MATLAB: Problem to solve an EDO

problem to solve an edo

hi, i'm tring to solve an EDO but i've got this error message : Index exceeds matrix dimensions Error in ==> f_cine at 3 f=abs(y(:,1)-y(:,2)-y(:,3))-sg0 and i don't understand.

Here this is my function describing the system: function dy=f_cine(y,t)

global C1 C2 D1 D2 Q b K n E sig0 ep

f=abs(y(1)-y(2)-y(3))-sg0

if f<0

    dy(4)=0

else

    dy(4)=(f/K)^n

end

dy(2)=C(1)*dy(5)-D1*y(2)*dy(4)

dy(3)=C(2)*dy(5)-D2*y(3)*dy(4)

dy(5)=sign(y(1)-y(2)-y(3))*dy(4) dy(1)=E*(ep-dy(5)) dy=dy' end

thanks for your help

Best Answer

Did you check the dimensions of sg0?

Related Solutions

MATLAB: 2nd order systems of differential equation

By adding 3 variables y4,y5 and y6 your system becomes a first order differential equations system.

%y4=dy1/dt, thus d2y1/dt2=dy4/dt
%y5=dy2/dt, thus d2y2/dt2=dy5/dt
%y6=dy3/dt, thus d2y3/dt2=dy6/dt
%The system of equation becomes
%dy1/dt=y11; 
%dy2/dt=y22; 
%dy3/dt=y33;
%dy4/dt+5*y4+y2^2-y1=0;
%dy5/dt+5*y5+y3^2-y2=0;
%dy6/dt+5*y6-y3=0;

% which can be programmed

function dy=myequ(t,y)
dy(1)=y(4)
dy(2)=y(5)
dy(3)=y(6)
dy(4)=-5*y4-y2^2+y1
dy(5)=-5*y5-y3^2+y2
dy(6)=-5*y6+y3

% you can call myequ

tspan=[0 10];
y0=[1 0 1 0 1 1]; % Initial conditions
[t,y]=ode45(@myequ,tspan,y0)

MATLAB: “Inputs must be floats, namely single or double”

function main
tspan=[0 5];
y0=[1; 1; 1; 0];
[t,y]=ode45(@fun,tspan,y0)
function dy=fun(t,y)
dy=zeros(4,1);
dy(1)=y(1);
dy(2)=y(2);
dy(3)=y(3);
funint=@(r)(y(3)^2+y(4)^2)*r;
dy(4)=integral(funint,-1,1);

Best wishes

Torsten.

Best Answer

Related Solutions

MATLAB: 2nd order systems of differential equation

MATLAB: “Inputs must be floats, namely single or double”

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