Recursive type equation solution in simscape

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Hello everybody, I am new in this community and have a related question. I have following code written in simscape. This is compiled ok as it is prepared in an existing block code. But its not working well. Infact I want to calculate fio2 and then assign its value to qo2 for the next timestep calculation. All the time i get qair = 0 and qo2 = 2.
variables (Access = private , ExternalAccess = observe)
qair = 1 % air flow
Parameters (ExternalAccess = observe)
fio2 = 2 %chamber o2
qo2 = fio2
fio2 == qair + qo2

Answers (1)

Yifeng Tang
Yifeng Tang on 27 Jul 2022
Feels like you are trying to use Simscape like MATLAB :p, by considering how to use iterations to do the numerical integration. If I understand your intention correctly, you governing equation for this block is
and fio2 is just there to record the integral from last time step.
If so, you can get rid of fio2 totally and define the equation as
der(qo2) == -qair
qo2.der == -qair
And, add qo2 to the variable list. The initial condition can be set in the block in the variable tab.


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