ploting second derivative from second order differential equationn

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Muhammad Sarmad Zahid 2021-3-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/776712-ploting-second-derivative-from-second-order-differential-equationn

评论： Jan 2021-3-20

Hi, Beloow is my code and i am solving second order differential equation numericaly and i am getting plot of first and zeroth derivation from ode45. is there any way to plot the second derivative as well by just calling ode45 ?

function fval = simulation( t,y )
x=y(1);
v=y(2);
   c=6850;
        m=450;
        k=0;
        f=2650;
        e=535;
        w=4410;
fval(1,1)=v;
 %fval(2,1)= -(c*v+k*x)/m
 fval(2,1)=(-c*v-f-e+w+k*x)/m;
end
%%%%main file%%%%%%
c=6850;
m=450;
 k=0;
f=2650;
e=535;
w=4410;
Y0= [0;3.86];
tspan= [0 1];
options= odeset ('Events', @event);
[tsol,ysol] = ode45(@(t,y) simulation(t,y), tspan,  Y0,options);
figure
plot(tsol,ysol(:,1), 'r-');
hold on;
figure
plot(tsol,ysol(:,2), 'g-');
hold on;
figure

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采纳的回答

Jan 2021-3-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/776712-ploting-second-derivative-from-second-order-differential-equationn#answer_651532

在 MATLAB Online 中打开

The easiest solution is to let the function to be integrated accept vectors as input and call it with the time steps and positions replied by ODE45:

[tsol, ysol] = ode45(@(t,y) simulation(t,y), tspan,  Y0,options);
dy = simulation(tsol, ysol.').';
d2y = dy(:, 2);
function fval = simulation(t, y)
x = y(1, :);
v = y(2, :);
c = 6850;
m = 450;
k = 0;
f = 2650;
e = 535;
w = 4410;
fval(1, :) = v;
fval(2, :) = (-c * v - f - e + w + k * x) / m;
end