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  • 1Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    M s: CT384, 3 Tn ch(KT in t VT, KT iu khin v C in t)

    TS. Nguyn Ch NgnB mn T ng Ha

    Khoa K thut Cng nghEmail: [email protected]

    ---2008---

    I HC CN TH

    2Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Ni DungChng 1: Tng quan v mng nron nhn to (ANN)Chng 2: Cu trc ca ANNChng 3: Cc gii thut hun luyn ANNChng 4: Mt s ng dng ca ANN (MATLAB) n mn hcChng 5: Mng nron m (Fuzzy-Neural Networks) Chng 6: Mt s nh hng nghin cu (Case Studies)n tp v tho lun

    Tham kho:1. Nguyn Ch Ngn, iu khin m hnh ni v Neural network: Chng 2 Mng n-

    ron nhn to, Lun n cao hc, HBK Tp. HCM, 2001.2. Nguyn nh Thc, Mng nron Phng php v ng dng, NXBGD, 2000.3. Simon Haykin, Neural Networks a comprehensive foundation, Prentice Hall, 1999. 4. Howard Demuth, Mark Beale and Martin Hagan, Neural Networks toolbox 5

    Users Guide, The Matworks Inc., 2007.

  • 3Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    T chc mn hcThi lng mn hc: 3TC

    2 TC l thuyt v bi tp trn lp1 TC n mn hc (03 SV thc hin 1 ti)

    Lch hc:Tun 1: Chng 1Tun 2 3: Chng 2 + Bi tpTun 4 5: Chng 3 + Bi tpTun 6 7: Chng 4 + Bi tpTun 8 11: n mn hcTun 12 13: Chng 5 + Bi tpTun 14: Chng 6Tun 15: n tp v tho lun

    nh gi n mn hc: 45%Thi ht mn: 55%

    4Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Chng 3Cc gii thut hun luyn ANN

    Gii thiuCc phng php hun luynMt s gii thut thng dng

    Hm mc tiuMt li v cc im cc tiu cc b

    Qui trnh thit k mt ANNCc k thut ph tr

    Minh ha bng MATLABBi tp

  • 5Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thiuGi thiu v cc phng php hun luynTm hiu mt s gii thut thng dng hun luyn ANN. Phn ny tp trung vo gii thut Gradient descent v cc gii thut ci tin ca nHm mc tiuMt li v cc im cc tiu cc bMt s v d v phng php hun luyn mng bng MATLABQui trnh thit k mt ANNCc k thut ph trHin tng qu khp ca ANN

    6Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Cc phng php hun luynHun luyn mng l qu trnh thay i cc trng s kt niv cc ngng ca n-ron, da trn cc mu d liu hc, sao cho tha mn mt s iu kin nht nh.

    C 3 phng php hc:Hc gim c st (supervised learning)Hc khng gim st (unsupervised learning)Hc tng cng (reinforcement learning).Sinh vin tham kho ti liu [1].

    Gio trnh ny ch tp trung vo phng php hc c gimst. Hai phng php cn li, sinh vin s c hc trongchng trnh Cao hc.

  • 7Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut hun luyn ANN (1)Trong phn ny chng ta tm hiu v gii thut truyn ngc(backpropagation) v cc gii thut ci tin ca n, p dng chophng php hc c gim st.Gii thut truyn ngc cp nht cc trng s theo nguyn tc:

    wij(k+1) = wij(k) + g(k)trong :

    wij(k) l trng s ca kt ni t n-ron j n n-ron i, thi im hin ti l tc hc (learning rate, 0< 1)g(k) l gradient hin ti

    C nhiu phng php xc nh gradient g(k), dn ti c nhiugii thut truyn ngc ci tin.

    8Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut hun luyn ANN (2) cp nht cc trng s cho mi chu k hun luyn, gii thuttruyn ngc cn 2 thao tc:Thao tc truyn thun (forward pass phase): p vect d liu votrong tp d liu hc cho ANN v tnh ton cc ng ra ca n.

    Thao tc truyn ngc (backward pass phase): Xc nh sai bit (li) gia ng ra thc t ca ANN v gi tr ng ra mong mun trong tp dliu hc. Sau , truyn ngc li ny t ng ra v ng vo ca ANN vtnh ton cc gi tr mi ca cc trng s, da trn gi tr li ny.

    p1(k)

    p2(k)

    pj(k)

    pR(k)

    wij(k)

    wi2(k)

    wi1(k)

    wRj(k)

    f ti(k)

    ei(k)

    ai(k)+ -

    Minh ha phng php iu chnh trng s n-ron th j ti thi im k

  • 9Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut gradient descent (1)Xt mt MLP 2 lp:

    pn

    p1

    p2

    pia2j

    a21

    a2m

    w2ij l trng s lp ra, t j n iw1ij l trng s lp n,

    t j n i

    Ng ra n-ron n l a1i

    Lp n

    10Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut gradient descent (2)Thao tc truyn thun

    Tnh ng ra lp n (hidden layer):n1i (k) = j w1ij (k) pj (k) ti thi im k a1i(k) = f1( n1i(k) )

    vi f1 l hm kch truyn ca cc n-ron trn lp n. Ng ra ca lp n l ng vo ca cc n-ron trn lp ra.

    Tnh ng ra ANN (output layer):n2i (k) = j w2ij (k) a1j (k) ti thi im k a2i(k) = f2( n2i(k) )vi f2 l hm truyn ca cc n-ron trn lp ra

  • 11Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut gradient descent (3)Thao tc truyn ngc

    Tnh tng bnh phng ca li:vi t(k) l ng ra mong mun ti kTnh sai s cc n-ron ng ra:

    Tnh sai s cc n-ron n:

    Cp nht trng s

    Sinh vin tham kho ti liu [3], trang 161-175.

    =i

    ii kaktkE22 )()(

    21)(

    [ ] )(')()()(

    )()( 222 knfkaktknkEk iii

    ii =

    =

    =

    =j

    jijii

    i wkknfknkEk )()('

    )()()( 111

    )()()()1(

    )()()()1(122

    1

    kakkwkw

    kpkkwkw

    jiijij

    jiijij

    +=+

    +=+

    lp n:

    lp ra:

    12Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (1)Xt mt ANN nh hnh v, vi cc n-ron tuyn tnh.

    Minh ha gii thut truyn ngc nh sau

    a21

    a22

    p1

    p2

    w111= -1

    w121= 0

    w112= 0w122= 1

    b11= 1b12= 1

    w211= 1

    w221= -1

    w212= 0w222= 1

    b21= 1 b22= 1

    Mr DuongSticky Notej ben phai, i ben trai

    Mr DuongSticky Notevi noron la lop an dau tien nen p=a. cap nhat trong so phai dua vao delta va a(p) cua 2 no ron nam 2 ben trong so.

  • 13Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (2) n gin, ta cho c cc ngng bng 1, v khng v ra y

    Gi s ta c ng vo p=[0 1] v ng ra mong mun t=[1 0]Ta s xem xt tng bc qu trnh cp nht trng s ca mngvi tc hc =0.1

    a21

    a22

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 1

    w221= -1

    w212= 0

    w222= 1

    14Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (3)Thao tc truyn thun. Tnh ng ra lp n:

    a21

    a22

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 1

    w221= -1

    w212= 0

    w222= 1

    a12 = 2

    a11 = 1

    a11 = f1(n11) = n11 =(-1*0 + 0*1) +1 = 1

    a12 = f1(n12)=n12 = (0*0 + 1*1) +1 = 2

  • 15Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (4)Tnh ng ra ca mng (lp ra):

    a21=2

    a22=2

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 1

    w221= -1

    w212= 0

    w222= 1

    a12 = 2

    a11 = 1

    a21 = f2(n21) = n21 =(1*1 + 0*2) +1 = 2

    a12 = f2(n22)=n22 = (-1*1 + 1*2) +1 = 2

    Ng ra a2 khc bit nhiu vi ng ra mong mun t=[1 0]

    16Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (5)Thao tc truyn ngc

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 1

    w221= -1

    w212= 0

    w222= 1

    a12 = 2

    a11 = 11= -1

    2= -2

    Vi ng ra mong mun t =[1, 0],Ta c cc error ng ra:

    1 = (t1 - a21 )= 1 2 = -12 = (t2 - a22 )= 0 2 = -2

    )()()()1( 122 kakkwkw jiijij +=+

    Mr DuongSticky Notemang no ron la tuyen tinh nen dao ham = 1.

  • 17Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (6)Tnh cc gradient lp ra

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 1

    w221= -1

    w212= 0

    w222= 1

    a12 = 2

    a11 = 11a11= -1

    2a12= -4

    1a12= -2

    2a11= -2

    18Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (7)Cp nht trng s lp ra

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    w211= 0.9

    w221= -1.2

    w212= -0.2w222= 0.6

    a12 = 2

    a11 = 1

    )()()()1( 122 kakkwkw jiijij +=+

    w211= 1 + 0.1*(-1) = 0.9w221= -1 + 0.1*(-2) = -1.2w212= 0 + 0.1*(-2) = -0.2w222= 1 + 0.1*(-4) = 0.6

    Mr DuongSticky Notecap nhat trong so,ta su dung tin hieu ben phai

  • 19Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    1= -1

    2= -2

    1 w11= -1

    2 w21= 21 w12= 0

    2 w22= -2

    Minh ha gii thut hun luyn (8)Tip tc truyn ngc

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    S dng li cc trng s trc khi cp nht cho lp ra, tnh gradient lp n

    =j

    jijii wkknfk )()(')(11

    20Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (9)Tnh cc error trn lp n

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    1 = 1 w11 + 2 w21 = -1 + 2 = 1

    2 = 1 w12 + 2 w22 = 0 - 2 = -2

    1= -1

    2= -2

    1= 1

    2 = -2

  • 21Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (10)Tnh gradient lp n

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0

    w122= 1

    1= -1

    2= -2

    1 p1 = 0

    2 p2 = -2

    2 p1 = 0

    1 p2 = 1

    22Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (11)Cp nht trng s lp n

    p1=0

    p2=1

    w111= -1

    w121= 0

    w112= 0.1w122= 0.8

    )()()()1(1 kpktwkw jiijij +=+

    w111= -1 + 0.1*0 = -1w121= 0 + 0.1*0 = 0w112= 0 + 0.1*1 = 0.1w122= 1 + 0.1*(-2) = 0.8

    1 p1 = 0

    2 p2 = -2

    2 p1 = 0

    1 p2 = 1

  • 23Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (12)Gi tr trng s mi:

    w111= -1

    w121= 0

    w112= 0.1w122= 0.8

    w211= 0.9

    w221= -1.2

    w212= -0.2w222= 0.6

    Qu trnh cp nht cc gi tr ngng hon ton tng t.

    24Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (13)Truyn thun 1 ln na xc nh ng ra ca mng vi gi trtrng s mi

    w111= -1

    w121= 0

    w112= 0.1w122= 0.8

    w211= 0.9

    w221= -1.2

    w212= -0.2w222= 0.6

    p1=0

    p2=1

    a12 = 1.6

    a11 = 1.2

  • 25Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha gii thut hun luyn (14)

    w111= -1

    w121= 0

    w112= 0.1w122= 0.8

    w211= 0.9

    w221= -1.2

    w212= -0.2w222= 0.6

    p1=0

    p2=1

    a12 = 1.6

    a11 = 1.2

    a22 = 0.32

    a21 = 1.66

    Gi tr ng ra by gi l a2 = [1.66 0.32]gn vi gi tr mongmun t=[1 0] hn.Bi tp: T kt qu ny, sinh vin hy thc hin thao tctruyn ngc v cp nht trng s ANN 1 ln na.

    26Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Hun luyn n khi no? s thi k (epochs) n nh trcHm mc tiu t gi tr mong munHm mc tiu phn k

  • 27Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Hm mc tiu MSE (1)Mean Square Error MSE l li bnh phng trung bnh, c xc nh trong qu trnh hun luyn mng. MSE cxem nh l mt trong nhng tiu chun nh gi s thnhcng ca qu trnh hun luyn. MSE cng nh, chnhxc ca ANN cng cao.nh ngha MSE:

    Gi s ta c tp mu hc: {p1,t1}, {p2,t2}, , {pN,tN}, vi p=[p1, p2, pN] l vect d liu ng vo, t= [t1, t2, , tN] l vect dliu ng ra mong mun. Gi a=[a1, a2, , aN] l vect d liu rathc t thu c khi a vect d liu vo p qua mng. MSE:

    c gi l hm mc tiu=

    =N

    iii atN

    MSE1

    21

    28Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Hm mc tiu MSE (2)V d 1: Cho ANN 2 lp tuyn tnh nh hnh v.p=[1 2 3; 0 1 1] l cc vect ng vo.t=[2 1 2] l vect ng ra mong mun.Tnh MSE.Gii:

    Ng ra lp n: a11=f(n11)=n11=[1.5 3.5 4.5]

    a12=f(n12)=n12=[0.2 2.2 2.2]

    Lp ra: a2=f(n2)=n2=[3.2 9.2 11.2]

    MSE =

    MSE = 51.1067

    .2

    .5

    p1

    p2

    2

    1

    1

    2

    1

    1

    0

    1a2

    a11

    a12 1

    0

    ( ) ( ) ( ) 2223

    1

    2 )2.112(2.912.3231

    31

    ++==i

    ii at

  • 29Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Hm mc tiu MSE (3)M phng: net=newff([-5 5; -5 5], [2 1], {'purelin', 'purelin'}); net.IW{1,1}=[1 1; 0 2]; % gn input weights net.LW{2,1}=[2 1]; % gn layer weights net.b{1}=[.5; .2]; % gn ngng n-ron lp n net.b{2}=0; % gn ngng n-ron lp ra p=[1 2 3; 0 1 1]; % vect d liu vo t=[2 1 2]; % ng ra mong mun a=sim(net,p) % ng ra thc t ca ANN mse(t-a) % tnh mse

    ans =51.1067

    30Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Hm mc tiu MSE (4)MSE c xc nh sau mi chu k hun luyn mng (epoch) vc xem nh 1 mc tiu cn t n. Qu trnh hun luyn ktthc (t kt qu tt) khi MSE nh.

  • 31Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (1)Bi ton: Xy dng mt ANN nhn dng m hnh vo ra cah thng iu khin tc motor DC sau:

    32Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (2)Nguyn tc:

    (k)=fANN[V(k), V(K-1), V(K-2), (k-1), (k-2)]

    Cc bc cn thit:Thu thp v x l d liu vo ra ca i tngChn la cu trc v xy dng ANNHun luyn ANN bng gii thut gradient descentKim tra chnh xc ca m hnh bng cc tn hiu khc

    Motor DC

    M hnhANN

    ng vo V ng ra

    ~

    e = - ~

    gradient descent

  • 33Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (3)Thc hin:

    M hnh Simulink thu thp d liu: data_Dcmotor.mdl

    Chun b d liu hun luyn: ANN_Dcmotor.mload data_DCmotor; % nap tap du lieu hocP=[datain'; dataout(:, 2:3)']; % [V(k), V(k-1), V(k-2), (k-1), (k-2)]T=dataout(:,1)'; % theta(k)

    V(k), V(k-1), V(k-2) (k), (k-1), (k-2)

    34Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (4)Thc hin:

    To ANN v hun luyn: ANN_Dcmotor.m>> net=train(net, Ptrain,Ttrain, [], [], VV,TV);

    Nhn xt:Tc hi t ca giithut Gradient descent qu chm.

    Sau 5000 Epochs, MSE ch t 6.10-4.

    Kt qu kim tra chothy li ln.

    Cn gii thut ci tin.

  • 35Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (5)Thc hin:

    M hnh kim tra chnh xc ANN: Test_Dcmotor.mdl

    (k)=fANN[V(k), V(K-1), V(K-2), (k-1), (k-2)]

    36Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    V d v GT Gradient descent (6)Kt qu:

    0 5 10 15 20 25 30 35 40 45 50-0.4

    -0.3

    -0.2

    -0.1

    0

    0.1

    0.2

    0.3

    0.4

    Time(s)

    (ra

    d)

    Testing result of DC_motor model

    DC_motor outputModel output

  • 37Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Cc tiu cc bnh hng ca tc hc

    Qu trnh hun luyn mng, giithut cn vt qua cc im cctiu cc b (v d: c th thay ih s momentum), t cim global minimum.

    E

    WLocal minimum global

    minimum

    38Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Mt li

    Cc tiu mong mun

  • 39Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gradient des. with momentum (1)Nhm ci tin tc hi t ca gii thut gradient descent, ngi ta a ra 1 nguyn tc cp nht trng s ca ANN:

    vi g(k): gradient; : tc hcij(k-1) l gi tr trc ca ij(k) : momentum

    t hiu qu hun luyn cao, nhiu tc gi nghi gi tnggi tr ca moment v tc hc nn gn bng 1:

    [0.8 1]; [0 0.2]

    )1()()(

    )()()1(

    +=

    +=+

    kwkgkw

    kwkwkw

    ijij

    ijijij

    40Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gradient des. with momentum (2)p dng cho bi ton nhn dng m hnh ca motor DC:

    Nhn xt: Sau 5000 Epochs,MSE t 4.10-4, nhanh hn giithut gradient descent.

  • 41Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    GD vi tc hc thch nghi (1)Tc hi t ca gii thut Gradient descent ph thuc vo tc hc . Nu ln gii thut hi t nhanh nhng bt n. Nu nh thi gian hi t s ln.Vic gi tc hc l mt hng s sut qu trnh hun luyn, t ra km hiu qu. Mt gii thut ci tin nhm thay i thchnghi tc hc theo nguyn tc:

    42Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    GD vi tc hc thch nghi (1)p dng cho bi ton nhn dng m hnh ca motor DC:

    Nhn xt: Sau 5000 Epochs,MSE t 10-4, nhanh hn giithut gradient descent with momentum

  • 43Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    (1)

    L gii thut gradient descent ci tin, m c tc hc v hs momentum c thay i thch nghi trong qu trnh hunluyn. Vic thay i thch nghi c thc hin tng th nh victhch nghi tc hc .Th tc cp nht trng s ging nh gii thut GD with momentum:

    vi g(k): gradient; : tc hc thch nghiij(k-1) l gi tr trc ca ij(k) : momentum thch nghi

    )1()()()()()1(+=

    +=+

    kwkgkwkwkwkw

    ijij

    ijijij

    44Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    (2)

    p dng cho bi ton nhn dng m hnh ca motor DC:

    Nhn xt: Sau 5000 Epochs,MSE t 3.10-5, nhanh hn giithut gradient descent with thch nghi

  • 45Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gradient direction

    GT. truyn ngc Resilient (1)Cc hm truyn Sigmoid nn cc ng vo v hn thnh cc ng rahu hn lm pht sinh mt im bt li l cc gradient s c gi trnh, lm cho cc trng s ch c iu chnh mt gi tr nh, mc dn cn xa gi tr ti u.Gii thut Resilient c pht trinnhm loi b im bt li ny bngcch s dng o hm ca hm li quyt nh hng tng/gim cagradient.

    Nu cng du:

    wij(k+1) c tng thm 1 lng inc

    Nu khc du: wij(k+1) c gim i 1 lng dec

    +

    ij

    k

    ij

    k

    wE

    wE 1&

    +

    ij

    k

    ij

    k

    wE

    wE 1&

    46Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    GT. truyn ngc Resilient (2)

  • 47Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    GT. truyn ngc Resilient (3)p dng cho bi ton nhn dng m hnh ca motor DC:

    Nhn xt: Sau 5000 Epochs,MSE t 8.10-6, nhanh hn giithut gradient descent with & thch nghi

    48Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut BFGS Quasi-NewtonSinh vin t c ti liu [1] v [3]p dng cho bi ton nhn dng m hnh motor DC:

    Nhn xt: Sau 1100 Epochs,MSE t 2.10-7, nhanh hn giithut Resilient

  • 49Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut Levenberg-Marquardt (1)Gii thut Levenberg-Marquardt c xy dng t tc hi t bc 2 m khng cn tnh n ma trn Hessian nh giithut BFGS Quasi-Newton.Ma trn Hessian c tnh xp x: H=JTJ v gi tr gradient c xc nh: g=JTetrong , J l ma trn Jacobian, cha o hm bc nht ca hmli (e/wij), vi e l vect li ca mng.Nguyn tc cp nht trng s:

    wij(k+1)=wij(k) [JTJ + mI]-1 JTe

    Nu m=0, th y l gii thut BFGS Quasi-Newton.Nu m c gi tr ln n l gii thut gradient descent.Gii thut Levenberg-Marquardt lun s dng gi tr m nh, do gii thut BFGS Quasi-Newton tt hn gii thut gradient descent.

    50Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thut Levenberg-Marquardt (1)p dng cho bi ton nhn dng m hnh ca motor DC:

    Nhn xt: Sau 20 Epochs,MSE t 1,7.10-7, nhanh hn giithut Newton

  • 51Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    So snh cc gii thutSo snh trn bi ton nhn dng m hnh mt i tng phi tuyn, c trnh by trong ti liu [1]:

    52Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Cc gii thut ca NN. toolboxTrainb Batch training with weight & bias learning rules.Trainbfg BFGS quasi-Newton backpropagation.Trainbr Bayesian regularization.Trainc Cyclical order incremental training w/learning functions.Traincgb Powell-Beale conjugate gradient backpropagation.Traincgf Fletcher-Powell conjugate gradient backpropagation.Traincgp Polak-Ribiere conjugate gradient backpropagation.Traingd Gradient descent backpropagation.Traingdm Gradient descent with momentum backpropagation.Traingda Gradient descent with adaptive lr backpropagation.Traingdx Gradient descent w/momentum & adaptive lr backpropagation.Trainlm Levenberg-Marquardt backpropagation.Trainoss One step secant backpropagation.Trainr Random order incremental training w/learning functions.Trainrp Resilient backpropagation (Rprop).Trains Sequential order incremental training w/learning functions.Trainscg Scaled conjugate gradient backpropagation.

  • 53Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Qui trnh thit k mt ANN

    B A

    B A

    54Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

  • 55Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Tin x l d liu (1)Phng php chun ha d liu:Chun ha tp d liu nm trong khong [-1 1].

    Gi p[pmin, pmax] l vect d liu vo

    ps l vect d liu sau khi chun ha, th:

    Nu ta a tp d liu c x l vo hun luyn mng, thcc trng s c iu chnh theo d liu ny. Nn gi tr ng raca mng cn c thao tc hu x l.Gi a l d liu ra ca mng, at gi tr hu x l, th:

    1pp

    pp2pminmax

    mins

    =

    D liu vop[pmin, pmax]

    Chun haps[-1, 1]

    ANN Hu x la

    at

    ( )( ) minminmaxt p pp1a21a ++=

    56Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Tin x l d liu (2)Phng php chun ha d liu (v d)

  • 57Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Tin x l d liu (3)Phng php tr trung bnh v lch chun:Tin x l tp d liu c tr trung bnh bng 0 (mean=0) v lch chun bng 1 (standard deviation=1).

    Gi p l vect d liu vo, c tr trung bnh l meanp v lch chun l stdp, th vect d liu c x l l:

    Gi a l vect d liu ra ca ANN, th vect d liu ng ra saukhi thc hin thao tc hu x l:

    p

    ps std

    eanmpp

    =

    ppt meanstdaa += *

    58Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Tin x l d liu (4)Phng php tr trung bnh v lch chun (v d)

    Mean = 0

    Std = 1

    Mean 0

    Std 1

  • 59Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Nng cao kh nng tng qut ha (1)Mt vn xut hin trong qu trnh hun luyn mng, lhin tng qu khp (overfitting). Khi kim tra mng bng tp d liu hun luyn, n cho ktqu tt (li thp). Nhng khi kim tra bng d liu mi, kt qurt ti (li ln). Do mng khng c kh nng tng qut ha cctnh hung mi (hc vt).C 2 phng php khc phc: Phng php nh ngha li hmmc tiu v phng php ngng sm.

    60Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Nng cao kh nng tng qut ha (2)Phng php nh ngha li hm mc tiu:

    Thng thng hm mc tiu c nh ngha l:

    Hm mc tiu c nh ngha li bng cch thm vo i lngtng bnh phng trung bnh ca cc trng s v ngng, MSW, khi :

    Vi l mt hng s t l vn tng s trng sv ngng ca mng

  • 61Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Nng cao kh nng tng qut ha (3)Phng php ngng sm:

    Phng php ny i hi chia tp d liu hc thnh 3 phn, gm d liu hun luyn, d liu kim tra v dliu gim st.

    P = [Ptrain, Ptest, Pvalidation]

    Sau li thi k hun luyn, tp d liu dm st Pvalidationc a vo mng kim tra li. Nu li thu cgim, qu trnh hun luyn c tip tc. Nu li thuc bt u tng (hin tng qu khp bt u xy ra), qu trnh hun luyn c dng li gi l ngng sm.Sinh vin c thm ti liu [1].

    62Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Minh ha bng MATLABBi ton:

    Nhn dng m hnh h thng m t, cphng trnh vi phn m t h:

    Vi i(t) [0, 4A] dng in ng voy(t) l khong cch t nam chm vnh cun nam chm in.cc tham s: =12, =15, g=9.8 v M=3.

  • 63Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Bi tp1. Sinh vin thc hin li bi ton nhn dng m hnh

    motor DC v hun luyn mng bng tt c cc giithut ca NN toolbox ca MATLAB. So snh tc hi t ca cc gii thut.

    64Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Chng 4Mt s ng dng ca ANN

    Gii thiuNhn dng k t (OCR)

    Nhn dng ting niThit k cc b iu khin

    Kt lunBi tp

  • 65Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Gii thiuGii thiu mt s hng ng dng ANNPht trin thnh Lun vn tt nghip hay tiNCKH sinh vin

    66Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Nhn dng k tMa trn ha bitmap ca k tGi lp cc hnh thc nhiuTp hp d liu hun luyn,mi k t l 1 vect d liung vo

    Qui c ng ra, gi s l mASCII tng ng ca k t.

    Xy dng cu v hun luyn ANN

  • 67Mng N-ron nhn to, Ts. Nguyn Ch Ngn, 2007 Chng 3 & 4

    Nhn dng ting ni

    Trch c trng tn hiu ting niTp hp d liu vo, qui c d liu raHun luyn v th nghimPhng php LPC & AMDF xc nh c trng ting ni

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