ode45 goes busy endlessly when using the sign of a state variable
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This term "- fr*Mass*9.8*sign(y(2))" makes ode45 busy forever specifically when using 'sign(y(2))'
I just need to make -fr*Mass*9.8=0 only when y(2)=0
Any explanations are highly welcomed.
clearvars
clc
close all
[t,y] = myexercise;
plot(t,y(:,2))
function [t,y] = myexercise
tspan = [0 , 10];
y0 = [ 0 ; 5 ];
Mass = 1300;
CD = 0.3;
fr = 0.015;
Af = 1.6;
traction = @(t) (t>3&t<5)*5*t;
[t,y] = ode45(@(t,y) deceleration(t,y) , tspan , y0);
function yp = deceleration(t,y)
yp = [ ...
y(2) ;...
( -0.5*1.23*CD*Af*y(2)^2 + traction(t) - fr*Mass*9.8*sign(y(2)) )/Mass ...
];
end
end
2 Comments
James Tursa
on 23 Apr 2021
Please explain the physical problem and post the differential equation you are trying to solve so we can understand why you think you need the sign function.
Accepted Answer
More Answers (1)
Walter Roberson
on 23 Apr 2021
You really should read ballode to see how to use event functions. https://www.mathworks.com/help/matlab/math/ode-event-location.html
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