Differential algebraic eqn solving using ode15s

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Jagadeesh Korukonda
评论： Jagadeesh Korukonda 2022-2-27
Ran in:
I've a 6Differential_Equations's and 6Algebraic_Equations's, with initial condition.
when I'm excecuting the code i'm getting error, which is given in the below image.
Thanks in advance😁
global G0 N0 v0;
G0 = 1; N0 = 1; v0 = 1;
L10 = 1; L20 = 2; L30 = 3;
w10 = 0.1; w20 = 0.2; w30 = 1- w10 -w20;
for i = 1:6
mu0(i) = w10*L10^i + w20*L20^i + w30*L30^i;
end
y0 = [mu0 w10 w20 w30 L10 L20 L30];
M = [eye(6),zeros(6);zeros(6,12)];
options = odeset('Mass',M,'RelTol',1e-4,'AbsTol',1e-6*ones(1,12));
tspan = linspace(0,1,10000);
[t,m] = ode15s(@myfun,tspan,y0,options);
Warning: Failure at t=7.186798e-01. Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.776357e-15) at time t.
function F = myfun(~,y)
global G0
mu0 = y(1); mu1 = y(2); mu2 = y(3); mu3 = y(4); mu4 = y(5); mu5 = y(6);
w1 = y(7); w2 = y(8); w3 = y(9); l1 = y(10); l2 = y(11); l3 = y(12);
F = zeros(12,1);
%Differential Equations
F(1) = 0;
F(2) = G0*(w1/l1 + w2/l2 + w3/l3);
F(3) = 2*G0*(w1 + w2 + w3);
F(4) = 3*G0*(l1*w1 + l2*w2 + l3*w3);
F(5) = 4*G0*(w1*l1^2 + w2*l2^2 + w3*l3^2);
F(6) = 5*G0*(w1*l1^3 + w2*l2^3 + w3*l3^3);
%Algebraic equations
F(7) = w1 + w2 + w3 - mu0;
F(8) = l1*w1 + l2*w2 + l3*w3 - mu1;
F(9) = w1*l1^2 + w2*l2^2 + w3*l3^2 - mu2;
F(10) = w1*l1^3 + w2*l2^3 + w3*l3^3 - mu3;
F(11) = w1*l1^4 + w2*l2^4 + w3*l3^4 - mu4;
F(12) = w1*l1^5 + w2*l2^5 + w3*l3^5 - mu5;
end

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回答（1 个）

Torsten
Torsten 2022-2-27
for i = 0:5
mu0(i+1) = w10*L10^i + w20*L20^i + w30*L30^i;
end
instead of
for i = 1:6
mu0(i) = w10*L10^i + w20*L20^i + w30*L30^i;
end
  3 个评论
显示 1更早的评论
Torsten
Torsten 2022-2-27
By the way your suggestion is not valid in my problem because,
Mu0(1) = W1 + W2 + W3,
IF I change according to your response it will be different
Mu0(1) = W1*L1 + W2*L2 + W3*L3
Wrong. You get
Mu0(1) = W1*L1 + W2*L2 + W3*L3
if you don't make the change according to my suggestion.
And for me, your code is working fine after the correction.
Jagadeesh Korukonda
Jagadeesh Korukonda 2022-2-27
Really, can you please send data file in .mat format.
My mail address is kjagadeesh817@gmail.com
But, I'm surprised why it is not working in my matlab?

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