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DOLOČANJE INTEGRITETE SATELITSKIH LOKACIJSKIH STORITEV V CESTNEM PROMETU
ŠTERN, ANDREJ (Avtor), Bešter, Janez (Mentor) Več o mentorju... Povezava se odpre v novem oknu, Kos, Anton (Komentor)

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Izvleček
Razvoj satelitskih navigacijskih sistemov in drugih informacijsko-komunikacijskih tehnologij prinaša na področje cestnega prometa nove storitve, združene pod okrilje inteligentnih transportnih sistemov. Njihov primarni namen je večanje varnosti, učinkovitosti in udobja, s pozitivnimi učinki tako za udeležence v prometu, kot tudi lastnike prometne infrastrukture in upravljavce voznih parkov. V storitvenem terminalu v vozilu, kjer se izvajajo posamezne aplikacije, se nabor potrebnih navigacijskih parametrov s sprejemnikov GNSS (angl. Global Navigation Satellite Systems) pogosto združuje še s senzorji za zaznavo gibanja in digitalnim zemljevidom, da zagotovimo višjo stopnjo kvalitete storitve in omilimo težave, ki se pojavljajo v težavnih okoljih. V primerjavi z letalskim prometom, kjer so zahteve po kvaliteti določanja položaja zelo visoke, okolje pa relativno predvidljivo, predstavljajo cestna okolja skupek raznolikih in dinamičnih kvarnih vplivov na določitev položaja. To lahko povzroči večja odstopanja v navigacijski rešitvi, ki morda nekaterim storitvam ne bodo predstavljale težav, druge pa bodo delovale izven pričakovanih meja. V prvem delu disertacije smo se osredotočili na pregled cestnih storitev s poudarkom na kritičnih, pri katerih lahko odstopanje navigacijskih parametrov v obliki položaja, hitrosti, smeri gibanja ali točnega časa privede do ogrožanja varnosti, finančne škode ali kršenja zakonodaje. Med njimi so obravnavane napredne storitve za pomoč vozniku, kooperativne storitve C-ITS (angl. Cooperative Intelligent Transport Systems), storitve avtonomne vožnje, sistemi elektronskega cestninjenja, zavarovalniške storitve, samodejni poziv v sili eKlic, digitalni tahografi in sledenje nevarnim snovem. Predstavili smo razširjen nabor kriterijev kvalitete navigacijskega sistema in določili temeljne v obliki točnosti, razpoložljivosti in integritete, ki so v nadaljevanju tudi predmet globljih analiz. S primerjavo razpoložljivih zahtev storitev iz različnih vrst prometa smo ugotovili in dokazali, da področje cestnega prometa zahtev po lociranju trenutno nima dobro določenih, kar onemogoča postopke certificiranja lokacijskega modula v vozilu. Zato smo v nadaljevanju izvedli primerjavo dveh nastajajočih standardov s področja rabe satelitskega določanja položaja v cestnih ITS, CEN EN 16803 in ETSI TS 103 246, kjer so določeni storitvene arhitekture, metrike ovrednotenja kriterijev zmogljivosti ter operativni scenariji. Standard CEN (angl. European Committee for Standardization) je mestoma dopolnjen z rezultati evropske COST-akcije SaPPART (angl. European Cooperation in Science and Technology - Satellite Positioning Performance Assessment for Road VIII Transport), kjer sem 4 leta od določitve teme disertacije aktivno sodeloval na področjih določitve ogrodja za certifikacijo storitev, mehanizmov laboratorijskih in terenskih testiranj ter modelov klasifikacije uporabniških lokacijskih terminalov. Metodologija izvedbe meritev v okviru lastne kratkoročne znanstvene misije septembra 2016 v okolici mesta Nantes v Franciji podaja podrobnosti vidikov merilnih scenarijev, merilnih okolij, nabora sprejemnikov GNSS in sistema za določitev sovpadajoče referenčne poti. Skladno s smernicami EN 16803 so predstavljene karakteristike 4 razpoložljivih okolij, to so obvoznica okoli mesta, avtocestni trikotnik proti notranjosti države, mestno središče s srednje visokimi stavbami in podeželsko območje v smeri Atlantika. Prikazane so lastnosti namestitve 3 skupin s skupno 18 sprejemniki GNSS v obliki geodetskih, avtomobilskih in telefonskih sprejemnikov z vozilom za namenske raziskave francoskega inštituta IFSTTAR (angl. French Institute of Science and Technology for Transport, Development and Networks). Po zajetju meritev smo preverili njihovo veljavnost in skladnost s predpisanimi podatkovnimi formati in prikazali pogoste napake, ki jih lahko pričakujejo tudi drugi merilci s podobnimi nizko cenovnimi sprejemniki. Osrednji del disertacije prikazuje rezultate analize vpliva okolja na integriteto položaja. Integriteta, kot ocena statistične mere zaupanja v ustreznost podatkov iz sprejemnika GNSS, je obravnavana skozi opazovanje spreminjanja točnosti položaja zaradi lastnosti satelitskih konstelacij, potovanje signalov skozi ionosfero in troposfero, vplive lokalnega okolja na zmanjšano vidljivost satelitov, odboje in dušenje satelitskih signalov ter lastnosti sprejemnikov. Pokazali smo, da mesto izvedbe meritev na zemeljski obli geometrijsko vpliva na pričakovano točnost skozi faktor DOP (angl. Dilution of Precision) ter iz 1,7 milijona zajetih vzorcev določili statistični model korelacije med oceno HDOP (angl. Horizontal DOP) in številom satelitov. S pomočjo dnevno oddanih efemerid, pridobljenih s spleta, smo izvedli vrednotenje števila nesprejetih in sprejetih satelitov, in predlagali inovativni način vrednotenja vplivnosti okolij s pomočjo matematičnega modela, ki podaja t.i. karakteristični kot elevacije, kjer glajeno razmerje med nesprejetimi in sprejetimi sateliti doseže določen odstotek (5%, 10% in 15%) oz. kjer se krivulje dotika tangenta s koeficientom -1. Za določitev modela uteži v postopkih izračuna položaja in določanja integritete je bil podrobno preučen parameter C/N0, ki v izhodnem formatu množičnih sprejemnikov NMEA (angl. National Marine Electronics Association) podaja razmerje med močjo nosilca satelitskega signala C in gostoto šuma N0 v 1 Hz pasovne širine. Prikazali smo porazdelitev razmerja v čistejšem avtocestnem in zastrtem mestnem okolju za sprejemnike s strešno anteno in telefone pod vetrobranskim steklom, kjer mestni vplivi povzročijo dodaten manjši vrh porazdelitve približno 20 dB nižje od glavnega vrha zaradi sprejema oslabljenih odbitih signalov. Zaradi povezave med elevacijo satelita in njegovim pričakovanim razmerjem C/N0 pri nemotenem sprejemu smo vzpostavili model predpostavljenega poteka funkcije, kjer pri utežeh razlika med pričakovano in izmerjeno vrednostjo predstavlja dodaten faktor uteži v eksponencialnem modelu. Opravljena in prikazana je tudi verifikacija modela z meritvami na strehi matične fakultete v trajanju 12 oz. 24 ur, ki potrjuje matematični model uteži. Doprinosi posameznih sprejemnikov k točnosti so bili preverjeni z metriko, ki smo jo določili v COST akciji SaPPART in temelji na 50., 75. in 95. centilu kumulativne porazdelitvene funkcije ter številčnih mejah po tehnološki in aplikacijski perspektivi. Postavljena začetna hipoteza o vidnih razlikah med geodetskimi, avtomobilskimi in sprejemniki v telefonih na grafu porazdelitvene kumulativne funkcije je bila v postopku analize rezultatov ovržena, saj npr. slabših predstavnikov skupine avtomobilskih sprejemnikov s strešno anteno s stališča porazdelitve točnosti položaja ni mogoče ločiti od boljših pametnih telefonov v notranjosti vozila. Tako smo izvedli tudi razdelitev sprejemnikov v podskupine po njihovih zmogljivostih, kar je podalo boljšo ločljivost med njimi. Temu sledi prikazana klasifikacija vplivnosti okolja in sprejemnikov po horizontalni, prečni in vzdolžni točnosti, ki dokazuje visoko točnost geodetskih sprejemnikov in slabšo pametnih telefonov, ter klasifikacija po razpoložljivosti, ki dokazuje obratno, saj pametni telefoni želijo podati lokacijo z visoko razpoložljivostjo za ceno točnosti, geodetski sprejemniki pa visoko točnost za ceno razpoložljivosti. Avtomobilski sprejemniki za rabo v cestnem prometu tako predstavljajo dober kompromis med obema skupinama, saj zagotavljajo dobro točnost in tudi visoko stopnjo razpoložljivosti. V zaključnem poglavju je podano določevanje integritete s pomočjo uteževanja meritev signalov posameznih satelitov, kjer je poudarjen pomen uteži pri določanju položaja in izračunu stopnje zaščite. Obravnavanih je več načinov določanja uteži z uporabo podatkov o elevacijah satelitov, s signalnim razmerjem C/N0 in s kombiniranimi metodami, kjer tipično potrebujemo še dodaten vir informacij, kot sta elektronski zemljevid ali kamera za odkrivanje zastrtosti neba. Za model sigma-ε z uporabo razmerij C/N0 je prikazan postopek kalibracije uteži za avtomobilski sprejemnik v vseh štirih razpoložljivih okoljih. S tako določenimi utežmi je podana primerjava med 4 različnimi pristopi k izračunu horizontalne stopnje zaščite, kar je v zaključnem delu poglavja tudi ovrednoteno s praktičnim preizkusom učinkovitosti uteženega modela integritete in s prikazi v stanfordskih diagramih.

Jezik:Slovenski jezik
Ključne besede:satelitska navigacija, cestni promet, kritične storitve, točnost, razpoložljivost, integriteta, ocenjevanje zmogljivosti, vplivi okolja, viri napak, določevanje uteži, matematični modeli, terenske meritve, standardizacija, COST-akcija SaPPART, klasifikacija sprejemnikov GNSS
Vrsta gradiva:Doktorsko delo/naloga (mb31)
Organizacija:FE - Fakulteta za elektrotehniko
Leto izida:2019
Število ogledov:470
Število prenosov:255
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Sekundarni jezik

Jezik:Angleški jezik
Naslov:INTEGRITY MONITORING OF ROAD SATELLITE BASED LOCATION SERVICES
Izvleček:
The progress in satellite navigation systems and other information and communication technologies enables the introduction of new services in the areas of road transport, merged under intelligent transport systems. Their primary purpose is to increase safety, efficiency and comfort, with positive effects for road users, transport infrastructure owners, and fleet managers. The on-board unit in the vehicle, where individual applications are implemented, often combines the necessary navigation parameters from the GNSS receivers with motion sensors and a digital map to ensure a higher level of service quality and alleviate the problems that occur in certain difficult environments. In comparison with aviation, where the requirements for positioning quality are very high and the environment is relatively predictable, road environments constitute a set of varied and dynamic faulty impacts on positioning. This can lead to larger deviations in the navigation solution, which may not be a problem for some services, while others will exceed the expected limits. In the first part of the dissertation, we focused on the types of road services with emphasis on critical services where the deviation of navigation parameters in the form of position, speed, direction of movement and exact time can lead to threats to safety, financial loss or regulatory violations. The overview includes advanced driver assistance services (ADAS), cooperative services (C-ITS), autonomous driving, electronic toll collection systems, insurance services, emergency service – eCall, digital tachographs and tracking of dangerous goods. We presented an expanded set of quality criteria for the navigation system and defined the basic criteria in the form of accuracy, availability and integrity, which are also the subject of deeper analyses. By comparing the available requirements of services from different types of traffic, we have found and demonstrated that currently there are no existing well-defined requirements in the road sector, which prevents the certification of the positioning module inside the vehicle. Therefore, we compared the two emerging standards in the field of GNSS-based positioning for road ITS, CEN EN 16803 and ETSI TS 103 246, where service architectures, metrics for performance assessment, and operational scenarios are defined. The CEN standard is additionally complemented with the results of the European COST Action SaPPART, where I actively participated in determining the service certification framework as well as the laboratory and field testing mechanisms, and in the classification of user location terminals for 4 years from this dissertation proposal. XII The methodology of performing measurements within a Short-Term Scientific Mission (STSM) in September 2016 in the suburbs of Nantes, France, provides detailed aspects of the operational scenarios, measurement environments, the set of GNSS receivers and the reference positioning system. In accordance with EN 16803, the characteristics of four available environments, a city periphery, a motorway section, a city centre with medium-sized buildings and a rural area are presented. The installation of 3 groups with a total of 18 GNSS geodetic, car, and smartphone receivers with a dedicated Vehicle for Experimental Research on Trajectories (VERT) of the French Institute IFSTTAR are shown. After collecting all the measurements, we verified their validity and compliance with the existing data formats and showed common errors that may appear while performing similar campaigns using low-cost receivers. The main part of the dissertation presents the results of an analysis of environmental impacts on the positioning integrity. Integrity, as a statistical measure of trust that can be placed in the correctness of the information supplied by the GNSS receiver, is addressed through the analyses of positioning accuracy changes due to the properties of satellite constellations, the signal propagation across the ionosphere and troposphere, the effects of the local environment on the obstructed visibility of satellites, reflections and attenuation of satellite signals, and the properties of receivers. We showed that the measurements position on the globe geometrically affects the expected accuracy through the DOP factor. From the 1.7 million samples captured, the statistical model of the correlation between the HDOP and the number of satellites was determined. By using available daily broadcasted ephemeris from the web, we performed an evaluation of the number of not-received and received satellites. We proposed an innovative way of environment evaluation through the mathematical model, which results in the characteristic elevation angle, where the smoothed ratio between the numbers of not-received and received satellites reaches a certain percentage (5%, 10% and 15% respectively), or where the tangent to the ratio curve reaches the coefficient -1. To determine the model of weights in the procedures for positioning and determining integrity, the C/N0 parameter was studied in detail, which in the output format NMEA of mass receivers provides the ratio between the power of the satellite carrier C and noise density N0 in 1 Hz bandwidth. We showed the distribution of the ratio in a clear-sky motorway and in obstructed urban environment for receivers with roof-placed antennas and smartphones behind the windshield, where urban influences cause an additional smaller peak of distribution about 20 dB lower than the main peakdue to the reception of attenuated reflected carriers. Due to the relation between the satellite elevation and its expected C/N0 ratio under clear-sky environment, a model of the template function was established, where, in the case of weights, the difference between the template and the measured value represents an additional weight factor in the exponential model. This model was verified with additional measurements on the roof of the Faculty of Electrical Engineering in duration of 24 hours, confirming the mathematical model of weights. The contributions of individual receivers to accuracy were verified by the metric defined in the COST action SaPPART, based on the 50th, 75th, and 95th percentiles of the cumulative distribution function, and the numerical limits set from the technological and application perspectives. The initial hypothesis on visual gaps between geodetic, automotive and smartphone receivers on the CDF was proven incorrect during the measurement analysis. For example, the accuracy CDF of low-performance representatives of the automotive receivers group with roof antennas could not be distinguished from high-performance smartphones inside the vehicle. Thus, we also carried out the subgrouping of receivers according to their performances, which provided cleaner subgroup gaps. This is followed by the classification of the receivers by horizontal, cross-track, and along-track accuracy, which demonstrates the high accuracy of geodetic receivers and low of smartphones, while the availability classification proves the opposite. Namely, smartphones try to provide a location with high availability at the cost of accuracy, while geodetic receivers provide high accuracy at the cost of availability. Automotive receivers thus represent a good balance between those two groups, as they ensure good accuracy and also a high degree of availability. In the final content chapter, integrity monitoring is presented by weighting the measurements of the signals of individual satellites, where the significance of the weights in position estimation and protection level calculation is emphasized. Several methods for determining weights are considered: using satellites’ elevations, C/N0 signal ratios and combined methods, where an additional source of information, such as an electronic map or an open-sky detection camera is needed. For the sigma-ε model using the C/N0 ratios, a calibration procedure for the automotive receiver is presented across all four available environments. With calibrated weights, a comparison is made between the four different approaches of calculating the horizontal level of protection, which is evaluated in the closing part of the chapter with a practical test of the effectiveness of the weighted integrity model and representations in Stanford plots.

Ključne besede:satellite navigation, road transport, critical services, accuracy, availability, integrity, performance assessment, environmental impact, error sources, weighting, protection levels, mathematical models, field measurements, standardization, COST Action SaPPART, GNSS receiver classification

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