Simulink presenting a convergence error

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Lucas duboc 2024-4-10

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评论： Lucas duboc 2024-4-11

I made a simple simulaltion of a x=Asen(wt) function in simulink using differential equations, but instead of a constant senoidal curve, it is converging to zero, although its very slow (w needs to be high or simulation time needs to be very long), here is the simulink code, and the scope output, the only custom things to simulink is a fixed simulation step of 0.01.

Original function is A*sin(wt), with A=2 and w = 60 modeled as a differential equation of x''(t) = -w² *x(t), x'(0) = Aw and x(0) = 0

I think the problem is a rounding error since it is very slow, but I don't know how to fix it

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Answer 1

Paul 2024-4-10

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https://ww2.mathworks.cn/matlabcentral/answers/2105271-simulink-presenting-a-convergence-error#answer_1439556

Setting the fixed-step solver to ode8 seems to work pretty well for the problem shown in the question with a fixed step of 0.01. Don't know how well ode8 will work for other choices of w and step size, but I suspect it will be better than any of the others for this particular system.