보행자 항법에서 계단 보행 시 진행 방향 신호의 형상 분석을 통한 층 결정 알고리즘

학위논문(석사) -- 서울대학교대학원 : 공과대학 항공우주공학과, 2022.2. 박찬국.This master’s thesis presents a new algorithm for determining floors in pedestrian navigation. In the proposed algorithm, the types of stairs are classified by shape analysis, and the floors are determined based on the stair type. In order to implement our algorithm, the walking direction estimated through the Pedestrian Dead Reckoning (PDR) system is used. The walking direction signal has different shapes depending on the stair types. Then, shape analysis is applied to the signal shapes of the walking direction to identify the types of stairs and determine the floor change. The proposed algorithm is verified through simulations and experiments, and it is confirmed that it works well even when moving through multiple floors with several different types of stairs. It is also verified that the performance is superior to the conventional floor determination algorithm.본 논문에서는 관성 측정 장치(IMU: Inertial Measurement Unit)를 이용한 실내 보행자 항법에서 계단을 통한 층 이동 시 계단의 종류를 파악하여 층을 결정하는 새로운 알고리즘을 제안한다. 이를 위해 보행자항법(PDR: Pedestrian Dead Reckoning) 시스템에서 추정된 고도, 걸음 검출 시간, 그리고 방향각을 사용한다. 이때 추정된 고도는 계단 보행을 시작하거나 마칠 때 평지 보행과 구분될 정도의 정확도만 필요하다. 따라서 본 알고리즘에서는 기존의 층 구분 알고리즘에서 필요로 하는 고도 추정치에 대한 의존성을 최소화할 수 있다. 제안한 알고리즘에서는 계단 보행 시에 나타나는 방향각의 신호에 통계적 형상 분석(statistical shape analysis) 기법을 적용하여 계단의 종류를 파악한 후 층을 구분하게 된다. 시뮬레이션과 실험을 통해 제안한 알고리즘의 정확도를 검증하며 여러 종류의 계단을 여러 층 오르내리는 경우에도 알고리즘이 잘 동작함을 확인한다. 그리고 기존의 층 구분 알고리즘에서 발생하는 시간 지연 문제를 해결하고 층 구분 정확도가 높아진 것을 확인한다. 또한 본 연구는 관성 측정장치 이외의 다른 센서나 무선통신 장치를 사용하지 않으며 층 높이와 같은 건물에 대한 기본 정보를 가정하지 않고도 층을 잘 결정할 수 있다는 유효성을 가진다.Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Objectives and Contributions 2 Chapter 2 Pedestrian Dead Reckoning System 4 2.1 Overview of Pedestrian Dead Reckoning 4 2.2 Integration Approach 5 2.2.1 Strapdown inertial navigation system 5 2.2.2 Extended Kalman filter 6 2.2.3 INS-EKF-ZUPT 7 Chapter 3 Shape Analysis 10 3.1 Euclidean Similarity Transformation 11 3.2 Full Procrustes Distance 12 Chapter 4 Floor Determination 14 4.1 Stair Types 15 4.2 Stair Type Classification Algorithm 17 4.3 Floor Determination Algorithm 18 Chapter 5 Simulation and Experimental Results 22 5.1 Simulation Results 22 5.2 Experimental Results Single Floor Change 30 5.3 Experimental Results Multiple Floor Changes 32 5.3.1 Scenario 1 32 5.3.2 Scenario 2 37 Chapter 6 Conclusion 40 6.1 Conclusion and Summary 40 6.2 Future Work 41 Bibliography 42 국문초록 46석

Indoor Localization for Personalized Ambient Assisted Living of Multiple Users in Multi-Floor Smart Environments

This paper presents a multifunctional interdisciplinary framework that makes four scientific contributions towards the development of personalized ambient assisted living, with a specific focus to address the different and dynamic needs of the diverse aging population in the future of smart living environments. First, it presents a probabilistic reasoning-based mathematical approach to model all possible forms of user interactions for any activity arising from the user diversity of multiple users in such environments. Second, it presents a system that uses this approach with a machine learning method to model individual user profiles and user-specific user interactions for detecting the dynamic indoor location of each specific user. Third, to address the need to develop highly accurate indoor localization systems for increased trust, reliance, and seamless user acceptance, the framework introduces a novel methodology where two boosting approaches Gradient Boosting and the AdaBoost algorithm are integrated and used on a decision tree-based learning model to perform indoor localization. Fourth, the framework introduces two novel functionalities to provide semantic context to indoor localization in terms of detecting each user's floor-specific location as well as tracking whether a specific user was located inside or outside a given spatial region in a multi-floor-based indoor setting. These novel functionalities of the proposed framework were tested on a dataset of localization-related Big Data collected from 18 different users who navigated in 3 buildings consisting of 5 floors and 254 indoor spatial regions. The results show that this approach of indoor localization for personalized AAL that models each specific user always achieves higher accuracy as compared to the traditional approach of modeling an average user

Development of hybrid techniques for wireless indoor positioning systems in multiple-floor building

ได้ทุนอุดหนุนการวิจัยจากมหาวิทยาลัยเทคโนโลยีสุรนารี ปีงบประมาณ พ.ศ.255

Adaptive indoor positioning system based on locating globally deployed WiFi signal sources

Recent trends in data driven applications have encouraged expanding location awareness to indoors. Various attributes driven by location data indoors require large scale deployment that could expand beyond specific venue to a city, country or even global coverage. Social media, assets or personnel tracking, marketing or advertising are examples of applications that heavily utilise location attributes. Various solutions suggest triangulation between WiFi access points to obtain location attribution indoors imitating the GPS accurate estimation through satellites constellations. However, locating signal sources deep indoors introduces various challenges that cannot be addressed via the traditional war-driving or war-walking methods. This research sets out to address the problem of locating WiFi signal sources deep indoors in unsupervised deployment, without previous training or calibration. To achieve this, we developed a grid approach to mitigate for none line of site (NLoS) conditions by clustering signal readings into multi-hypothesis Gaussians distributions. We have also employed hypothesis testing classification to estimate signal attenuation through unknown layouts to remove dependencies on indoor maps availability. Furthermore, we introduced novel methods for locating signal sources deep indoors and presented the concept of WiFi access point (WAP) temporal profiles as an adaptive radio-map with global coverage. Nevertheless, the primary contribution of this research appears in utilisation of data streaming, creation and maintenance of self-organising networks of WAPs through an adaptive deployment of mass-spring relaxation algorithm. In addition, complementary database utilisation components such as error estimation, position estimation and expanding to 3D have been discussed. To justify the outcome of this research, we present results for testing the proposed system on large scale dataset covering various indoor environments in different parts of the world. Finally, we propose scalable indoor positioning system based on received signal strength (RSSI) measurements of WiFi access points to resolve the indoor positioning challenge. To enable the adoption of the proposed solution to global scale, we deployed a piece of software on multitude of smartphone devices to collect data occasionally without the context of venue, environment or custom hardware. To conclude, this thesis provides learning for novel adaptive crowd-sourcing system that automatically deals with tolerance of imprecise data when locating signal sources

A Wearable Indoor Navigation System for Blind and Visually Impaired Individuals

Indoor positioning and navigation for blind and visually impaired individuals has become an active field of research. The development of a reliable positioning and navigational system will reduce the suffering of the people with visual disabilities, help them live more independently, and promote their employment opportunities. In this work, a coarse-to-fine multi-resolution model is proposed for indoor navigation in hallway environments based on the use of a wearable computer called the eButton. This self-constructed device contains multiple sensors which are used for indoor positioning and localization in three layers of resolution: a global positioning system (GPS) layer for building identification; a Wi-Fi - barometer layer for rough position localization; and a digital camera - motion sensor layer for precise localization. In this multi-resolution model, a new theoretical framework is developed which uses the change of atmospheric pressure to determine the floor number in a multistory building. The digital camera and motion sensors within the eButton acquire both pictorial and motion data as a person with a normal vision walks along a hallway to establish a database. Precise indoor positioning and localization information is provided to the visually impaired individual based on a Kalman filter fusion algorithm and an automatic matching algorithm between the acquired images and those in the pre-established database. Motion calculation is based on the data from motion sensors is used to refine the localization result. Experiments were conducted to evaluate the performance of the algorithms. Our results show that the new device and algorithms can precisely determine the floor level and indoor location along hallways in multistory buildings, providing a powerful and unobtrusive navigational tool for blind and visually impaired individuals

Kernel and Multi-Class Classifiers for Multi-Floor WLAN Localisation

Indoor localisation techniques in multi-floor environments are emerging for location based service applications. Developing an accurate location determination and time-efficient technique is crucial for online location estimation of the multi-floor localisation system. The localisation accuracy and computational complexity of the localisation system mainly relies on the performance of the algorithms embedded with the system. Unfortunately, existing algorithms are either time-consuming or inaccurate for simultaneous determination of floor and horizontal locations in multi-floor environment. This thesis proposes an improved multi-floor localisation technique by integrating three important elements of the system; radio map fingerprint database optimisation, floor or vertical localisation, and horizontal localisation. The main focus of this work is to extend the kernel density approach and implement multi- class machine learning classifiers to improve the localisation accuracy and processing time of the each and overall elements of the proposed technique. For fingerprint database optimisation, novel access point (AP) selection algorithms which are based on variant AP selection are investigated to improve computational accuracy compared to existing AP selection algorithms such as Max-Mean and InfoGain. The variant AP selection is further improved by grouping AP based on signal distribution. In this work, two AP selection algorithms are proposed which are Max Kernel and Kernel Logistic Discriminant that implement the knowledge of kernel density estimate and logistic regression machine learning classification. For floor localisation, the strategy is based on developing the algorithm to determine the floor by utilising fingerprint clustering technique. The clustering method is based on simple signal strength clustering which sorts the signals of APs in each fingerprint according to the strongest value. Two new floor localisation algorithms namely Averaged Kernel Floor (AKF) and Kernel Logistic Floor (KLF) are studied. The former is based on modification of univariate kernel algorithm which is proposed for single-floor localisation, while the latter applies the theory kernel logistic regression which is similar to AP selection approach but for classification purpose. For horizontal localisation, different algorithm based on multi-class k-nearest neighbour classifiers with optimisation parameter is presented. Unlike the classical kNN algorithm which is a regression type algorithm, the proposed localisation algorithms utilise machine learning classification for both linear and kernel types. The multi-class classification strategy is used to ensure quick estimation of the multi-class NN algorithms. All of the algorithms are later combined to provide device location estimation for multi-floor environment. Improvement of 43.5% of within 2 meters location accuracy and reduction of 15.2 times computational time are seen as compared to existing multi-floor localisation techniques by Gansemer and Marques. The improved accuracy is due to better performance of proposed floor and horizontal localisation algorithm while the computational time is reduced due to introduction of AP selection algorithm

Estimation Algorithms for Non-Gaussian State-Space Models with Application to Positioning

State-space models (SSMs) are used to model systems with hidden time-varying state and observable measurement output. In statistical SSMs, the state dynamics is assumed known up to a random term referred to as the process noise, and the measurements contain random measurement noise. Kalman filter (KF) and Rauch– Tung–Striebel smoother (RTSS) are widely-applied closed-form algorithms that provide the parameters of the exact Bayesian filtering and smoothing distributions for discrete-time linear statistical SSMs where the process and measurement noises follow Gaussian distributions. However, when the SSM involves nonlinear functions and/or non-Gaussian noises, the Bayesian filtering and smoothing distributions cannot in general be solved using closed-form algorithms. This thesis addresses approximate Bayesian time-series inference for two positioning-related problems where the assumption of Gaussian noises cannot capture all useful knowledge of the considered system’s statistical properties: map-assisted indoor positioning and positioning using time-delay measurements.The motion constraints imposed by the indoor map are typically incorporated in the position estimate using the particle filter (PF) algorithm. The PF is a Monte Carlo algorithm especially suited for statistical SSMs where the Bayesian posterior distributions are too complicated to be adequately approximated using a well-known distribution family with a low-dimensional parameter space. In mapassisted indoor positioning, the trajectories that cross walls or floor levels get a low probability in the model. In this thesis, improvements to three different PF algorithms for map-assisted indoor positioning are proposed and compared. In the wall-collision PF, weighted random samples, also known as particles, are moved based on inertial sensor measurements, and the particles that collide with the walls are downweighted. When the inertial sensor measurements are very noisy, map information is used to guide the particles such that fewer particles collide with the walls, which implies that more particles contribute to the estimation. When no inertial sensor information is used, the particles are moved along the links of a graph that is dense enough to approximate the set of expected user paths.Time-delay based ranging measurements of e.g. ultra-wideband (UWB) and Global Navigation Satellite Systems (GNSSs) contain occasional positive measurement errors that are large relative to the majority of the errors due to multipath effects and denied line of sight. In this thesis, computationally efficient approximate Bayesian filters and smoothers are proposed for statistical SSMs where the measurement noise follows a skew t -distribution, and the algorithms are applied to positioning using time-delay based ranging measurements. The skew t -distribution is an extension of the Gaussian distribution, which has two additional parameters that affect the heavytailedness and skewness of the distribution. When the measurement noise model is heavy-tailed, the optimal Bayesian algorithm is robust to occasional large measurement errors, and when the model is positively (or negatively) skewed, the algorithms account for the fact that most large errors are known to be positive (or negative). Therefore, the skew t -distribution is more flexible than the Gaussian distribution and captures more statistical features of the error distributions of UWB and GNSS measurements. Furthermore, the skew t -distribution admits a conditionally Gaussian hierarchical form that enables approximating the filtering and smoothing posteriors with Gaussian distributions using variational Bayes (VB) algorithms. The proposed algorithms can thus be computationally efficient compared to Monte Carlo algorithms especially when the state is high-dimensional. It is shown in this thesis that the skew-t filter improves the accuracy of UWB based indoor positioning and GNSS based outdoor positioning in urban areas compared to the extended KF. The skew-t filter’s computational burden is higher than that of the extended KF but of the same magnitude.Tila-avaruusmalleilla mallinnetaan järjestelmiä, joilla on tuntema-ton ajassa muuttuva tila sekä mitatattava ulostulo. Tilastollisissa tila-avaruusmalleissa järjestelmän tilan muutos tunnetaan lukuunotta-matta prosessikohinaksi kutsuttua satunnaista termiä, ja mittauk-set sisältävät satunnaista mittauskohinaa. Kalmanin suodatin sekäRauchin Tungin ja Striebelin siloitin ovat yleisesti käytettyjä sulje-tun muodon estimointialgoritmeja, jotka tuottavat tarkat bayesiläi-set suodatus- ja siloitusjakaumat diskreettiaikaisille lineaarisille ti-lastollisille tila-avaruusmalleille, joissa prosessi- ja mittauskohinatnoudattavat gaussisia jakaumia. Jos käsiteltyyn tila-avaruusmalliinkuitenkin liittyy epälineaarisia funktioita tai epägaussisia kohinoita,bayesiläisiä suodatus- ja siloitusjakaumia ei yleensä voida ratkais-ta suljetun muodon algoritmeilla. Tässä väitöskirjassa tutkitaan ap-proksimatiivista bayesiläistä aikasarjapäättelyä ja sen soveltamistakahteen paikannusongelmaan, joissa gaussinen jakauma ei mallinnariittävän hyvin kaikkea hyödyllistä tietoa tutkitun järjestelmän tilas-tollisista ominaisuuksista: kartta-avusteinen sisätilapaikannus sekäsignaalin kulkuaikamittauksiin perustuva paikannus.Sisätilakartan tuottamat liikerajoitteet voidaan liittää paikkaestimaat-tiin käyttäen partikkelisuodattimeksi kutsuttua algoritmia. Partik-kelisuodatin on Monte Carlo -algoritmi, joka soveltuu erityisesti ti-lastollisille tila-avaruusmalleille, joissa bayesiläisen posteriorijakau-man tiheysfunktio on niin monimutkainen, että sen approksimointitunnetuilla matalan parametridimension jakaumilla ei ole mielekäs-tä. Kartta-avusteisessa sisätilapaikannuksessa reitit, jotka leikkaavatseiniä tai kerrostasoja, saavat muita pienemmät todennäköisyydet.Tässä väitöskirjassa esitetään parannuksia kolmeen eri partikkelisuo-datusalgoritmiin, joita sovelletaan kartta-avusteiseen sisätilapaikan-vnukseen. Seinätörmayssuodattimessa painolliset satunnaisnäytteeteli partikkelit liikkuvat inertiasensorimittausten mukaisesti, ja sei-nään törmäävät partikkelit saavat pienet painot. Kun inertiasensori-mittauksissa on paljon kohinaa, partikkeleita voidaan ohjata siten,että seinätörmäysten määrä vähenee, jolloin suurempi osa partikke-leista vaikuttaa estimaattiin. Kun inertiasensorimittauksia ei käytetälainkaan, sisätilakartta voidaan esittää graafina, jonka kaarilla partik-kelit liikkuvat ja joka on riittävän tiheä approksimoimaan odotetta-vissa olevien reittien joukkoa.Esimerkiksi laajan taajuuskaistan radioista (UWB, ultra-wideband)tai paikannussatelliiteista saatavat radiosignaalin kulkuaikaan pe-rustuvat etäisyysmittaukset taas voivat sisältää monipolkuheijastus-ten ja suoran reitin estymisen aiheuttamia positiivismerkkisiä vir-heitä, jotka ovat huomattavan suuria useimpiin mittausvirheisiinverrattuna. Tässä väitöskirjassa esitetään laskennallisesti tehokkaitabayesiläisen suodattimen ja siloittimen approksimaatioita tilastol-lisille tila-avaruusmalleille, joissa mittauskohina noudattaa vinoat -jakaumaa. Vino t -jakauma on gaussisen jakauman laajennos, jasillä on kaksi lisäparametria, jotka vaikuttavat jakauman paksuhän-täisyyteen ja vinouteen. Kun mittauskohinaa mallintava jakaumaoletetaan paksuhäntäiseksi, optimaalinen bayesiläinen algoritmi eiole herkkä yksittäisille suurille mittausvirheille, ja kun jakauma olete-taan positiivisesti (tai negatiivisesti) vinoksi, algoritmit hyödyntävättietoa, että suurin osa suurista virheistä on positiivisia (tai negatiivi-sia). Vino t -jakauma on siis gaussista jakaumaa joustavampi, ja sillävoidaan mallintaa kulkuaikaan perustuvien mittausten virhejakau-maa tarkemmin kuin gaussisella jakaumalla. Vinolla t -jakaumalla onmyös ehdollisesti gaussinen esitys, joka soveltuu suodatus- ja siloi-tusposteriorien approksimointiin variaatio-Bayes-algoritmilla. Näinollen esitetyt algoritmit voivat olla laskennallisesti tehokkaampiakuin Monte Carlo -algoritmit erityisesti tilan ollessa korkeaulotteinen.Tässä väitöskirjassa näytetään, että vino-t -virhejakauman käyttö pa-rantaa UWB-radioon perustuvan sisätilapaikannuksen tarkkuuttasekä satelliittipohjaisen ulkopaikannuksen tarkkuutta kaupunkiym-päristössä verrattuna laajennettuun Kalmanin suodattimeen. Vino-t -suodatuksen laskennallinen vaativuus on suurempi mutta samaakertaluokkaa kuin laajennetun Kalmanin suodattimen