MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Depart,rnent of Electrical Engineering arlrl Cornpllt,er Science
Spring Terrr~2007
Lat) 1U
Introduction
The goal of t,lle lal)orat,ory is t l ~ edesign of a. velocit>i <:ontrolloop t,llrongl~tlle use of t,lle rnathernati<:al rrlorlel
ol~tainerlfor t l ~ eservornr<:hanis~r~
in Lab 1.4. kleasnrernents are rrlarle in t l ~ elal)orat,ory t,o verify reslllts
<:alcl~laterl
in tlle prelal). Use a rrlotor stat,ior~wit11 a flyml~eelon tlle servo for tlle erlt,ire lal).
Equipment
For this lal). yon will need to pick 111)the follorrir~git,errls frorr~tlle eq~~iprnent
desk: five UKC c:al)les, 3 BNC
T-conne<:tors,arlrl a 2 /IF capa<:it,or.
Measurements
Confignre t,lle servorr~ecl~ar~isrr~
as sllorvr~1)elorv. Use t l ~ e.'Snrnrning .4rnp / Cornpensat,or" section in t l ~ e
center of tlle I)ox. Set it,s s\%-it,ch
tn the "flat," settir~gand dial in tlle v?%lnenf gain t,llat yo^^ calcl~late~l
in t l ~ e
prelat). Not,e illat t l ~ epotentiornet,er car1 1)e 11sec1t~ set the c n ~ r ~ p e ~ ~ sgr%i11
a t ( >i11
r t,lle range t)et,wee~~
0 r%rld10
(a pot sett,ir~gof .'S42" rno~ll(itllns corresponrl to a. corrlpensator gain of S.42).
compensator
input G,:
power amp
-2 Y/J:
motor
1'L
&
l',,, ( 3 )
d
1. Drive t,lle systerrl i11put wit11 a syirmf! v ~ n o r 'of volt,age and (iisplay H,,,, to rrleasnre t,lle 10%~-90%risetirr~e
of t,lle rrlot,or velocity. Cornpare yollr rnean~rernent\%-it,ht l ~ ecalcl~laterlvahle frorr~tlle prelat). Ue
sure illat yo^^ (lon't over-drive and satnrate tlle syst,e~r~
while t>%kingyour rise tirrle rneasl~rernent.By
ot)servir~gT"L, (iet,er~r~ir~e
t,lle i r ~ p ~clrive
~ t , x r ~ p l i t , ~ ~~v11i~:h
r l e is reqnired t,n ~ r ~ n ~ r ~ e r ~ s?~tnrate
t , a r i l j ~ t,l~e
systern.
2. Drive tlle systern \%-it,ha sriir' i i ~ a v r !of voltage and fir111tlle freqnen<:yrrl~eret l ~ err~ag~~it,l~(le
of tlle closecl
loop gain has rlropperl to 0.707 of it,s DC vahle (this is t,lle 3dB freq~lency).How rloes t,l~isfreq~lency
relate to tlle t,irrle <:onstant rrleasnrerl in t,lle preceding step response?
3. Drive tlle systerrl wit11 a srjolim rolioe of voltage and rrleasnre t l ~ est,eacly st,ate error to a ur~itstep
inpnt. It rnay l)e helpfi~lto use t,lle "<:hannelr r ~ a t (&)"
l ~ fim<:tion of t,lle oscilloscope in facilit,at,ingthis
rrleasnrerrleIlt.
Place a. 2 lrF capacitor across tlle "C~,," t,errr~irlalsof t,lle <:ornpensat,orand rrlove it,s s ~ v i t c to
l ~ the " P + I
setting. Tlle systerrl is IIOW (:nr~fignredwit11 a proportional plus ir~tegral<:ontroller.
4. 1Ieas11re t,lle st,eacly state error of t,lle systerrl in respor~seto a ur~itst,ep i n p ~ ~and
t , cornpare illis \%-it,h
t l ~ ereslllt nl)tr%i~led
wit11 t,lle proport,ional <:ontroller.
Cite as: James Roberge, course materials for 6.302 Feedback Systems, Spring 2007.
MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY].
klove t,lle cornpensator sr%-it,ch
l~ackto t l ~ e.'flat," ~~osit,ion
arlrl rerrlove t l ~ ecapacitor. Dial in the cornpensator gain calcl~laterlin t l ~ eprelal] for t,lle loop <:onfig~lration
r%-it,ha <:~~rrent-rlrive~~
rnot,or. klove t,l~eporrer
amplifier srrit<:hto t,lle "-0.1 A/\"' sett,ing.
5. 1Ieas11re t l ~ e10%-90% rise tirrle (r%-it,ha. square warre input,), t,lle 31113 frrq~lency(rvith a sim~soi(ial
i n p ~ ~ tarlrl
) . the st,eacly stat,e error to a. step (r%-it,ha square wave i n p ~ ~of
t ) t l ~ esyst,ern. Cornpare t l ~ e
result,s rritl~tllose ol~tainr(iin t,lle voltage driven case. Are the res~lltsas you expect,ed'? Explair~.
Write Up
T l ~ er%-rit,e
1111
for this la11 sl~ol~lrl
l)e prepared in t l ~ esarrle spirit as last meek's: short, sirnple. arlrl informal.
Useful Formulae
Cite as: James Roberge, course materials for 6.302 Feedback Systems, Spring 2007.
MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY].