ofmagneti3ing saturation curve. At that "ortion of thecurve the mmf ineary varies !ith e7citation

current. That means tor%ue deveo"ed in the 0motor is directy "ro"ortiona to the ,ed currentbeo! the knee "oint of magneti3ing saturationcurve.


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rom genera tor%ue e%uation of 0 motorit is found that# tor%ue T > =I

a

. here# = is

,ed ;u7 and Ia is armature current.

9ut in ,ed controed 0 servo motor# thearmature is e7cited by constant current

source # hence Ia is constant here. =As ,ed of this 0 servo motor is e7cited byam"i,ed error signa# the tor%ue of themotor i.e. rotation of the motor can becontroed by am"i,ed error signa. If theconstant armature current is arge enough

then# every itte change in ,ed currentcauses corres ondin chan e in tor ue on

Continued


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The direction of rotation can aso be ateredby using s"it ,ed 0 motor# !here the ,ed

!inding is divided into t!o "arts# one haf ofthe !inding is !ound in cock!ise directionand other haf in !ound in anticock!isedirection.

The am"i,ed error signa is fed to the ?unction "oint of these t!o haves of the ,edas sho!n beo!. The magnetic ,ed of bothhaves of the ,ed !inding o""oses each

other.0uring o"eration of the motor# magnetic ,edstrength of one haf dominates otherde"ending u"on the vaue of am"i,ed errorsigna fed bet!een these haves.

Continued


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*rmature Contro##ed DC Servo MotorTheor%:

The ,gure beo! sho!s the schematic diagram for

an armature controed 0 servo motor.


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Again# at saturation the ,ed ;u7 is ma7imum.As !e said earier# the genera tor%ue e%uation

of 0 motor is# tor%ue T > =Ia.

@o! if = is arge enough# for every itte changein armature current Ia there !i be a "rominent

changer in motor tor%ue. That means servomotor becomes much sensitive to the armaturecurrent.As the armature of 0 motor is ess inductiveand more resistive# time constant of armature

!inding is sma enough. This causes %uickchange of armature current due to suddenchange in armature votage. That is !hydynamic res"onse of armature controed 0

servo motor is much faster than that of ,ed

Continued


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Wor'ing:'. The servo motor has some contro circuits and a

"otentiometer 6a variabe resistor# aka "ot( that is

connected to the out"ut shaft.). The "otentiometer ao!s the contro circuitry to monitorthe current ange of the servo motor. If the shaft is at thecorrect ange# then the motor shuts o&.

*. If the circuit ,nds that the ange is not correct# it !i turn

the motor the correct direction unti the ange is correct.+. The out"ut shaft of the servo is ca"abe of traveingsome!here around 'B degrees. 2suay# its some!here inthe )'B degree range# but it varies by manufacturer.

C. A norma servo is used to contro an anguar motion of

bet!een B and 'B degrees. A norma servo ismechanicay not ca"abe of turning any farther due to amechanica sto" buit on to the main out"ut gear.

D. The amount of "o!er a""ied to the motor is "ro"ortionato the distance it needs to trave.

. /o# if the shaft needs to turn a arge distance# the motor!i run at fu s"eed. If it needs to turn ony a sma

W 'i i )CM


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Wor'ing using )CM:'. The contro !ire is used to communicate the ange.). The ange is determined by the duration of a "use that is a""ied to

the contro !ire. This is caed Puse oded Foduation.*. The servo e7"ects to see a "use every )B miiseconds 6.B)

seconds(. The ength of the "use !i determine ho! far the motorturns.

+. A '.C miisecond "use# for e7am"e# !i make the motor turn to theB degree "osition 6often caed the neutra "osition(.

C. If the "use is shorter than '.C ms# then the motor !i turn the shaftto coser to B degrees.

D. If the "use is onger than '.Cms# the shaft turns coser to 'Bdegrees.


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Tor&ue-S"eed Chara!teristi!s: The tor%ue-s"eed characteristics of se"aratey e7citeddc servo-motor is sho!n in beo! mentioned ,gure.

Their armature is deiberateydesigned to have arge resistanceso that tor%ue s"eedcharacteristics are inear and havearge negative so"e as sho!n in

,gure. The negative so" serves the"ur"ose of "roviding the viscousdam"ing for the servo drive system

As sho!n in ,gure the armature mmf and e7citation,ed mmf are in %uadrature this fact "rovides the fasttor%ue res"onse because tor%ue and ;u7 becomedecou"ed accordingy a ste" change in armaturevotage or current a %uick change in the "osition or

s"eed of the rotor.


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The motor out"ut tor%ueis "ro"ortiona to the

votage a""ied to it 6i.e.controed votagedeveo"ed by am"i,er inres"onse to an error

signa(. The instantaneous"oarity of contro votagegoverns the direction of

tor%ue deveo"ed byservomotors.

The variation in tor%ue-s"eed characteristics due

to variation intem erature is sho!n in

Some other Chara!teristi!s:


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Some !ontro##ing !ir!uitsused:


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)+D H P5P5TI@AL I@TE5G5AL 0E5IATIE


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Feed$a!' sensor used:


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)erforman!e S"e!i!ations:0 servomotors share many "erformance s"eci,cations that area""icabe to a ty"es of 0 motors. To "ro"ery si3e a motor#

these s"eci,cations must be matched according to the oadre%uirements of the a""ication.

Shaft s"eed R)M. de,nes the s"eed at !hich theshaft rotates# e7"ressed in rotations "er minute 65PF(. Ty"icay# the s"eed "rovided by the manufacturer is the no-

oad s"eed of the out"ut shaft# or the s"eed at !hich themotorKs out"ut tor%ue is 3ero.

Termina# vo#tage refers to the design votage of the 0motor. Essentiay the votage determines the s"eed of a 0motor# and s"eed is controed by raising or o!ering thevotage su""ied to the motor.

Tor&ue is the rotationa force generated by the motorshaft. The tor%ue re%uired for the motor is determined by thes"eed-tor%ue characteristics of the various oads e7"eriencedin the target a""ication.Starting tor&ue - The tor%ue re%uired !hen starting themotor# !hich is ty"icay higher than the continuous tor%ue.

Some ratings of d! servo motor avai#a$#e:


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Shaft S"eed:•Less than '#D'B r"m•'#D'B to *#' r"m•

*#' to +#BB r"m•+#BB to #BB r"m•#BB r"m and u"

Termina# Vo#tage:•

Less than )B 0•)B to CB 0•CB to 'BB 0•'BB to 'B 0•'B 0 and u"

Continuous Current:•Less than ' am"s•' to + am"s•+ to am"s• to ' am"s•' am"s and u"

Continuous Tor&ue:•Less than B.+C @m•B.+C @m to '.B @m•'.B @m to C @m•C @m to ' @m•' @m and u"

Continuous Out"ut

)oer:•Less than B.+


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Some name-"#ates of d! servo-motor avai#a$#e:


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and !eight.Encoder determines accuracy andresoution.


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5e%uires MtuningM to stabii3e feedback oo".Fotor Mruns a!ayM !hen something breaks./afety circuits are re%uired.om"e7. 5e%uires encoder.9rush !ear out imits ife to )#BBB hrs. /erviceis then re%uired.Peak tor%ue is imited to a ' duty cyce.Fotor can be damaged by sustained overoad.9e!idering choice of motors# encoders# andservo-drives.Po!er su""y current 'B times average to use"eak tor%ue.Fotor deveo"s "eak "o!er at higher s"eeds.Gearing often re%uired.Poor motor cooing. entiated motors are

easiy contaminated.

Disadvantages:


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*""#i!ations:0 servomotors ,nds its a""ications in variousdomain. /ome of them are given beo!:

or very high votage "o!er systems# dc motorsare "referred because they o"erate moree1cienty than com"arabe ac servomotor.It has aso ,nd its a""ication in ink?et "rinters

and 5 heico"ters. To drive conveyors used in Industriamanufacturing and assembing units to "ass anob?ect from one assemby station to another.

It is aso used in soar tracking system.0 servomotors are !idey used in robots# toycars and other "osition controed devices.idey used in radars# com"uters# robots#machine toos tracking system# "rocess

controers etc.


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ome animations shoing *""#i!ations:


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h a n

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)re"ared $%:

So#an'i /eegnesh012132024256.

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Dcservo Motor 150404122524 Conversion Gate01