16 research outputs found
Recommended from our members
Motion Planning for Optimal Information Gathering in Opportunistic Navigation Systems
Motion planning for optimal information gathering in an opportunistic navigation (OpNav)
environment is considered. An OpNav environment can be thought of as a radio
frequency signal landscape within which a receiver locates itself in space and time by extracting
information from ambient signals of opportunity (SOPs). The receiver is assumed
to draw only pseudorange-type observations from the SOPs, and such observations are
fused through an estimator to produce an estimate of the receiverâs own states. Since
not all SOP states in the OpNav environment may be known a priori, the receiver must
estimate the unknown SOP states of interest simultaneously with its own states. In this
work, the following problem is studied. A receiver with no a priori knowledge about its
own states is dropped in an unknown, yet observable, OpNav environment. Assuming that
the receiver can prescribe its own trajectory, what motion planning strategy should the
receiver adopt in order to build a high-fidelity map of the OpNav signal landscape, while
simultaneously localizing itself within this map in space and time? To answer this question,
first, the minimum conditions under which the OpNav environment is fully observable are
established, and the need for receiver maneuvering to achieve full observability is highlighted.
Then, motivated by the fact that not all trajectories a receiver may take in the
environment are equally beneficial from an information gathering point of view, a strategy
for planning the motion of the receiver is proposed. The strategy is formulated in a
coupled estimation and optimal control framework of a gradually identified system, where
optimality is defined through various information-theoretic measures. Simulation results
are presented to illustrate the improvements gained from adopting the proposed strategy
over random and pre-defined receiver trajectories.Aerospace Engineering and Engineering Mechanic
The Price of Anarchy in Active Signal Landscape Map Building
Multiple receivers with a priori knowledge about
their own initial states are assumed to be dropped in an unknown
environment comprising multiple signals of opportunity (SOPs)
transmitters. The receivers draw pseudorange observations from
the SOPs. The receiversâ objective is to build a high-fidelity
signal landscape map of the environment, which would enable
the receivers to navigate accurately with the aid of the SOPs.
The receivers could command their own maneuvers and such
commands are computed so to maximize the information gathered
about the SOPs in a greedy fashion. Several information
fusion and decision making architectures are possible. This
paper studies the price of anarchy in building signal landscape
maps to assess the degradation in the map quality should the
receivers produce their own maps and make their own maneuver
decisions versus a completely centralized approach. In addition,
a hierarchical architecture is proposed in which the receivers
build their own maps and make their own decisions, but share
relevant information. Such architecture is shown to produce maps
of comparable quality to the completely centralized approach.Aerospace Engineering and Engineering Mechanic
Recommended from our members
Analysis and synthesis of collaborative opportunistic navigation systems
textNavigation is an invisible utility that is often taken for granted with considerable societal and economic impacts. Not only is navigation essential to our modern life, but the more it advances, the more possibilities are created. Navigation is at the heart of three emerging fields: autonomous vehicles, location-based services, and intelligent transportation systems. Global navigation satellite systems (GNSS) are insufficient for reliable anytime, anywhere navigation, particularly indoors, in deep urban canyons, and in environments under malicious attacks (e.g., jamming and spoofing). The conventional approach to overcome the limitations of GNSS-based navigation is to couple GNSS receivers with dead reckoning sensors. A new paradigm, termed opportunistic navigation (OpNav), is emerging. OpNav is analogous to how living creatures naturally navigate: by learning their environment. OpNav aims to exploit the plenitude of ambient radio frequency signals of opportunity (SOPs) in the environment. OpNav radio receivers, which may be handheld or vehicle-mounted, continuously search for opportune signals from which to draw position and timing information, employing on-the-fly signal characterization as necessary. In collaborative opportunistic navigation (COpNav), multiple receivers share information to construct and continuously refine a global signal landscape. For the sake of motivation, consider the following problem. A number of receivers with no a priori knowledge about their own states are dropped in an environment comprising multiple unknown terrestrial SOPs. The receivers draw pseudorange observations from the SOPs. The receivers' objective is to build a high-fidelity signal landscape map of the environment within which they localize themselves in space and time. We then ask: (i) Under what conditions is the environment fully observable? (ii) In cases where the environment is not fully observable, what are the observable states? (iii) How would receiver-controlled maneuvers affect observability? (iv) What is the degree of observability of the various states in the environment? (v) What motion planning strategy should the receivers employ for optimal information gathering? (vi) How effective are receding horizon strategies over greedy for receiver trajectory optimization, and what are their limitations? (vii) What level of collaboration between the receivers achieves a minimal price of anarchy? This dissertation addresses these fundamental questions and validates the theoretical conclusions numerically and experimentally.Electrical and Computer Engineerin
Recommended from our members
Tightly-Coupled Opportunistic Navigation for Deep Urban and Indoor Positioning
A strategy is presented for exploiting the frequency stability,
transmit location, and timing information of ambient radio-frequency âsignals of opportunityâ for the purpose of
navigating in deep urban and indoor environments. The
strategy, referred to as tightly-coupled opportunistic navigation
(TCON), involves a receiver continually searching
for signals from which to extract navigation and timing
information. The receiver begins by characterizing these
signals, whether downloading characterizations from a collaborative
online database or performing characterizations
on-the-fly. Signal observables are subsequently combined
within a central estimator to produce an optimal estimate
of position and time. A simple demonstration of the
TCON strategy focused on timing shows that a TCONenabled
receiver can characterize and use CDMA cellular
signals to correct its local clock variations, allowing it to
coherently integrate GNSS signals beyond 100 seconds.Aerospace Engineering and Engineering Mechanic
Recommended from our members
Adaptive Estimation of Signals of Opportunity
To exploit unknown ambient radio frequency signals of
opportunity (SOPs) for positioning and navigation, one
must estimate their states along with a set of parameters
that characterize the stability of their oscillators. SOPs
can be modeled as stochastic dynamical systems driven
by process noise. The statistics of such process noise is
typically unknown to the receiver wanting to exploit the
SOPs for positioning and navigation. Incorrect statistical
models jeopardize the estimation optimality and may
cause filter divergence. This necessitates the development
of adaptive filters, which provide a significant improvementover fixed filters through the filter learning process. This
paper develops two such adaptive filters: an innovationbased
maximum likelihood filter and an interacting multiple
model filter and compares their performance and complexity.
Numerical and experimental results are presented
demonstrating the superiority of these filters over fixed,
mismatched filters.Aerospace Engineering and Engineering Mechanic
The four key challenges of advanced multisensor navigation and positioning
The next generation of navigation and positioning
systems must provide greater accuracy and reliability in a range
of challenging environments to meet the needs of a variety of
mission-critical applications. No single navigation technology is
robust enough to meet these requirements on its own, so a
multisensor solution is required. Although many new navigation
and positioning methods have been developed in recent years,
little has been done to bring them together into a robust, reliable,
and cost-effective integrated system. To achieve this, four key
challenges must be met: complexity, context, ambiguity, and
environmental data handling. This paper addresses each of these
challenges. It describes the problems, discusses possible
approaches, and proposes a program of research and
standardization activities to solve them. The discussion is
illustrated with results from research into urban GNSS
positioning, GNSS shadow matching, environmental feature
matching, and context detection
Cooperative Relative Positioning for Vehicular Environments
Fahrerassistenzsysteme sind ein wesentlicher Baustein zur Steigerung der Sicherheit im StraĂenverkehr. Vor allem sicherheitsrelevante Applikationen benötigen eine genaue Information ĂŒber den Ort und der Geschwindigkeit der Fahrzeuge in der unmittelbaren Umgebung, um mögliche Gefahrensituationen vorherzusehen, den Fahrer zu warnen oder eigenstĂ€ndig einzugreifen. ReprĂ€sentative Beispiele fĂŒr Assistenzsysteme, die auf eine genaue, kontinuierliche und zuverlĂ€ssige Relativpositionierung anderer Verkehrsteilnehmer angewiesen sind, sind Notbremsassitenten, Spurwechselassitenten und Abstandsregeltempomate.
Moderne LösungsansÀtze benutzen Umfeldsensorik wie zum Beispiel Radar, Laser Scanner oder Kameras, um die Position benachbarter Fahrzeuge zu schÀtzen. Dieser Sensorsysteme gemeinsame Nachteile sind deren limitierte Erfassungsreichweite und die Notwendigkeit einer direkten und nicht blockierten Sichtlinie zum Nachbarfahrzeug. Kooperative Lösungen basierend auf einer Fahrzeug-zu-Fahrzeug Kommunikation können die eigene Wahrnehmungsreichweite erhöhen, in dem Positionsinformationen zwischen den Verkehrsteilnehmern ausgetauscht werden.
In dieser Dissertation soll die Möglichkeit der kooperativen Relativpositionierung von StraĂenfahrzeugen mittels Fahrzeug-zu-Fahrzeug Kommunikation auf ihre Genauigkeit, KontinuitĂ€t und Robustheit untersucht werden. Anstatt die in jedem Fahrzeug unabhĂ€ngig ermittelte Position zu ĂŒbertragen, werden in einem neuartigem Ansatz GNSS-Rohdaten, wie Pseudoranges und Doppler-Messungen, ausgetauscht. Dies hat den Vorteil, dass sich korrelierte Fehler in beiden Fahrzeugen potentiell herauskĂŒrzen. Dies wird in dieser Dissertation mathematisch untersucht, simulativ modelliert und experimentell verifiziert. Um die ZuverlĂ€ssigkeit und KontinuitĂ€t auch in "gestörten" Umgebungen zu erhöhen, werden in einem Bayesischen Filter die GNSS-Rohdaten mit Inertialsensormessungen aus zwei Fahrzeugen fusioniert. Die Validierung des Sensorfusionsansatzes wurde im Rahmen dieser Dissertation in einem Verkehrs- sowie in einem GNSS-Simulator durchgefĂŒhrt. Zur experimentellen Untersuchung wurden zwei Testfahrzeuge mit den verschiedenen Sensoren ausgestattet und Messungen in diversen Umgebungen gefahren.
In dieser Arbeit wird gezeigt, dass auf Autobahnen, die Relativposition eines anderen Fahrzeugs mit einer Genauigkeit von unter einem Meter kontinuierlich geschĂ€tzt werden kann. Eine hohe ZuverlĂ€ssigkeit in der longitudinalen und lateralen Richtung können erzielt werden und das System erweist 90% der Zeit eine Unsicherheit unter 2.5m. In lĂ€ndlichen Umgebungen wĂ€chst die Unsicherheit in der relativen Position. Mit Hilfe der on-board Sensoren können Fehler bei der Fahrt durch WĂ€lder und Dörfer korrekt gestĂŒtzt werden. In stĂ€dtischen Umgebungen werden die Limitierungen des Systems deutlich. Durch die erschwerte SchĂ€tzung der Fahrtrichtung des Ego-Fahrzeugs ist vor Allem die longitudinale Komponente der Relativen Position in stĂ€dtischen Umgebungen stark verfĂ€lscht.Advanced driver assistance systems play an important role in increasing the safety on today's roads. The knowledge about the other vehicles' positions is a fundamental prerequisite for numerous safety critical applications, making it possible to foresee critical situations, warn the driver or autonomously intervene. Forward collision avoidance systems, lane change assistants or adaptive cruise control are examples of safety relevant applications that require an accurate, continuous and reliable relative position of surrounding vehicles.
Currently, the positions of surrounding vehicles is estimated by measuring the distance with e.g. radar, laser scanners or camera systems. However, all these techniques have limitations in their perception range, as all of them can only detect objects in their line-of-sight. The limited perception range of today's vehicles can be extended in future by using cooperative approaches based on Vehicle-to-Vehicle (V2V) communication.
In this thesis, the capabilities of cooperative relative positioning for vehicles will be assessed in terms of its accuracy, continuity and reliability. A novel approach where Global Navigation Satellite System (GNSS) raw data is exchanged between the vehicles is presented. Vehicles use GNSS pseudorange and Doppler measurements from surrounding vehicles to estimate the relative positioning vector in a cooperative way. In this thesis, this approach is shown to outperform the absolute position subtraction as it is able to effectively cancel out common errors to both GNSS receivers. This is modeled theoretically and demonstrated empirically using simulated signals from a GNSS constellation simulator.
In order to cope with GNSS outages and to have a sufficiently good relative position estimate even in strong multipath environments, a sensor fusion approach is proposed. In addition to the GNSS raw data, inertial measurements from speedometers, accelerometers and turn rate sensors from each vehicle are exchanged over V2V communication links. A Bayesian approach is applied to consider the uncertainties inherently to each of the information sources. In a dynamic Bayesian network, the temporal relationship of the relative position estimate is predicted by using relative vehicle movement models.
Also real world measurements in highway, rural and urban scenarios are performed in the scope of this work to demonstrate the performance of the cooperative relative positioning approach based on sensor fusion. The results show that the relative position of another vehicle towards the ego vehicle can be estimated with sub-meter accuracy in highway scenarios. Here, good reliability and 90% availability with an uncertainty of less than 2.5m is achieved. In rural environments, drives through forests and towns are correctly bridged with the support of on-board sensors. In an urban environment, the difficult estimation of the ego vehicle heading has a mayor impact in the relative position estimate, yielding large errors in its longitudinal component