Solution of spring mass system with cubic stiffness

Question

Murat Yetkin 2018-10-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/423396-solution-of-spring-mass-system-with-cubic-stiffness

回答： Torsten 2018-10-11

I have below equation to solve with a given time series of gaussian white noise as f(t). Here is my code but it gives dimension error between result and the initial conditions vector. Is there any idea to fix it? Here is the error message:

Error using odearguments (line 92)
 @(T,Y)SPRING(T,Y,M,C,K,K2,K3,F) returns a vector of length 10001, but the length of initial conditions vector is 2. The vector returned by @(T,Y)SPRING(T,Y,M,C,K,K2,K3,F) and the initial conditions vector must have the same number of elements.
    Error in ode45 (line 115)
    odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);*

my''+cy'+ky+k2*y^2+k3*y^3=f(t)

   m=1; c=1; k=10; k2=20; k3=20;
   f=randn(10000,1);
   tspan=[0 10000];
   y0=[0;1];
   function dydt=spring(t,y,m,c,k,k2,k3,f)
   dydt=[y(2); (f-c*y(2)-k*y(1)-k2*y(1)^2-k3*y(1)^3)/m];
   end
   [t,y]=ode45(@(t,y) spring(t,y,m,c,k,k2,k3,f), tspan, y0);

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

Torsten 2018-10-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/423396-solution-of-spring-mass-system-with-cubic-stiffness#answer_340849

在 MATLAB Online 中打开

   function main
   m=1; c=1; k=10; k2=20; k3=20;
   tspan=[0 10000];
   y0=[0;1];
   f=randn(10000,1);
   tf = linspace(tspan(1),tspan(end),10000);  % time vector at which the f-values occured
   [t,y]=ode45(@(t,y) spring(t,y,m,c,k,k2,k3,tf,f), tspan, y0)
   end
   function dydt=spring(t,y,m,c,k,k2,k3,tf,f)
   f_actual = interp1(tf,f,t);
   dydt=[y(2); (f_actual-c*y(2)-k*y(1)-k2*y(1)^2-k3*y(1)^3)/m];
   end