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Deuk-Woo,<br>
<br>
I have thought of this a lot before and will outline my experience
below, in summary, if you are looking for accurate dynamical systems
matrices from a building energy model (other than a hand-built RC
network model), you will probably want to learn <b>Modelica</b>.
Folks in the Modelica community have been using this method to study
dynamics and controls for over a decade in the automotive,
aerospace, and other industries.<br>
<br>
As for other simulation environments, its really up to the one you
pick. Remember that the equations in an energy model are an
approximation to reality. The numerical solution of these equations
are yet another approximation to the dynamics in the equations. So,
if you are going to do system identification on the model, you are
going to get artifacts of both approximations. In my experience,
the numerical solvers in programs like E+ and TRNSYS are not
developed for accuracy in dynamics that you would need for this
approach. They are developed more for long term analysis and
numerical stability - both of which they do a great job on.<br>
<br>
I have been involved with a project to try and obtain ABCD matrices
from <b>TRNSYS</b>. In this project, we went into the fortran code
and wrote extra code to perturb state variables to observe how they
relax and obtain matrices from this. We were successful in
implementing this but did not trust the results because we felt the
solver was overwriting the short term dynamics in the equations.<br>
<br>
I also worked on ABCD matrices using <b>EnergyPlus</b>, this time
using a different approach. In this approach, I wrote an analytical
model that can 'talk' to the EnergyPlus input file and .sql database
files. In the sql file, there is most of the information about
materials (e.g. capacitance), as well as all the bookkeeping on view
factors and which constructions pertain to which zones. I wrote
some scripts that read this file and automatically generate a
linearized model. The linearized model does not take any time trace
information (it does take some operating point information). It was
a lot of work and although I trust the results, I wouldn't pass on
the code to anyone else because it was a bit of a mess in the end.
I have published this work this year and if you would like the
papers, please write me personally.<br>
<br>
A fourth data point: <b>IDA-ICE</b> is another modeling tool that
has a nice solver should capture short term dynamics. I asked Per
Sahlin at IBPSA London this September if there was a way to produce
ABCD matrices from the model and he said his customers were not
interested (my paraphrasing - hopefully correct) - which is
completely fair. My understanding is that the historical
intersection of control analysis and building energy models has been
on longer time scales (e.g. setback / setpoint analysis) or just
time trace analysis - very little stability, frequency domain, or
other advanced traditional techniques.<br>
<br>
Good luck! Since I have thought of this for some time, I'd be
interested to discuss further with you, especially if you obtain any
good results.<br>
<br>
Bryan<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/30/2012 6:32 PM, 김덕우 wrote:<br>
</div>
<blockquote cite="mid:000001cdb707$90fa4fb0$b2eeef10$@skku.edu"
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US">Thank you for your
reply. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US">Unfortunately, I’m not
familiar with Modelica simulation environments. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US">If you don’t mind,
could you please let me know any other ways? <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US">Best Regards, <br>
Deuk-Woo Kim </span><span
style="font-size:10.0pt;font-family:"Georgia","serif";color:#1F497D"
lang="EN-US"><o:p></o:p></span></p>
<p class="MsoNormal" style="word-break:break-hangul"><span
style="font-size:10.0pt;font-family:"맑은
고딕";color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> Michael Wetter [<a class="moz-txt-link-freetext" href="mailto:mwetter@lbl.gov">mailto:mwetter@lbl.gov</a>] <br>
<b>Sent:</b> Wednesday, October 31, 2012 1:49 AM<br>
<b>To:</b> </span><span style="font-size:10.0pt">김덕우</span><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> Re: [Bldg-sim] Estimating system matrix A
from simulation engine<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Most Modelica simulation
environments allow you to linearize a model at the current
state and save the A,B,C and D matrix that are its
state-space representation at the point of linearization.
See<o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-US">Michael Wetter.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><a
moz-do-not-send="true"
href="http://dx.doi.org/10.1080/19401490902818259">Modelica-based
Modeling and Simulation to Support Research and
Development in Building Energy and Control Systems.</a><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><i><span lang="EN-US">Journal of Building
Performance Simulation</span></i><span lang="EN-US">,
2(2):143-161, 2009.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Also available as LBNL
Technical Report <a moz-do-not-send="true"
href="http://simulationresearch.lbl.gov/wetter/download/LBNL-2740E.pdf">LBNL-2740E.pdf</a>.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">where this is
demonstrated for a nonlinear heat exchanger model. The
Modelica Buildings library (<a moz-do-not-send="true"
href="http://simulationresearch.lbl.gov/modelica/">http://simulationresearch.lbl.gov/modelica/</a>)
contains a room model which you should be able to use for
the same process to get the A,B,C and D matrices for a
building model.<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Best,<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Michael<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-US">On Sun, Oct 28, 2012
at 6:54 AM, </span>김덕우<span lang="EN-US"> <<a
moz-do-not-send="true"
href="mailto:deukwookim@skku.edu" target="_blank">deukwookim@skku.edu</a>>
wrote:<o:p></o:p></span></p>
<div>
<div>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">Dear all, <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">Is there a method to estimate system
matrix <b>A</b> (of zone or building) from
simulation engines such as E+, ESP-r?? <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">(The<b> A</b> is commonly found in
state-space equation, e.g. x’ = <b>A</b>x + Bu.)<o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">As far as I know, only system
identification method can be applied in this
situation.<o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">(but, I not sure that it is reliable)<o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">If there is more advanced way or
efficient way to estimate <b>A, </b>please let me
know. <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">Any comments would be appreciated. <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">Thanks in advance. <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US">Best Regards, <br>
Deuk-Woo Kim <o:p></o:p></span></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span
lang="EN-US"> <o:p></o:p></span></p>
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lang="EN-US"><br>
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