839 research outputs found
Hybrid UWB-Inertial TDoA-based Target Tracking with Concentrated Anchors
In this paper, hybrid radio/inertial mobile target tracking for accurate and smooth path estimation is considered. The proposed tracking approach builds upon an Ultra WideBand (UWB)-based positioning algorithm, based on the Linear Hyperbolic Positioning System (LinHPS), with Time Difference of Arrival (TDoA) processing and anchors concentrated on a single hotspot at the center of the environment where the target moves. First, we design an Adaptive Radio-based Extended Kalman Filter (AREKF), which does not require a priori statistical knowledge of the noise in the target movement model and estimates the measurement noise covariance, at each sampling time, according to a proper LookUp Table (LUT). In order to improve the performance of AREKF, we incorporate inertial data collected from the target and propose three “hybrid” radio/inertial algorithms, denoted as Hybrid Inertial Measurement Unit (IMU)-aided Radio-based EKF (HIREKF), Hybrid Noisy Control EKF (HNCEKF), and Hybrid Control EKF (HCEKF). Our results on experimentally acquired paths show that the proposed algorithms achieve an average instantaneous position estimation error on the order of a few centimeters. Moreover, the minimum target path length estimation error, obtained with HCEKF, is on the order of 6% and 1% for two paths with lengths equal to approximately 17 m and 46 m, respectively
Opportunistic timing signals for pervasive mobile localization
Mención Internacional en el título de doctorThe proliferation of handheld devices and the pressing need of location-based services call for
precise and accurate ubiquitous geographic mobile positioning that can serve a vast set of devices.
Despite the large investments and efforts in academic and industrial communities, a pin-point solution
is however still far from reality. Mobile devices mainly rely on Global Navigation Satellite
System (GNSS) to position themselves. GNSS systems are known to perform poorly in dense urban
areas and indoor environments, where the visibility of GNSS satellites is reduced drastically.
In order to ensure interoperability between the technologies used indoor and outdoor, a pervasive
positioning system should still rely on GNSS, yet complemented with technologies that can
guarantee reliable radio signals in indoor scenarios. The key fact that we exploit is that GNSS signals
are made of data with timing information. We then investigate solutions where opportunistic
timing signals can be extracted out of terrestrial technologies. These signals can then be used as
additional inputs of the multi-lateration problem. Thus, we design and investigate a hybrid system
that combines range measurements from the Global Positioning System (GPS), the world’s
most utilized GNSS system, and terrestrial technologies; the most suitable one to consider in our
investigation is WiFi, thanks to its large deployment in indoor areas. In this context, we first start
investigating standalone WiFi Time-of-flight (ToF)-based localization. Time-of-flight echo techniques
have been recently suggested for ranging mobile devices overWiFi radios. However, these
techniques have yielded only moderate accuracy in indoor environments because WiFi ToF measurements
suffer from extensive device-related noise which makes it challenging to differentiate
between direct path from non-direct path signal components when estimating the ranges. Existing
multipath mitigation techniques tend to fail at identifying the direct path when the device-related
Gaussian noise is in the same order of magnitude, or larger than the multipath noise. In order to
address this challenge, we propose a new method for filtering ranging measurements that is better
suited for the inherent large noise as found in WiFi radios. Our technique combines statistical
learning and robust statistics in a single filter. The filter is lightweight in the sense that it does not
require specialized hardware, the intervention of the user, or cumbersome on-site manual calibration.
This makes the method we propose as the first contribution of the present work particularly
suitable for indoor localization in large-scale deployments using existing legacy WiFi infrastructures.
We evaluate our technique for indoor mobile tracking scenarios in multipath environments,
and, through extensive evaluations across four different testbeds covering areas up to 1000m2, the filter is able to achieve a median ranging error between 1:7 and 2:4 meters.
The next step we envisioned towards preparing theoretical and practical basis for the aforementioned
hybrid positioning system is a deep inspection and investigation of WiFi and GPS ToF
ranges, and initial foundations of single-technology self-localization. Self-localization systems
based on the Time-of-Flight of radio signals are highly susceptible to noise and their performance
therefore heavily rely on the design and parametrization of robust algorithms. We study the noise
sources of GPS and WiFi ToF ranging techniques and compare the performance of different selfpositioning
algorithms at a mobile node using those ranges. Our results show that the localization
error varies greatly depending on the ranging technology, algorithm selection, and appropriate
tuning of the algorithms. We characterize the localization error using real-world measurements
and different parameter settings to provide guidance for the design of robust location estimators
in realistic settings.
These tools and foundations are necessary to tackle the problem of hybrid positioning system
providing high localization capabilities across indoor and outdoor environments. In this context,
the lack of a single positioning system that is able the fulfill the specific requirements of
diverse indoor and outdoor applications settings has led the development of a multitude of localization
technologies. Existing mobile devices such as smartphones therefore commonly rely on
a multi-RAT (Radio Access Technology) architecture to provide pervasive location information
in various environmental contexts as the user is moving. Yet, existing multi-RAT architectures
consider the different localization technologies as monolithic entities and choose the final navigation
position from the RAT that is foreseen to provide the highest accuracy in the particular
context. In contrast, we propose in this work to fuse timing range (Time-of-Flight) measurements
of diverse radio technologies in order to circumvent the limitations of the individual radio access
technologies and improve the overall localization accuracy in different contexts. We introduce
an Extended Kalman filter, modeling the unique noise sources of each ranging technology. As a
rich set of multiple ranges can be available across different RATs, the intelligent selection of the
subset of ranges with accurate timing information is critical to achieve the best positioning accuracy.
We introduce a novel geometrical-statistical approach to best fuse the set of timing ranging
measurements. We also address practical problems of the design space, such as removal of WiFi
chipset and environmental calibration to make the positioning system as autonomous as possible.
Experimental results show that our solution considerably outperforms the use of monolithic
technologies and methods based on classical fault detection and identification typically applied in
standalone GPS technology.
All the contributions and research questions described previously in localization and positioning
related topics suppose full knowledge of the anchors positions. In the last part of this work, we
study the problem of deriving proximity metrics without any prior knowledge of the positions of
the WiFi access points based on WiFi fingerprints, that is, tuples of WiFi Access Points (AP) and
respective received signal strength indicator (RSSI) values. Applications that benefit from proximity
metrics are movement estimation of a single node over time, WiFi fingerprint matching for localization systems and attacks on privacy. Using a large-scale, real-world WiFi fingerprint data
set consisting of 200,000 fingerprints resulting from a large deployment of wearable WiFi sensors,
we show that metrics from related work perform poorly on real-world data. We analyze the
cause for this poor performance, and show that imperfect observations of APs with commodity
WiFi clients in the neighborhood are the root cause. We then propose improved metrics to provide
such proximity estimates, without requiring knowledge of location for the observed AP. We
address the challenge of imperfect observations of APs in the design of these improved metrics.
Our metrics allow to derive a relative distance estimate based on two observed WiFi fingerprints.
We demonstrate that their performance is superior to the related work metrics.This work has been supported by IMDEA Networks InstitutePrograma Oficial de Doctorado en Ingeniería TelemáticaPresidente: Francisco Barceló Arroyo.- Secretario: Paolo Casari.- Vocal: Marco Fior
A hybrid visual-based SLAM architecture: local filter-based SLAM with keyframe-based global mapping
This work presents a hybrid visual-based SLAM architecture that aims to take advantage of the strengths of each of the two main methodologies currently available for implementing visual-based SLAM systems, while at the same time minimizing some of their drawbacks. The main idea is to implement a local SLAM process using a filter-based technique, and enable the tasks of building and maintaining a consistent global map of the environment, including the loop closure problem, to use the processes implemented using optimization-based techniques. Different variants of visual-based SLAM systems can be implemented using the proposed architecture. This work also presents the implementation case of a full monocular-based SLAM system for unmanned aerial vehicles that integrates additional sensory inputs. Experiments using real data obtained from the sensors of a quadrotor are presented to validate the feasibility of the proposed approachPostprint (published version
Accurate Range-based Indoor Localization Using PSO-Kalman Filter Fusion
Accurate indoor localization often depends on infrastructure support for distance estimation in range-based techniques. One can also trade off accuracy to reduce infrastructure investment by using relative positions of other nodes, as in range-free localization. Even for range-based methods where accurate Ultra-WideBand (UWB) signals are used, non line-of-sight (NLOS) conditions pose significant difficulty in accurate indoor localization. Existing solutions rely on additional measurements from sensors and typically correct the noise using a Kalman filter (KF). Solutions can also be customized to specific environments through extensive profiling. In this work, a range-based indoor localization algorithm called PSO - Kalman Filter Fusion (PKFF) is proposed that minimizes the effects of NLOS on localization error without using additional sensors or profiling. Location estimates from a windowed Particle Swarm Optimization (PSO) and a dynamically adjusted KF are fused based on a weighted variance factor. PKFF achieved a 40% lower 90-percentile root-mean-square localization error (RMSE) over the standard least squares trilateration algorithm at 61 cm compared to 102 cm
Precise positioning of autonomous vehicles combining UWB ranging estimations with on-board sensors
In this paper, we analyze the performance of a positioning system based on the fusion of
Ultra-Wideband (UWB) ranging estimates together with odometry and inertial data from the vehicle.
For carrying out this data fusion, an Extended Kalman Filter (EKF) has been used. Furthermore,
a post-processing algorithm has been designed to remove the Non Line-Of-Sight (NLOS) UWB
ranging estimates to further improve the accuracy of the proposed solution. This solution has been
tested using both a simulated environment and a real environment. This research work is in the scope
of the PRoPART European Project. The different real tests have been performed on the AstaZero
proving ground using a Radio Control car (RC car) developed by RISE (Research Institutes of Sweden)
as testing platform. Thus, a real time positioning solution has been achieved complying with the
accuracy requirements for the PRoPART use case
UWB system and algorithms for indoor positioning
This research work presents of study of ultra-wide band (UWB) indoor positioning
considering different type of obstacles that can affect the localization accuracy. In the
actual warehouse, a variety of obstacles including metal, board, worker and other
obstacles will have NLOS (non-line-of-sight) impact on the positioning of the logistics
package, which influence the measurement of the distance between the logistics package
and the anchor , thereby affecting positioning accuracy. A new developed method
attempts to improve the accuracy of UWB indoor positioning, through and improved
positioning algorithm and filtering algorithm. In this project, simulate the warehouse
environment in the laboratory, several simulation proves that the used Kalman filter
algorithm and Markov algorithm can effectively reduce the error of NLOS. Experimental
validation is carried out considering a mobile tag mounted on a robot platform.Este trabalho de pesquisa apresenta um estudo de posicionamento de banda ultra-larga
(UWB) em ambientes internos considerando diferentes tipos de obstáculos que podem
afetar a precisão de localização. No armazém real, uma variedade de obstáculos incluindo
metal, placa, trabalhador e outros obstáculos terão impacto NLOS (não linha de visão) no
posicionamento do pacote logístico, o que influencia a medição da distância entre o
pacote logístico e a âncora, afetando assim a precisão do posicionamento. Um novo
método desenvolvido tenta melhorar a precisão do posicionamento interno UWB, através
de um algoritmo de posicionamento e algoritmo de filtragem aprimorados. Neste projeto,
para simular o ambiente de warehouse em laboratório, diversas simulações comprovam
que o algoritmo de filtro de Kalman e o algoritmo de Markov usados podem efetivamente
reduzir o erro de NLOS. A validação experimental é realizada considerando um tag móvel
montado em uma plataforma de robô
Stein-MAP: A Sequential Variational Inference Framework for Maximum A Posteriori Estimation
State estimation poses substantial challenges in robotics, often involving
encounters with multimodality in real-world scenarios. To address these
challenges, it is essential to calculate Maximum a posteriori (MAP) sequences
from joint probability distributions of latent states and observations over
time. However, it generally involves a trade-off between approximation errors
and computational complexity. In this article, we propose a new method for MAP
sequence estimation called Stein-MAP, which effectively manages multimodality
with fewer approximation errors while significantly reducing computational and
memory burdens. Our key contribution lies in the introduction of a sequential
variational inference framework designed to handle temporal dependencies among
transition states within dynamical system models. The framework integrates
Stein's identity from probability theory and reproducing kernel Hilbert space
(RKHS) theory, enabling computationally efficient MAP sequence estimation. As a
MAP sequence estimator, Stein-MAP boasts a computational complexity of O(N),
where N is the number of particles, in contrast to the O(N^2) complexity of the
Viterbi algorithm. The proposed method is empirically validated through
real-world experiments focused on range-only (wireless) localization. The
results demonstrate a substantial enhancement in state estimation compared to
existing methods. A remarkable feature of Stein-MAP is that it can attain
improved state estimation with only 40 to 50 particles, as opposed to the 1000
particles that the particle filter or its variants require.Comment: 13 page
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