What's the alternative of ode45 function ?

Question

Mallouli Marwa 2016-5-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/285922-what-s-the-alternative-of-ode45-function

评论： Sebastian Castro 2016-5-26

Hi, i have done this function to resolve a second order differential equation but i want to fix the time as a constant equal to 10 by changing the ode45 by another function:

function xdot = equacte(t,x,rload)

% Function file for mass with spring.

% Position is first variable, velocity is second variable,load is the third variable

freq=100;

w=2*pi*freq;

m=0.0112;

k=279.9919 ;

teta =-7.3333e+03;

cp= 1.8492*10^-7;

A = [0,1,0;-k/m,0,-teta/m;(-teta/rload),0,-1/(rload*cp)];

B = [0;1/m;0];

f =sin(w*t);

xdot = A*x+B*f;

end

Then in principle program:

rload=5000;

[t,x]=ode45(@(t,x) equacte(t,x,rload),[0:0.000001:5],[0,0,0]);

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Sebastian Castro 2016-5-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/285922-what-s-the-alternative-of-ode45-function#answer_223505

How about this:

http://www.mathworks.com/matlabcentral/answers/98293-is-there-a-fixed-step-ordinary-differential-equation-ode-solver-in-matlab-8-0-r2012b

Keep in mind that the variable-step ode45 may be taking much smaller time steps to keep the integration error down. With a fixed-step solver, you have no guarantees of meeting error tolerances and your sample time will have to be carefully chosen.

- Sebastian

4 个评论
显示 2更早的评论隐藏 2更早的评论

Mallouli Marwa 2016-5-26

No i haven't simulink. Can i use lsim as a relative of ode45 and how ? Please help me

Sebastian Castro 2016-5-26

That might work. You could get away with discretizing the system to your sample rate of 10 using c2d and then passing it in to lsim. According to the documentation,

Discrete-time systems are simulated with ltitr (state space) or filter (transfer function and zero-pole-gain).

- Sebastian

请先登录，再进行评论。