Time varying force with ode23
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Christo van Rensburg
el 25 de Abr. de 2020
Comentada: Christo van Rensburg
el 25 de Abr. de 2020
Hi there
I have the following code:
tf = 1;
t = linspace(0,3);
Ft = zeros(length(t),1);
% Here I generate the force values at different time intervals.
for i = 1:length(t)
if t(i) <= tf
Ft(i) = Fo*sin(2*pi*t(i)/tf);
elseif t(i) > tf
Ft(i) = 0;
end
end
ic = [0, 0]; % Initial conditions
dXdt = @(t, x) [x(2);
Ft * 1/(m1+m2)];
[t, x] = ode23(dXdt, [0, 3], ic);
I'm struggling to incorportate this time varying force F(t) into the ode23 function.
Any help as to how I can maybe get this done?
Thanks in advance!
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Respuesta aceptada
darova
el 25 de Abr. de 2020
Use function handle
Ft = @(t) (t<=tf)*Fo*sin(2*pi*t/tf);
dXdt = @(t, x) [x(2);
Ft(t) * 1/(m1+m2)];
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Walter Roberson
el 25 de Abr. de 2020
You cannot do that the way you want. The ode* routines cannot handle discontinuities in the driving functions. You need to break it up into two time periods, one with the force and one without the force.
tf = 1;
dXdt_F = @(t, x) [x(2); Fo*sin(2*pi*t/tf) / (m1+m2)];
dXdt_NF = @(t, x) [x(2); 0];
ic = [0, 0]; % Initial conditions
[t1, x1] = ode23(dXdt_F, [0, tf], ic);
ic2 = x1(end,:);
[t2, x2] = ode23(dXdt_NF, [tf, 3], ic2);
t = [t1; t2(2:end)];
x = [x1; x2(2:end,:)];
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