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I'm trying to solve the following differential equation

$\ddot{y}(t)=F\cos(\Omega t)-\frac{1}{m}\left(c-\frac{\alpha^2}{R_l+R_i}\right)\dot{y}(t)-\frac{k}{m}y(t)-\frac{k_3}{m}y^3(t)-g$

with initial condition $y(0)=y_0$. Note that the parameters $F,\ \Omega,\ m,\ c,\ \alpha,\ R_l,\ R_i,\ k, \ k_3,\ g$ and $y_0$ are arbitrary.

I tried using the following code 

ode:=diff(y(t),t,t)=F*cos(Omega*t)-(c-alpha^2/(R_l+R_i))*(diff(y(t), t))/m-k*y(t)/m-k3*y(t)^3/m-g;

dsolve({ode, y(0) = y0});

in Maple, but I didn't obtain any solution. Can somebody help me?

Thank you, Ana.

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  • $\begingroup$ Mathematica DSolve can't solve it either. Do you think this nonlinear ODE has analytical solution? Why not use numerical solver? $\endgroup$
    – Nasser
    May 3, 2018 at 8:51
  • $\begingroup$ btw, a second oder ODE needs to initial conditions, not one, for full solution. $\endgroup$
    – Nasser
    May 3, 2018 at 8:58
  • $\begingroup$ I guess you are aware that this is the Duffing equation. Analytical solutions are not available you will have to simulate and use the numerical solver. $\endgroup$
    – Hugh
    May 3, 2018 at 17:54

1 Answer 1

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Mathematica DSolve can't solve it analytically. But you can try asymptotic approximation solution. I used y[0]==1 and y'[0]==0 below. Change as needed. Here solution expanded around t=0 with 4 terms.

ClearAll[y,t,f,omega,m,g,rL,ri,c,alpha,k,k3];
ode=y''[t]==f*Cos[omega t]-(c-alpha^2/(rL+ri))*y'[t]/m - k*y[t]/m- k3*y[t]^3/m-g;
AsymptoticDSolveValue[{ode,y[0]==1,y'[0]==0},y[t],{t,0,4}]

Mathematica graphics

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