Giám sát công trình dùng phân tích rung trên các cảm biến gia tốc 3 chiều

Bang giai thich cac chir viet tat MEMS MicroElectroMechanical System ERA Eigensystem Realization Algorithm FRF Frequency Response Function DOF Degrees of freedom FFT Fast Fourier Transf

ĐẠI HỌC QUỐC GIA HÀ NỘI

TRƯỜNG ĐẠI HỌC CÔNG NGHỆ

GIÁM SÁT CÔNG TRÌNH DÙNG PHÂN TÍCH RUNG TRÊN CÁC CẢM BIẾN GIA TỐC 3

CHIỀU

Mã số: QC 08.13

Chủ nhiệm đề tài: ThS Trần Đức Tân

Hà nội - 2009

MUC LUC

1 Bang giai thich cac chir viet tat

2 Danh sach nhung nguoi tham gia thirc Men da tai

3 Danh muc cac bang so lieu

4 Danh muc cac hinh

5 Tom tat cac ket qua nghien cuu chinh ciia da tai

6 BAG CAO TONG KET

6.1 Dat vanda

6.2 Tong quan cac van de nghian cuu

6.3 Muc tiau vaNpi dung Nghian cimciiaDa tai

6.4 Dia diam, thai gian va phuong phap nghian cuu

6.5 Ket qua nghien cuu

6.6 Thao luan

6.7 Ket luan va kien nghi

6.8 Tai lieu tham khao

7 PHULUC

DAI HOC Q L O C GIA HA NQi

TRUNG fA<vi iHOi-vlG UN T H O VlEN OGGbOOOOOgt

f^. i

1 Bang giai thich cac chir viet tat

MEMS (MicroElectroMechanical System)

ERA (Eigensystem Realization Algorithm)

FRF (Frequency Response Function)

DOF (Degrees of freedom)

FFT (Fast Fourier Transform)

SHM (Structural Health Monitoring)

MAC (Modal Assurance Criterion)

PSD (Power Spectral Density)

MA (Modal Analysis)

MS (Mode Shape)

ODS, OS (Operating Deflection Shape)

SEM (Strain Energy Method)

RPA (Rational Polynomial Approximation)

He vi CO dien tir Thuat toan dac trung he thong Ham dap ung tan so

Bac tu do Bien doi Fourier nhanh Giam sat tinh trang cong trinh

Dp tin cay theo phuong phap MA Mat dp pho cong suat

Phan tich dao dpng (rieng) Hinh dang dao dpng Dang dp lech khi kich boat Phuong phap nang lugng Xap xi theo da thirc hiru ty

2 Danh sach nbumg ngiroi tham gia thyc hien de tai

Co* quan cong tac

Bp mon Vi co dien tir va

3 Danh muc cac bang so lieu

Bang I: So sanh dp phuc tap ciia 2 thuat toan DFT vaFFT L

Bang 2: Bang danh gia mot so ciraso L

Bang 3: Cac cha dp nhay 1! Bang 4: He so suy hao tuong ung 3:

Bang 5: LToc lugng cac thong so thong ka diing Monte Carlo va Bootstrap 3;

Bang 6: LToc lugng cac thong so thong ke diing ERA 3'

Bang 7: Tan so cong huong tuong img truoc va sau hu hong 3*

4 Danh muc cac hinh

Hinh 1 Mot chiac caubi sap '

Hinh 2 He thong giam sat liantuc i

Hinh 3 Mode shape ddu tian ciia cAu luc truoc (a) va sau khi hu hai (b) ^

Hinh 4 Do dap ung rung ^ Hinh 5 Dac trung tan s6 thu dugc diing phuong phap lap: truoc va sau khi hu hai ^

Hinh 6 So do FFT-8 diem chia 2 1]

Hinh 7 FFT 8 diem i: Hinh 8 FFT 2 diem i: Hinh 9 Phan tich FFT khi dimg va khong dimg cira so: so sanh ro pho 1^

Hinh 10 Phan tich FFT khi dimg va khong dimg cira so: so sanh dp phan giai 1

Hinh 11 Tin hieu chim trong nhiau 1^

Hinh 12 Phan tich FFT khi dimg va khong dimg ciraso: tin hieu trpn nhieu \i

Hinh 13 So do tong quan \t

Hinh 14Sad6kh6iMMA7260Q l '

Hinh 15 Cam bien gia toe MMA7260Q vabo mach dieu khien IS

Hinh 16VidilukhilnDSPIC30f4013 1^

Hinh 17 So do nguyen ly 2C Hinh 18 Chuong trinh giam sat 21

Hinh 19 So dd thuat toan 21

Hinh 20 Ban mach vi diau khien 21

Hinh 21 Ban mach cam bian gia toe 21

Hinh 22 Bp tao rung va ban mach cam bien 22

Hinh 23 He thong do rung 22

Hinh 24 May phatxung(f= 29.574Hz) 2A

Hinh 25 Kat qua chuong trinh phan tich pho, F =29.9 Hz 2A

Hinh 26 May phatxungf^31.218Hz 2f

Hinh 27 Ket qua chucmg trinh phan tich pho, F = 32.3Hz 2

Hinh 28 Quan sat tin hieu theo thoi gian tren kenh Z 2t

Hinh 29 Quan sat FFT ciia ca tap dii lieu thu dugc 2

Hinh 30 Tin hieu thu tran 3 kanh (da dugc triet DC) 2

Hinh 31 Minh boa va phan bo chuan [11] 3(

Hmh 32 Do cac FRF tran mot cau true xay dung 3(

Hinh 33 Biia chuyendung va bp tao rung [5] 31

Hinh 34 Cay cau Alamosa Canyon [7] 31

Hmh 35 Cach bo tri diem vao/ra tren cau (a) nguyan ly, (b) mo hinh trong MATLAB 3:

Hinh 36 Tin hieu thu dugc tran cac nut (mianthoi gian) 3:

Hinh 37 FRF thu dugc tran cau Alamosa Canyon, phep do SISO 3^

Hinh 38 OS tai mode cong huong dau tien 3^

Hinh 39 OS tai mode cong huong thu hai f^8.0698 3^

Hinh 40 Thong so MAC voi 2 mode da tinh toan dugc 3t

Hmh 41 FRF khi sir dung xap xi theo dathue hiruty 3(

Hinh 42 OS tai mode cong huong dau tian dung xap xi theo da thirc huu ty 3(

Hmh 43 OS tai mode cong huong thu hai f=8.0698 (xapxi theo da thue hiruty) 3(

Hinh 44 Cay c^u 1-40 tai New Mexico [8] 3 J

Hinh 45 B6 tri thi nghiem tran c4u 1-40 [7] 3^

Hinh 46 FRF tai niitgan (so 3) vamit xa(s6 12) 3^

Hinh 47 FRF truoc luc saihong 4( Hinh 48 FRF sau khi saihong 4( Hinh 49 OS ciia cau tai cimg 1 mode cong huong truoc va sau huhong 4(

Hinh 50 Nguyan tac phuong phap nang lugng theo sue cang SEM [9] 4]

Hinh 51 Nhan dang sai hong tai vi tri la nut 20 (toa dp X=2500 cm Y=400 cm) 41

Hmh 52 Nhan dang sai hong diing phuong phap mem deo 41

6 BAO CAO TONG KET

6.1 Dat van de

•

Cimg voi toe dp xay dung cac cong trinh cau duang, nha xuong hien nay thi a Viet nam ciing da xay ra khong it nhimg tai nan sap cau hay sup nha Tir do co the thay viec giam sat cac cong trinh xay dung la quy trinh v6 ciing can thiat Nhiing thanh tuu trong linh

vuc xu ly tin hieu khi dugc ket hgp voi cac kian thirc ve co hpc da cho phep xay dung cac

he thong giam sat cong trinh dang tin cay Mot trong nhimg nguyan tac truyan thong cua cac he thong giam sat nay la phuong phap phan tich rung Phan tich rung dpng co tha dimg kiem tra su hu hai cua cac cong trinh xay dung va vi tri cua cac diam hu hai nay Phan tich rung ciing co the sir dung de xac dinh su xuong cap cua cac cong trinh xay dung sau mot thoi gian dai dua vao sir dung Ap dung cac ky thuat phan tich rung co tha dua ra cac thiat

ka xay dung co hieu qua, tin cay hon trong thi cong xay dung dong thoi giiip cho viec thay the va sua chixa tai cac vi tri chinh xac

Hinh I Mot chiec cau hi sap

6.2 Tong quan cac van de nghien ciru

Giam sat cong trinh (SHM) dugc dinh nghia nhu chuoi qua trinh thu thap, xir li va

phan tich dn lieu nham tao diau kien thuan Igi cho viec quan li cong trinh xay dung Cho toi

nay da co rat nhiau cong trinh nghien cuu ve van de nay tuy nhien van con rat nhiau van da can phai tiep tuc dau tu nghian cuu Da thuc hien qua trinh giam sat nay thi phai quan sat dugc dap ung dpng cua he thong trong mot khoang thai gian xac dinh Viec quan sat dupe thuc hien nha sir dung mot to hgp cac cam bien dugc lap dat tren cac cong trinh can theo doi Nhimg thong tin vl hu hong hien tai (nau co) ciia cong trmh se dat dugc nhof cac kat qua do luong nay kat hgp voi cac phan tich thong ka

Voi cac giam sat dai han, thong tin dau ra cua he thong giam sat se dugc cap nhat deu dan, phuc vu cho viec theo doi tinh trang ciia cong trinh theo thoi gian va cac tac dpng moi truong Khi trai qua cac bian co bat nga nhu dpng dat hay qua tai thi SHM dupe dimg

nhu mot he thong giam sat "thai gian thuc" ve tmh trang cua cong trinh Mot he thong giam

sat lien tuc duoc mo ta nhu tran hinh 2

Cong trinh To horp cam bien

Hmh 2 He thong giam sat lien tuc

Nhung phan tich rung thuc nghiem va thong ka la cac phuong phap nhieu trien vpng cho linh vuc SHM Nguyan tac cua phep do la do tran be mat cua cau true cong trinh

Nhimg hu hong se dugc xem la nhung thay doi khac biet ve dac trung he thong khi boat

dpng tot so voi tinh trang hien tai (hoac tuong lai)

Trong thuc te tin hieu rung dpng biau dian trong mien thai gian thuong khong phai la dang tin hieu dieu hoa ma thuong la mot tin hieu rat phuc tap Diau nay co nghia rung dpng thu dugc la do rat nhiau thanh phan rung gay nan Hay noi each khac do la tong hgp cua nhieu nguon rung khac nhau

Mot phep phan tich rung chi tot khi dii lieu sir dung la dii tin cay, do do thiat bi dimg

de thu thap dxt lieu la rat quan trpng Co ba loai thiat bi co tha dimg de do luong va theo doi

rung dpng: dau do dich chuyan, bp bien doi van toe va gia toe ka Moi mot thiet bi do co mot gioi ban va ung dung riang trong do do gia toe la phuong phap tot nhat de xac dinh lire tir cac may rung Cam bian gia toe se bien doi cac nang lugng co hpc thanh tin hieu dien Dac diam noi bat ciia cac cam bian gia toe MEMS la chat lugng tot va gia thanh re nen da ung dung vao thuc ta dai song

Phuong phap rung co the dugc mo ta ban dau bang phuong trinh ciia dinh luat II Newton Trong mo hinh nay chung ta can quan tam tai ngoai luc va dap ung cua he thong theo thai gian Nau kich thich cau true boi mot xung (tuong tu nhu go mot tieng chuong) thi dap ung thu dugc se la mot dao dpng bi suy hao Co tha thay ro vai tro cua khoi lugng,

dp cung, he so suy hao va dieu kien bien trong bai toan nay

Dao dong cong huong gay boi su tuong tac giiia tinh chat quan tinh va dan hoi cua

vat lieu trong cau true cong trinh Tat ca rung dpng dugc coi la ket hgp cua luc va cong huong Dao dpng kilu luc bao gom cac noi luc, sir mat can bang, ngoai luc va kich thich moi truong Dao dpng cong huong xay ra khi cong trinh bi tac dpng a mot tan so cong huong nao do cua cau true Cac mode cong huong phu thupc vao tinh chat cua cau true cong trinh Cac tan so cong huong dugc xac dinh boi cac tinh chat vat lieu (khoi lugng, dp cung, va he s6 suy hao) va diau kien bian cua cau true Da thay rang khi tinh chat vat lieu

thay doi hoac diau kien bien thay doi thi cac mode cong huong cung bi thay doi (do chinh

la nguyen ly ca ban cua viec giam sat cong trinh theo kiau rung) Tat ca cac tham so rung thuc nghiem se thu dugc bang each do dac trung tan so cua he thong Dac trung tan so co dugc khi tac dpng len cau true cac rung dpng voi tan so khac nhau (hinh 3) Tat ca cac cau true deu co tai 6 mode cong huong (ba tinh tian va ba quay)

Hinh 3 Mode shape dau tien cua cau luc truac (a) vd sau khi hu hai (b)

Cac thuc nghiem se dugc tien hanh true tiap tran cau va la minh hoa cho tinh huong

dimg phuong phap rung de phat hien thanh cong su hu hai cua cong trinh Hinh 4 la so do

dap ung rung ciia mot cong trinh xay dung va hinh 5 la minh hoa cho viec nhan dinh he thong bi hu hai

Giam sat rung Kich thich rung nhan t^o

thai f)^

gian dap ung xung dap ung

Rung dong do moi trudng xungquanh

6.3 Muc tieu va Noi dung Nghien cuu cua De tai

Muc tieu cua de tai nay la ung dung do rung cua cam bian gia toe ba chieu che tac

tren cong nghe vi co dien tir (MEMS) vao cac muc tieu dan dung Cu the o day la sir dung

cam bien de do rung, phuc vu cho viec giam sat tinh trang boat dpng cua cau

De dat dugc cac muc tieu tren, tap the nghian cuu cua de tai da thuc hien cac noi

dung nghian cuu dugc trinh bay cu tha trong cac muc dual day

6.3.1 Phan tich rung diing bien doi Fourier

a Bien doi Fourier cua tin hieu rai rgc DTFT

Xet tin hieu x(n) la rai rac v6 han, dugc lay mau tir tin hieu tuong tu voi tan so T

Voi Q= o).T Ham DTFT dugc dinh nghia nhu sau:

X ( " ) = 2;x(«).exp(-yQ«) (1

Ta nhan xet thay tuy tin hieu roi rac trong mien thoi gian nhung DTFT lai lian tuc va

tuan hoan trong mien tan so DTFT chinh la ham phirc theo bian tan so thuc Ta gpi DTFT

la pho phuc (complex spectrum) hay ngan gpn la pho cua tin hieu roi rac x[n] Tir day ta

thay can thiat phai xay dung bien doi Fourier roi rac cho truong hgp day x(n) hiru ban

b Bien ddi Fourier cua tin hieu rai rgc DFT

Truong hgp x(n) hiru ban, chieu dai N (0 < n < N-1)

- Lugng phep tinh: DFT phai thuc hien N^ phep nhan phuc va N(N-I) phep cong phuc

Suy ra so phep tinh cong va nhan so thuc:

+ 2N^ phep tinh lugng giac

+ 4N^ phep nhan so thuc

+ N (4N-I) phep cong so thuc

+ Mot so phep toan chi so va dia chi da nap x(n)

Nhugc diem: thai gian tinh toan se qua dai va dung lugng nha cua thiet bi se phai Ion

c Bien doi Fourier nhanh FFT

Truong hgp N=2'

TV

Ta chia day x(n) thanh 2 day co chiau dai —:

- Day g(n) gom cac gia tri chan: g(r) = x(2r)

K 3 : - JtC?:

fDFT)-H(0) H(l) H(2) H(3)

Ta CO t h i tilp tuc phan chia moi day g(n) va h(n) thanh 2 day con de giam dp phuc tap cua DFT

So sanh hieu qua tinh toan:

Bang 1: So sanh do phirc tap cua 2 thuat toan DFT vd FFT

Chit v: Hien tugng ro pho (leakage) xay ra trong mien tan so Ro pho la hien tugng pho cua

tin hieu bi do vao 1 loat cac tan so xung quanh tan so cua tin hieu Nguyen nhan la do su cat ngan tin hieu Khi do tin hieu x(n) khong tuan hoan, tran mian tan so se thu dugc khoang tan so rpng trong pho FFT

De giam hien tugng ro pho ta dimg 1 ham cira so nhan voi tin hieu vao de tro thanh tin

hieu tuan hoan Khi do bian dp moi tan so ly tuong se dugc nam bat chinh xac, khong co ro pho

Lua chon ham cua so: Tiiy vao ung dung ta chpn loai cira so se dimg Dang ham cira so anh

huong rat Ion den dp chinh xac cua viec xap xi ham tan so Viec chpn ham cira so nao de xap xi hoa ham tan so, khong chi phu thupc vao dp chinh xac yeu cau, ma con phu thupc

vao ban che ve thai gian tinh toan, vi ham cira so cho dp chinh xac cang cao thi viec tinh

toan se cang phirc tap, va thai gian tinh se cang Ion Do do viec chpn ham cira so phu thupc vao su toi uu giiia dp chinh xac yau cau va thoi gian tinh

3dng ddnh gia mot so cira so

Dp phan giai tan

T6t

Kem

Kem T6t

Dp chinh xac

Khong tot

Tot

Khong tot Khong tot

Tot

Kem

Kem Khong tot

d Mot so ket qua md phong

Chuong trinh 1

Chuong trinh nay nham minh hoa im diem cua viec diing cua so (o day la cira so Harming) khac phuc hien tugng ro pho Code dugc trmh bay trong phu luc 7.1

Kat qua dugc tha hien trong hinh duoi day:

Hinh 9 Phan tich FFT khi diing vd khong diing cica so: so sanh ropho

Chvrang trinh 2

Tuy bi nhugc diam la bi ro pho nhung khi(kh6ng)dung cira so thi dp phan giai pho lai tot hon Trong chuong trinh nay thi tin hieu can phan tich la tong hgp cua hai tin hieu hinh sin

350 va 352 Hz, dugc lay mau a xkn so 1000 Hz trong thoi gian 0.8 giay (nhiau ban chuong

trinh 1) Code dugc trmh bay trong phu luc 7.1 Kat qua thu dugc nhu hinh duoi cho thay khi khong sir dung cua so thi viec tach 2 tin hieu hinh sin lai hieu qua hon (dp phan giai tot hon)

0 0.02 0.04 0 06 0.08 0.1 0 12 0 14 0 16 OK

hai tin hieu hinh sin + nhieu

Ket qua phan tich pho cho th^y van co thi nhan hik cac thanh phAn t i n s6 khi dimg bien

J L

300 310 320 330 340 350 360 370 380 390 400

Hz

Hinh 12 Phan tich FFT khi dung vd khong dung cua so: tin hieu tron nhieu

6.3.2 Phan citng he thong

So do tong quan

Chuung trinh canh bao

Cong COM COMPUTER

Hinh 13 Sado tong quan

Cac linh kien

Cam bien gia too MMA7260Q vd mach dieu khien

La loai cam bien gia toe dugc cha tao tran cong nghe vi ca dien tu

+ Dua ra thong so tren 3 true tpa dp X, Y, Z

+ Gia thanh re de thiet ke mach dieu khien

Bao gom :

+ G-Cell Sensor : chuyen gia toe -> gia tri dien dung

+ Oscillator : bp tao dao dpng

+ Clock Generator : tao xung

+ C to V converter : chuyen gia tri dien dung -> dien ap

+ Gain, Filter : khuach dai va Ipc

+ X, Y, Z temp comp : gia tri tam

+ Control logic EEPROM trim circuits

g-Sefectl 9-Seiect2o-ra

Sleep Moce( G-C«il

X-Terrp Comp

Control Lege EEPROM TrFT Cira)ts

Y-TfifTD Corrp

Z-Teirp Corrp

Vss

Hinh I4Sadokh6iMMA7260Q

Nguyan ly va tinh nang dac biet

Nguyan ly:

+ Khoi G-Cell trong cam bian co cau true 2 tu back-to-baek

+ Khi gia toe thay doi -> gia tri dien dung thay doi: C = A E / D

Tinh nang dac biet:

+ Cho phep chpn lira 4 che dp nhay

17

• O Y j , ,

-OZ-DAI HOC QUOC GIA HA NQI

B > i G J A M THONG TIN rna VIEN

Bang 3: Cdc che do nhay

Sensitivity 800mV/g 600mV/g 300mV/g 200mV/g + Che dp nghi cho Sleep Mode de tiet kiem nang lugng boat dpng o muc tich cue thap

Khi b cha dp nay dong tieu thu se giam ve muc 3uA

+ Co cac bp Ipc ban trong

+ He so tuyan tinh

Mot so img dung cua cam bian gia toe MMA7260Q:

+ Do va diau khian muc rung

+ Dinh huong 3D trong khong gian

+ Phat hien va cham, nhimg thong tin ve gia toe, van toe va dp dich chuyen giup phan bi^t viec va cham va khong xay ra va cham

+ Dieu khien du doan kha nang lam viec cua may moc thiat bj

+ Dpc mot so thong so sinh hpc trong co tha nguoi

Vi dieu khiin DSPIC30F4013

+ It tieu ton dien nang, khoang nhiet rpng

+ Kha nang lap trinh

Ghep noi may tinh bang cong COM (xem phu luc 7.2)

+ Truyan du lieu noi tiap khong dong bp

+ Toe dp truyan nhan cue dai la 10Kbps

Sa do nguyen ly

r L •*• I 1 ii 1 I i i I I I , 1 I ,

///«/; 75 C(iw ^/e« g/'o foe MMA7260Q vd bo mach dieu khien

OSCIJCLKIH OSC2/:XlKJ/RC15 IKTO/RAU

E U U C 2 X X ; l K D 0 EMUD2KX:2<HD1

O C 3 « D 2 OC4/RD3

l C i y i N T l f l a > 8

' L J 32.768k

-AN2JSS1/L VDIH*CH*fl?B2 AK3JCH5/RB3 AH4flC7*c:K6/RB4 AH5nC8*CN7/KB5 PGC«MUC/AN6JOCrA»RB6 PGD/EMUD/AN7/RB7 AN8/RBS AH9>CSCKJRB9 AHIO^CSDI/RBIO

A N l l j C S E X i / R B l l

CRXl/RTO D1 RX/SDIlADAJRf::

EMUD3/D1 TX>SDO 1 /SCL/RTS U2RX;CH17/Rr4 U2TXJCM18/Rr3 EMUC3*SCK1/Rr6

EMTID1 JSOSClJT2CICai I A T X K N 1 / E C 13 DSPIC3DF4013

1 SPA B T l

B T 2

44 SCL 3^ Aux_Rx

2 A u x _ T

4 3 L C p B * c k L i e h t

Hinh 16 Vi dieu khien DSPIC30/4013

Viec can chuan cam bien dugc trinh bay trong phan phu luc ciia bao cao nay

6*3.3 Cdc ket qua thuc nghiem

Mo ta: tin hieu rung dugc cam bien thu nhan va chuyan thanh tin hieu dien 6 loi ra, roi

dugc dua vao vi diau khian qua ADC, qua day thu dugc tin hieu roi rac thai gian theo 3 chieu => truyen noi tiap qua cong COM Cong viec cuoi cimg la cua may tinh, nhan dir

li^u va tinh pho SFFT

Mo ta chuong trinh:

Giam sat rung

Kich thich nhan tao hoac

do moi trirong xung quanh

then

gian

Tinh \ ^^^^^ ^P ^ ^ •

- tan so toan

Hinh 18 Chuong trinh gidm sat

So do thuat toan:

N h a n du lieu 3 kenh Tinh pho F F T Hien thj p h o Tinh F m a x

Hinh 19Sado thuat todn

Tao tin hieu rung boi mot bp tao rung voi tan so rung dugc diau chinh boi may phat xung Gin cam bien gia toe lan bp tao rung Thu dugc mot so ket qua sau:

Hinh 20 Bdn mach vi dieu khien

Hinh 21 Bdn mach cam bien gia toe

Hmh 24 May phat xung (f=29.5 74Hz)

Hmh 25 Ket qua chuong trinh phan tich pho, F =29.9 Hz

Hinh 26 May phdt xungf=31.218Hz

Hinh 2 7 Ket qua chuong trinh phan tich pho, F = 32.3Hz

25

Nhan xet: kit qua phan tich pho thai gian thuc cua chuong trinh co dp chinh xac tot

(kho^g 3% gia tri do) cho thay kha nang ap dung tot cua chuong trinh cho cac thuat toan giam sat cong trinh sau nay Su sai khac 3% co tha dugc giai thich do dp chinh xac cua may phat song hinh sm, do dp phan giai cua chuong trinh tinh FFT-256, va co the khac phuc nho cau hinh phan cung tot hon nixa

Cac ket qua trong hinh 25, 27 thuc chat la ket qua tinh pho tin hieu tai 1 thai diem xac dinh FFT-256 diem Ngoai ra chuong trinh con co tha hien thi tin hieu rung theo thai gian Tuy nhien viae lam dung do hoa may tinh se gay nen hao phi tai nguyan (khi di vao thuc ta thi vi^c hien thi pho theo do hoa nhu hinh 25, 27 la khong can thiet ma chi can cac kat qua luu tni dugc)

Hinh 28 la ket qua thu tren kenh thang dung - true Z (dugc phong to trong 1 khoang thai gian ngan de thay dang hinh sin) trong suot thoi gian thir nghiem (hon 30 giay) va hinh 29

la ket qua phan tich pho, cho chinh xac tin so rung la Hz Da thay rang voi tap du lieu rat nhieu (6544 mau) thi dang pho thu dugc la cue ki ro net, diau nay phii hgp cac cac ly thuyat xtr li tin hieu Ve ban chat each tinh FFT trong hinh 25, 27 la SFFT (Short FFT) mot thao tac CO y nghia han nhieu voi FFT binh thuong vi co tha mo ta su thay doi ve pho theo timg thai diem

-1 -1

tan so (Hz)

80

Hinh 29 Quan sdt FFT cua cd tap du lieu thu duac

Bai toan canh bao canh bao dugc xay dung khi xac dinh dugc tiin so rung va dp Ion khi tac dpng len he thong can giam sat

Mat khac viec quan sat 3 kenh khi dung yen ciing cung cap cho ta nhung thong tin ve sai so cua c ^ bien (hinh duoi)

6.3.4 Gidm sdt cong trinh xay dimg: cau

Vi khuon kho giai ban cua mot da tai va vi viec thuc hien cac thi nghiem gan cam

bien len cau roi tac dpng len cau bang bua ta hay may tao rung dpng la khong kha thi (kinh

phi, sir cap phep) Nhimg thi nghiem ke tren co the thuc hien dugc khi da tai dugc mo rpng,

lien ket voi cac co quan huu quan de dugc phep thuc hien thi nghiem tran mot doi tugng

cau cu the Khong lam mat tinh tong quit cua mot cong trinh nghien cuu, chiing toi da sir

dung cac tap du lieu va cong cu DIAMOND tir thu vien mian phi cua nhom nghian cuu My

Los Alamos National Laboratory (LANL) Cong cu DIAMOND la cong cu nguon mo phat

trien tren moi truong MATLAB (nguoi dimg khong phai tra tien mua DIAMOND ma chi

phai tra tien mua MATLAB) Vi DIAMOND cung dang trong qua trmh phat trien nen

nguoi su dung co the tuy y phat trien cac thuat toan SHM tren DIAMOND nhung ciing

khong nhan dugc sir ho trg nao tir LANL Ngoai ra chung toi se con sir dung phan mam

thuong mai CIVIL/ANSYS la phan mem ho trg cho viec mo hinh boa cac cong trmh xay

d\mg (o day chung ta quan tam toi cau) trong cac nghien cuu tiep theo Be xuat cua nhom

tac gii do la kat hgp CIVIL va DIAMOND, do la su kat hgp mai va hieu qua trong viec

nghien cim va SHM

Phep phan tich dao dpng riang (MA) la cong cu hieu qua cho viec mo hmh hoa dac

trung dpng cua mpt he thong xac dinh MA dugc thiat lap dua tran ly thuyat ve gia tri riang

va vecto rieng cua he thong Dua tran ly thuyet MA ma cac thuc nghiem tuong ung ciing da

dugc thuc hien rat hieu qua va kha don gian Phep phan tich MA se cho phep tinh dugc tan

so dao dpng rieng, he so suy hao va dang dao dpng cua cau true

Phuong trinh vi phan mo ta dao dpng cua cau true tuan theo dinh luat Newton ap dung

tren tat ca cac bac tu do cua cau true do Voi mot bac tu do xac djnh thi phuong trinh dugc

mo ta nhu sau:

[A/Jx(/)+[cMr)+[/:MO=/(0 (11)

Voi cac ma tran [M], [C], [K] la cac hang so; f(t) la vecto ngoai luc tac dung theo thai gian

t lien tuc

Khi cau true chiu tac dung boi ngoai luc f(t) co nhiin^ tan so khac nhau thi co the chia

thanh hai loai dao dpng: (1) tan so dao dpng khac voi cac tan so cong huong cua cau tnic va

(2) tan so dao dpng trimg voi tan so cong huong cua cau true Mot cau true c6 the c6 nhieu

tan so cong huong khac nhau, tir do c6 nhiau dang dao dpng khac nhau Mot dang dao dpng

lai dugc dinh nghia bao gom tan so cong huong (tan so dao dpng rieng) tuong ung, he so

suy hao, va hinh dang dao dpng riang (mode shape - MS)

Khi tin so luc tic dung bang tin so dao dpng riang chung ta co mot MS tuong ung,

con neu khic chung ta co mot hinh dang dao dpng ODS yau hon Co tha coi MS la mot

truong hgp dac biet cua ODS Khi tian hanh thuc nghiem bang cich chii dpng tie dpng vao

cau tnic cic rung dpng xac dinh, cai ma chung ta do dugc li ODS, tir do moi xic dinh cic

thong so trong phep phan tich MA

Co hai ky thuat thuong dugc sir dung de uoc lugng cac tham so MA la phuong phip

mo phong Monte Carlo va phuong phap lap

Phuong phip Monte Carlo: lap di lap lai thi nghiem da thu dugc cic tap dir lieu

nhieu lin voi gia thiat rang c6 su bian doi ngau nhian tran cic lan do Tir do

xay dung phep phan tich MA tuong ung da thu dugc cic tham so MA co phan

bo thong ka xic dinh

- Phuong phap bootstrap: sir dung cic dip img tan so (FRF) do dugc (bang cich

do lap di lap lai) de to hgp thanh mot dip ung trung binh voi cic trpng so khic

nhau Cic trpng so nay se dugc sir dung de xiy dung cic tham so ciia phan tich

MA

Sir khic biet co bin cua hai phuong phip niy do la phuong phap Monte Carlo yau cau

phai CO phan bo dir lieu do xic dinh con phuong phip lap thi khong Phuong phip Monte

Carlo chi co the uoc lugng cic loi ngau nhian trong khi phuong phip lap thi c6 the uoc

lugng loi ngau nhian va ca cic loi he thong vi du nhu moi truong thay doi Tuy nhien,

phuong phip bootstrap lai yau cau dp phuc tap cao ban phuong phip Monte Carlo do luon

phai thuc hien viec tinh toin va luu trir FRF trong qui trinh thu thap du: lieu

R6 rang, buac dau tien cua phan tich MA do la phai thu dugc tin hieu tic dpng dau

vao x(t) va dip img ra y(t) Tir do co the chuyan tin hieu sang mien tin so: ham mat dp pho

Gxx(tt)) va Gyy(ft)), ham mat dp pho cheo Gxy(co) Sau do tinh cic FRF nhu sau:

hoac CO the tinh cic ham lian ket:

Ham lien kat phin inh su tuong quan giira tin hieu vio vi ra, nau cau true dugc xem la mot

he thong tuyen tinh bit bian LTI thi him lien kat nhan gii tri thuc bang 1 Con nau tin hieu

ra la nhieu chang ban thi ham lian ket bang 0 Thong thuong thi no nhan gii tri thay doi

trong dii 0 toi 1

Nhan xet rang cic FRF trong cic phuong trinh tren moi khi tien hanh do dac va tinh toin lai

cho nhung ket qua khac nhau Dieu nay thuc su da giii thich vi c6 rit nhieu nguyan nhan

gay nen su sai khic niy, nhung nhin chung co tha phan thanh 2 loai la tit dinh (tir viec lech

offset cim bian va mach dien, lay mau tin hieu, uoc lugng pho) va ngau nhian (tir cam bien,

mach dien, nguon kich thich phu khong do dugc, he phi tuyan)

Viec xir li sai so tat dinh luon de dang hon loi ngau nhien Nhirng no luc cua cic nha nghien

cuu vi tha dugc tap trung da xir ly loai sai so ngau nhian nay Voi nhirng sai so co su tuong

quan voi nguon kich thich (da dinh gii cong trinh) thi rat kho xir li nan trong khuon kho da

tai niy chung ta chap nhan gia dinh la cic loi ngiu nhian la dpc lap voi kich thich dau vao

(gii dinh niy ciing thuan Igi nhu khi lay trung binh FRF ciia cic lan do khac nhau thi gii tri

thu dugc se giam dugc loi ngau nhian)

Dp lech chuan cua mot phep do dugc tinh theo cong thirc

Voi n>l thi de nhan thay (yn^<y

Hinh 31 Minh hog ve phan bo chuan [11]

Liic nay, theo [1,2] thi chiing ta co the tinh dugc dp lech chuan cua uoc lugng dac trung bien dp va pha cua ham truyen Hxy(co) nhu sau:

(16)

(17)

Hinh 32 Do cdc FRF tren mot cau true xay dung

Tren th\rc ta thi do FRF co the tien hanh theo cich don giin hon, sir dung mot trong hai loai thiet bi de kich thich diu vio la bua dap chuyan dung va bp tao rung (hinh 33) nhu sau: 1) Co dinh diem do diu ra (vi du nhu co dinh cam bien gia toe tai nut 1), thay doi cic diem kich thich (tir niit 2 den 6 trong hinh 32) Thi nghiem kiau niy phii hgp voi thiet bi de kich thich dau vao la biia dap chuyen dung vi co the di chuyen de ding

2) Co dinh dau vao kich thich (vi du nhu dat co dinh mot miy tao rung tai mit 1), thay doi

^ cic diem do (tir niit 2 toi niit 6 trong hinh 32)

3) Neu thiet lap co 2 dau vao va 2 diem do tro len thi gpi la phep do MIMO (nhieu dau vio nhieu dau do)

Hinh 33 Biia chuyen dung vd bo tao rung [5]

De thuc hien phep phan tich MA theo phuong phip Monte Carlo va Bootstrap, chiing ta can tinh dugc cic tan so dao dpng rieng, he so suy hao, va MS nhu sau:

;,;T Phuong phap Bootstrap Phuong phap Monte Carlo

1 Do va luu n mau FRF Hxy(co) tran L Tinh tri trung binh va dp lech chuan timg diem do dau ra cua dac trung bian dp v i pha cua FRF

2 Lay to hgp trung binh ngau nhian nid Hxy(a))

mau FRF tir n mau thu dugc Hi(co) 2 Thu dugc tri trung binh Hi(co) dua

3 Dimg thuat toin nhan dang ciia tren dac trung bian dp va pha co thong so phuong phip phin tich dao dpng thong ke xic dinh nhu sau: rieng de tinh tan so dao dpng riang

cOj, he so suy hao C,[ v i MS

4 Lap cic buoc 1-3 da tinh histogram

cua cic thong so tran (kiem tra hoi

3 Tinh cOj, Q v i MS tir Hi(co)

4 Thuc hien cic phep tinh thong ka cac thong so tran va kiam tra tinh hoi tu

5 Cho ra ket qui cuoi cimg cua |a(cOi),

0 ( C D , ) v "

Nhimg so sinh chi tiat ban nu:a ve hai phuong phip niy co the tham khio tai [2]

Su- dung cong cu DIAMOND/MATLAB trong bai toan chan doan tinh trang can

Cong cy DIAMOND la cong cu mo ma bat cu nguoi sir dung nio ciing dugc phep thay doi v^ phat trien them cac thuat toin dua tran phan tich dao dpng rieng De minh hoa cho cac

thu§t toan thi cic d\i lieu thuc nghiem dugc sir dung la dij lieu do tren cac cay cau thyc te [6,

7] De tien hanh nhirng nghien cuu SHM thi nhirng kian thuc co bin ve ciu (cy the 6 day li

be tong c6t thep) la rit can thiat [10]

Diamond gom 3 modun

a Phan tich dao dpng rieng

b N h ^ dang sai hong

c Hi^u chinh dimg mo hinh FEM (phan tir hiru ban): khong de cap trong bio cio niy, se la

su phat trien ke tiep khi ket hgp DL\MOND/MATLAB voi CIVIL/ANSYS

a Phan tich dao dong rieng

Co nhiau phuong phip phan tich dao dpng riang, trong pham vi bio cio niy thi ap dung cic phuong phip sau:

- ODS: quan sat ma tran FRF tai tan so xic dinh [34]

- RPA: Xap xi theo da thuc hiru ty: uoc lugng bac cao tren mien tan so [14]

- ERA: uoc lugng tham so theo phuong phip dao dpng rieng tren mian thai gian (bac thap)

Luu y rang voi cic thuat toin ke tran thi dau diing voi phuong phip Monte Carlo nhu da

trinh biy a tran Cic kat qua thong ka sau do dugc dimg de xic dinh dp tin cay cua cic

thong s6 MA

De kiem chimg thuat toin, doi tugng nghien cuu o day la cay cau Alamosa Canyon tai phia nam cua New Mexico (hinh 34) Cay cau dugc xay dung voi muc dich de thir nghiem SHM Day la cay cau co 7 nhip, moi nhip dai 15.2 m vi rpng 7.3 m Giira hai nhip cau lian tiep 6 phia duoi li mot try cau Moi nhip cau co 6 ram cau bang thep (hinh 35) Viec do luong dugc tien hanh tran nhip cau dau tian, cu 5 cam bian gia toe dugc lap dat dpc theo mot ram cau Cam bian khong dugc lap dat tai vi tri mo cau hay try cau (xem hinh 35) Tran hinh nay ciing mo t i 2 dau vao kich thich boi biia chuyan dung va 30 diam do tuong ung

Hinh 34 Cay cau Alamosa Canyon [7]

Hmh 35 mo ta cich bo tri diem kich thich vi cic dau do tran cau trong do hinh (a) li nguyen ly, hmh (b) la mo hmh xay dung troiig DIAMOND/MATLAB Luu y trong hinh (b) thi cac niit tir 38-43 tuong ung voi vi tri m6 ciu (khong dat cam biln do) va 32-37 tuong ling voi vi tri try cau (ciing khong dat cim bien do) Nhiing diem niy nau co dat dau do thi tin hi?u ciing co the coi la rat nho

aSu vSo 2 trSn mat c^u

Hinh 36 li ket qui thu dugc tren 3 niit tieu bieu, da nhan thiy su suy hao bien dp thay doi

ro ret theo vi tri ciia cic mit (niit 2 gin diem kich thich nhit, niit 29 la xa nhat)

- ODS: quan sdt ma tran FRF tai tan so xac dinh

Do dac ODS [34] co the cho ta nhiing thong tin nhu: ciu tnic bi dich chuyen the nao, dich chuyen 6 vi tri nao va huong nao la Ion nhat, chuyan dpng tuong doi cua mot diem so voi diem khic the nio (ciing la dinh nghia ODS), tan s6 cong huong va MS

10 16 2D 25 30 to 45 50

tan so (Hz)

Hinh 3 7 FRF thu duac tren cau Alamosa Canyon, phep do SISO

OS cua mode 1 (tai tan so cong huong diu tien) hien thi trong hinh duoi

300 0

Hinh 38 OS tai mode cong huong dau tien

OS cua mode 2 (tai tan so cong huong dau tian) hien thi trong hinh duoi day

300 0

Hinh 39 OS tai mode cong huong thic haif=8.0698

Voi 2 mode ke tren, c6 the tinh toin thong s6 MAC nhu trong hinh 40

Hinh 40 Thong so MAC vai 2 mode da dnh todn duac

Bing 4 la ket qua he so suy hao tuong ung voi cic tan so cong huong da tinh 6 tran

Bdng 4: He so suy hao tuong ung

Mode

1

2

T i n so 7.356 8.070

He so suy sao (%) 1.524

1.129

Bang 5 la kat qui so sanh giua hai phuong phip Monte Carlo vi Bootstrap trong viec uoc lugng tan so cong huong, he so suy hao tuong ling Ca hai phuong phip dau cho cic kat qua sit nhau (thong qua phan tram sai khic chi vai phin tram), cang khang dinh tham dp chinh xic ciia viec uoc lugng [7]

Bdng 5: Ifac luong cdc thong so thong ke dung Monte Carlo vd Bootstrap

^1

(Monte Carlo) 0.0174 0.0014

^1

(Bootstrap)

0.0184 0.0011

f2

(Monte Carlo) 8.111 0.0128

f2

(Bootstrap)

8.122 0.0161

C2 (Monte Carlo) 0.0166 0.0019

^ 2

(Bootstrap)

0.0174 0.0019

- Xap xi theo da thirc hiru ty

La phuong phip xay dyng lai him truyen ciia ciu tnic tir thong tin dip img tan so da do dugc [14] Ham truyan dugc coi la mot he thong tuyan tinh bat bian LTI, se dugc tii tao

b ^ g mpt ham truyen hiru ty ma o do tir so va mau so la cic da thuc voi bian la toin tir Laplace Sai so giira thong tin do dugc va mo hinh xiy dung boi ham truyan hiru ti dugc coi

la mpt qui trinh ngau nhien

Voi phuong phap niy, lua chpn 2 tan so tuong ung fi=6.8125 v i f2= 7.6875 (dii tin fi-f2 chiia tin s6 cong huong dau tien cua ciu) nhu hinh 41

" ^ ^ i

Hinh 41 FRF khi sic dung xap xi theo da thicc huu ty

Ket qui OS tinh dugc nhu trong hinh duoi (kat qua nay tuong ty nhu hinh 38)

300 0

Hinh 42 OS tai mode cong huong dau tien dung xap xi theo da thicc hiru ty

Tuong tu nhu tha mode thu 2 cho OS tuong tu nhu hinh 39

12 b 43

300 0

Hinh 43 OS tai mode cong huong thic haif=8.0698 (xap xi theo da thicc hint ty)

-ERA:

Khac voi viec sir dung ham truyen, he thong dugc mo ta theo mo hinh trang thii:

yk=Cxk (19)

6 do x la vecto n chieu, u li loi vao diau khien m chiau, y la vecto do luong, A la ma tran

chuyen trang thii nxn chieu ERA chinh la viae chiing ta do duoc yk, tir do xic dinh A, B,

O do PH, DH li cic ma tran true giao vi DH la ma tran cheo hoi cua cac gii tri rieng Kich

thuoc cua ma tran co the dugc cat bat neu ta bo qua cic gii tri riang nho va toi uu ve kich

thuoc duoi dang:

A^U:^"P:H,Q„B:" (23)

Trong truong hgp cau tnic co nut gay (xuat hien cic dinh gia trong FRF) thi A ciing khong

the tich dugc cic dinh gii niy ma phai sir dyng (tham) cic ky thuat khic

Cic tan so cong huong va he so suy hao se dugc tinh tir cic gia tri riang cua ma tran A duoi

dang:

X,=e^ ^ (24)

6 do X la gii tri riang tai mode thii i, C^ la he so suy hao, co la tin so cong huong va At

Bang 6 li ket qui khi sir dyng thuat toin ERA [ 12] trong viec uoc lugng tan so cong huong,

he so suy hao tuong ung voi 14 mode dau

Bdng 6: Ifdc luong cdc thong so thong ke diing ERA

He so suy hao (%) 2.84

7.09 1.37 3.60 3.03 1.88 3.07

He so suy hao (%) 1.90

1.50 4.87 2.62 1.54 5.06 1.39

b Nhan dang sai hong

Vi$c thyc nghiem dugc tien hanh bang cich do rung liic cau o trang thii chua co sai hong

va sau khi da tao ra nhimg sai hong tran ciu

Voi pham vi bio cio nay, chiing ta de cap hai phuong phap:

- Phuong phip nang lugng SEM (Strain Energy Method)

- Phuong phip mem deo

Cay cau o day la 1-40 tai Albuquerque dugc lua chpn lam doi tugng thi nghiem Cau gom 2

lan duang rieng re Cau che tao voi san ba tong, dugc do boi cac ram doi ban bang thep v i

3 xa ngang thep de do Tii trpng tir xa ngang truyan xuong cic rim thong qua cic thanh

dam

Cau gom 3 nhip, nhip 1 v i 3 co cimg chieu dai (khoang 39.9 m) con nhip 2 dai co 49.4 m

De CO 3 nhip cau niy chiing ta da ghep 5 rim doi thep (cin 4 moi ghep cho 5 rim va cac vat nut sau nay ciing dugc cho la giy boi hien tugng cong ciia cic rim ngang nay)

Hinh 44 Cay cau 1-40 tai New Mexico [8]

Viec bo tri diu vao dau ra dugc mo ta nhu hinh duoi day Cam bien dugc gan tren than cau (vi tri ma cic thanh dam ngang dugc ban voi than cau) Vat nut dii 122 cm can nhan dien ciing nam tren thin cau Viec kich boat diu vio sir dung miy tao rung Sandia co Ion Miy tao rung niy co the rung voi tin hieu sin hoac tin hieu ngau nhian trong dai tan 2 toi 12 Hz

Vet nut gan niit 7

\

rung

(a) Nguyen ly

Tan so cong huong (Hz) Sau khi hu hai 2.2699 2.8339 3.4874 3.9896 4.1470 4.5245

Nh$n thiy ro rang co sy khac nhau ro rang ve gii tri tin so cong huong cua cic mode tuong ling nen co the ket luan da co sy sai hong xiy ra Hai hinh duoi day la FRF tuong ung voi tinh huong truoc va sau sai hong de co tha lam ro hon nhan xet niy

Hinh 47 FRF truac liic sai hong

Hinh 48 FRF sau khi sai hong

Hinh 48 chinh OS ciia cau 1-40 tai cimg 1 mode cong huong (mode 4) ma tir do ciing cho thay sy khic biet giira truoc va sau khi co khuyat tat tren cau tnic cau Co tha nhan thay rang dimg phan tich MA co tha nhan biat dugc c6 sai hong xiy ra hay khong nhung chua chi ra dugc vi tri cua sai hong Noi dung niy se dugc trinh bay o phan sau

trifd^c

Hinh 49 OS cua cau tai ciing 1 mode cong huong truac vd sau hu hong

- Phwtmgphdp nang liromg SEM (Strain Energy Method)

Mpt cich de nhan dien sai hong cua cong trinh li sir dung SEM [15] nhu minh boa tran hiiih duoi day Cac sai hong dugc phit hien boi sy thay doi SE gay ra do su thay doi dp Cling tai vi tri do Dip ung ciia cich phan tich MA dugc sir dyng de tii tao ra cic MS (chi can CO MS liic truoc va sau khi sai hong la co the nhan dugc vat nut, khong can nhung thong tin ve dp cung hay khoi lugng cau) Sau do, SE dugc tinh toin va so sinh voi SE liic dau (khi chua c6 sai hong) Bat ky sai hong nao trong ciu tnic se dugc chi ra tren hieu cua

2 ket qua nang lugng tren Chi so hu hai Pjj cho thinh phan thu j v i mode thii i cua 1 thanh dim (dugc chia thanh cic thinh phan chiau dai L) dugc tinh boi:

Cau true xuat hien sai hong

Dudng nSng lu-cmg co s6 Oudng nSng lu-ang cua cau true sai hong

(truoc kill CO sai liong)

Sir sai khac tao ra cac dnh -> vi th sai hong

Hinh 50 Nguyen tac phuang phdp nang luong theo sice cang SEM [9]