what is 'Derivative of state in block at time t is not finite. There may be a singularity in the solution.' error? how to address it?

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Muhammad Ali 2024-8-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2144954-what-is-derivative-of-state-in-block-at-time-t-is-not-finite-there-may-be-a-singularity-in-the-sol

评论： Yifeng Tang 2024-8-27

pumpandpipe13082024b.slx

I am trying to simulate a thermal fluid system. As soon as I introduce gas-charged accumulator circled red in the circuit, it gives me following error

An error occurred while running the simulation and the simulation was terminated

Caused by:

Derivative of state 'pumpandpipe13082024b.Gas_Charged_Accumulator_TL.T_I' in block 'pumpandpipe13082024b/Gas-Charged Accumulator (TL)' at time 20.0 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)

Also, when I introduce elevation gain from port A to port B in pipes TL circled red, i have the following error

An error occurred while running the simulation and the simulation was terminated

Caused by:

Derivative of state 'pumpandpipe13082024b.Centrifugal_Pump_TL1.A.T' in block 'pumpandpipe13082024b/Centrifugal Pump (TL)1' at time 16.666666666666668 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)

what do these errors mean?

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Muhammad Ali 2024-8-27

If using a stiff solver for fluid systems is almost a must, what would happen in the case of real-time simulation, since one of the requirements for this is to 'Choose a fixed-step solver' [from: https://uk.mathworks.com/company/technical-articles/real-time-simulation-of-physical-systems-using-simscape.html].

correct me if I am wrong: the stiff solver is only available with variable-step solver.

Yifeng Tang 2024-8-27

Simscape local solver is what you'll very very likely to turn on for real-time simulation. It contains implicit solvers designed for handling stiffness to some degree. Of course, you won't have the luxury of reducing time step when needed, so the numerical efficiency of the model may need closer attention. See the link below for the real-time workflow in Simscape:

https://www.mathworks.com/help/simscape/real-time-simulation.html

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