Query regarding solving differential equation

I'm trying to solve equation of a mass damper system shown in the image. The x (LHS) is the unknown displacement which is to be solved from the equation.I know y and dy/dx values at each instant of time (obtained from experiments). While solving using ode45 I'm not able to update the value of y and dy/dx for each time interval. How else can I solve the equation to get value of x. I used central difference scheme but the answer is diverging from the expected values drastically, when marched in time. Thank you in advance.

Answer 1

[sloppydisk]

I'm guessing you are trying to use ode45 with variable timestep, make sure to pass y and dy/dx as an interpolation function such that it is defined for any point in time. For example like this:

yInterp = @(thisTime) interp1(t, y, thisTime);

Answer 2

[Torsten]

The example

ODE with Time-Dependent Terms

under

https://de.mathworks.com/help/matlab/ref/ode45.html

shows how to solve your problem using ODE45.

Your y and dy/dt should take the role of f and g in the example.

Best wishes

Torsten.