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State Space Export
Posted 26 avr. 2013, 07:16 UTC−4 Interfacing 7 Replies
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i have build a simple cantilever beam model using time depented model.
after defining the points of forces and parameters, i want to export the model to matlb (State Space Matrices) so i could "play" with the paramters and their location.
for example applying force at the tip = 100sin(theta(t)) and applying more forces to restrain the system.
i have searched the forum and found the mphstate function but i wasn't able to use it.
would like to get some help and tipps :)
(sorry for my poor english)
Regards, Eyal
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this is a delicate but very important subject, I'm very often needing this capability, but in reduced modal representation, so far I havent managed to get it working efficiently for "true models", a simple canteliever might work.
Check carefully the doc, do a search on "state space", you need to define a probe plot for the output, and define the state space export as a sub node to the solver case, with excitation in and probe out (I wounder now if it isnt rather in frequency domain you should try, rather than true transient)
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Good luck
Ivar
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in my project i need to define several points to measure the deflection.
it means that i need to define several probs ?
i saw the help file on this problem and tried to work with it but i had several erros on matlab.
is it possible that you will help me with pasting the commands to import the model , adding the probs until i will get reduced matrices ?
thank you in advance for your help.
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have you repeated the example oh the help "state space export" for the heat_transient_axi example ?
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Good luck
Ivar
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I did repeat the example , but I've got the following problem:
The returned matrix MB is full of zeros so the solution obtained with ode23s is the zero solution. Hence the final y is the constant solution iqual to T0. Completely different from what it was expected.
I'm enclosing the example.
What do you think that might be wrong?
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I finally came back to this question. I think that the comsol 4.3 tutorial doc example is not correct. Where there is:
M = mphstate(model,'sol1','out',{'Mc' 'MA' 'MB' 'C' 'D'},...
'input','T0', 'output', 'mod1.ppb1');
There should be:
M = mphstate(model,'sol1','out',{'Mc' 'MA' 'MB' 'C' 'D'},...
'input','Tinput', 'output', 'mod1.ppb1');
In fact the input parameter's name is Tinput and not T0.
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There is indeed a typo in the LiveLink for MATLAB 4.3b documentation, one should read:
M = mphstate(model,'sol1','out',{'Mc' 'MA' 'MB' 'C' 'D' 'x0'},...
'input','Tinput', 'output', 'mod1.ppb1');
u = 1;
T0= 1273.15;
opt = odeset('mass', M.Mc);
func = @(t,x) M.MA*x + M.MB*u;
[t,x] = ode23s(func, [0:10:190], M.x0, opt);
y = M.C*x'+M.D*u+T0;
where T0 is the Temprature value around the linearization point.
Thank you for pointing this out!
Rémi Magnard