Runge-Kutta matlab library

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JC
JC on 22 Apr 2022
Edited: James Tursa on 3 May 2022
Hi everybody, I am currently trying to understand this code that I have taken from this research paper: https://waterloouav.files.wordpress.com/2010/01/parachute.pdf
I have 2 questions:
1) I am trying to figure out if RK4_TI is a matlab library or did he manually write his own runge katta code as i couldnt find it in his research paper.
2) i realised he didnt assign the value of T*step to a variable, but i am unsure on what i should assign it to instead.
Hope somebody can give me some advice on this! Thank you.
clear;
T = 0.01;
end_time = 10;
num_of_steps = floor(end_time / T);
u=cell(1,num_of_steps);
x=cell(1,num_of_steps);
x{1} = [0; 0; 0; 0; 0; 0; 7; 0; 2; 0; 0; 0];
for count = 1:num_of_steps
u{count} = zeros(2,1);
end
disp = 0;
for step = 1:num_of_steps
x{step+1}=RK4_TI(@six_dof_parachute,T,x{step},u{step});
if disp == 100
disp = 0;
T*step
else
disp = disp + 1;
end
end
six_dof_plot(x,u,num_of_steps,T)
  4 Comments
Walter Roberson
Walter Roberson on 22 Apr 2022
The only other reference to RK4_TI that I can seem to find is https://people.math.sc.edu/Burkardt/f_src/stochastic_rk/stochastic_rk.html in the context of Stochastic Differential Equations . However, the paper you are looking at does not appear to be using Stochastic Differential Equations.
JC
JC on 23 Apr 2022
Thank you for searching for other references to RK4_TI, but you are right. I should be looking in the context of using ODEs instead.
JC

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Answers (1)

Benjamin Thompson
Benjamin Thompson on 22 Apr 2022
ode45 is the closest Runge Kutta implementation for what you are describing. Type "doc ode45" for details.
  1 Comment
JC
JC on 23 Apr 2022
Thank you for the suggestion! I'll look it up to see if it would be implementable or not. Cheers!
JC

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