NGHIEN cufu - TRAO DOI
y. XAY DU'NG CAU TRUC THUAT TOAN KHI U'NG DUNG LOGIC M O C H A N D O A N HU* HdNG DONG CO DIESEL
CONSTRUCTION STRUCTURE AT APPLICATION ALGORITHM FUZZY LOGIC DIAGNOSIS DIESEL ENGINE FAILURE
TS. Dao Chi Cudng TrUdng Dai hgc SU pham Ky thuat HUng Yen
T O M TAT
Logic md ngdy cdng dUdc Ung dung rong rdi trong chdn dodn ky thudt. De thUc hien chdn dodn hu hong cua dgng cd diesel bdng Logic md, cdc cdu true thudt todn cdn dUdc mo td tUdng minh nhd bieu diin do hga nhdnh cdy hU hong - trieu chUng. Bdi bdo ndy gidi thieu phUdng phdp xdy diing cdu triic thudt todn trong Logic md de chdn dodn mgt trUdng hdp hU hong ldm vi du, do la trUdng hgp ket voi phun d mgt trong bon xilanh cua dgng cd diesel.
TiT khoa: Logic md; Cdu true thudt todn.
ABSTRACT
Fuzzy logic has been widely used in diagnostic techniques. To make a diagnosis of diesel engines damaged by fuzzy logic, the algorithm structure should be described explicitly represented by graphical tree branch damaged - Symptoms. This paper introduces methods of structuring fuzzy logic algorithm in order to diagnose a case of damage, for example, that is the case in a nozzle stuck in four-cylinder diesel engine.
Keywords: Fuzzy logic; Structure algorithm. ^
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NGHIEN cufu-TRAO DOI
1. DAT VAN DE IF - THEN vdi toan tU Minimum.
Nhiem vu cua cong tac chan doan ky thuat khdng chi la danh gia trang thai ky thuat chung cua dpng cP ma cdn phai phat hien dUde cac hu hdng cu the trong cac he thong, ed eau ciia dpng ca. Cic dang hU hdng khac nhau se cd cac trieu chUng bieu hien ra ben ngoai khac nhau. Neu quan he giUa hU hdng va trieu chdng la quan he ddn yeu td thi cd the ket luan ngay trang thai hU hdng. Tuy nhien, trong nhieu trUdng hpp, cac bieu hien nay khdng rd rang va cd tinh dan xen, binh thudng rat kho de xac dinh mgt each chinh xac cae hU hdng. Vdi cac thuat toan suy luan ddn gian eua logic md, cd the xd ly cae kien thdc chan doan bieu dien tren bang quan he hU hdng - trieu chdng nhd trd giup cua may tinh de ed lap va tim ra eae hU hdng mpt each nhanh chdng va tin cay.
Khi dng dung Logic md trong ehan doan ddng cP can phan tich xay dUng ed sd kien thUc ve quan he hU hdng - trieu chUng (chuan hda cac trieu ehdng hu hdng, lam md hda cac trieu chUng hu hdng, bieu diln moi quan he hu hdng - trieu chUng) eung nhU lUa chgn ham phu thupc va xac dinh thuat toan chan doan.
ThUc te eho thay, mUc dp ehinh xac cua eau true thuat toan quyet dinh dp ehinh xae ket qua chan doan.
2. CO S 6 X A Y D U K G CAU TRUC THUAT TOAN
Logic md la mdt phUdng phap de bieu diln va xd Iy thdng tin trong eae he thong cd eae sU kien khdng rd rang. Dac biet trong linh vUe chan doan, ed the bieu diln va xU ly cac kien thdc giai tieh hay xac suat d dang cac thuat toan logic md. Thuat toan lUa chgn de thUc hien chan doan trang thai ky thuat cua ddng ed va tim hu hdng dUa tren cac trieu chdng trong trudng hdp nay la thuat toan logic AND va luat
Khac vdi logic nhi phan, logic md ed kha nang xU ly cac su kien khong hoan toan dung ma cung chang hoan toan sai. Cac sU kien khong dupe dien dat bang cac gia tri nhi phan ma d i l n dat bang cac gia tri xac suat md. Ket qua chan doan hU hdng n h d logic md cd t h i cung cap thdng tin ve mUc dp hay so do doi vdi kha nang cua mgt hU hdng. Khi do, gia tri xac suat cua cac dieu kien hay tien de va cua ca hU hdng dupc chuan hda ve khoang [0,1]. Neu cac trieu chUng khdng nam trong viing mhi theo mUc dp phu thupc (ham phu thupc) thi kha nang hU hdng cd the lay gan vdi diem 0. Neu trieu chdng mau dien dat theo ngdn ngd cang tUdng thich vdi mdu hU hdng thi mUc xac suat hu hong do cang gan vdi 1. Neu mUc xac suat gan vdi 0, cd th^ danh gia rang hU hdng dd cd nhieu kha nang khdng xuat hien. Tai mdt gia tri xae suat gan vdi 1, cd rat nhieu kha nang xuat hien hd hdng. Mac du rat tUdng tU vdi viee xtf ly tin hieu thed phUdng phap thd, sdng khdng the ap dung khai niem xac suat, bdi vi d day khdng sU dung cac thdng tin thong ke ve cac trieu chdng va hU hdng.
De chan doan hU hdng tren ddng cd ed the xay ddng mdt md hinh ddn gian de chan doan vdi logic md. Tren md hinh nay, moi hd hdng dupc bieu dien bang mdt thuat toan cd chda tat ca cac dieu kien can thiet dien dat bang ngdn ngfl de nhan biet hU hdng. MUc do thdc hien cae tien de cho biet trUe tiep mUc xac suat eua hu hdng. De ehan doan theo logic md can tien hanh cac bUdc md hda va danh gia tien de de danh gia cac thuat toan ehan doan.
• Md hoa cac sU kien
Khi xd ly cac kien thdc chan doan ddng ca diesel bang thuat toan logic md cd the sd dung each dien dat ngdn ngfl cf dang-
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Neu < Trieu chdng S_ am tinh > thi < Ket luan > dUde md ta bdi mdt tap md sau:
Trong phan dieu kien (tien de) cua thuat toan, gia tri ngdn ngfl "am tinh" dfldc thong bao d dang mdt bieu hien ngdn ngfl (khai ni?m) "trieu chdng S^ am tinh" cua bien ngdn ngfl "trieuchdngS".
Khac vdi logic nhi phan, khi do mdt phan td thudc ve mdt tap hdp hoac khdng.
Trong logic md thdng bao mdt mUc dp phu thude vao bien ngdn ngfl "am tinh" cho mdt gia tri "net" cua trieu chdng S^ thdng qua mdt tap md. Tap md "am tinh" trong trUdng hdp nay la so do md ta tap hpp, bang each sap xep moi gia tri net S tU tap ca sd cua cac gia tri so S mdt mdc phu thupc qua mdt ham phu thupc fi^^ (s).
Moi gia tri ngdn ngfl thudc mdt bien ngdn ngfl
A m t i i i h = { ( S , f V g ( s ) ) | s e S i } Dang ham phu thugc \i^ (s) co the dupc lUa chgn bat ky. De thiet lap cac ham phu thudc, ed the cd rat nhieu kha nang, ngoai cac ham r, ham tam giac, ham hinh thang cd the sd dung cac ham Gauss, ham luy thda... Cac ham phu thugc cd the cd dang dUdng tuyen tinh hay cac dang dfldng eong tuy y gan vdi cac ham dai sd ed ban. Trong ehan doan trang thai va dieu khien md thudng chpn la cac ham tuyen tinh (cd mdc chuyen doi tuyen tinh). Trong cae phan mem cho trUdc, cac ham phu thudc dUde ehpn va sau dd hieu ehinh theo khai niem dat ra. Bang 1 la cae dang ham cd mdc chuyen doi tuyen tinh thudng dung trong chan doan va each bieu thi nd bang cdng thdc tUdng Ung [4].
5 1. Cdc dgng hdm phu thugc thudng dung trong chdn dodn
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Khdng phu thudc vao dang ham phu thupc, cac gia tri cua mdc phu thudc thUdng nam trong khoang (0 < (i < 1) de cd the npi suy cac gia tri xac suat. Mdt trUdng hpp dae biet cua tap rad la ddn tri, cae ham phu thudc eua nd chi tiep nhan tai mdt vi tri mdt gia tri gifla 0 va 1.
Hinh 1, the hien mdt vi du md hda mdt trieu chUng d.i chan doan ddng cP.
td VA, HOAC va PHU NHAN. Cac toan td nay tUdng Ung trong ly thuyet tap hdp la hpp logic, giao logic va bu logic. ThUc te cho thay viec thUc hien toan td VA cd the nhd toan td Minimum, cdn toan td HOAC cd the nhd toan td Maximum la du. TU dd mdc phu thudc cua cae tien de khi da cho cac ham phu thupc |i^ va Pg dUde tinh toan nhU sau:
Hlnh I: Mdhoa mgt trieu chdng chudn hoa
Doi vdi mdt trieu chUng S cd gia tri net la S= - 0,8 mdc phu thudc \x cd gia tri md "am tinh" la -0.4 va gia tri md "am tinh manh" la -0.6. MUc phu thudc cua cac tap md khac bang 0. Ham phu thudc dupe sU dung la ham tuyen tinh tdng khuc d dang hinh thang va d dang bac thang md tren hoae md dUdi. Cac dang ham nay cho kha nang khdng gidi han de thuc hien va danh gia dpn gian [5], [6].
VA: fiA n HB = min (JIA = MB ) HOAC: MA'^l^=max((iA,lte) PHU NHAN: fiA' = l-fiA
Viec ket ndi tat ca cac mdc dp phu thudc eua cac bieu hien tUpng dng vdi cac toan td cho ra mdc dp phu thugc cua tien de. Vdi mdc dp phu thudc cua tien de cd the xac dinh dong thdi mdc dp phu thudc eua ket luan.
H
Mo hoa I
ra
Hinh 2. Sd do chdn dodn nhd logic md ddn gidn vdi todn tit VA
• Danh gia tien de va suy luan Trong mo hinh logic mci ddn gian, viec danh gia tien de da cung cap cac gia tri xac suat hoac mijfc phu thuoc cua hU hong, bdi vi mOi triidng hop hU hong chi co the mo ta bdi mot thuat toan rieng biet. Trong pham vi danh gia tien de, phric hgp cac miJc phu thugc cua mot bieu hien rieng le ttlong thich vdi nhau va xac dinh miJc phu thugc ctia tien de. Cac bieu hien ciia cac khai niem ngon ngfl mo ta bang logic md khi do cd quan he vdi nhau theo cac toan
Hinh 2, gidi thieu so do don gian de chan doan hiJ hdng theo toan tri VA cua cac tien de. Ham phu thugc ciia hU hdng la thong so ra dugc md ta bdi mgt tap don tri (Single ton) cung cap ket luan tuong flng vdi cac mile phu thugc cua tien de trong khoang [0,1].
Neu <Si duong manh> va <Sj am manh> thi <
Hu hdng Fk >
Viec ket noi tat ca cac miic dd phu thugc cua cac bieu hien t u g n g iing vdi cac toan ttf
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NGHIEN cufu - TRAO DOI
dUa ra mdc dp phu thudc cua tien de. Vdi mdc do phu thupc cua ti^n de cd the xac dinh ddng thdi mdc dp phu thupc cua ket luan. Tren hinh 2 the hien ket luan cua chan doan theo cac tien d^. Ham phu thudc cua hU hdng tU thdng so ra va dugc md hinh hda bdi cac ham bac thang.
3. X A Y BXSNG CAU TRUC T H U A T TOAN
CHXN DOAN H U HONG DONG CO
DIESEL
De thUc hien chan doan hU hdng cua ddng ca diesel, trUdc het eae eau true thuat toan can dUpc md ta tUdng minh nhd bieu dien do hga nhanh cay hU hdng - trieu chUng. Ve nguyen tac can thiet md ta tat ea cae quan he giUa hu hdng va cac trieu chdng hU hdng da lUu trfl trong bang quan he hU hdng - trieu chdng).
Tuy nhien, trong khudn kho bai bao, chung tdi chi gidi thieu mdt trUdng hdp hU hdng lam vi du, dd la trUdng hpp ket vdi phun d mpt trong bon xi lanh cua ddng cd diesel (hinh 3).
Trang thai < ket vdi phun thU i > dan den hai sU kien quan trgng la: Khdng cd qua trinh bien ddi nang lUdng trong xi lanh i (cdn ggi la bd may hay bd lifa) va giam lUdng cung cap khdang 'A so vdi binh thudng.
SU kien thU nhat E, d i n den trieu ehdng Sj, giam manh va deu d dUdng ehi phi nhien lieu gid.
Su kien thU hai E^ dan den ba trieu chdng S , S^, S^ la giam manh md men danh nghia, md men eUc dai va tdc dp quay khong tai edc dai, ddng thdi dan den hai sU kien ke tiep E3 v^ E^.
Hinh 3: Do hga nhdnh cdy suy ludn hU hong - tneu chiing trong tnidng hdp <ket vdt phun thd i d trgng
thdi ddng>
Su kien E^ la giam ap suat eUc dai trong xi lanh i do khdng co qua trinh chay dan den trieu ehdng S^ - giam xung ap suat cac te tUdng Ung xi lanh i.
Su kien E^ la 3 xi lanh cdn lai bj qua tai khi phai tang toe va keo xi lanh 1 dan den trieu chdng Sj - tang khdi khi thai.
Trong cac phan tich nhanh eay co dien, cac thuat toan duge xd ly nhd suy luan nhi phan, d day sd dung suy luan md de ket luan ve tinh chae ehan cua viee xuat hien hU hdng va ket luan xap xi trang thai hU hdng eua dpng cd.
DUa vao cac ed sd khoa hpc da phan tich, chung tdi lay mgt vi du cu the thUc hien ehan doan theo logic md cho cac trUdng hdp
"ket vdi phun thU i d trang thai ddng" va "hU hdng nang xec mang trong xi lanh thd 1".
Nhu da phan tieh tren do hpa nhanh eay hU hdng - trieu chUng, khi xuat hien cac trieu ehdng giam manh md men danh nghia SAM^ (dUdng manh) va dd tang ididi d che dp danh nghia SAD,, tang (dUdng), cd the ket luan cd hien tUpng bd lifa hoac chay qua yeu d mdt xi lanh nao do. Xuat hien bo Ida dan den mdt dieu ^
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kien can de ket luan cd dang hU hdng "ket vdi phun" hoac "hU hong xec mang". Viec tach cac hu hdng "ket vdi phun" va "hU hdng nang xec mang" dugc thUc hien nhd vao viec phan tieh tiep cac trieu chdng dp giam Idpng cung cap d che do danh nghia SAmB^^ va trieu chdng dp tang ap suat khi cac te SAP.. Neu xuat hien trieu chdng dp giam lUdng cung cap d che dp danh nghia SAmB^ giam manh (dUdng manh) va trieu chdng dp tang ap suat khi cac te SAP^
giam (am) thi ed the ket luan chae chan ed dang hu hdng "ket vdi phun thd i d trang thai ddng".
Neu xuat hien trieu chdng dp tang ap suat khi cac te SAP tang manh (dUPng manh) va lUpng nhien lieu cung cap tai che do danh nghia SAmB^khdng giam (khdng the hien), thi cd the ket luan chae chan la "hu hdng nang xec mang".
Tinh chat cua cac trieu chdng dan den sU kien
"bd Ida xi lanh i" co the dUde md ta bdi thuat toan logic md nhU sau:
NEU < SzlM^ dUdng manh > va < SAD^
dUpng > thi < Bd Ida xi lanh i, EAzi >
Hinh 4: Ddnh gia cdc trieu chUng S^^,^ vd S^^^ tren cd sd logic md de tinh todn khd ndng xudt hiin sU
kien "Bo lUa xi lanh i"
Tren hinh 4 gidi thieu ham Idgie md de tinh toan kha nang xuat hien sU kien bd Ida E . Viee danh gia tap md tUOng dng eung cap mde xae suat cho mdi tien de. Quan he VA cua cae mde xac suat vdi toan td Minimum dUa ra kha nang |i^^^ cho sU kien "bd Ida xi lanh i", khi dd
bien ra dflpc md ta ddn gian bdi mdt t i p md ddn tri dat tai d i l m 0. N^u cac gia tri n^^, cang gan 1 thi kha nang xuat hien sU kien cang ldn.
Thuat toan cho hU hdng "ket vdi phun d sela:
NEU < SmB^ dUdng manh > va < SAp^ am >
va < Bd Ida xi lanh i, (E^^,) > THl < Ket vdi phun thd i , ( F ^ ^ , , ) >
Hinh 5: Ddnh gid cdc trieu chdng 5^^^^^, S vd sU kien E^^^ tren cd sd logic md de tinh todn khd nang
xudt hiin sii kien "ket voi phun thU i"
Tren hinh 5 gidi thieu ham logic md de tinh toan kha nang xuat hien hd hong "ket voi phun thU i". Cach thdc danh gia tUdng tU tren hinh 3, tuy nhien, ed them tien de bo sung E^^^.
Do da m d hda nen mde xae suat cua sd kien [i^^^ dupc ket ndi trUe tiep vdi mde xae suat cua eae tien de khac qua toan td Minimum dS xac dinh kha nang hU hdng "ket vdi phun thd i"
Neu cd xuat hien sU kien bd Ida trong xi lanh i ma khdng cd hU hdng ket vdi phun, thi cd the chi do hU hdng nang xec mang, piston.
Nhu vay, khi bd Ida, mdc xac suat cua hU hong
" hu hdng nang xec mang" tddng Ung vdi phan bu eua hu hdng " ket vdi phun thd i" cd nghia la:
A, = A^ ( 1 - A„^„). (1.1)
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Viec danh gia tren cp sd logic md tren hinh 4 va hinh 5 dUde bieu diln ddn gian d dang cay chan doan (hinh 6). MUc xac suat cua cac tien de va sU kien cung nhU kha nang hU hdng ddpc cho tai cac nut.
Hinh 6: Suy ludn theo cdy chdn dodn trUdng hdp ket voi phun thdi
a) Tgo sii kien bo liia xy lanh i (E^^);
b) Tinh todn khd ndng hU hong "ket voi phun i"
Viec xd ly md hinh chan doan md, td viee nhap va xay dUng eae bien vao, ra, xay dUng cac thuat toan va danh gia ket qua, ed the sd dung md dun fuzzy- logic trong Toolbox cua phan mem MATLAB/SIMULINK [1], [2], [4].
Ddi vdi tat ca eae quan he gifla tneu chdng va hU hdng cdn lai da dUpe lUu gifl trong cd sd kien thdc ehan doan, deu cd the xay dUng md hinh chan doan md, phan tich, danh gia va chan doan md tUdng tU.
4. KET LUAN
De chan doan dpng cd ddt trong ndi chung va ddng ed diesel ndi rieng can tien hanh eae bddc md hda va danh gia tien de de danh gia cac thuat toan chan doan. Mdi tinh chat cua mgt trieu chdng dan den sU kien hU hdng cd the dflpc md ta bdi thuat toan logic md, mdc d0 chinh xac cua ket qua chan doan phu thudc vao vi?c xay dflng eau true thuat toan. TrUdc het can bieu dien va phan tich cae quan he hU
hdng - trieu chdng mdt each tUdng minh theo bieu dien do hpa rdianh cay (cay hU hdng - trieu chdng), day chinh la tien de, la ca sd de xay dflng eau true thuat toan trong chan doan bang logic md. Nhiem vu cua ehan doan khi do la: Xuat phat td cac thdng tin dau vao, cac trieu chdng bieu hien hU hdng de ket luan ve cac thdng so ra, cae trang thai hfl hdng theo y nghia chan doan: Trieu chdng - sU kien - hU hdng.
Kien thdc chan doan ve cae quan he hu hdng - trieu ehdng dflpc chd trong cac thuat toan nut d dang thuat toan chan doan: Neu < Dieu kien
> thi < Ket luan >. TU ket qua eua eau trde thuat toan da xay dUng, se xay dflng cac thuat toan va danh gia ket qua trong md dun fuzzy- logic cua phan mem MATLAB/SIMULINK [1], [2],
Ngay nhan bai: 05/7/2014 Ngay phan bien: 10/8/2014 Tai lieu tham khao:
[1]. Dao Chi Cu6ng (2006), Xdy dUnghe thong chdn dodn da ngoai cho dong cd diesel tren cdc phUdng tien giao thong van tdi vd mdy chuyen diing, de tai NCKH cap Bo, iiias6B2006-21-02.
[2]. Dao Chi Cifcfng (2011), Nghien ciiu xdy dUng cd sd da lieu cho he thong chdn dodn dgng cd diesel diing trong nong nghiip, nong than Viet Nam, Luan an Tien si ley thuat, TrUdng Dai hpc Nong nghiep Ha Ngi.
[3|. Pham Thi Thu HUOng (1999), Nghien ciiu xdy dUng he trp gliip chdn doan tinh trang ky thuat cdc phUdng tien giao thong van tdi tren cd sd logic md, De lai nghien cilu khoa hoc cap bo, ma so B99-35-94.
[4]. Nguyen Khdc Trai (2004), Ky thudt chdn dodn Oto, NXB. Giao thong Van tai.
[5]. Dieter Brunotte (2005), Einsatzmoghchkciten ernes Fuzzy-Logik-Systems fur das Antriebsstrangmanagement eines Traktors, Instituts fiir Landmaschinen und Fluidtechnik e.V,
[6]. Frank Kimmich (2004), Modellbasierte Fehlerverkennung und Diagnose der Einspritzung und Verbrennung von Dieselmotoren, Fortschritt - Berichte VDI, Reihe 12 Verkehrstechnik/Fahrzeugtechnik, Nr 569.
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