Recursive Bayesian Initialization of Localization Based on Ranging and Dead Reckoning

The initialization of the state estimation in a localization scenario based on ranging and dead reckoning is studied. Specifically, we start with a cooperative localization setup and consider the problem of recursively arriving at a uni-modal state estimate with sufficiently low covariance such that covariance based filters can be used to estimate an agent's state subsequently. A number of simplifications/assumptions are made such that the estimation problem can be seen as that of estimating the initial agent state given a deterministic surrounding and dead reckoning. This problem is solved by means of a particle filter and it is described how continual states and covariance estimates are derived from the solution. Finally, simulations are used to illustrate the characteristics of the method and experimental data are briefly presented

Understanding the Global in Global Finance and Regulation

A simple and statistically robust method for passive clock synchronization in sensor networks is presented. The method is not limited to passive (one-way communication) synchronization, but this scenario justifies the method. The recursive nature of the method and the targeted passive setup mean that it adds a minimum of requirements on the system in which it is used. Statistical characteristics of the method are quantified and real measurements are used to illustrate the robustness and performance gain relative to a naive Kalman filter based clock synchronization. Finally, C++ code that implements the suggested clock synchronization method, is provided in this article.QC 20140423</p

Cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging

The implementation challenges of cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging are discussed and work on the subject is reviewed. System architecture and sensor fusion are identified as key challenges. A partially decentralized system architecture based on step-wise inertial navigation and step-wise dead reckoning is presented. This architecture is argued to reduce the computational cost and required communication bandwidth by around two orders of magnitude while only giving negligible information loss in comparison with a naive centralized implementation. This makes a joint global state estimation feasible for up to a platoon-sized group of agents. Furthermore, robust and low-cost sensor fusion for the considered setup, based on state space transformation and marginalization, is presented. The transformation and marginalization are used to give the necessary flexibility for presented sampling based updates for the inter-agent ranging and ranging free fusion of the two feet of an individual agent. Finally, characteristics of the suggested implementation are demonstrated with simulations and a real-time system implementation.Comment: 14 page

Step-wise smoothing para ZUPT-aided INSs

Debido a la naturaleza recursiva de la mayoría de los sistemas de navegación inercial (Inertial navigation systems, INSs) foot-mounted zero-velocity-updated-aided (ZUPT-aided), la covarianza del error va incrementando a lo largo de cada paso y "colapsa" al final de éste, donde se hace la corrección debido a la ZUPT. Esto da lugar a bruscas correcciones y discontinuidades en la trayectoria estimada. Para aplicaciones con estrictas exigencias de tiempo real este comportamiento es inevitable, ya que cada estimación corresponde a la mejor estimación usando toda la informacion hasta ese instante de tiempo. Sin embargo, para muchas aplicaciones un cierto grado de retardo (no causalidad) puede ser tolerado y la información proporcionada por las ZUPTs al final del paso, que causa las correcciones abruptas, puede hacerse disponible a lo largo de todo el paso. En consecuencia la implementación de un filtro de alisado (smoothing) para un ZUPT-aided INS es considerada en esta tesis para eliminar las correcciones bruscas y la covarianza no simétrica a lo largo de los pasos. Que sepamos, no se ha presentado tratamiento formal de smoothing para sistemas ZUPT-aided INS, pese a que existe una gran variedad de literatura acerca del tema general de smoothing. Debido al habitual filtro complementario de lazo cerrado empleado en aided INSs, las distintas técnicas de smoothing estándar no se pueden aplicar directamente. Además las medidas (las ZUPTs) están espaciadas irregularmente y aparecen en grupos. Por tanto, se requiere de algún tipo de regla de smoothing de retardo variable. En este proyecto se sugiere un método basado en una mezcla de filtro complementario de lazo abierto-cerrado combinado con un smoothing Rauch-Tung-Striebel (RTS). Se analizan distintos tipos de reglas de smoothing de retardo variable. Para aplicaciones próximas a tiempo real, el smoothing se aplica a los datos paso a paso. Los intervalos (pasos) para el smoothing se determinan en base a disponibilidad de las medidas y a umbrales de tiempo y covarianza. Por otro lado, para un procesado completo off-line, se analizan sets completos de datos. Finalmente, se cuantifican las consecuencias del smoothing y del filtro en bucle abierto-cerrado basándose en datos reales. El impacto del smoothing se ilustra y analiza a lo largo de los pasos

Latvijas ūdeņu vides pētījumi un aizsardzība: rakstu krājums (Rīga, 2017. gada 2. februāris)

The limitations of zero-velocity-updates (ZUPTs) for aiding a foot-mounted inertial navigation system (INS) are studied. Multiple significant modeling errors related to the ZUPTs are pointed out and quantified. Their implications for the possibility to estimate systematic inertial sensor errors are discussed and it is argued that modeling and estimating such errors, in foot-mounted ZUPT-aided INSs, should be avoided in many cases.QC 20130116</p

Deterring Holdout Creditors in a Restructuring of PDVSA Bonds and Promissory Notes (¿Cómo disuadir a acreedores \u27holdout\u27 en una restructuración de bonos y pagarés de PDVSA?)

The prospect of the potential mischief that may be caused by holdout creditors in a Venezuelan sovereign debt restructuring is probably the main reason why the Maduro administration has not attempted such an exercise. The next administration in Venezuela — whenever and however it may arrive — will not want for suggestions about how to minimize or neutralize this holdout creditor threat. This short article is another contribution to that growing literature. Were the Republic of Venezuela to acknowledge that there really is only one public sector credit risk in the country, and that the distinction between Republic bonds and PDVSA bonds is an artificial construct, the Republic could offer to exchange PDVSA bonds for new Republic bonds at par. This would be the preliminary to a generalized debt restructuring of some kind affecting all outstanding bonds. The question will be, as it always is, how to discourage PDVSA creditors from declining to participate in such an exchange offer. One method might be for PDVSA to pledge all of its assets to the Republic in consideration for the Republic\u27s assumption of PDVSA\u27s indebtedness under its outstanding bonds and promissory notes. This is a step expressly permitted by PDVSA\u27s bonds and promissory notes. Existing PDVSA creditors would be perfectly free to decline to exchange their exposure for new Republic bonds, but they would face the prospect that a senior lienholder (the Republic) would have a first priority claim over any PDVSA assets that the holdout may attempt to attach to satisfy a judgment against PDVSA. That realization should make them think twice about the wisdom of holding out. Los cálculos sobre el potencial daño que los acreedores “holdout” podrían ocasionar en una restructuración de la deuda soberana de Venezuela son probablemente las razones más importantes por las cuales el gobierno de Maduro no ha intentado aún este ejercicio. Al próximo gobierno venezolano – cuando quiera y como quiera que esto ocurra — no le faltará asesoría sobre las distintas opciones para poder minimizar o neutralizar la amenaza que representan estos acreedores “holdout”. Este breve artículo pretende ser una contribución más a la literatura creciente sobre el tema. En el supuesto que la República de Venezuela reconozca que en el país existe, en realidad, un único riesgo crediticio del sector público y que la distinción entre los bonos de la República y los bonos de PDVSA es una construcción artificial, la República podría ofrecer un intercambio de los bonos existentes de PDVSA por bonos nuevos de la República a valor nominal. Esta oferta de intercambio, de hacerla, sería de alguna manera el preámbulo a una restructuración general de la deuda que incluiría todos los bonos vigentes pendientes. La pregunta será, como siempre, ¿cómo persuadir a los acreedores de PDVSA para que participen en una oferta de intercambio de este tipo? Un método para hacerlo podría ser que PDVSA pignore todos sus activos a favor de la República en contraprestación para que, a su vez, la República se subrogue en la totalidad de las obligaciones de PDVSA documentada en bonos y pagarés. Esta posibilidad está expresamente permitida en la documentación de los bonos y pagarés de PDVSA. Consecuentemente, los actuales acreedores tendrían la plena libertad de declinar intercambiar sus acreencias por bonos nuevos de la República. Sin embargo, de hacerlo, tendrían que asumir la posibilidad que un acreedor prendario preferente -- a saber, la República – sería el acreedor preferente sobre los activos de PDVSA. Así, la República tendría el derecho preferente frente a cualquier acreedor “holdout” que pueda intentar embargar tales activos para satisfacer una sentencia a su favor en contra de PDVSA. Esta posibilidad debería hacer pensar dos veces a cualquier acreedor sobre las ventajas de ser un “holdout”

Fusing information from two navigation system using an upper bound on their maximum spatial separation

Abstract-A method is proposed to fuse the information from two navigation systems whose relative position is unknown, but where there exists an upper limit on how far apart the two systems can be. The proposed information fusion method is applied to a scenario in which a pedestrian is equipped with two foot-mounted zero-velocity-aided inertial navigation systems; one system on each foot. The performance of the method is studied using experimental data. The results show that the method has the capability to significantly improve the navigation performance when compared to using two uncoupled foot-mounted systems

Брэгговское отражение световых волн от сверхрешеток вблизи экситонных резонансов

A real-time cooperative localization system,utilizing dual foot-mounted low-cost inertial sensors and RFbasedinter-agent ranging, has been developed. Scenario-basedtests have been performed, using fully-equipped firefightersmimicking a search operation in a partly smoke-filledenvironment, to evaluate the performance of the TOR (TacticallOcatoR) system. The performed tests included realisticfirefighter movements and inter-agent distances, factors that arecrucial in order to provide realistic evaluations of the expectedperformance in real-world operations. The tests indicate that theTOR system may be able to provide a position accuracy ofapproximately two to three meters during realistic firefighteroperations, with only two smoke diving firefighters and onesupervising firefighter within range.QC 20140619</p