noi_dung

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CHNG 1

GII THIU V TI

1.1 t vn

Trong ging dy, c rt nhiu phng php iu khin tc ng c DC

nhng thut ton PID t ra hiu qu nht, thng c dng minh ha cho cc v d thit

k h thng trong mn hc iu khin t ng.

Lut iu khin PID l mt thut ton iu khin d v n gin cc kha cnh:

l thuyt n gin, d ch to, d p dng, d s dng... m vn t hiu qu l p ng

c vic iu khin mt qu trnh no gi tr mong mun nn c dng nhiu

trong cng nghip nh iu khin nhit , p sut, lu lng v.v...

Con lc ngc c ng dng rt nhiu trong k thut v c th s dng thut ton

PID iu khin h thng ny. V vy nhm chn ti nghin cu l NG DNG

PID TRONG IU KHIN CON LC NGC.

M hnh con lc ngc c hai m hnh chnh l Rotary v Liner, trong ti ny

nhm iu khin m hnh Liner.

1.2 Tnh hnh nghin cu trong v ngoi nc

B iu khin PID hin nay c hai loi: analog v digital.

Cc b iu khin PID c trn th trng ca cc hng ln thng c ng gi

thnh sn phm hon chnh, khi lp t vo h thng khng cn phi lm g thm ngoi

vic thit lp cc thng s hot ng.

Cng trnh nghin cu v thit k b iu chnh PID s trong cc ti liu nghin cu

nc ngoi ch yu l thit k hon chnh mt module iu khin duy nht t thnh phn

x l tn hiu, x l v tnh ton trung tm, cng sut v.v... Bn cnh , phn mm

(chng trnh iu khin) trn my tnh ch yu vn l giao din kiu Terminal.


Trong nc cng c nhiu ti nghin cu v ng dng b iu khin PID,

nhng ph bin vn l dng PID analog, b iu khin PID s vn cn t v cha tht

hon chnh.


CHNG 2

C S L THUYT

L thuyt iu khin t ng.

2.1.Khi nim:

a.iu khin.

L qu trnh thu tp thng tin, x l thng tin v tc ng ln h thng p ng h

thng tha yu cu t ra.

iu khin t ng l qu trnh iu khin khng c s can thip ca con ngi.

b.H thng iu khin.

Gm ba thnh phn c bn: B iu khin, i tng iu khin, Thit b o. Nh

hnh sau :

B iu khin

i tngiu khin

Thit b o

B soe(t) u(t)

z(t)

y(ht)

y(t)r(t)

Thit b iu khin

Hnh 2.1: cu trc c bn ca h thng diu khin.


Trong :

r(t): tn hiu vo. e(t) : tn hiu sai lch. u(t) : tn hiu iu khin. z(t): tn hiu nhiu. y(t) : tn hiu ra. yht(t) : tn hiu hi tip

c. B iu khin.

Dng tn hiu sai lch e to tn hiu iu khin u. Thut ton xc nh u(t)

gi l thut ton iu khin.

B iu khin lin tc c th thc hin bng c cu c kh, thit b kh nn, mch

in RLC, mch khuych i thut ton.

B iu khin s thc cht l cc chng trnh phn mm chy trn vi x l hay

my tnh.

d. Cc nguyn tc iu khin.

Nguyn tc gi n nh. Gi tn hiu ra bng tn hiu vo. C ba nguyn tc iu khin gi n nh.


iu khin b nhiu.

i tngiu khin

u(t)

z(t)

y(t)r(t) B iu khin

Hnh 2.2: s diu khin b nhiu.

H thng lng trc nhiu tnh ton, b tr sai s trc khi nhiu nh hng

n i tng. V khng th lng ht cc nhiu nn iu khin b nhiu cht lng

khng cao.

iu khin san bng sai lch.

B iu khin

i tngiu khin

Thit b o

e(t) u(t)

z(t)

y(t)r(t)

Hnh 2.3: S iu khin cn bng sai lch.


Tn hiu ra y(t) c o v phn hi v so snh vi tn hiu vo r(t). B iu khin

s dng sai lch vo-ra tnh ton tn hiu iu khin u(t). Nguyn tc ny c th

trit tiu cc nhiu khng bit trc v khng o c. Tuy nhin, n iu khin sau khi

nhiu thc s nh hng n i tng.

iu khin phi hp.

B iu khin

i tngiu khin

Thit b o

e(t) u(t)

z(t)

y(t)r(t)

Hnh 2.4: s iu khin phi hp.

Nguyn tc iu khin theo chng trnh. Tn hiu ra thay i theo mt hm thi gian nh trc.


Nguyn tc iu khin thch nghi.

i tngiu khin

u(t)

z(t)

y(t)r(t) B iu khin

Chnh nh

Hnh 2.5: s iu khin thch nghi

Khi cn iu khin cc i tng phc tp, c thng s d b thay i, hoc nhiu

i tng ng thi m phi m bo cho mt tn hiu c gi tr cc tr, hay mt ch tiu

ti u no .

2.2.B iu chnh PID lin tc.

a.S khi:

eG(s)

yKp

Ki/s

KD.s

B PID

r

Hnh 2.6: s khi b iu khin PID lin tc


b. Phng trnh vi phn:

Hnh 2.7: ng c tnh ng hc b PID

Trong :

KP : h s khuych i. KI : tc tch phn. KD: hng s thi gian vi phn. TI: thi gian hiu chnh. TD:thi gian tc ng sm.


c.K hiu PID:

Hnh 2.8: k hiu b PID

d.Hm truyn :

2d p i

d

K s K s KKiG(s) Kp K ss s

+ += + + =

e.c tnh qu :

Hnh 2.9: biu c tnh qu ca b PID

Khi khng c thnh phn I,D ta c b iu khin P. Tng t ta c b iu khin

PI, PD.


f. So snh cc khu hiu chnh PI, PD, PID.

Hnh 2.10: p ng qu h thng

Nhn xt :

Khu PI tc p ng nhanh, gim thi gian qu nhng vt l tng.

Khu PD gim vt l, khng nh hng sai s v gim dao ng.

Khu PID vi thng s thch hp c th hiu chnh h thng n nh vi sai s xc lp bng 0, vt l v thi gian qu t yu

cu mong mun.


u im ca b PID:

e(t) ln : thng qua up(t), tn hiu diu khin u(t) cng ln.

e(t) cha bng 0: thng qua uI(t), PID vn cn to tn hiu iu khin.

e(t) thay i ln : thng qua uD(t), phn ng ca u(t) cng nhanh.

2.3. B iu chnh PID s (ri rc).

a.S khi.

r(t) e(t)PID s ZOH G(s)

e(k)

T

u(k) y(t)

Hnh 2.11: s khi b PID ri rc

b.Phng trnh vi phn PID lin tc.

Ri rc ha phng trnh vi phn b iu chnh PID lin tc, thu c b iu

chnh PID s nh sau:


U(t) thay bng UK=U(k).

P I DK K K KU U U U= + +

Khu t l:

Up(t) = Kp.e(t) thay bi UKP = Kp.eK

Khu vi phn:

D Dde(t)U (t) K

dt=

thay bi D K K 1K D

e eU KT

=

Khu tch phn:

IK I KU K e (t)dt=

thay bi I I K 1 KK K 1 I

e eU U K T2

+= +

Phng trnh PID s :

I K 1 K K K 1K P K K 1 I D

e e e eU K e (U KT ) K2 T

+ = + + +


CHNG 3

CC THIT B

3.1.ng c DC

3.1.1.nh ngha:

ng c in mt chiu (DC) c s dng trong cng nghip trong nhiu nm

qua. Cng vi cc b iu khin DC, ng c in mt chiu cung cp s iu khin rt

chnh xc. ng c in mt chiu c s ng nhng ni yu cu moment m my

ln hoc yu cu iu chnh tc bng phng v phm vi rng nh bng ti, thang my,

my p, nhng ng dng trong ngnh hng hi, cn vt liu, giy, cao su

ng c sevor DC l ng c DC thng thng c hi tip encorder hoc

tachometer.

Hnh 3.1: ng c DC servo


Cu to chung ca ng c DC gm: v, trc, bi, phn cm (stato), phn ng

(roto), c gp v chi in

Hnh 3.2: cu to ng c in 1 chiu kch t c lp

Ngun in mt chiu DC tc ng ln cun ng qua c gp. Cng t trng

khng thay i. Tc ng c ch c th iu khin thng qua dng roto. C th o

chiu chuyn ng bng cch o chiu dng in qua roto

Hnh 3.3: ng c DC t tng vnh cu


Uu

Ukt

+

Rf

I

-

Rkt

+

Ckt

-

A -+

MG2

1 2

Hnh 3.4: S ni dy ca ng c KTL

3.1.2. Phng trnh c tnh c:

o U = E + (R + Rf)*I

Trong :

U : in p phn ng (V)

E : sc in ng phn ng (V)

R : in tr mch phn ng () Rf : in tr ph trong mch phn ng () I : dng in trong mch phn ng (A)

o R = r + rcf + ri + rct

Trong :

r : in tr cun dy phn ng

rcf : in tr cun dy cc t ph

ri : in tr cun b

rct : in tr tip xc ca chi in

Sc in ng E ca phn ng ng c c xc nh theo biu thc :


o == KapNEu 2

Trong :

P : s i cc t chnh

N : s thanh dn tc dng ca cun dy phn ng

a : s i mch nhnh song song ca cun dy phn ng

: t thng kch t di mt cc (Wb)

: tc gc rad/s

a

pNK 2= : h s cu to ca ng c

o ufuu I

KRR

KU

+=

y l phng trnh c tnh c in ca ng c.

Mt khc moment in t ca ng c c xc nh bi:

o MT = uIK

Nu b qua tn tht c tn tht thp th moment c trn trc ng c bng moment

in t k hiu l M

o ( ) MKRR

KU fuu

2+=

y l phng trnh c tnh c ca ng c in DC kch t c lp

Gi thit phn ng phn ng c b t thng thng = const, th cc phng

trnh c tnh c in v phng trnh c tnh c l tuyn tnh. th ca chng c

biu din trn hnh 5, 6


NMI

dmo

I

DMI

Hnh 3.5: c tnh c in ca ng c DC kch t c lp

Hnh 3.6: c tnh c ca ng c DC kch t c lp

ng dng. -Robot.

-iu khin X,Y.

-Dng trong c kh chnh xc.


3.2.Encoder:

Thng thng encoder c:

+ 1 chn VCC

+ 1 chn GND

+ c th c 3 li ra: A, B ( cn c vo y bit hng, vn tc) v Z ( im 0

hay dy trung tnh)

Hnh 3.7: ng c DC c gng encoder

1. Cung cp ngun h thng

2. B iu khin s

3. Module iu khin

3.2.1 Cc loi encoder:

a. Encoder s:

Mi mt Encoder s bao gm mt a trn vi cc vch k mu trn. Cc vch

mu ny c c bp cc u cm bin. a ny thng i km vi trc quay ca n,

trc ny lm quay nhng mu pht tn hiu cho mi v tr nhn c. Cch ghi cc m

trn a ph thuc vo cc mu trn n

Phn loi theo cu to vt l th hin nay Encoder thng c ba loi: Encoder tip

xc, Encoder t trng v Encoder quang


b.Encoder tip xc:

im tip xc thc t ca loi Encoder ny l gia a v c thng qua chi than.

Loi ny c nhc im l to ma st, hao mn, bi bn do mi than, xut hin in tr

tip xc, gy ra rung ng lm gim chnh xc v tui th

phn gii ca Encoder ph thuc vo ng rnh v chnh xc nh nht ca

mt rnh c th c c trn a, phn gii c th t 10 rnh trn a. phn gii c

th tng ln bng cch ghp nhiu tng a hoc dng b dm 9ln xung cho trng thi

cao nht ca bit

c.Encoder t trng:

i vi Encoder t trng th a quay ca n c trng mt lp vt liu t, trong

nhng vch mu khng c ph.Cc vch ny c c bng mt u c nam

chm.R rng vi u im ny th Encoder t trng c tui th cao hn Encoder tip

xc

d.Encoder quang:

Encoder quang l loi thng dng nht nh c chnh xc cao v dng nh sng

ca bn dn. Encoder c ba b phn: a segment c nhng phn trong sut cho nh sng

i qua v nhng phn khng cho nh sng i qua, mt ngun sng cng vi mt h thng

h tr chiu sng,b phn cm bin nh sng

Hu ht Encoder c sn xut vi chnh xc cao, mt Segment c b dy xp

x 12 micros. phn gii ca Encoder quang thng thng c th t n 14 bits.

Hnh 3.8:Mt s Encoder quang


e.B gii m tuyt i:

L loi thit b m ha m cc tn hiu m u ra song song ch th gc quay

tuyt i ca trc. Loi ny khng cn b m m xung m vn c th bit gc quay

ca trc thit b m ha

Hnh 3.9: a Encoder quang

Cng ging nh nhiu loi Encoder khc, b gii m tuyt i gm mt a trn,

trn c nhng khong trong sut v c. nh sng c th xuyn qua nhng phn trong

sut n b cm bin quang, khi a quay th b cm bin bt ln 1 v phn nh sng b

chn bi phn c lm cm bin quang xng 0. Nh vy cm bin quang s to thnh

nhng xung tun t

Khi thit b m ha ny c s dng vi cng mt thit b khc, th v tr 0 ca

trc xam nh gc tc . Khi trc ca thit b m ha quay v ta gc ny th gc quay

c th c hin th trn b ch th ca my. Tn hiu u ra ca thit b m ha khng b

nh hng bi nhiu ca thit b ng, ngt v khng yu cu iu chnh gc quay chnh

xc. Hn na, thm ch nu tn hiu m ha u ra khng th c v trc quay qu nhanh,

th gc quay chnh xc c ghi khi tc quay gim xung, hoc ngay khi ngun cho

thit b m ha b ngt. Thm na, m ha s khng hot ng do s rung ng ca cc

thit b s dng n

Loi thit b m ha tuyt i, c phn gii cao hn v cho ra cc gi tr thay

i trong phm vi rng hn so vi thit b m ha tng dn.


f. Thit b m ha tng dn:

Hnh 3.10: Thit b m ha tng dn trong Encoder

L loi thit b m ha c dy xung ra ph hp vi gc ca trc quay. Thit b m

ha ny khng c xung ra khi trc khng lm vic. Do cn c mt b m m

xung ra

Thit b m ha ch bit v tr ca trc quay bng s xung c m. Dng thit b

m ha ny ch c 1 hay 2 knh nh ra:

Loi 1 chiu (ch c u knh A) l loi ch sinh ra xung khi trc quay

Loi 2 chiu (c u ra knh A v B) cng c th cho bit chiu ca trc quay,

ngha l thun chiu kim ng h. Ngoi ra cn c u dy trung tnh (xung Z) cho mi

vng quay, c ngha l nu quay c 1 vng th xung Z ln 1

Khi a quay theo chiu kim ng h th xung track 1 (B) tr pha hn xung track 2

(A)


g. Quay thun chiu kim ng h:

Hnh 3.11: Cc knh tn hiu ra ca Encoder

Hnh 3.12: Cc knh tn hiu ra ca Encoder khi ng c quay thun

u A vt qu B ( lch pha) = 90O + 45O (T/4 + T/8)

h.Quay ngc chiu kim ng h:

Hnh 3.13: Cc knh tn hiu ra ca Encoder khi ng c quay nghch


3.3.Mch kch Atmega8

T1

ADC3

MISO

R17390

+5V

J4 DIPSOC-14x2

1

23

45

6

7

8

9

10

11

1213

14

282726252423

22

21

20

1918171615

PC6(RESET)

PD0 (RXD)PD1 (TXD)

PD2 (INT0)PD3 (INT1)

PD4 (XCK/T0)

VCC

GND

PB6 (XTAL1/TOSC1)

PB7 (XTAL2/TOSC2)

PD5 (T1)

PD6 (AIN0)PD7 (AIN1)

PB0 (ICP1)

PC5 (ADC5/SCL)PC4 (ADC4/SDA)

PC3 (ADC3)PC2 (ADC2)PC1 (ADC1)PC0 (ADC0)

GND

AREF

AVCC

PB5 (SCK)PB4 (MISO)

PB3 (MOSI/OC2)PB2 (SS/OC1B

PB1 OC1A

R1

47K

RXD

SCK

RXD_RF

JP41

2

3

Le Tan Cuong


3.4.Mch cu H

U2A

4001

1

23

U4

IR2184

3 4

8

1

5

2 6

7

COM LO

VB

IN

VCC

SD VS

HO

U9PC817

12

43

Q4IRF540

DIR

D4POWER LED


3.5.Kt cu c kh

Hnh 3.16: Phn cng ca c kh ca con lc ngc

3.6. Mch iu Khin

Hnh 3.17: Mch iu khin


CHNG 4

VI NT V AVR V PHN MM CODEVISIONAVR

4.1. Tng Quan AVR

Vi iu khin AVR do hng Atmel ( Hoa K ) sn xut c gi thiu ln u

nm1996. AVR c rt nhiu dng khc nhau bao gm dng Tiny AVR ( nh AT tiny 13,

ATtiny 22) c kch thc b nh nh, t b phn ngoi vi, ri n dng AVR ( chn

hn AT90S8535, AT90S8515,) c kch thc b nh vo loi trung bnh v mnh hn

l dng Mega ( nh ATmega32, ATmega128,) vi b nh c kch thc vi Kbyte n

vi trm Kb cng vi cc b ngoi vi a dng c tch hp trn chip, cng c dng tch

hp c b LCD trn chip ( dng LCD AVR ). Tc ca dng Mega cng cao hn so vi

cc dng khc. S khc nhau c bn gia cc dng chnh l cu trc ngoi vi, cn nhn

th vn nh nhau, Hnh 4.1. t bit, nm 2008, Atmel li tip tc cho ra i dng AVR

mi l XmegaAVR, vi nhng tnh nng mnh m cha tng c cc dng AVR trc .

C th ni XmegaAVR l dng MCU 8 bit mnh m nht hin nay.

Hnh4.1 Cc dng AVR khc nhau: Tiny, AVR v Mega

Cu trc c bn ca vi iu khin AVR c th hin hnh 4.2.


Hnh 4.2. Cu trc ca Vi iu khin AVR


4.2. Cu trc AVR

4.2.1.Cc tnh nng chnh:

Microcontroller s dng chp ATMega32 ca Atmel, tn s thch anh 16MHz

RJ45 socket s dng lai tch hp bin p.

Giao tip Ethernet s dng chip ENC28J60 MAC/PHY ca Microchip, provides 10Base-

T Ethernet

AVR v Chip Ethernet giao tip qua giao thc SPI. Giao din ethernet c th gi v nhn

bt k gi thng tin no TCP/UDP/IP, Appletalk, NetBIOS, v.v

Cc thng tin v cu hnh c th c thit lp qua cng COM, 115200 baud 8n1 nh IP

ADDRESS, NETMASK, GATEWAY...

Ngun cung cp s dng DC Adaptor 7 n 12V DC

Cc OI khng s dng ca ATMega32 c a ra ngoi, sn sng kt ni vi thit b

ngoi vi khc. ngoi ra cn cung cp sn ng ISP np chng trnh chip MCU

a s linh kin SMD c s dng cho kch thc nh gn Led bo ngun v Led ch bo

Ethernet tch hp sn rt tin li theo di

4.2.2. Cc thanh ghi chnh ca VDK :

Thanh ghi trng thi - SREG (STATUS REGISTRY).

Nm trong vng nh I/O, thanh ghi SREG c a ch I/O l 0x003F v a ch b

nh l 0x005F (thng y l v tr cui cng ca vng nh I/O) l mt trong s cc thanh

ghi quan trng nht ca AVR, v th m ti dnh phn ny gii thiu v thanh ghi ny.

Thanh ghi SREG cha 8 bit c (flag) ch trng thi ca b x l, tt c cc bit ny u b

xa sau khi reset, cc bit ny cng c th c c v ghi bi chng trnh. Chc nng

ca tng bit c m t nh sau:


Thanh ghi MCUCR cha cc bits cho php chng ta chn 1 trong 4 MODE trn cho cc ngt ngoi. Di y l cu trc thanh ghi MCUCR c trch ra t datasheet ca

chip atmega8.

MCUCR l mt thanh ghi 8 bit nhng i vi hot ng ngt ngoi, chng ta ch

quan tm n 4 bit thp ca thanh ghi ny (4 bit cao dng cho Power manager v Sleep

Mode), 4 bit thp l cc bit Interrupt Sense Control (ISC), 2 bit ISC11, ISC10 dng cho

INT1 v ISC01, ISC00 dng cho INT0. Hy nhn vo bng tm tt bn di bit chc

nng ca cc bit trn, y l bng chn tr ca 2 bit ISC11, ISC10. Bng chn tr cho

cc bit ISC01, ISC00 hon ton tng t.

Thanh ghi iu khin ngt chung GICR (General Interrupt Control Register)

(trn cc chip AVR c, nh cc chip AT90Sxxxx, thanh ghi ny c tn l thanh ghi mt

n ngt thng thng GIMSK, bn tham kho thm datasheet ca cc chip ny nu cn s

dng n). GICR cng l 1 thanh ghi 8 bit nhng ch c 2 bit cao (bit 6 v bit 7) l c

s dng cho iu khin ngt, cu trc thanh ghi nh bn di (trch datasheet).


Bit 7 INT1 gi l bit cho php ngt 1(Interrupt Enable), set bit ny bng 1 ngha

bn cho php ngt INT1 hot ng, tng t, bit INT0 iu khin ngt INT0.

Thanh ghi c ngt chung GIFR (General Interrupt Flag Register) c 2 bit INTF1

v INTF0 l cc bit trng thi (hay bit c - Flag) ca 2 ngt INT1 v INT0, nu c 1 s

kin ngt ph hp xy ra trn chn INT1, bit INTF1 c t ng set bng 1 (tng t

cho trng hp ca INTF0), chng ta c th s dng cc bit ny nhn ra cc ngt, tuy

nhin iu ny l khng cn thit nu chng ta cho php ngt t ng, v vy thanh ghi

ny thng khng c quan tm khi lp trnh ngt ngoi. Cu trc thanh ghi GIFR c

trnh by trong hnh ngay bn di.

Cc thanh ghi khai bo

I/O


-

4.3. CODEVISIONAVR

4.3.1. Gii thiu phn mm CodeVisionAVR:

Trnh bin dch CodeVisionAVR l mt trong rt nhiu trnh bin dch C h tr cho vi

iu khin AVR ca Atmel. Khng nh cc trnh bin dch khc c iu chnh cho ph

hp vi tp lnh AVR, CodeVisionAVR c vit ch dnh ring cho AVR. Do ,

chng trnh to ra bi CodeVisionAVR lun c s chnh xc cao v khng b ph bt k

chc nng no ca AVR. So vi cc trnh bin dch khc, CodeVisionAVR to ra on

m c dung lng nh hn nhng hiu qu hn. Hn na, CodeVisionAVR c thnh

phn CodeWizard mt cng c h tr to code v cng hiu qu i vi ngi lp trnh.

CodeVisionAVR bao gm gn nh ton b cc thnh phn ca ngn ng ANSI C c

th dng trong cu trc AVR. Chng trnh cn tch hp thm vi chc nng khc h

tr cho cu trc c bit ca AVR v nhng yu cu ca h thng nhng.


CodeVision h tr chng trnh np trc tip cho vi iu khin AVR theo tiu chun

SPI, qua cng COM, I2C, cng my in v cng USB. Chc nng Terminal cho php

ngi lp trnh c th thc hin vic giao tip gia my tnh vi vi iu khin qua cng

COM.

Trong cc th vin sn c ca CodeVision, ngoi cc th vin chun ca ngn ng C,

cn c cc th vin h tr c bit nh sau:

- Module LCD kiu k t.

- Giao tip I2C ca Phillips.

- Cm bin nhit LM75 ca National Semiconductor.

- Cc IC Phillips PCF8563, PCF8583, Dallas DS1302 v ng h thi gian thc

DS1307.

- Giao tip 1 dy ca Dallas.

- Cm bin nhit DS1802 / DS18S02.

- Thermometer / Thermostat DS1621.

- EEPROM DS2430 v DS2433.

- SPI.

- Qun l ngun nng lng.

- Delay.

- Chuyn i m Grey.

CodeVision cn c chc nng t ng to m chng trnh (Code Wizard), cho php

to ra cc chng trnh con vi cc chc nng c bit, gip ngi lp trnh tit kim thi

gian v c c nhng on chng trnh con c chnh xc v chun mc cao. Cc

chc nng c h tr gm c:

- Thit lp giao tip b nh ngoi.

- Phn bit ngun reset.


- Khi to ng vo/ra.

- Khi to ngt ngoi.

- Khi to Timer/Counter.

- Khi to Watchdog Timer.

- Thit lp truyn d liu USART.

- So snh analog.

- ADC.

- Giao tip SPI.

- I2C, cm bin LM75,

- Giao tip 1 dy (1 wire).

- LCD.

4.3.1. Lp trnh vi CodeVisionAVR:

CodeVision l phn mm c giao din thn thin vi ngi dng. Cc phn ca

CodeVision u d dng s dng v ngi dng c th quen vi cc thao tc sau 1 vi ln

thc hin. Phn ln cc chc nng nh to File, m/ng File, lu File, u khng c

s khc bit vi cc phn mm chy trn nn Windows. Do , ngi dng d dng lm

quen v s dng CodeVision mt cch thnh tho.

Cc thao tc quan trng trong khi s dng CodeVision:

- To File mi:

Thc hin thao tc File/New, mn hnh xut hin hp thoi:


Hnh 4.3 Hp thoi New File

Nhn chn Source v chn OK, mn hnh son tho s hin ra vi tn file l

untiltled.c. Ngi lp trnh c th lu file vi tn khc ty chn.

- To mt Project mi:

Nhn File/New, xut hin hp thoi:

Hnh 4.4 Hp thoi New File

Chn Project v OK, xut hin hp thoi tip theo:

Hnh 4.5 Hp thoi Confirm

to mt project mi hon ton, bn chn No. Sau t tn cho project mi v

chn add ly file ngun vo project.


Vic to project bng CodeWizard:

Chn File/New, sau chn Project. Khi xut hin hp thoi Confirm nh trn th

chn Yes vo CodeWizard. Xut hin khung la chn nh sau:

Hnh 4.6 Ca s CodeWizard

Cc Tab xut hin ngi lp trnh chn la, t loi chip, tn s xung clock n vic

thit lp cc ng dng ca AVR nh: LCD, ng vo / ra, ngt, timer, counter, giao tip

I2C, SPI, 1 wire, 2 wire, analog comparator, USART

Sau khi thit lp cc thng s theo mun, nhn File


Hnh 4.7 Lu Project

Chn Generate, Save and Exit. Sau s xut hin ca s yu cu bn lu tn file.

Khi thc hin xong cc bc trn, chng trnh s hin ra ca s son tho vi cc

on m C c sn ph hp vi nhng la chn bn thit lp trong CodeWizard.

Ca s son tho CodeVision:


Hnh 4.8 Ca s son tho CodeVision

Cch vit chng trnh trong CodeVision hon ton ging vi chng trnh C bnh

thng, t khai bo th vin, hm, bin, con tr, V th, ngi vit chng trnh ch

cn bit s dng ngn ng C l c th d dng lp trnh vi CodeVision.

Khi vit xong chng trnh, bn thc hin sot li bng cch chn trn thanh

toolbar nt Project/Check Syntax. Nu c li pht sinh th chng trnh s hin th cc

thng bo ca s Message pha di.

Khi kim sot v thy khng c li, bn Compile chng trnh bng cch nhn

Project/Compile hoc nhn F9. Chng trnh t ng to ra file np cho vi iu khin.


4.3.2. Cu trc mt chng trnh vit bng CodeVisionAVR:

// Khai bo cc th vin

#include

#include

//Thc hin cc chng trnh ngt

//Bao gm ngt ngoi, ngt truyn nhn, ngt trn Timer/Counter,

interrupt [EXT_INT0] void ext_int0_isr(void)

{

//on code trong chng trnh ngt

}

//Khai bo bin ton cc

//Khai bo hoc vit cc hm, chng trnh con

//Chng trnh chnh

void main(void)


{

//Khai bo bin cc b

//Khi to trng thi ban u ca vi iu khin

.......................................

//Cho php ngt ton cc

#asm(sei)

//Vng lp v tn

while (1)

{

//Vit code cho chng trnh chnh

};

}

c bit, khi cn chn mt on code Assembly vo chng trnh th ta thao tc

nh sau:

#asm

//on code asm

#end asm


4.3.3 Cc kiu d liu ca CodeVision:


CHNG 5

THIT K B PID CHO CON LC NGC

5.1.Thit k b PID s:

Thng s KP, KI ,KD ca phng trnh PID s thng c chn trn c s

xc nh c m hnh ton hc ca i tng v yu cu ca bi ton thit k.

Trong trng hp m hnh ton hc ca i tng khng xc nh c. Cc

thng s ca b iu khin xc nh theo phng php thc nghim.

Cc phng php iu khin PID s:

5.1.1Phng php Ziegler-Nichols:

Zieger Nichols a ra phng php xc nh thng s ti u ca b PID hoc t

p ng qu ca i tng (phng php Zieger-Nichols th nht) hoc t p ng

qu ca h thng kn (phng php Zieger-Nichols th hai).

Phng php Zeigler Nichols th nht: Ziegler Nichols a ra phng php xc nh thng s ti u ca b PID l

da trn th hm qu ca i tng hoc da trn cc gi tr ti hn thu c qua

thc nghim

S dng hm qu ca i tng :

Phng php ny cn c tn l phng php th nht ca Ziegler Nichols. N c

nhim v xc nh cc thng s Kp, TN, TV cho cc b iu khin P, PI v PID trn c s

di tng c th m t xp x bi hm truyn t dng :

t-T sK eG (s) =

Ts + 1

Sao cho h thng nhanh chng v trng thi xc lp v vt l max khng vt qu mt gii hn cho php, khong 40% so vi

=

tthh )(lim)(


%40)(max

max =hh

Ba tham s Tt ( thi gian tr ), K ( h s khuch i ) v T (hng s thi gian qun

tnh) ca m hnh xp x c th xc nh c gn ng t th hm qu h(t) ca i

tng. Nu i tng c dng nh (hnh 14) m t th t th hm h(t) ta c ra

c.

- Tt l khong thi gian tn hiu ra h(t) cha c hn ng ngay vi tn hiu kch

thch 1(t) ti u vo

- K l gi tr gii hn

=t

thh )(lim)(

- Gi A l im kt thc khong thi gian tr, tc l im trn trc honh c

honh bng Tt. Khi T l khong cn thit sau Tt tip tuyn ca h(t) ti A t

c gi tr K.

a b

Hnh 5.1: Xc nh tham s cho m hnh xp x bc nht c tr

Trng hp hm qu h(t) khng c dng l tng nh hnh 14a, nhng co

dng gn gin nh hnh ch S ca khu qun tnh bc 2 hoc bc n nh m t hnh 14b

th ba tham s K, Tt, T c xc nh xp x nh sau:


- K l gi tr gii hn )(h

- K ng tip tuyn ca h(t) ti im un ca n. Khi Tt s l honh giao

im ca tip tuyn vi trc honh v T l khong thi gian cn thit dng tip tuyn

i c t gi tr 0 ti gi tr K

Nh vy ta thy iu kin p dng c phng php xp x m hnh bc nht

c tr ca i tng l i tng phi n nh, khng c giao ng v t nht hm qu

ca n phi c dng hnh ch S. Sau khi c cc tham s cho m hnh xp x ca i

tng ta chn cc thng s ca b iu khin theo bng sau:

B

iu khin

KP TN TV

P tTKT.

_

_

PI tTKT.

9,0tT3

10

_

PID tTKT.

2,1 tT.2 tT.5,0

Bng 1: tnh ton cc thng s b iu khin

T suy ra:

H s tch phn:

P

IN

KK =T


H s vi phn :

D P VK =K .T

Tn: thi gian d tr.

Tv: thi gian vt sm.

Phng php Zieger-Nichols th hai S dng cc gi tr ti hn thu c t thc nghim:

Trong trng hp khng th xy dng phng php m hnh cho i tng th

phng php thit k thch hp l phng php thc nghim. Thc nghim ch c th tin

hnh nu h thng m bo iu kin: khi a trng thi lm vic ca h thng n bin

gii n nh th mi gi tr ca tn hiu trong h thng u phi nm trong gii hn cho

php

iu c bit l phng php ny khng s dng m hnh ton hc ca i tng

iu khin, ngay c m hnh xp x gn ng

Cc bc tin hnh nh sau:

Trc tin, s dng bt P lp vo h kn ( hoc dng b PID v chnh cc thnh

phn KI v KD v gi tr 0 ). Khi ng qu trnh vi h s khuch i KP thp, sau

tng dn KP ti gi tr ti hn KPcrit h kn ch gii hn n nh, tc l tn hiu ra

h(t) c dng dao ng iu ha. Xc nh chu k ti hn ca dao ng


Hnh 5.2 : Xc nh ch khuch i ti hn

Xc nh thng s ca b iu khin theo bng sau:

B iu

khin

KP KI KD

P 0.5 KPcrit

PI 0.45 KPcrit 0.83Tcrit

PID

0.6 KPcrit

0.5 Tcrit

0.125Tcrit

Bng 2: Thng s b iu khin theo thc nghim

5.1.2.Phng php Takahashi:

Takahashi c phng php tng t phng php Ziegler-Nichols,Takahashi a

ra phng php xc nh thng s KP, KI ,KD ca b PID s t th hm qu ca i

tng c dng ch S sau:


Hnh 5.3: th p ng trong phng php Takahashi

tK Limh(t)>=

Nu thi gian ly mu : T2Tu v da vo th th tham s KP, KI, KD ca PID s c

xc nh nh bng sau:

Loi iu

khin

KP TI TV

P g

s u

TK (T T)+ X X

PI gs u

0,9TK (T T / 2)+

u3,33(T T / 2)+ X

PID gs u

1, 2TK (T T)+

2u

U

2(T T / 2)T T++

u0,5(T T)+

Bng 3:thng s b iu khin theo phng php Takahashi

Trong :

D P DK xTK=

P

II

KKT

=


Cc phng php chien, hrones v reswick gn ging vi phng php Zieger-

Nichols th nht.

5.2.Cht lng h thng iu khin:

Khi tc ng vo h thng mt tn hiu bc thang n v 1(t) th p ng u ra c

dng in hnh l dao ng tt dn.

Hnh 5.4:biu cht lng h thng

Cht lng h thng c nh gi thng qua cc thng s:

Thi gian qu ts ( setting time) : tn hiu ra t v duy tr c gi tr sai s cho php.

vt l % hay Pot (Percent Overshoot) : sai lch gia gi tr cc i v gi tr xc lp ca p ng, tnh theo phn trm:


maxy y( )Pot % 100%

y( ) = =

Sai s xc lp : e( ) hay ess ( steady-state error): l sai lch gia tn hiu vo v tn hiu hi tip v.

Vi h hi tip m n v v tn hiu vo l hm 1(t):

e( ) =1- y( ) Thi gian tng trng tr( rise time) : l thi gian cn thit p ng tng t 10% n

90% gi tr xc lp y( ) . Thi gian ln nh : tP=tpeak : thi gian cn tn hiu ra t cc i.


5.3. Chng trnh iu khin CON LC NGC

vi iu khin:


CHNG 6

KT QU V HNG PHT TRIN

6.1.Kt qu

Qua qu trnh thc hin ti chng em tm hiu c nhiu kin thc t thy

c, bn b v tm kim c nhiu kin thc mi.

Kt qu ca ti l h thng mi n nh c 5s. Thut ton PID c

chng em ng dng rt tt trong vic iu khin CON LC NGC.

6.2. Hng pht trin

Do cn nhiu hn ch nn h thng CON LC NGC cha th hot ng n

nh. V th n cn nhiu iu cn khc phc v pht trin l:

- Cn thit kt li phn cng.

- S dng hai con AVR thc hin ti.

- Thit k v tin hnh nghin cu con lc t cn bng.


TI LIU THAM KHO

[1] Nguyn Th Hng. iu khin t ng. Trng H SPKT TP.HCM, Khoa C Kh Ch To My. 2006.

[2] Hunh Thi Hong Nguyn Th Phng H. L thuyt iu khin t ng. NXB H Quc Gia TP.HCM. 2005

[7] Ng Din Tp. Vi iu Khin vi Lp Trnh C. Nh xut bn Khoa Hc v K Thut. 2006.

[4] HP Info Tech. Code VisionAVR 1.24.6 - User Manual. [5] Aaron Millerand Jerry Lee Ford, Jr. Microsoft Visual C++ 2005 Express Edition

Programming for the Absolute Beginner. Mt s Website:

- www.en.wikipedia.com - www.atmel.com - www.embedded.com - http://support.steema.com

- www.msdn.com

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