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In order to estimate parameters of permanent magnet synchronous motor (PMSM) on-line and real-time, an adaptive on-line identification method for motor parameters is proposed. Resistance, inductance and PM flux of PMSM are achieved at the same time in the presented model. By means of Popov’s hyper-stability theory, the model of parameter identification is built in the rotor reference frame. And, PMSM d, q-axis voltage, current and their errors are used to obtain the adaptive laws of parameters. Popov’s hyper-stability theory guarantees stability of the system and convergence of the estimated parameters under certain conditions. The simulation and experimental results illustrate the validity and efficiency of the proposed method.


 

restart: with(LinearAlgebra):

# Motion equation (  Vibration of a cracked composite beam using general solution)  Edited by Adjal Yassine #

####################################################################

Motion equation of flexural  vibration in normalized form 

EI*W^(iv)-m*omega^2*W=0;

EI*W^iv-m*omega^2*W = 0

(1)

 

The general solution form of bending vibration equation

W1:=A[1]*cosh(mu*x)+A[2]*sinh(mu*x)+A[3]*cos(mu*x)+A[4]*sin(mu*x);

A[1]*cosh(mu*x)+A[2]*sinh(mu*x)+A[3]*cos(mu*x)+A[4]*sin(mu*x)

(2)

where

E:=2682e6;L:=0.18;h:=0.004;b:=0.02;rho:=2600;area=b*h;m:=rho*h*b;II:=(h*b^3)/12:

0.2682e10

 

.18

 

0.4e-2

 

0.2e-1

 

2600

 

area = 0.8e-4

 

.20800

(3)

mu:=((m*omega^2*L^4/EI)^(1/4)):

 

 Expression of cross-sectional rotation , the bending moment shear  force and torsional moment  are given as follows respectively

theta1 := (1/L)*(A[1]*mu*sinh(mu*x)+A[2]*mu*cosh(mu*x)-A[3]*mu*sin(mu*x)+A[4]*mu*cos(mu*x));

(A[1]*mu*sinh(mu*x)+A[2]*mu*cosh(mu*x)-A[3]*mu*sin(mu*x)+A[4]*mu*cos(mu*x))/L

(4)

M1:= (EI/L^2)*(A[1]*mu^2*cosh(mu*x)+A[2]*mu^2*sinh(mu*x)-A[3]*mu^2*cos(mu*x)-A[4]*mu^2*sin(mu*x));

EI*(A[1]*mu^2*cosh(mu*x)+A[2]*mu^2*sinh(mu*x)-A[3]*mu^2*cos(mu*x)-A[4]*mu^2*sin(mu*x))/L^2

(5)

S1:= (-EI/L^3)*(A[1]*mu^3*sinh(mu*x)+A[2]*mu^3*cosh(mu*x)+A[3]*mu^3*sin(mu*x)-A[4]*mu^3*cos(mu*x));

-EI*(A[1]*mu^3*sinh(mu*x)+A[2]*mu^3*cosh(mu*x)+A[3]*mu^3*sin(mu*x)-A[4]*mu^3*cos(mu*x))/L^3

(6)

 

W2:=A[5]*cosh(mu*x)+A[6]*sinh(mu*x)+A[7]*cos(mu*x)+A[8]*sin(mu*x);

A[5]*cosh(mu*x)+A[6]*sinh(mu*x)+A[7]*cos(mu*x)+A[8]*sin(mu*x)

(7)

 

theta2:= (1/L)*(A[5]*mu*sinh(mu*x)+A[6]*mu*cosh(mu*x)-A[7]*mu*sin(mu*x)+A[8]*mu*cos(mu*x));

(A[5]*mu*sinh(mu*x)+A[6]*mu*cosh(mu*x)-A[7]*mu*sin(mu*x)+A[8]*mu*cos(mu*x))/L

(8)

M2:= (EI/L^2)*(A[5]*mu^2*cosh(mu*x)+A[6]*mu^2*sinh(mu*x)-A[7]*mu^2*cos(mu*x)-A[8]*mu^2*sin(mu*x));

EI*(A[5]*mu^2*cosh(mu*x)+A[6]*mu^2*sinh(mu*x)-A[7]*mu^2*cos(mu*x)-A[8]*mu^2*sin(mu*x))/L^2

(9)

S2:= -(EI/L^3)*(A[5]*mu^3*sinh(mu*x)+A[6]*mu^3*cosh(mu*x)+A[7]*mu^3*sin(mu*x)-A[8]*mu^3*cos(mu*x));

-EI*(A[5]*mu^3*sinh(mu*x)+A[6]*mu^3*cosh(mu*x)+A[7]*mu^3*sin(mu*x)-A[8]*mu^3*cos(mu*x))/L^3

(10)

 

The boundary conditions at fixed end W1(0)=Theta(0)=0

X1:=eval(subs(x=0,W1));

A[1]+A[3]

(11)

X2:=eval(subs(x=0,theta1));

(mu*A[2]+mu*A[4])/L

(12)

X2:=collect(X2,mu)*(L/mu);

A[2]+A[4]

(13)

 

The boundary condtions at free end M2(1)=S2(1)=0

X3:=eval(subs(x=1,M2));

EI*(A[5]*mu^2*cosh(mu)+A[6]*mu^2*sinh(mu)-A[7]*mu^2*cos(mu)-A[8]*mu^2*sin(mu))/L^2

(14)

X3:=collect(X3,mu)*(L^2/mu^2/EI);

cosh(mu)*A[5]+sinh(mu)*A[6]-cos(mu)*A[7]-sin(mu)*A[8]

(15)

X4:=eval(subs(x=1,S2));

-EI*(A[5]*mu^3*sinh(mu)+A[6]*mu^3*cosh(mu)+A[7]*mu^3*sin(mu)-A[8]*mu^3*cos(mu))/L^3

(16)

X4:=collect(X4,mu);

-EI*(cosh(mu)*A[6]+sinh(mu)*A[5]-cos(mu)*A[8]+sin(mu)*A[7])*mu^3/L^3

(17)

X4:=collect(X4,EI)*(L^3/mu^3/EI);

-cosh(mu)*A[6]-sinh(mu)*A[5]+cos(mu)*A[8]-sin(mu)*A[7]

(18)

 

The additional boundary conditions at crack location

X5:=combine(M1-M2);

(EI*cosh(mu*x)*mu^2*A[1]-EI*cosh(mu*x)*mu^2*A[5]+EI*sinh(mu*x)*mu^2*A[2]-EI*sinh(mu*x)*mu^2*A[6]-EI*cos(mu*x)*mu^2*A[3]+EI*cos(mu*x)*mu^2*A[7]-EI*sin(mu*x)*mu^2*A[4]+EI*sin(mu*x)*mu^2*A[8])/L^2

(19)

X5:=collect(X5,mu);

(EI*cosh(mu*x)*A[1]-EI*cosh(mu*x)*A[5]+EI*sinh(mu*x)*A[2]-EI*sinh(mu*x)*A[6]-cos(mu*x)*EI*A[3]+A[7]*cos(mu*x)*EI-A[4]*sin(mu*x)*EI+A[8]*sin(mu*x)*EI)*mu^2/L^2

(20)

X5:=collect(X5,EI)*(L^2/mu^2/EI);

A[1]*cosh(mu*x)-A[5]*cosh(mu*x)+A[2]*sinh(mu*x)-A[6]*sinh(mu*x)-A[3]*cos(mu*x)+A[7]*cos(mu*x)-A[4]*sin(mu*x)+A[8]*sin(mu*x)

(21)

X6:=combine(S1-S2);

(-EI*cosh(mu*x)*mu^3*A[2]+EI*cosh(mu*x)*mu^3*A[6]-EI*sinh(mu*x)*mu^3*A[1]+EI*sinh(mu*x)*mu^3*A[5]+EI*cos(mu*x)*mu^3*A[4]-EI*cos(mu*x)*mu^3*A[8]-EI*sin(mu*x)*mu^3*A[3]+EI*sin(mu*x)*mu^3*A[7])/L^3

(22)

X6:=collect(X6,mu);

(-EI*cosh(mu*x)*A[2]+EI*cosh(mu*x)*A[6]-EI*sinh(mu*x)*A[1]+EI*A[5]*sinh(mu*x)+cos(mu*x)*A[4]*EI-cos(mu*x)*A[8]*EI-sin(mu*x)*EI*A[3]+sin(mu*x)*A[7]*EI)*mu^3/L^3

(23)

X6:=collect(X6,EI)*(L^3/mu^3/EI);

-cosh(mu*x)*A[2]+cosh(mu*x)*A[6]-sinh(mu*x)*A[1]+sinh(mu*x)*A[5]+cos(mu*x)*A[4]-cos(mu*x)*A[8]-sin(mu*x)*A[3]+sin(mu*x)*A[7]

(24)

 

X7:=combine(W2-(W1+c8*S1));

(EI*cosh(mu*x)*c8*mu^3*A[2]+EI*sinh(mu*x)*c8*mu^3*A[1]-EI*cos(mu*x)*c8*mu^3*A[4]+EI*sin(mu*x)*c8*mu^3*A[3]-cosh(mu*x)*A[1]*L^3+cosh(mu*x)*A[5]*L^3-sinh(mu*x)*A[2]*L^3+sinh(mu*x)*A[6]*L^3-cos(mu*x)*A[3]*L^3+cos(mu*x)*A[7]*L^3-sin(mu*x)*A[4]*L^3+sin(mu*x)*A[8]*L^3)/L^3

(25)

X8:=combine (theta2-(theta1+c44*M1));

(-EI*cosh(mu*x)*c44*mu^2*A[1]-EI*sinh(mu*x)*c44*mu^2*A[2]+EI*cos(mu*x)*c44*mu^2*A[3]+EI*sin(mu*x)*c44*mu^2*A[4]-L*cosh(mu*x)*mu*A[2]+L*cosh(mu*x)*mu*A[6]-L*sinh(mu*x)*mu*A[1]+L*sinh(mu*x)*mu*A[5]-L*cos(mu*x)*mu*A[4]+L*cos(mu*x)*mu*A[8]+L*sin(mu*x)*mu*A[3]-L*sin(mu*x)*mu*A[7])/L^2

(26)

 

The characteristic matrix function of frequency

FD8:=subs(A[1]=1,A[3]=0,X1);FD12:=subs(A[1]=0,A[3]=0,X1);FD13:=subs(A[1]=0,A[3]=1,X1);FD14:=subs(A[1]=0,A[3]=0,X1);FD15:=subs(A[1]=0,A[3]=0,X1);FD16:=subs(A[1]=0,A[3]=0,X1);FD17:=subs(A[1]=0,A[3]=0,X1);FD18:=subs(A[1]=0,A[3]=0,X1);

1

 

0

 

1

 

0

 

0

 

0

 

0

 

0

(27)

FD21:=subs(A[2]=0,A[4]=0,X2);FD22:=subs(A[2]=1,A[4]=0,X2);FD23:=subs(A[2]=0,A[4]=0,X2);FD24:=subs(A[2]=0,A[4]=1,X2);FD25:=subs(A[2]=0,A[4]=0,X2);FD26:=subs(A[2]=0,A[4]=0,X2);FD27:=subs(A[2]=0,A[4]=0,X2);FD28:=subs(A[2]=0,A[4]=0,X2);

0

 

1

 

0

 

1

 

0

 

0

 

0

 

0

(28)

 

FD31:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD32:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD33:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD34:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD35:=subs(A[5]=1,A[6]=0,A[7]=0,A[8]=0,X3);;FD36:=subs(A[5]=0,A[6]=1,A[7]=0,A[8]=0,X3);FD37:=subs(A[5]=0,A[6]=0,A[7]=1,A[8]=0,X3);FD38:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=1,X3);

0

 

0

 

0

 

0

 

cosh(mu)

 

sinh(mu)

 

-cos(mu)

 

-sin(mu)

(29)

FD41:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD42:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD43:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD44:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD45:=subs(A[5]=1,A[6]=0,A[7]=0,A[8]=0,X4);FD46:=subs(A[5]=0,A[6]=1,A[7]=0,A[8]=0,X4);FD47:=subs(A[5]=0,A[6]=0,A[7]=1,A[8]=0,X4);FD48:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=1,X4);

0

 

0

 

0

 

0

 

-sinh(mu)

 

-cosh(mu)

 

-sin(mu)

 

cos(mu)

(30)

 

FD51:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD52:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD53:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD54:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD55:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X5);FD56:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X5);FD57:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X5);FD58:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X5);

cosh(mu*x)

 

sinh(mu*x)

 

-cos(mu*x)

 

-sin(mu*x)

 

-cosh(mu*x)

 

-sinh(mu*x)

 

cos(mu*x)

 

sin(mu*x)

(31)

FD61:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD62:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD63:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD64:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD65:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X6);FD66:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X6);FD67:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X6);FD68:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X6);

-sinh(mu*x)

 

-cosh(mu*x)

 

-sin(mu*x)

 

cos(mu*x)

 

sinh(mu*x)

 

cosh(mu*x)

 

sin(mu*x)

 

-cos(mu*x)

(32)

 

FD71:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD72:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD73:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD74:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD75:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X7);FD76:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X7);FD77:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X7);FD78:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X7);

(EI*sinh(mu*x)*c8*mu^3-cosh(mu*x)*L^3)/L^3

 

(EI*cosh(mu*x)*c8*mu^3-sinh(mu*x)*L^3)/L^3

 

(EI*sin(mu*x)*c8*mu^3-L^3*cos(mu*x))/L^3

 

(-EI*cos(mu*x)*c8*mu^3-sin(mu*x)*L^3)/L^3

 

cosh(mu*x)

 

sinh(mu*x)

 

cos(mu*x)

 

sin(mu*x)

(33)

FD81:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD82:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD83:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD84:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD85:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X8);FD86:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X8);FD87:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X8);FD88:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X8);

(-EI*cosh(mu*x)*c44*mu^2-L*sinh(mu*x)*mu)/L^2

 

(-EI*sinh(mu*x)*c44*mu^2-L*cosh(mu*x)*mu)/L^2

 

(EI*cos(mu*x)*c44*mu^2+L*sin(mu*x)*mu)/L^2

 

(EI*sin(mu*x)*c44*mu^2-L*cos(mu*x)*mu)/L^2

 

sinh(mu*x)*mu/L

 

cosh(mu*x)*mu/L

 

-sin(mu*x)*mu/L

 

cos(mu*x)*mu/L

(34)

 

MM:=matrix(8,8,[[FD11,FD12,FD13,FD14,FD15,FD16,FD17,FD18],[FD21,FD22,FD23,FD24,FD25,FD26,FD27,FD28],[FD31,FD32,FD33,FD34,FD35,FD36,FD37,FD38],[FD41,FD42,FD43,FD44,FD45,FD46,FD47,FD48],[FD51,FD52,FD53,FD54,FD55,FD56,FD57,FD58],[FD61,FD62,FD63,FD64,FD65,FD66,FD67,FD68],[FD71,FD72,FD73,FD74,FD75,FD76,FD77,FD78],[FD81,FD82,FD83,FD84,FD85,FD86,FD87,FD88]]);

MM := Matrix(8, 8, {(1, 1) = FD11, (1, 2) = 0, (1, 3) = 1, (1, 4) = 0, (1, 5) = 0, (1, 6) = 0, (1, 7) = 0, (1, 8) = 0, (2, 1) = 0, (2, 2) = 1, (2, 3) = 0, (2, 4) = 1, (2, 5) = 0, (2, 6) = 0, (2, 7) = 0, (2, 8) = 0, (3, 1) = 0, (3, 2) = 0, (3, 3) = 0, (3, 4) = 0, (3, 5) = cosh(mu), (3, 6) = sinh(mu), (3, 7) = -cos(mu), (3, 8) = -sin(mu), (4, 1) = 0, (4, 2) = 0, (4, 3) = 0, (4, 4) = 0, (4, 5) = -sinh(mu), (4, 6) = -cosh(mu), (4, 7) = -sin(mu), (4, 8) = cos(mu), (5, 1) = cosh(mu*x), (5, 2) = sinh(mu*x), (5, 3) = -cos(mu*x), (5, 4) = -sin(mu*x), (5, 5) = -cosh(mu*x), (5, 6) = -sinh(mu*x), (5, 7) = cos(mu*x), (5, 8) = sin(mu*x), (6, 1) = -sinh(mu*x), (6, 2) = -cosh(mu*x), (6, 3) = -sin(mu*x), (6, 4) = cos(mu*x), (6, 5) = sinh(mu*x), (6, 6) = cosh(mu*x), (6, 7) = sin(mu*x), (6, 8) = -cos(mu*x), (7, 1) = (EI*sinh(mu*x)*c8*mu^3-cosh(mu*x)*L^3)/L^3, (7, 2) = (EI*cosh(mu*x)*c8*mu^3-sinh(mu*x)*L^3)/L^3, (7, 3) = (EI*sin(mu*x)*c8*mu^3-L^3*cos(mu*x))/L^3, (7, 4) = (-EI*cos(mu*x)*c8*mu^3-sin(mu*x)*L^3)/L^3, (7, 5) = cosh(mu*x), (7, 6) = sinh(mu*x), (7, 7) = cos(mu*x), (7, 8) = sin(mu*x), (8, 1) = (-EI*cosh(mu*x)*c44*mu^2-L*sinh(mu*x)*mu)/L^2, (8, 2) = (-EI*sinh(mu*x)*c44*mu^2-L*cosh(mu*x)*mu)/L^2, (8, 3) = (EI*cos(mu*x)*c44*mu^2+L*sin(mu*x)*mu)/L^2, (8, 4) = (EI*sin(mu*x)*c44*mu^2-L*cos(mu*x)*mu)/L^2, (8, 5) = sinh(mu*x)*mu/L, (8, 6) = cosh(mu*x)*mu/L, (8, 7) = -sin(mu*x)*mu/L, (8, 8) = cos(mu*x)*mu/L})

(35)

Program end

 

NULL

 

``


 

Download Vibration_of_a_cracked_composite_beam.mw
 

restart: with(LinearAlgebra):

# Motion equation (  Vibration of a cracked composite beam using general solution)  Edited by Adjal Yassine #

####################################################################

Motion equation of flexural  vibration in normalized form 

EI*W^(iv)-m*omega^2*W=0;

EI*W^iv-m*omega^2*W = 0

(1)

 

The general solution form of bending vibration equation

W1:=A[1]*cosh(mu*x)+A[2]*sinh(mu*x)+A[3]*cos(mu*x)+A[4]*sin(mu*x);

A[1]*cosh(mu*x)+A[2]*sinh(mu*x)+A[3]*cos(mu*x)+A[4]*sin(mu*x)

(2)

where

E:=2682e6;L:=0.18;h:=0.004;b:=0.02;rho:=2600;area=b*h;m:=rho*h*b;II:=(h*b^3)/12:

0.2682e10

 

.18

 

0.4e-2

 

0.2e-1

 

2600

 

area = 0.8e-4

 

.20800

(3)

mu:=((m*omega^2*L^4/EI)^(1/4)):

 

 Expression of cross-sectional rotation , the bending moment shear  force and torsional moment  are given as follows respectively

theta1 := (1/L)*(A[1]*mu*sinh(mu*x)+A[2]*mu*cosh(mu*x)-A[3]*mu*sin(mu*x)+A[4]*mu*cos(mu*x));

(A[1]*mu*sinh(mu*x)+A[2]*mu*cosh(mu*x)-A[3]*mu*sin(mu*x)+A[4]*mu*cos(mu*x))/L

(4)

M1:= (EI/L^2)*(A[1]*mu^2*cosh(mu*x)+A[2]*mu^2*sinh(mu*x)-A[3]*mu^2*cos(mu*x)-A[4]*mu^2*sin(mu*x));

EI*(A[1]*mu^2*cosh(mu*x)+A[2]*mu^2*sinh(mu*x)-A[3]*mu^2*cos(mu*x)-A[4]*mu^2*sin(mu*x))/L^2

(5)

S1:= (-EI/L^3)*(A[1]*mu^3*sinh(mu*x)+A[2]*mu^3*cosh(mu*x)+A[3]*mu^3*sin(mu*x)-A[4]*mu^3*cos(mu*x));

-EI*(A[1]*mu^3*sinh(mu*x)+A[2]*mu^3*cosh(mu*x)+A[3]*mu^3*sin(mu*x)-A[4]*mu^3*cos(mu*x))/L^3

(6)

 

W2:=A[5]*cosh(mu*x)+A[6]*sinh(mu*x)+A[7]*cos(mu*x)+A[8]*sin(mu*x);

A[5]*cosh(mu*x)+A[6]*sinh(mu*x)+A[7]*cos(mu*x)+A[8]*sin(mu*x)

(7)

 

theta2:= (1/L)*(A[5]*mu*sinh(mu*x)+A[6]*mu*cosh(mu*x)-A[7]*mu*sin(mu*x)+A[8]*mu*cos(mu*x));

(A[5]*mu*sinh(mu*x)+A[6]*mu*cosh(mu*x)-A[7]*mu*sin(mu*x)+A[8]*mu*cos(mu*x))/L

(8)

M2:= (EI/L^2)*(A[5]*mu^2*cosh(mu*x)+A[6]*mu^2*sinh(mu*x)-A[7]*mu^2*cos(mu*x)-A[8]*mu^2*sin(mu*x));

EI*(A[5]*mu^2*cosh(mu*x)+A[6]*mu^2*sinh(mu*x)-A[7]*mu^2*cos(mu*x)-A[8]*mu^2*sin(mu*x))/L^2

(9)

S2:= -(EI/L^3)*(A[5]*mu^3*sinh(mu*x)+A[6]*mu^3*cosh(mu*x)+A[7]*mu^3*sin(mu*x)-A[8]*mu^3*cos(mu*x));

-EI*(A[5]*mu^3*sinh(mu*x)+A[6]*mu^3*cosh(mu*x)+A[7]*mu^3*sin(mu*x)-A[8]*mu^3*cos(mu*x))/L^3

(10)

 

The boundary conditions at fixed end W1(0)=Theta(0)=0

X1:=eval(subs(x=0,W1));

A[1]+A[3]

(11)

X2:=eval(subs(x=0,theta1));

(mu*A[2]+mu*A[4])/L

(12)

X2:=collect(X2,mu)*(L/mu);

A[2]+A[4]

(13)

 

The boundary condtions at free end M2(1)=S2(1)=0

X3:=eval(subs(x=1,M2));

EI*(A[5]*mu^2*cosh(mu)+A[6]*mu^2*sinh(mu)-A[7]*mu^2*cos(mu)-A[8]*mu^2*sin(mu))/L^2

(14)

X3:=collect(X3,mu)*(L^2/mu^2/EI);

cosh(mu)*A[5]+sinh(mu)*A[6]-cos(mu)*A[7]-sin(mu)*A[8]

(15)

X4:=eval(subs(x=1,S2));

-EI*(A[5]*mu^3*sinh(mu)+A[6]*mu^3*cosh(mu)+A[7]*mu^3*sin(mu)-A[8]*mu^3*cos(mu))/L^3

(16)

X4:=collect(X4,mu);

-EI*(cosh(mu)*A[6]+sinh(mu)*A[5]-cos(mu)*A[8]+sin(mu)*A[7])*mu^3/L^3

(17)

X4:=collect(X4,EI)*(L^3/mu^3/EI);

-cosh(mu)*A[6]-sinh(mu)*A[5]+cos(mu)*A[8]-sin(mu)*A[7]

(18)

 

The additional boundary conditions at crack location

X5:=combine(M1-M2);

(EI*cosh(mu*x)*mu^2*A[1]-EI*cosh(mu*x)*mu^2*A[5]+EI*sinh(mu*x)*mu^2*A[2]-EI*sinh(mu*x)*mu^2*A[6]-EI*cos(mu*x)*mu^2*A[3]+EI*cos(mu*x)*mu^2*A[7]-EI*sin(mu*x)*mu^2*A[4]+EI*sin(mu*x)*mu^2*A[8])/L^2

(19)

X5:=collect(X5,mu);

(EI*cosh(mu*x)*A[1]-EI*cosh(mu*x)*A[5]+EI*sinh(mu*x)*A[2]-EI*sinh(mu*x)*A[6]-cos(mu*x)*EI*A[3]+A[7]*cos(mu*x)*EI-A[4]*sin(mu*x)*EI+A[8]*sin(mu*x)*EI)*mu^2/L^2

(20)

X5:=collect(X5,EI)*(L^2/mu^2/EI);

A[1]*cosh(mu*x)-A[5]*cosh(mu*x)+A[2]*sinh(mu*x)-A[6]*sinh(mu*x)-A[3]*cos(mu*x)+A[7]*cos(mu*x)-A[4]*sin(mu*x)+A[8]*sin(mu*x)

(21)

X6:=combine(S1-S2);

(-EI*cosh(mu*x)*mu^3*A[2]+EI*cosh(mu*x)*mu^3*A[6]-EI*sinh(mu*x)*mu^3*A[1]+EI*sinh(mu*x)*mu^3*A[5]+EI*cos(mu*x)*mu^3*A[4]-EI*cos(mu*x)*mu^3*A[8]-EI*sin(mu*x)*mu^3*A[3]+EI*sin(mu*x)*mu^3*A[7])/L^3

(22)

X6:=collect(X6,mu);

(-EI*cosh(mu*x)*A[2]+EI*cosh(mu*x)*A[6]-EI*sinh(mu*x)*A[1]+EI*A[5]*sinh(mu*x)+cos(mu*x)*A[4]*EI-cos(mu*x)*A[8]*EI-sin(mu*x)*EI*A[3]+sin(mu*x)*A[7]*EI)*mu^3/L^3

(23)

X6:=collect(X6,EI)*(L^3/mu^3/EI);

-cosh(mu*x)*A[2]+cosh(mu*x)*A[6]-sinh(mu*x)*A[1]+sinh(mu*x)*A[5]+cos(mu*x)*A[4]-cos(mu*x)*A[8]-sin(mu*x)*A[3]+sin(mu*x)*A[7]

(24)

 

X7:=combine(W2-(W1+c8*S1));

(EI*cosh(mu*x)*c8*mu^3*A[2]+EI*sinh(mu*x)*c8*mu^3*A[1]-EI*cos(mu*x)*c8*mu^3*A[4]+EI*sin(mu*x)*c8*mu^3*A[3]-cosh(mu*x)*A[1]*L^3+cosh(mu*x)*A[5]*L^3-sinh(mu*x)*A[2]*L^3+sinh(mu*x)*A[6]*L^3-cos(mu*x)*A[3]*L^3+cos(mu*x)*A[7]*L^3-sin(mu*x)*A[4]*L^3+sin(mu*x)*A[8]*L^3)/L^3

(25)

X8:=combine (theta2-(theta1+c44*M1));

(-EI*cosh(mu*x)*c44*mu^2*A[1]-EI*sinh(mu*x)*c44*mu^2*A[2]+EI*cos(mu*x)*c44*mu^2*A[3]+EI*sin(mu*x)*c44*mu^2*A[4]-L*cosh(mu*x)*mu*A[2]+L*cosh(mu*x)*mu*A[6]-L*sinh(mu*x)*mu*A[1]+L*sinh(mu*x)*mu*A[5]-L*cos(mu*x)*mu*A[4]+L*cos(mu*x)*mu*A[8]+L*sin(mu*x)*mu*A[3]-L*sin(mu*x)*mu*A[7])/L^2

(26)

 

The characteristic matrix function of frequency

FD8:=subs(A[1]=1,A[3]=0,X1);FD12:=subs(A[1]=0,A[3]=0,X1);FD13:=subs(A[1]=0,A[3]=1,X1);FD14:=subs(A[1]=0,A[3]=0,X1);FD15:=subs(A[1]=0,A[3]=0,X1);FD16:=subs(A[1]=0,A[3]=0,X1);FD17:=subs(A[1]=0,A[3]=0,X1);FD18:=subs(A[1]=0,A[3]=0,X1);

1

 

0

 

1

 

0

 

0

 

0

 

0

 

0

(27)

FD21:=subs(A[2]=0,A[4]=0,X2);FD22:=subs(A[2]=1,A[4]=0,X2);FD23:=subs(A[2]=0,A[4]=0,X2);FD24:=subs(A[2]=0,A[4]=1,X2);FD25:=subs(A[2]=0,A[4]=0,X2);FD26:=subs(A[2]=0,A[4]=0,X2);FD27:=subs(A[2]=0,A[4]=0,X2);FD28:=subs(A[2]=0,A[4]=0,X2);

0

 

1

 

0

 

1

 

0

 

0

 

0

 

0

(28)

 

FD31:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD32:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD33:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD34:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X3);FD35:=subs(A[5]=1,A[6]=0,A[7]=0,A[8]=0,X3);;FD36:=subs(A[5]=0,A[6]=1,A[7]=0,A[8]=0,X3);FD37:=subs(A[5]=0,A[6]=0,A[7]=1,A[8]=0,X3);FD38:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=1,X3);

0

 

0

 

0

 

0

 

cosh(mu)

 

sinh(mu)

 

-cos(mu)

 

-sin(mu)

(29)

FD41:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD42:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD43:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD44:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=0,X4);FD45:=subs(A[5]=1,A[6]=0,A[7]=0,A[8]=0,X4);FD46:=subs(A[5]=0,A[6]=1,A[7]=0,A[8]=0,X4);FD47:=subs(A[5]=0,A[6]=0,A[7]=1,A[8]=0,X4);FD48:=subs(A[5]=0,A[6]=0,A[7]=0,A[8]=1,X4);

0

 

0

 

0

 

0

 

-sinh(mu)

 

-cosh(mu)

 

-sin(mu)

 

cos(mu)

(30)

 

FD51:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD52:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD53:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD54:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X5);FD55:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X5);FD56:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X5);FD57:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X5);FD58:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X5);

cosh(mu*x)

 

sinh(mu*x)

 

-cos(mu*x)

 

-sin(mu*x)

 

-cosh(mu*x)

 

-sinh(mu*x)

 

cos(mu*x)

 

sin(mu*x)

(31)

FD61:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD62:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD63:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD64:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X6);FD65:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X6);FD66:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X6);FD67:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X6);FD68:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X6);

-sinh(mu*x)

 

-cosh(mu*x)

 

-sin(mu*x)

 

cos(mu*x)

 

sinh(mu*x)

 

cosh(mu*x)

 

sin(mu*x)

 

-cos(mu*x)

(32)

 

FD71:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD72:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD73:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD74:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X7);FD75:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X7);FD76:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X7);FD77:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X7);FD78:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X7);

(EI*sinh(mu*x)*c8*mu^3-cosh(mu*x)*L^3)/L^3

 

(EI*cosh(mu*x)*c8*mu^3-sinh(mu*x)*L^3)/L^3

 

(EI*sin(mu*x)*c8*mu^3-L^3*cos(mu*x))/L^3

 

(-EI*cos(mu*x)*c8*mu^3-sin(mu*x)*L^3)/L^3

 

cosh(mu*x)

 

sinh(mu*x)

 

cos(mu*x)

 

sin(mu*x)

(33)

FD81:=subs(A[1]=1,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD82:=subs(A[1]=0,A[2]=1,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD83:=subs(A[1]=0,A[2]=0,A[3]=1,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD84:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=1,A[5]=0,A[6]=0,A[7]=0,A[8]=0,X8);FD85:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=1,A[6]=0,A[7]=0,A[8]=0,X8);FD86:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=1,A[7]=0,A[8]=0,X8);FD87:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=1,A[8]=0,X8);FD88:=subs(A[1]=0,A[2]=0,A[3]=0,A[4]=0,A[5]=0,A[6]=0,A[7]=0,A[8]=1,X8);

(-EI*cosh(mu*x)*c44*mu^2-L*sinh(mu*x)*mu)/L^2

 

(-EI*sinh(mu*x)*c44*mu^2-L*cosh(mu*x)*mu)/L^2

 

(EI*cos(mu*x)*c44*mu^2+L*sin(mu*x)*mu)/L^2

 

(EI*sin(mu*x)*c44*mu^2-L*cos(mu*x)*mu)/L^2

 

sinh(mu*x)*mu/L

 

cosh(mu*x)*mu/L

 

-sin(mu*x)*mu/L

 

cos(mu*x)*mu/L

(34)

 

MM:=matrix(8,8,[[FD11,FD12,FD13,FD14,FD15,FD16,FD17,FD18],[FD21,FD22,FD23,FD24,FD25,FD26,FD27,FD28],[FD31,FD32,FD33,FD34,FD35,FD36,FD37,FD38],[FD41,FD42,FD43,FD44,FD45,FD46,FD47,FD48],[FD51,FD52,FD53,FD54,FD55,FD56,FD57,FD58],[FD61,FD62,FD63,FD64,FD65,FD66,FD67,FD68],[FD71,FD72,FD73,FD74,FD75,FD76,FD77,FD78],[FD81,FD82,FD83,FD84,FD85,FD86,FD87,FD88]]);

MM := Matrix(8, 8, {(1, 1) = FD11, (1, 2) = 0, (1, 3) = 1, (1, 4) = 0, (1, 5) = 0, (1, 6) = 0, (1, 7) = 0, (1, 8) = 0, (2, 1) = 0, (2, 2) = 1, (2, 3) = 0, (2, 4) = 1, (2, 5) = 0, (2, 6) = 0, (2, 7) = 0, (2, 8) = 0, (3, 1) = 0, (3, 2) = 0, (3, 3) = 0, (3, 4) = 0, (3, 5) = cosh(mu), (3, 6) = sinh(mu), (3, 7) = -cos(mu), (3, 8) = -sin(mu), (4, 1) = 0, (4, 2) = 0, (4, 3) = 0, (4, 4) = 0, (4, 5) = -sinh(mu), (4, 6) = -cosh(mu), (4, 7) = -sin(mu), (4, 8) = cos(mu), (5, 1) = cosh(mu*x), (5, 2) = sinh(mu*x), (5, 3) = -cos(mu*x), (5, 4) = -sin(mu*x), (5, 5) = -cosh(mu*x), (5, 6) = -sinh(mu*x), (5, 7) = cos(mu*x), (5, 8) = sin(mu*x), (6, 1) = -sinh(mu*x), (6, 2) = -cosh(mu*x), (6, 3) = -sin(mu*x), (6, 4) = cos(mu*x), (6, 5) = sinh(mu*x), (6, 6) = cosh(mu*x), (6, 7) = sin(mu*x), (6, 8) = -cos(mu*x), (7, 1) = (EI*sinh(mu*x)*c8*mu^3-cosh(mu*x)*L^3)/L^3, (7, 2) = (EI*cosh(mu*x)*c8*mu^3-sinh(mu*x)*L^3)/L^3, (7, 3) = (EI*sin(mu*x)*c8*mu^3-L^3*cos(mu*x))/L^3, (7, 4) = (-EI*cos(mu*x)*c8*mu^3-sin(mu*x)*L^3)/L^3, (7, 5) = cosh(mu*x), (7, 6) = sinh(mu*x), (7, 7) = cos(mu*x), (7, 8) = sin(mu*x), (8, 1) = (-EI*cosh(mu*x)*c44*mu^2-L*sinh(mu*x)*mu)/L^2, (8, 2) = (-EI*sinh(mu*x)*c44*mu^2-L*cosh(mu*x)*mu)/L^2, (8, 3) = (EI*cos(mu*x)*c44*mu^2+L*sin(mu*x)*mu)/L^2, (8, 4) = (EI*sin(mu*x)*c44*mu^2-L*cos(mu*x)*mu)/L^2, (8, 5) = sinh(mu*x)*mu/L, (8, 6) = cosh(mu*x)*mu/L, (8, 7) = -sin(mu*x)*mu/L, (8, 8) = cos(mu*x)*mu/L})

(35)

Program end

 

NULL

 

``


 

Download Vibration_of_a_cracked_composite_beam.mwVibration_of_a_cracked_composite_beam.mwVibration_of_a_cracked_composite_beam.mw

 

Splitting PDE parameterized symmetries

and Parameter-continuous symmetry transformations

The determination of symmetries for partial differential equation systems (PDE) is relevant in several contexts, the most obvious of which is of course the determination of the PDE solutions. For instance, generally speaking, the knowledge of a N-dimensional Lie symmetry group can be used to reduce the number of independent variables of PDE by N. So if PDE depends only on N independent variables, that amounts to completely solving it. If only N-1 symmetries are known or can be successfully used then PDE becomes and ODE; etc., all advantageous situations. In Maple, a complete set of symmetry commands, to perform each step of the symmetry approach or several of them in one go, is part of the PDEtools  package.

 

Besides the dependent and independent variables, PDE frequently depends on some constant parameters, and besides the PDE symmetries for arbitrary values of those parameters, for some particular values of them, PDE transforms into a completely different problem, admitting different symmetries. The question then is: how can you determine those particular values of the parameters and the corresponding different symmetries? That was the underlying subject of a recent question in Mapleprimes. The answer to those questions is relatively simple and yet not entirely obvious for most of us, motivating this post, organized briefly around one example.

 

To reproduce the input/output below you need Maple 2019 and to have installed the Physics Updates v.449 or higher.

 

Consider the family of Korteweg-de Vries equation for u(x, t)involving three constant parameters a, b, q. For convenience (simpler input and more readable output) use the diff_table  and declare  commands

with(PDEtools)

U := diff_table(u(x, t))

pde := b*U[]*U[x]+a*U[x]+q*U[x, x, x]+U[t] = 0

b*u(x, t)*(diff(u(x, t), x))+a*(diff(u(x, t), x))+q*(diff(diff(diff(u(x, t), x), x), x))+diff(u(x, t), t) = 0

(1)

declare(U[])

` u`(x, t)*`will now be displayed as`*u

(2)

This pde admits a 4-dimensional symmetry group, whose infinitesimals - for arbitrary values of the parameters a, b, q- are given by

I__1 := Infinitesimals(pde, [u], specialize_Cn = false)

[_xi[x](x, t, u) = (1/3)*_C1*x+_C3*t+_C4, _xi[t](x, t, u) = _C1*t+_C2, _eta[u](x, t, u) = (1/3)*((-2*b*u-2*a)*_C1+3*_C3)/b]

(3)

Looking at pde (1) as a nonlinear problem in u, a, b and q, it splits into four cases for some particular values of the parameter:

pde__cases := casesplit(b*u(x, t)*(diff(u(x, t), x))+a*(diff(u(x, t), x))+q*(diff(diff(diff(u(x, t), x), x), x))+diff(u(x, t), t) = 0, parameters = {a, b, q}, caseplot)

`========= Pivots Legend =========`

 

p1 = q

 

p2 = b*u(x, t)+a

 

p3 = b

 

 

`casesplit/ans`([diff(diff(diff(u(x, t), x), x), x) = -(b*u(x, t)*(diff(u(x, t), x))+a*(diff(u(x, t), x))+diff(u(x, t), t))/q], [q <> 0]), `casesplit/ans`([diff(u(x, t), x) = -(diff(u(x, t), t))/(b*u(x, t)+a), q = 0], [b*u(x, t)+a <> 0]), `casesplit/ans`([u(x, t) = -a/b, q = 0], [b <> 0]), `casesplit/ans`([diff(u(x, t), t) = 0, a = 0, b = 0, q = 0], [])

(4)

The legend above indicates the pivots and the tree of cases, depending on whether each pivot is equal or different from 0. At the end there is the algebraic sequence of cases. The first case is the general case, for which the symmetry infinitesimals were computed as I__1 above, but clearly the other three cases admit more general symmetries. Consider for instance the second case, pass the ignoreparameterizingequations to ignore the parameterizing equation q = 0, and you get

I__2 := Infinitesimals(pde__cases[2], ignore)

`* Partial match of  'ignore' against keyword 'ignoreparameterizingequations'`

 

[_xi[x](x, t, u) = _F3(x, t, u), _xi[t](x, t, u) = Intat(((b*u+a)*(D[1](_F3))(_a, ((b*u+a)*t-x+_a)/(b*u+a), u)-_F1(u, ((b*u+a)*t-x)/(b*u+a))*b+(D[2](_F3))(_a, ((b*u+a)*t-x+_a)/(b*u+a), u))/(b*u+a)^2, _a = x)+_F2(u, ((b*u+a)*t-x)/(b*u+a)), _eta[u](x, t, u) = _F1(u, ((b*u+a)*t-x)/(b*u+a))]

(5)

These infinitesimals are indeed much more general than I__1, in fact so general that (5) is almost unreadable ... Specialize the three arbitrary functions into something "easy" just to be able follow - e.g. take _F1 to be just the + operator, _F2 the * operator and _F3 = 1

eval(I__2, [_F1 = `+`, _F2 = `*`, _F3 = 1])

[_xi[x](x, t, u) = 1, _xi[t](x, t, u) = Intat(-(u+((b*u+a)*t-x)/(b*u+a))*b/(b*u+a)^2, _a = x)+u*((b*u+a)*t-x)/(b*u+a), _eta[u](x, t, u) = u+((b*u+a)*t-x)/(b*u+a)]

(6)

simplify(value([_xi[x](x, t, u) = 1, _xi[t](x, t, u) = Intat(-(u+((b*u+a)*t-x)/(b*u+a))*b/(b*u+a)^2, _a = x)+u*((b*u+a)*t-x)/(b*u+a), _eta[u](x, t, u) = u+((b*u+a)*t-x)/(b*u+a)]))

[_xi[x](x, t, u) = 1, _xi[t](x, t, u) = (b^3*t*u^4+((3*a*t-x)*u^3-u^2*x-t*x*u)*b^2+((3*a^2*t-2*a*x)*u^2-a*u*x-a*t*x+x^2)*b+a^2*u*(a*t-x))/(b*u+a)^3, _eta[u](x, t, u) = (b*u^2+(b*t+a)*u+a*t-x)/(b*u+a)]

(7)

This symmetry is of course completely different than [_xi[x](x, t, u) = (1/3)*_C1*x+_C3*t+_C4, _xi[t](x, t, u) = _C1*t+_C2, _eta[u](x, t, u) = ((-2*b*u-2*a)*_C1+3*_C3)/(3*b)]computed for the general case.

 

The symmetry (7) can be verified against pde__cases[2] or directly against pde after substituting q = 0.

[_xi[x](x, t, u) = (1/3)*_C1*x+_C3*t+_C4, _xi[t](x, t, u) = _C1*t+_C2, _eta[u](x, t, u) = (1/3)*((-2*b*u-2*a)*_C1+3*_C3)/b]

(8)

SymmetryTest([_xi[x](x, t, u) = 1, _xi[t](x, t, u) = (b^3*t*u^4+((3*a*t-x)*u^3-u^2*x-t*x*u)*b^2+((3*a^2*t-2*a*x)*u^2-a*u*x-a*t*x+x^2)*b+a^2*u*(a*t-x))/(b*u+a)^3, _eta[u](x, t, u) = (b*u^2+(b*t+a)*u+a*t-x)/(b*u+a)], pde__cases[2], ignore)

`* Partial match of  'ignore' against keyword 'ignoreparameterizingequations'`

 

{0}

(9)

SymmetryTest([_xi[x](x, t, u) = 1, _xi[t](x, t, u) = (b^3*t*u^4+((3*a*t-x)*u^3-u^2*x-t*x*u)*b^2+((3*a^2*t-2*a*x)*u^2-a*u*x-a*t*x+x^2)*b+a^2*u*(a*t-x))/(b*u+a)^3, _eta[u](x, t, u) = (b*u^2+(b*t+a)*u+a*t-x)/(b*u+a)], subs(q = 0, pde))

{0}

(10)

Summarizing: "to split PDE symmetries into cases according to the values of the PDE parameters, split the PDE into cases with respect to these parameters (command PDEtools:-casesplit ) then compute the symmetries for each case"