further small changes
This commit is contained in:
@@ -69,7 +69,7 @@ It implements the standard Android sensor functionalities and provides a very si
|
||||
As smartphones we used either a Samsung Note 2, Google Pixel One or Motorola Nexus 6.
|
||||
The computation of the state estimation as well as the \docWIFI{} optimization are done offline using an Intel Core i7-4702HQ CPU with a frequency of \SI{2.2}{GHz} running \add{\SI{8}{threads} on \SI{4}{cores}} and \SI{16}{GB} main memory.
|
||||
\add{An offline computation has practical advantages, such as easier evaluation of the results or shorter waiting times due to higher computing power.
|
||||
Nevertheless, Android App and offline application are both based on the same C++ backend for localization.}
|
||||
Nevertheless, Android app and offline application are both based on the same C++ backend for localization.}
|
||||
|
||||
|
||||
%However, similar to our \add{previously presented system}, the setup is able to run completely on commercial smartphones as it \add{is} written in high performant C++ code \cite{torres2017smartphone}.
|
||||
@@ -118,7 +118,9 @@ Finally, the respective estimation methods are discussed in section \ref{sec:eva
|
||||
\end{figure}
|
||||
|
||||
To compare our old graph-based model with our novel transition model presented within section \ref {sec:transition}, we chose a simple scenario, in which a tester walks up and down a staircase several times.
|
||||
We used 1000 particles and did not perform an evaluation and resampling step to maintain the pure performance of the transition (step and heading).
|
||||
We used \SI{5000}{} particles and did not perform an evaluation and resampling step to maintain the pure performance of the transition (step and heading).
|
||||
\add{The number of particles was heuristically chosen and is based on our previous experience from other scenarios and competitions.
|
||||
In addition, it sill allows a stable performance of our Android app for localization.}
|
||||
The filter starts at a fixed position and is updated after every newly recognized step.
|
||||
We set $\sigma_\text{step} = 0.1$ and $\sigma_\text{turn} = 0.1$ likewise.
|
||||
The cells of the gridded graph were \SI{20}{} x \SI{20}{\centi\meter} in size and the transition implemented as described in \cite{Ebner-16}.
|
||||
@@ -268,7 +270,7 @@ Here, we differ between the respective anti-impoverishment techniques presented
|
||||
The simple anti-impoverishment method is added to the resampling step and thus uses the transition method presented in chapter \ref{sec:transition}.
|
||||
In contrast, the $D_\text{KL}$-based method extends the transition and thus uses a standard cumulative resampling step.
|
||||
We set $l_\text{max} =$ \SI{-75}{dBm} and $l_\text{min} =$ \SI{-90}{dBm}.
|
||||
For a better overview, we only used the KDE-based estimation, as the errors compared to the weighted-average estimation differ by only a few centimeter.
|
||||
For a better overview, we only used the KDE-based estimation, as the errors compared to the weighted-average estimation differ by only a few centimeter.
|
||||
|
||||
\begin{table}[t]
|
||||
\centering
|
||||
@@ -310,7 +312,7 @@ Walking down the stairs at \SI{80}{\second} does also recover the localization s
|
||||
\begin{figure}
|
||||
\centering
|
||||
\input{gfx/errorOverTimeWalk0/errorOverTime.tex}
|
||||
\caption{Error development over time of a single Monte Carlo run of walk 0. Between \SI{10}{\second} and \SI{24}{\second} the Wi-Fi signal was highly attenuated, causing the system to get stuck and producing high errors. Both, the simple and the $D_\text{KL}$ anti-impoverishment method are able to recover early. However, between \SI{65}{\second} and \SI{74}{\second} the simple method produces high errors due to the high random factor involved.}
|
||||
\caption{Error development over time of a single particle filter run of walk 0. Between \SI{10}{\second} and \SI{24}{\second} the Wi-Fi signal was highly attenuated, causing the system to get stuck and producing high errors. Both, the simple and the $D_\text{KL}$ anti-impoverishment method are able to recover early. However, between \SI{65}{\second} and \SI{74}{\second} the simple method produces high errors due to the high random factor involved.}
|
||||
\label{fig:errorOverTimeWalk0}
|
||||
\end{figure}
|
||||
|
||||
@@ -379,7 +381,8 @@ Ironically, this is again some type of sample impoverishment, caused by the afor
|
||||
\subsection{Activity Recognition}
|
||||
\label{sec:eval:act}
|
||||
|
||||
Wie gut ist die Activity...
|
||||
\commentByToni{Wie gut ist die Activity...}
|
||||
|
||||
|
||||
|
||||
%%estimation
|
||||
@@ -421,7 +424,7 @@ Due to a right turn the lower red particles are walking against a wall and thus
|
||||
|
||||
Although, situations as displayed in fig. \ref{fig:walk1:kde} frequently occur, the KDE-estimation is not able to improve the overall estimation results.
|
||||
This can be seen in the corresponding error development over time plot given by fig. \ref{fig:walk1:kdeovertime}.
|
||||
Here, the KDE-estimation performs slightly better then the weighted-average, however after deploying \SI{100}{} Monte Carlo runs, the difference becomes insignificant.
|
||||
Here, the KDE-estimation performs slightly better then the weighted-average, however after deploying \SI{100}{} runs of the particle filter, the difference becomes insignificant.
|
||||
It is obvious, that the above mentioned "correct" mode, not always provides the lowest error.
|
||||
In some situations the weighted-average estimation is often closer to the ground truth.
|
||||
Within our experiments this happened especially when entering or leaving thick-walled rooms, causing slow and attenuated Wi-Fi signals.
|
||||
@@ -472,7 +475,8 @@ We hope to further improve such situations in future work by enabling the transi
|
||||
|
||||
To summarize, the KDE-based approach for estimation is able to resolve multimodalities.
|
||||
It does not provide a smooth estimated path, since it depends more on an accurate sensor model than a weighted-average approach, but is suitable as a good indicator about the real performance of a sensor fusion system.
|
||||
At the end, in the here shown examples we only searched for a global maxima, even though the KDE approach opens a wide range of other possibilities for finding a best estimate.
|
||||
At the end, in the here shown examples we only searched for a global maxima, even though the KDE approach opens a wide range of other possibilities for finding a best estimate.
|
||||
\add{A detailed examination of the runtime performance of the used estimation methods in comparison to the state-of-the-art can be found in \cite{Bullmann-18}.}
|
||||
|
||||
\commentByToni{Diskussion, wie die Contributions uns jetzt geholfen haben. Nochmal zusammengefasst.}
|
||||
|
||||
|
||||
@@ -80,13 +80,14 @@ The estimated parameters can be refined using additional walks.
|
||||
Within this work we present a similar optimization approach for estimating the AP's location in 3D.
|
||||
However, instead of taking multiple measuring walks, the locations are optimized based only on some reference measurements, further decreasing the setup-time.
|
||||
Additionally, we will show that such an optimization scheme can partly compensate for the above abolished intersection-tests.
|
||||
\commentByToni{Die Quelle aus den Reviews. Wir können auch Kontinuierlich. Der hat das Problem das er entweder überall gewesen sein muss, oder interpolieren.}
|
||||
|
||||
%immpf
|
||||
Besides well chosen probabilistic models, the system's performance is also highly affected by handling problems which are based on the nature of \add{a} particle filter.
|
||||
They are often caused by restrictive assumptions about the dynamic system, like seen from the aforementioned problem of sample impoverishment.
|
||||
The authors of \cite{Sun2013} handled the problem by using an adaptive number of particles instead of a fixed one.
|
||||
The key idea is to choose a small number of samples if the distribution is focused on a small part of the state space and a large number of particles if the distribution is much more spread out and requires a higher diversity of samples.
|
||||
The problem of sample impoverishment is then addressed by adapting the number of particles dependent upon the system's current uncertainty \cite{Fetzer-17}.
|
||||
The problem of sample impoverishment is then addressed by adapting the number of particles dependent upon the system's current uncertainty.
|
||||
%\commentByFrank{ich glaube encountered ist das falsche wort. du willst doch auf 'es wird gefixed' raus, oder? addressed? mitigated?}
|
||||
|
||||
In practice, sample impoverishment is often a problem of environmental restrictions and system dynamics.
|
||||
@@ -98,8 +99,8 @@ Thus, a much simpler, but heuristic method is presented within this paper.
|
||||
|
||||
%estimation
|
||||
Finally, as the name recursive state estimation says, it requires to find the most probable state within the state space, to provide the "best estimate" of the underlying problem.
|
||||
In the discrete manner of a particle representation this is often done by providing a single value, also known as sample statistic, to serve as a best guess \cite{Bullmann-18}.
|
||||
Examples are the weighted-average over all particles or the particle with the highest weight.
|
||||
In the discrete manner of a particle representation this is often done by providing a single value, also known as sample statistic, to serve as a best guess \cite{bar2004estimation}.
|
||||
Examples are the weighted-average over all particles or the particle with the highest weight \cite{blanco2009phd}.
|
||||
However, in complex scenarios like a multimodal representation of the posterior, such methods fail to provide an accurate statement about the most probable state.
|
||||
Thus, in \cite{Bullmann-18} we present a \del{rapid computation} \add{approximation} scheme of kernel density estimates (KDE).
|
||||
Recovering the probability density function using an efficient KDE algorithm yields a promising approach to solve the state estimation problem in a more profound way.
|
||||
|
||||
@@ -2177,10 +2177,10 @@ IGNOREmonth={Apr},
|
||||
@PHDTHESIS{blanco2009phd,
|
||||
author = {Blanco, Jos{\'{e}}-Luis},
|
||||
IGNOREmonth = {{nov}},
|
||||
title = {Contributions to Localization, Mapping and Navigation in Mobile Robotics},
|
||||
title = {{Contributions to Localization, Mapping and Navigation in Mobile Robotics}},
|
||||
year = {2009},
|
||||
school = {PhD. in Electrical Engineering, University of Malaga},
|
||||
url = {http://www.mrpt.org/Paper:J.L._Blanco_Phd_Thesis}
|
||||
IGNOREurl = {http://www.mrpt.org/Paper:J.L._Blanco_Phd_Thesis}
|
||||
}
|
||||
|
||||
@article{kunsch2005recursive,
|
||||
@@ -2990,3 +2990,10 @@ address = {{Rothenburg, Germany}},
|
||||
REM_ISSN={2153-0866},
|
||||
REM_month={Sept},
|
||||
}
|
||||
|
||||
@book{bar2004estimation,
|
||||
title={{Estimation with Applications to Tracking and Navigation: Theory Algorithms and Software}},
|
||||
author={Bar-Shalom, Yaakov and Li, X Rong and Kirubarajan, Thiagalingam},
|
||||
year={2004},
|
||||
publisher={John Wiley \& Sons}
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user