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Query regarding solving differential equation

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Bharath Ram
Bharath Ram on 24 May 2018
Closed: MATLAB Answer Bot on 20 Aug 2021
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.

Answers (2)

sloppydisk
sloppydisk on 24 May 2018
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);

Torsten
Torsten on 24 May 2018
Edited: Torsten on 24 May 2018
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.

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