MATLAB: Solving rlc circuit using ode45

homeworkode45rlc

i have homework to solve rlc circuit using ode45 i tried this code and the question is how to plot Vl1 anyone can help me please and if there is any mistake in this code

function RLC=homework(t,x)
R1=20;R2=30;L1=4*10^-3;L2=2*10^-3;C=0.004;u=100;
RLC(1)=(R1/L1)*(x(1))+(1/L1)*(x(2))-(1/L1)*u;
RLC(2)=-(R2/L2)*(x(2))+(1/L2)*(x(3));
RLC(3)=(-1/C)*(x(1))-(1/C)*(x(2));
RLC=RLC';

   [t,x]=ode45('homework',[0 10],[2;2;2]);

Best Answer

If you were to use the code;

    [t,y] = ode45(@homework,t,[0 0 0]');

the y here is your i1, i2, and vc.

From here you should know how to get desired Voltages (Kirschof law etc.).

The subplot command will be used as;

   subplot(4,1,1),plot(t,Vl1) % "subplot(4,1,2)" means there will be 
   subplot(4,1,2),plot(t,Vr2) % 4 rows and 1 column in total for 
   subplot(4,1,3),plot(t,Vr1) % the plots and this one is the 2nd 
   subplot(4,1,4),plot(t,Vc)  % plot

Similar thing for the currents.

In part 4, you just need to replace u in the function with the sine wave.

Is there any particular question you have other than these?

Related Solutions

MATLAB: Solve system of large linear symbolic equations

On my system, Maple ran out of memory trying to solve() that equation. There is a possibility that a system with more memory might be able to arrive at an answer, given enough time.

Solving the entire system of 12 equations when they are each this large, would take a lot of time and memory.

I would recommend following John's advice to simplify the system.

MATLAB: How to solve s system of coupled nonlinear ODES already given the state vector

You need to solve for all xdots simultaneously - this is done in matrix format below. There were also a number of errors in your equations. The following works:

tspan = [0 10];
x0=[0;0;0;0;0;0];
[t, x] = ode23(@fun_1, tspan, x0);
plot(t,x(:,3))
xlabel('t')
ylabel('theta(t)')
function f = fun_1(t,x)
m0 = 0.25; m1 = 0.1; m2= 0.08;
L1 = 0.25; L2 = 0.2;
g = 9.81;
F = sin(t); % If F is zero and all the initial values of x are zero the result is
            % inevitably a flat line!  Replace with your own forcing function.
            
% Constants for use below            
k24 = ((L1*cos(x(3))*(m1+2*m2))/(2*(m0+m1+m2)));
k26 = ((m2*L2*cos(x(5)))/(2*(m0+m1+m2)));
k42 = ((6*L1*cos(x(3))*(m1+2*m2))/(4*L1^2*(m1+3*m2)));
k46 = ((6*m2*L1*L2*cos(x(3)-x(5)))/(4*L1^2*(m1+3*m2)));
k62 = ((6*m2*L2*cos(x(5)))/(4*m2*L2^2));
k64 = ((6*m2*L1*L2*cos(x(3)-x(5)))/(4*m2*L2^2));
% LHS matrix of coefficients
M = [1 0   0 0   0 0;
     0 1   0 k24 0 k26;
     0 0   1 0   0 0;
     0 k42 0 1   0 k46;
     0 0   0 0   1 0;
     0 k62 0 k64 0 1];
 % RHS vector of constants
V = [x(2);
     ((L1*sin(x(3))*(m1+2*m2))/(2*(m0+m1+m2)))*x(4)^2+((m2*L2*sin(x(5)))/(2*(m0+m1+m2)))*x(6)^2+2*F/(2*(m0+m1+m2));
     x(4);
     -6*m2*L1*L2*sin(x(3)-x(5))/(4*L1^2*(m1+3*m2))*x(6)^2+6*g*L1*(m1+2*m2)*sin(x(3))/(4*L1^2*(m1+3*m2));
     x(6);
     6*m2*L1*L2*sin(x(3)-x(5))/(4*m2*L2^2)*x(4)^2 + 6*m2*g*L2*sin(x(5))/(4*m2*L2^2)];
% M*f = V    where f is the vector of dxdt's
f = M\V;
end

Best Answer

Related Solutions

MATLAB: Solve system of large linear symbolic equations

MATLAB: How to solve s system of coupled nonlinear ODES already given the state vector

Related Question