MATLAB Answers

Matlab Simulink simulations throwing error

I am trying to run a simulation for the simulink model, but it is getting stopped just after I run it. Below is the error message
Derivative of state '1' in block 'DeltaSigma3order_TFSystem_CompStage2_T1/I2' at time 4.8464412658547207E-5
is not finite. The simulation will be stopped. There may be a singularity in the solution. If not, try
reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)
Anyone know, why this error occurs? What is the solution?

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1 Answer

Answer by Walter Roberson
on 10 Jul 2019
 Accepted Answer

When the simulation time shown is 0 then the problem is typically initial conditions to avoid an initial 0/0
When the simulation time is very small like eps or 1e-13 but non-zero then variable step size is typically involved and typically either initial conditions are at fault or the blocks are not wired right
If the simulation time is a bit larger and equal to the fixed step size then a fixed size solver is in use and initial conditions are at fault or the blocks are not wired right.
If the simulation time is a very small number of steps, no more than step time multiplied by number of derivatives, then initial conditions or blocks not wired right.
Otherwise, your system is unstable. Possibly different initial conditions would allow it to escape the unstable zone but more often your equations or parameters are wrong.
In your particular situation that simulation time does not appear fixed step or initial steps to me. I think your system is unstable, at least for those initial conditions.

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Thanks Roberson,
Currently the initial conditions are set to zero for all the integrators. Should I change it to a lower value other than zero?

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