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Stochastic Adaptive Control (02421)

www.imm.dtu.dk/courses/02421

Niels Kjølstad Poulsen

Build. 303B, room 048 Section for Dynamical Systems

Dept. of Applied Mathematics and Computer Science The Technical University of Denmark

Email: nkpo@dtu.dk phone: +45 4525 3356 mobile: +45 2890 3797

2019-04-29 20:09

Adaptive systems (L22-24)

L23

(2)

Wikipedia:Adaptive behavior is a type of behavior that is used to adjust to another type of behavior or situation.

Here: device, algorithm or method with the ability ajust itself (or its behavior) to the actual system.

Prediction, Filtering and smoothing Detection, isolation and fault estimation

Control

2 / 70

(3)

Adaptive Control

w y

e

u System and disturbances

Model of Objectives Constraints

System Controller

Design

Model

y e u

ID Uncertainty

Knowledge Objective

System

(4)

Self Tuning Controller (STC)

w

Controller System

Design

e u

y ID

4 / 70

(5)

Adaptive Control - the line of arguments

PID: Process information aroundwc. Robust. Not necessarily optimal (rarely optimal wrt.

disturbances).

Stochastic Control: requires a precise model (also of the disturbances).

w y

e

u System and disturbances

Model of

Objectives Constraints

System Controller

Design

(6)

System Identification: Parameter estimation. Validation.

Model

y e

u

ID Uncertainty

Knowledge Objective

System

6 / 70

(7)

Adaptive Control

Adaptive Control: Parameter changes (time variations, nonlinear system).

w

Controller System

Design

e u

y ID

(8)

w y e

u System and disturbances

Model of

Objectives Constraints

System Controller

Design

-3 -2 -1 0 1 2 3 4 5

0 2 4 6 8 10 12 14 16 18 20

Optimal

Suboptimal

→hhn et al.

8 / 70

(9)

Gain Scheduling (GS), Linear Parameter Variation (LPV)

Controller System

Schedule

Measured point of operation

w u

e

y

Examples: Tank system. Wind turbine. Ship. Aircraft.

To be considered as an open loop adaptive controller or a methods for dealing with nonlinear systems.

(10)

System Controller

Adaption Model

w

u y

error ym

10 / 70

(11)

The Basic Self Tuner

w

Controller System

Design

e u

y ID

(12)

Explicit STC

Implicit Cautious

CE based STC

Suboptimal dual controllers Optimal dual controllers

MRAC STC Gain Schedule

Dual

Gradient optimization

Stability optimization

12 / 70

(13)

Recap: Polynomials and vectors

Let us consider the result of a polynomium operating on a signal S(q1)yt = s0yt+s1yt−1+ ...+snyt−n

= γTϑ where

γT =

yt yt−1 ... yt−n ϑT=

s0 s1 ... sn

(14)

14 / 70

(15)

The Basic Self Tuner (Explicit version)

System:

A(q1)yt=q−kB(q1)ut+C(q1)et

ID:

yttθ+et

θˆt=arg M in

t

X

i=0

ε2i pem or plr

Control:MV.

ut=arg M inEn yt+k2 o

(16)

A(q1)yt=q−kB(q1)ut+C(q1)et

ID:

θ = (... ai, ... bi, ... ci...)

ϕt = (... −yt−i, ... ut−i, ... et−i...)

θˆt = θˆt−1+ P¯tψt

1 +ψttψt

εt εt=yt−ϕt θˆt

Pt = P¯t− P¯tψψtt

1 +ψttψt

t=f unk(Pt−1, εt,ϕˆt, ψt) Forgetting ψt= 1

t−1

ˆ ϕt

16 / 70

(17)

Control: The Basic Self Tuner - Explicit version

J=E n

yt+k2 o

Minimum variance control

Cˆ= ˆAG+q−kS yt+k= 1

BGuˆ t+Syt

+Get+k

Rut=−Syt R= ˆBG

Controller:

Rut+Syt= 0

γt = (ut, ut−1, ... yt, yt−1, ...) ϑ = (r0, , r1, ... s0, s1, ...) ut=arg Sol

γtTϑ= 0

(18)

System:

yt−0.9yt−1= 1ut−2+et NB: an ARX system Model:

yt+ ˆa yt−1= ˆb ut−2t

Estimation:

εt=yt+ ˆat−1yt−1−ˆbt−1ut−2 ϕTt =

−yt−1 ut−2

θT= a b

θˆt = θˆt−1+ P¯tϕt

1 +ϕttϕt

εt

Pt = P¯t− P¯tϕtϕtt

1 +ϕttϕt

t=f unk(Pt−1, εt,ϕˆt, ψt)

Je=

t

X

i=1

ε2i ≃tσ2 εt=et for correct parameters

18 / 70

(19)

Example

(hard coded design)

Design:

1 = (1 + ˆatq1)(1 +gq1) +q2s G= 1−ˆatq1 S= ˆa2t Controller:

ˆbt(1−aˆtq1)ut=−ˆa2tyt

or

ut= ˆatut−1−ˆa2t ˆbt

yt

Jc=

t

X

i=0

yi2≃E n

yt2 o

t≃1.81σ2t In closed loop (for correct parameters)

yt= (1 + 0.9q1)et

(20)

0 20 40 60 80 100 -2

-1.5 -1 -0.5 0 0.5 1 1.5 2

System parameters

20 / 70

(21)

Example

0 20 40 60 80 100

-1.5 -1.4 -1.3 -1.2 -1.1 -1 -0.9 -0.8 -0.7 -0.6 -0.5

Control parameters

(22)

0 20 40 60 80 100 50

100 150 200

Accumulated control and est. losses

Acc. Loss

22 / 70

(23)

Example

20 40 60 80 100 0

50 100 150 200 Loss

Acc. Loss

20 40 60 80 100 50

100 150 200 250 Loss

Acc. Loss

20 40 60 80 100 50

100 150 200 250 Loss

Acc. Loss

20 40 60 80 100 0

200 400 600 800 1000 Loss

Acc. Loss

(24)

J=E n

yt+k2 o

A(q1)yt=B(q1)ut−k+C(q1)et

Cˆ= ˆAG+q−kS yt+k= 1

BGuˆ t+Syt

+Get+k

Rut=−Syt R= ˆBG

Controller:

Rut+Syt= 0

γt = (ut, ut−1, ... yt, yt−1, ...) ϑ = (r0, , r1, ... s0, s1, ...) ut=arg Sol

γtTϑ= 0

24 / 70

(25)

The Basic Self Tuner - Explicit simple version

Prelude to implicit version J=E

n yt+12

o

A(q1)yt=B(q1)ut−1+et

k= 1 C(q1) = 1

1 = ˆA+q1S G(q1) = 1 S(q1) =q(1−A) = ˜ˆ A yt+1=Buˆ t+Syt

+et+1

Rut=−Syt R= ˆB

Controller:

Rut+Syt= 0

γt = (ut, ut−1, ... yt, yt−1, ...) ϑ = (r0, , r1, ... s0, s1, ...) ut=arg Sol

γtTϑ= 0

(26)

26 / 70

(27)

The Basic Self Tuner II (Implicit version)

A(q−1)yt=B(q−1)ut−1+et C= 1 k= 1

MV: J=En

y2t+1o

C=AG+q−kS yt+k= 1

C

BGut+Syt

+Get+k Rut=−Syt R=BG

1 =A∗1 +q1S G= 1 S=q(1−A) =−a1−a2q1− ... −anq1−n yt+1= [But+Syt]+et+1 But=−Syt Notice the simple design

yt+1= [Syt+Rut]+et+1t+1θ+et+1

ϕt+1=

yt yt−1 ... ut ...

θT =

s0 s1 ... r0 ...

θˆ: yttθˆt−1t; Je=1 t

t

X

i=0

ε2i ut: ϕt+1ˆθt= 0 Jc=E

n y2t+1

o

(28)

A(q−1)yt=q−kB(q−1)ut+et

C= 1 k≥1

MV: J=E

n y2t+ko

BGut=−Syt

1 =AG+q−kS

yt+k= [Syt+BGut]+Get+k

yt+k = [Syt+Rut]+Get+k

= ϕt+kθ+Get+k

θˆ: yttθˆt−1t; Je=1 t

t

X

i=0

ε2i

ut: ϕt+kθˆt= 0 Jc=E n

y2t+k o

28 / 70

(29)

The Basic Self Tuner IV

A(q−1)yt=q−kB(q−1)ut+C(q−1)et

MV: J=En

y2t+ko

BGut=−Syt

C=AG+q−kS yt+k= 1

C[Syt+BGut]+Get+k

RLS: yt+k = [Syt+Rut] +Get+k Notice the missing C

= ϕt+kθ+Get+k θˆ: yttθˆt−1t; Je= 1

N

t

X

i=0

ε2i

ut: ϕt+kθˆt= 0 Jc=E n

y2t+k o

(30)

Advantage:

Design simple, RLS (even ifC6= 1), Je≃Jc

Disadvantage:

More parameters (k >>1),

Not all strategies can be transformed into an implicitte strategy.

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(31)

Convergence analysis

Isθ0a possible convergence point.

S : yt= 1

C ϕtθ0+Get

M : yt= ϕtθˆ+εt

En ϕtεt

o

= 0

εt = yt−ϕtθˆ= 1

C ϕtθ0+Get−ϕt θˆ

= Get + 1−C

C ϕt θ0 for θˆ=θ0

(32)

Synergy Control:Jc=En

y2t+ko

=En ε2t+ko Estimation:Je= 1

N Pε2i

Fixation

Controller:

ut=−S Ryt

Model:

yt+k= [Rut+Syt] +Get+k

1 2 <r0

b0

32 / 70

(33)

Stochastic Adaptive Control (02421)

www.imm.dtu.dk/courses/02421

Niels Kjølstad Poulsen

Build. 303B, room 048 Section for Dynamical Systems

Dept. of Applied Mathematics and Computer Science The Technical University of Denmark

Email: nkpo@dtu.dk phone: +45 4525 3356 mobile: +45 2890 3797

2019-04-29 20:09

Adaptive Control II (L23)

(34)

Explicit STC

Implicit Cautious

CE based STC

Suboptimal dual controllers Optimal dual controllers

MRAC STC Gain Schedule

Dual

Gradient optimization

Stability optimization

34 / 70

(35)

Certainty Equivalence principle

State space control

xt+1=Axt+But+vt

yt=Cxt+et

Complete state information ut=−Lxt

Incomplete state information ut=−Lˆxt

CE valid

Adaptive control

A(q1)y=q−kB(q1)ut+C(q1)et

MV for known system C=AG+q−kS BGut=−Syt

Adaptive MV Cˆ= ˆAG+q−kS BGuˆ t=−Syt

CE convinient

(36)

36 / 70

(37)

Explicit STC (CE based)

w

Controller System

Design

e u

y ID

Minimalvariance, MV0

PZ, GSP GMV (MVi) GPC (or MPC) LQG (SS or Xreg) Deadbeat, PID ao.

Kalmanfilter/observer Polplacement controller LQG

Robust

(38)

System (assumed known):

A(q1)yt=q−kB(q1)ut+C(q1)et+d Cost:

J=En

(yt+k−wt)2o

Controller:

BGut=Cwt−Syt−Gd Design:

C=AG+q−kS

G(0) = 1 ord(G) =k−1 ord(S) =max(na−1, nc−k)

wt

Gd

ut C

et d

yt A1

−S 1

C BG qk B

38 / 70

(39)

Main loop

measinit; % Initilialise the measurement system for it=1:nstp,

w=wt(it);

[y,t]=meas; % Measure output

u=...

act(u); % Actuate control

end

(40)

Rut=Qwt−Syt−δ

xrt+1 = Arxrt+Br wt

yt

ut = CrxRt +Dr wt

yt

+u0

40 / 70

(41)

Cannonical realization

%--- [A,B,k,C,s2]=sysinit(dets); % Determine linear model (ie. get system)

%--- [Q,R,S,G]=dsnmv0(A,B,k,C);

%--- [Ar,Br,Cr,Dr]=qrs2ss(Q,R,S);

nr=length(Ar); Xr=zeros(nr,1);

%--- measinit; % Initilialise the measurement system

for it=1:nstp,

w=wt(it); wf=wft(it);

[y,t]=meas;

u=Cr*Xr+Dr*[wf;y]+u0;

act(u); % Actuate control Xr=Ar*Xr+Br*[wf;y];

end

(42)

Rut=Qwt−Syt−δ Rut−Qwt+Syt+δ= 0

ϕT

t =

ut, ut−1, ...−wt,−wt−1, ... yt, yt−1, ...1

ϕ=ϕr

θT =

r0, r1, ... q0, q1, ... s0, s1, ... δ

ut=−ϕ˜T

tθ˜ r0

θ˜=θ(2 :end);

ϕT

t−1=

ut−1, ut−2, ... −wt−1,−wt−2, ... yt−1, yt−2, ...1

42 / 70

(43)

Direct realization

%--- [A,B,k,C,d,s2]=sysinit(dets); % Determine linear model (ie. get system)

%--- [Q,R,S,G]=dsnmv0(A,B,k,C);

%--- nr=length([R Q S])+1; fir=zeros(nr,1); thr=[R Q S G(1)*d]’;

pil=1+[0 length(R) length([R Q])];

%--- measinit; % Initilialise the measurement system

for it=1:nstp, w=wt(it);

[y,t]=meas; % Measure output

% Ru=Qw-Sy-Gd

fir(2:end)=fir(1:end-1);

fir(pil)=[0 -w y];

u=-fir’*thr/thr(1);

fir(1)=u;

act(u); % Actuate control end

(44)

A(q1)yt=q−kB(q1)ut+C(q1)et+d

ID:

θ = (... ai, ... bi, ... ci... d)

ϕt = (... −yt−i, ... ut−i, ... et−i...1)

θˆt = θˆt−1+ P¯tψt

1 +ψttψt

εt εt=yt−ϕt θˆt

Pt = P¯t− P¯tψψtt

1 +ψttψt

t=f unk(Pt−1, εt,ϕˆt, ψt) Forgetting ψt= 1

t−1

ˆ ϕt

44 / 70

(45)

Explicit MV

0

controller

%--- [A,B,k,C,d,s2]=sysinit(dets); % Determine linear model (ie. get system)

%--- na=length(A)-1; mb=length(B); nc=length(C)-1;

th=[A(2:end) B C(2:end) d]’; th0=th;

th=th*0;

pil=[na mb];

pil=[0 cumsum(pil)]+1;

fi=zeros(size(th));

p0=10000;

P=eye(size(th,1))*p0;

%--- [Q,R,S,G]=dsnmv0(A,B,k,C); % just for the structure

%--- nr=length([R Q S]); fir=zeros(nr,1); fir=[fir; 1]; thr=[R Q S G(1)*d]’;

pilr=1+[0 length(R) length([R Q])];

%---

(46)

Main loop

measinit; % Initilialise the measurement system for it=1:nstp,

w=wt(it);

[y,t]=meas; % Measure output

% ID block res=y-fi’*th;

K=P*fi/(1+fi’*P*fi);

P=P-K*fi’*P;

th=th+K*res;

% Design block

A=[1 th(1:na)’]; B=th(pil(2):pil(3)-1)’;

C=[1 th(pil(3):end)’]; d=th(end);

[Q,R,S,G]=dsnmv0(A,B,k,C);

thr=[R Q S G(1)*d]’;

46 / 70

(47)

Explicit MV

0

controller

% Ru=Qw-Sy Controller

fir(2:end)=fir(1:end-1);

fir(pilr)=[0 -w y];

u=-fir’*thr/thr(1);

fir(1)=u;

fi(2:end)=fi(1:end-1);

fi(pil(1:2))=[-y u]’;

act(u); % Actuate control end

(48)

System:

Ayt=q−kBut+Cet+d Cost:

J=En

(Amyt+k−Bmwt)2o

Controller:

BGut=BmCwt−Syt−Gd Design:

AmC=AG+q−kS

G(0) = 1 ord(G) =k−1 ord(S) =max(na−1, nc+nam−k)

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(49)

Explicit PZ controller

%--- [A,B,k,C,d,s2]=sysinit(dets); % Determine linear model (ie. get system)

%--- na=length(A)-1; mb=length(B); nc=length(C)-1;

th=[A(2:end) B C(2:end)d]’; th0=th;

th=th*0;

pil=[na mb];

pil=[0 cumsum(pil)]+1;

fi=zeros(size(th));

p0=10000;

P=eye(size(th,1))*p0;

%--- Am=[1 -0.6];

Bm=sum(Am);

[Q,R,S,G]=dsnpz(A,B,k,C,Am,Bm); % just for the structure

%--- nr=length([R Q S]); fir=zeros(nr,1); fir=[fir; 1]; thr=[R Q S G(1)*d]’;

pilr=1+[0 length(R) length([R Q])];

%---

(50)

Main loop

measinit; % Initilialise the measurement system for it=1:nstp,

w=wt(it);

[y,t]=meas; % Measure output

% ID block res=y-fi’*th;

K=P*fi/(1+fi’*P*fi);

P=P-K*fi’*P;

th=th+K*res;

% Design block

A=[1 th(1:na)’]; B=th(pil(2):pil(3)-1)’;

C=[1 th(pil(3):end)’]; d=th(end);

[Q,R,S,G]=dsnpz(A,B,k,C,Am,Bm);

thr=[R Q S G(1)*d]’;

50 / 70

(51)

Explicit PZ-control

% Ru=Qw-Sy Controller

fir(2:end)=fir(1:end-1);

fir(pilr)=[0 -w y];

u=-fir’*thr/thr(1);

fir(1)=u;

fi(2:end)=fi(1:end-1);

fi(pil(1:2))=[-y u]’;

act(u); % Actuate control end

(52)

0 10 20 30 40 50 60 70 80 90 -1

-0.5 0 0.5 1

Y, W

t in sec

yt wt

0 10 20 30 40 50 60 70 80 90

-1 -0.5 0 0.5 1

U

t in sec ut

52 / 70

(53)

Explicit PZ-control

0 10 20 30 40 50 60 70 80 90

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

θ

t in sec

θ

(54)

0 10 20 30 40 50 60 70 80 90 -0.4

-0.2 0 0.2 0.4

Y, W

t in sec

yt wt

0 10 20 30 40 50 60 70 80 90

-0.4 -0.2 0 0.2 0.4

U

t in sec

ut

54 / 70

(55)

Explicit PZ-control

0 10 20 30 40 50 60 70 80 90 100

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Je

t in sec Accumulated losses

0 10 20 30 40 50 60 70 80 90 100

0 0.5 1 1.5 2

Ju

t in sec

(56)

0 10 20 30 40 50 60 70 80 90 -2

-1.5 -1 -0.5 0 0.5 1 1.5 2

θ

t in sec

θ

56 / 70

(57)

Implicit Adaptive Control

(58)

w

Controller System

Design

e u

y ID

Implicit Adaptive Control (STC)

The model is rephrased in terms of the control parameters, which are estimated. The adaptation mechanism (estimation procedure) is working on the control parameters directly.

58 / 70

(59)

Implicit MV

0

J=En

(yt+k−wt)2o

A(q1)yt=q−kB(q1)ut+C(q1)et+d

C=AG+q−kS R=BG δ=G(1)d ξt+k = yt+k−wt

= 1

C[Syt+Rut−Cwt+δ] +Get+k

= 1

t+kθ+ ¯et+k

Model: ξt = yt−wt−k

= ϕtθˆt−1t NoC

Control: ut = argSol

ϕt+kθˆt= 0.

(60)

RLS-algorithm

Computer burden (design)

Active (estimation) and passive (control) have similar cost function.

Has to knowk.

The min phase problem.

60 / 70

(61)

Implicit MV

0

J=E n

(yt+k−wt)2o

1 Measureyt.

2 Createξt=yt−wt−k.

3 Createϕt= (yt−k, ... , ut−k, ... ,−wt−k,1)Tandϕt+k. 4 Update the estimates:

ǫt = ξt−ϕtθˆt−1 (1)

Pt1 = Pt−11tϕTt (2)

θˆt = θˆt−1+Ptϕtǫt (3)

5 Determineutsuch that:

ϕTt+kθˆt= 0 (4)

6 Actuate the control.

(62)

J=E n

(Am(q1)yt+k−Bm(q1)wt)2o

AmC=AG+q−kS R=BG Q=BmC δ=Gd ξt+k = Amyt+k−Bmwt

= 1

C[Syt+Rut−Qwt+δ] +Get+k

= 1

t+kθ+ ¯et+k

Model: ξt = Amyt−Bmwt−k

= ϕtθˆt−1t

Control: ut = argSol

ϕt+kθˆt= 0.

62 / 70

(63)

Implicit PZ-regulator

J=En

(Am(q−1)yt+k−Bm(q−1)wt)2o

1 Measureyt.

2 Createξt=Am(q1)yt−Bm(q1)wt−k.

3 Createϕt= (yt−k, ... , ut−k, ... ,−wt−k,1)TogϕTt+k. 4 Update the estimates:

ǫtt−ϕtθˆt−1 (5)

Pt1=Pt−11tϕTt (6)

θˆt= ˆθt−1+Ptϕtǫt (7)

5 Determineutsuch that:ϕTt+kθˆt= 0.

(64)

%--- [A,B,k,C,d,s2]=sysinit(dets); % Determine linear model (ie. get system)

%--- Am=[1 -0.6];

Bm=sum(Am);

[Ax,Bx,Cx,Dx]=armax2ss(1,Bm,k,Am);

nx=length(Ax); Xm=zeros(nx,1);

%--- [Q,R,S,G]=dsnpz(A,B,k,C,Am,Bm);

nr=length([R Q S d]); fi=zeros(nr,1);

th=[R Q S G(1)*d]’; th0=th; % th=th*0;

pil=1+[0 length(R) length([R Q])];

p0=10000;

P=eye(nr)*p0;

th(pil(2))=Q(1); % First coefficient in Q=C*Bm is known P(pil(2),pil(2))=0;

%th(pil(1))=R(1); % Fixed b0

%P(pil(1),pil(1))=0;

%---

64 / 70

(65)

Implicit PZ-regulator

measinit; % Initilialise the measurement system for it=1:nstp,

w=wt(it);

[y,t]=meas; % Measure output

xi=Cx*Xm+Dx*[-w;y];

% ID block res=xi-fi’*th;

K=P*fi/(1+fi’*P*fi);

P=P-K*fi’*P;

th=th+K*res; % th’

fi(2:end)=fi(1:end-1);

fi(pil)=[0 -w y]’;

u=-fi’*th/th(1);

fi(pil(1))=u;

act(u); % Actuate control Xm=Ax*Xm+Bx*[-w;y];

end

(66)

Deterministic:

0 10 20 30 40 50 60 70 80 90

-1 -0.5 0 0.5 1

Y, W

t in sec

yt wt

0 10 20 30 40 50 60 70 80 90

-1 -0.5 0 0.5 1

U

t in sec ut

66 / 70

(67)

Implicit PZ-regulator

0 10 20 30 40 50 60 70 80 90

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

θ

t in sec

θ

(68)

J=En By

Ay

yt+k−Bw

Aw

wt

2

+ρ Bu

Au

ut

2

o

AmC=ByAG+q−kS

R=AuBG+αBuC δ=Gd

ξt+k = y˜t+k−w˜t+α˜ut

= 1

C[Sˇyt+Rˇut−Qwˇt+δ] +Get+k

= 1

t+kθ+ ¯et+k

ˇ y= 1

Ay

y wˇ= ˜w=Bw

Aw

w uˇ= 1 Au

u

68 / 70

(69)

Implicit GMV-regulator

Model: ξt = ˜yt−w˜t−k+α˜ut−k

= ϕtθˆt−1t

Control: ut = argSol

ϕt+kθˆt= 0.

(70)

J=EnBy

Ay

yt+k−Bw

Aw

wt

2

+ρ Bu

Au

ut

2

o

1 Measureyt.

2 Createξt=y˜t−w˜t−k+α˜ut−k h

α=bρ

0

i .

3 Createϕt= (ˇyt−k, ...,uˇt−k, ...,−wˇt−k, ...,1)Togϕt+k. 4 Update the estimates:

ǫtt−ϕtθˆt−1 (8)

Pt1=Pt−11tϕTt (9)

θˆt= ˆθt−1+Ptϕtǫt (10)

5 Determineuˇtsuch that:ϕTt+kθˆt= 0.

6 Determineut=Aut.

70 / 70

Referencer

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