Azzera filtri
Azzera filtri

ode45 returns NAN, HOW could I modify it?

1 visualizzazione (ultimi 30 giorni)
roya afshar
roya afshar il 25 Dic 2018
Modificato: madhan ravi il 25 Dic 2018
clear
clc
[t,x]=ode45(@eqns,[0.1:0.2:100],[10;0.01;100;-0.0225;10;-0.01]);
for i=1:6
plot(t,x(:,i))
hold on
end
function dxdt = eqns(t,x) % function definition
m=9.0807;
v1=6;
v2=150;
rc=1;
dxdt = [x(2);
2*v1*x(4)+v2*x(3)+v1^2*x(1)-(m*(rc+x(1)))/(((rc+x(1))^2+(x(3))^2+(x(5))^2)^1.5)+(m/rc^2);
x(4);
2*v1*x(2)-v2*x(1)+(v1^2)*x(3)-m*x(3)/(((rc+x(1))^2+x(3)^2+x(5)^2)^1.5);
x(6);
(-m*x(5))/(((rc+x(1))^2+x(3)^2+x(5)^2)^1.5);]
end

Risposte (2)

madhan ravi
madhan ravi il 25 Dic 2018
Modificato: madhan ravi il 25 Dic 2018
Reduce the time span and increase time steps (or don't put any time step let matlab assume it) for instance from 0 to 1 -> [0 1] .
Add figure before plot(...) and remove hold on so that each solution can be viewed nicely.
[t,x]=ode45(@eqns,[0 10],[10;0.01;100;-0.0225;10;-0.01]); % change to this
% ^^----example
for i=1:6
figure % add this
plot(t,x(:,i))
% hold on %% remove this
end

Star Strider
Star Strider il 25 Dic 2018
After about ‘t=60’, your differential equation saturates (becomes greater than realmax (link)), and subsequent values are NaN. You need to examine your differential equations to be certain that you have coded them correctly, and that the constants are correct.
Take a look at a higher-resolution version of the output of your system:
tspan = linspace(0, 10, 5000);
[t,x]=ode45(@eqns,tspan,[10;0.01;100;-0.0225;10;-0.01]);
semilogy(t,abs(x))
That could give you some idea of where the problems are.
Also see the documentation section on how to Debug a MATLAB Program (link).

Tag

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by