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\section{Results}\label{sec:results}
\section{Full-year Simulation Results}\label{sec:results}
This section focuses on the presentation and interpretation of the year-long
simulation of the control schemes present previously. All the control schemes
analysed in this Section have been done with a sampling time of 15 minutes and a
control horizon of 8 steps.
simulation of the control schemes presented previously. All the control schemes
analysed in this Section have used a sampling time of 15 minutes and a control
horizon of 8 steps.
Section~\ref{sec:GP_results} analyses the results of a conventional
\acrlong{gp} Model trained on the first five days of gathered data. The models
\acrlong{gp} Model trained on the first five days of gathered data. The model
is then used for the rest of the year, with the goal of tracking the defined
reference temperature.
Section~\ref{sec:SVGP_results} goes into details on the analysis of the Learning
Section~\ref{sec:SVGP_results} goes into details on the analysis of the learning
scheme using a \acrshort{svgp} Model. In this scenario, the model is first
trained on the first five days of data, and updates every day at midnight with
the new information gathered from closed-loop operation.
@ -19,7 +19,7 @@ the new information gathered from closed-loop operation.
\subsection{Conventional Gaussian Processes}\label{sec:GP_results}
The first simulation, to be used as a baseline comparison with the
\acrshort{svgp} Models developed further consists of using a `static'
\acrshort{svgp} Models developed further, consists of using a `static'
\acrshort{gp} model trained on five days worth of experimental data. This model
is then employed for the rest of the year.
@ -94,7 +94,7 @@ $\degree$C respectively.
\end{figure}
This large difference of performance could be explained by the change in outside
weather (Solar Irradiance and Outside Temperature --- the exogenous inputs) from
weather (solar irradiance and outside temperature --- the exogenous inputs) from
the one present during the training phase. It can be seen in
Figure~\ref{fig:Dataset_outside_temperature} that already at 500 points in the
simulation both the GHI and the Outside Temperature are outside of the training
@ -143,11 +143,11 @@ at midnight using the newly accumulated data from closed-loop operation.
The results of this setup are presented in
Figure~\ref{fig:SVGP_fullyear_simulation}. It can already be seen that this
setup performs much better than the initial one. The only large deviations from
the reference temperature are due to cold --- when the \acrshort{hvac}'s limited
heat capacity is unable to maintain the proper temperature. Additionnaly, the
\acrshort{svgp} controller takes around 250-300ms of computation time for each
simulation time, decreasing the computational cost of the original \acrshort{gp}
by a factor of six.
the reference temperature are due to cold weather, when the \acrshort{hvac}'s
limited heat capacity is unable to maintain the proper temperature.
Additionnaly, the \acrshort{svgp} controller takes around 250 - 300ms of
computation time for each simulation time, decreasing the computational cost of
the original \acrshort{gp} by a factor of six.
@ -161,7 +161,7 @@ by a factor of six.
\clearpage
Comparing the Absolute Error of the Measured vs Reference temperature for the
Comparing the absolute error of the measured vs reference temperature for the
duration of the experiment (cf. Figure~\ref{fig:SVGP_fullyear_abserr}) with the
one of the original experiment, the average absolute error is reduced from 1.33
$\degree$C to only 0.05 $\degree$C, with the majority of the values being lower
@ -210,7 +210,7 @@ behaviour of the plant over all the experimental steps in the first two cases.
It still has a noticeable error when predicting the behaviour of the plant on
new data (i.e. simulations starting at steps 10750 and 11000), but it is much
less than before. This gives a hint at the fact that the \acrshort{svgp} model's
performance ameliorates throughout the year, but it does require much more data
performance improves throughout the year, but it does require much more data
than the classical \acrshort{gp} model to capture the building dynamics.
\begin{figure}[ht]
@ -361,10 +361,10 @@ Analyzing the results of a simulation done on only one day's worth of initial
simulation data (cf. Figures~\ref{fig:SVGP_96pts_fullyear_simulation}
and~\ref{fig:SVGP_96pts_abserr}) it is very notable that the model performs
almost identically to the one identified in the previous sections. This
nightlights one of the practical benefits of the \acrshort{svgp} implementations
compared to the classical \acrlong{gp} -- it is possible to start with a more
rough controller trained on less data and refine it over time, reducing the need
for cumbersome and potentially costly initial experiments for gathering data.
highlights one of the practical benefits of the \acrshort{svgp} implementations
compared to the classical \acrlong{gp} -- it is possible to start with a rougher
controller trained on less data and refine it over time, reducing the need for
cumbersome and potentially costly initial experiments for gathering data.
\begin{figure}[ht]
\centering
@ -400,7 +400,7 @@ based on closed-loop operation.
\end{figure}
As it can be seen in Figure~\ref{fig:SVGP_480window_fullyear_simulation}, this
model is unable to properly track the reference temperature. In fact, five days
model is unable to exhaustively track the reference temperature. In fact, five days
after the identification, the model forgets all the initial data and becomes
unstable. This instability then generates enough excitation of the plant for the
model, to again learn its behaviour. This cycle repeats every five days, when the
@ -470,7 +470,7 @@ models can be deployed with less explicit identification data, but they will
continue to improve over the course of the year, as the building passes through
different regions of the state space and more data is collected.
These results do not, however, discredit the use of \acrlong{gp} for employment
However, these results do not discredit the use of \acrlong{gp} for employment
in a multi-seasonal situation. As shown before, given the same amount of data
and ignoring the computational cost, they perform better than the alternative
\acrshort{svgp} models. The bad initial performance could be mitigated by