Euler's Method check

2013 6 3
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Hello, I am trying to model a first order ODE using Euler's Method. I have shown the Euler's step in the code below and I wanted somebody to double-check it and see if it is written correctly. All the R,C,L, Ron values are given. Thankx for the help
h = 0.0001; % Adjustable time-step
t = 0:h:0.002;
for i = 1:length(t)-1
switch (switch_state)
case 1
k11 = x2(i)*1/L - x1(i)*1/(R*C);
k12 = x2(i)*-Ron/L - x1(i)*1/L + Vi*1/L;
otherwise
k11 = x2(i)*1/L - x1(i)*1/(R*C);
k12 = x2(i)*-Ron/L - x1(i)*1/L;
end
x1(i+1) = x1(i) + h*k11;
x2(i+1) = x2(i) + h*k12;
end
plot(t,x1)
plot(t,x2)

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Iain
Iain 2013-6-3

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You've implemented euler's method correctly. Whether or not you have calculated k11 and k12 correctly, and chosen sensible values for h, and LCR is another question.

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I am retracing my steps and reviewing every single part. Thankx for the help
Hello, I have an additional question. Instead of using equation form, would this matrix form of the Euler's be correct? Assuming A and B were calculated correctly. Thankx for your help again.
for j=1:f
switch (switch_state)
case 1
A = [ -Ron/L -1/L
1/C -1/(R*C)];
B = [ 1/L
0 ];
otherwise
A = [ -Ron/L -1/L
1/C -1/(R*C)];
B = [ 0
0 ];
end
for i = 1:length(t)-1
k1 = A*x(:,i) + B*Vi;
x(:,i+1) = x(:,i) + h*k1;
end
end
plot(x(1,:))
plot(x(2,:))
Iain
Iain 2013-6-5
编辑：Iain 2013-6-5
They're not the same equations.
Remember, matrix multiplication is Row times column
But, yes, the euler implementation is correct providing that k1 is the differential of x.
Right. Row times column. Correct me if I'm wrong. So basically, the loop would take each row of A and multiply it by the corresponding column of x and add it B*Vi. And k1 would be [k11 k12]' from the earlier code. right?

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