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Benefits from a multi-receiver architecture for GNSS precise positioning
Get PDFPrecise positioning with a stand-alone GPS receiver or using differential corrections is known to be strongly degraded in an urban or sub-urban environment due to frequent signal masking, strong multipath effect, frequent cycle slips on carrier phase, etc. The objective of this Ph.D. thesis is to explore the possibility of achieving precise positioning with a low-cost architecture using multiple installed low-cost single-frequency receivers with known geometry whose one of them is RTK positioned w.r.t an external reference receiver. This setup is thought to enable vehicle attitude determination and RTK performance amelioration. In this thesis, we firstly proposed a method that includes an array of receivers with known geometry to enhance the performance of the RTK in different environments. Taking advantage of the attitude information and the known geometry of the installed array of receivers, the improvement of some internal steps of RTK w.r.t an external reference receiver can be achieved. The navigation module to be implemented in this work is an Extended Kalman Filter (EKF). The performance of a proposed two-receiver navigation architecture is then studied to quantify the improvements brought by the measurement redundancy. This concept is firstly tested on a simulator in order to validate the proposed algorithm and to give a reference result of our multi-receiver system’s performance. The pseudorange measurements and carrier phase measurements mathematical models are implemented in a realistic simulator. Different scenarios are conducted, including varying the distance between the 2 antennas of the receiver array, the satellite constellation geometry, and the amplitude of the noise measurement, in order to determine the influence of the use of an array of receivers. The simulation results show that our multi-receiver RTK system w.r.t an external reference receiver is more robust to noise and degraded satellite geometry, in terms of ambiguity fixing rate, and gets a better position accuracy under the same conditions when compared with the single receiver system. Additionally, our method achieves a relatively accurate estimation of the attitude of the vehicle which provides additional information beyond the positioning. In order to optimize our processing, the correlation of the measurement errors affecting observations taken by our array of receivers has been determined. Then, the performance of our real-time single frequency cycle-slip detection and repair algorithm has been assessed. These two investigations yielded important information so as to tune our Kalman Filter. The results obtained from the simulation made us eager to use actual data to verify and improve our multi-receiver RTK and attitude system. Tests based on real data collected around Toulouse, France, are used to test the performance of the whole methodology, where different scenarios are conducted, including varying the distance between the 2 antennas of the receiver array as well as the environmental conditions (open sky, suburban, and constrained urban environments). The thesis also tried to take advantage of a dual GNSS constellation, GPS and Galileo, to further strengthen the position solution and the reliable use of carrier phase measurements. The results show that our multi-receiver RTK system is more robust to degraded GNSS environments. Our experiments correlate favorably with our previous simulation results and further support the idea of using an array of receivers with known geometry to improve the RTK performance
Scheduling and Rescheduling Operations Using Decision Support Systems: Insights From Emotional Influences on Decision-Making
Get PDFFor many years, manufacturers have focused on improving their productivity. Production scheduling operations are critical for this objective. However, in modern manufacturing systems, the original schedule must be regularly updated as it takes places in a dynamic and uncertain environment. The modern manufacturing environment is therefore very stressful for the managers in charge of the production process because they have to cope with many disruptions and uncertainties. To help them in their decision-making process, several decision support systems (DSSs) have been developed. A recent and enormous challenge is the implementation of DSSs to efficiently manage the aforementioned issues. Nowadays, these DSSs are assumed to reduce the users' stress and workload because they automatically (re)schedule the production by applying algorithms. However, to the best of our knowledge, the reciprocal influence of users' mental state (i.e., cognitive and affective states) and the use of these DSSs have received limited attention in the literature. Particularly, the influence of users' unrelated emotions has received even less attention. However, these influences are of particular interest because they can account for explaining the efficiency of DSSs, especially in modulating DSS feedback processing. As a result, we assumed that investigating the reciprocal influences of DSSs and users' mental states could provide useful avenues of investigation. The intention of this article is then to provide recommendations for future research on scheduling and rescheduling operations by suggesting the investigation of users' mental state and encouraging to conduct such research within the neuroergonomic approach
Experimental Study of Aerodynamic Disturbance Rejection On Multirotor Unmanned Aerial Vehicles
Get PDFPID (Proportional-Integral-Derivative) controllers are the most widely used control algorithms
in different industrial applications. Multirotor Unmanned Aerial Vehicles (UAVs) are not an
exception in this regard. This success is due to the efficiency of this type of algorithms. In
fact, they are easy to understand, to tune and to implement. Added to that, PID controllers
perform surprisingly well in most operational cases, even when those start to become
challenging. But this effectiveness becomes questionable when the conditions are far fro
Cramér-Rao bound for a mixture of real- and integer-valued parameter vectors and its application to the linear regression model
Get PDFPerformance lower bounds are known to be a fundamental design tool in parametric estimation theory. A plethora of deterministic bounds exist in the literature, ranging from the general Barankin bound to the well-known Cramér-Rao bound (CRB), the latter providing the optimal mean square error performance of locally unbiased estimators. In this contribution, we are interested in the estimation of mixed real- and integer-valued parameter vectors. We propose a closed-form lower bound expression leveraging on the general CRB formulation, being the limiting form of the McAulay-Seidman bound. Such formulation is the key point to take into account integer-valued parameters. As a particular case of the general form, we provide closed-form expressions for the Gaussian observation model. One noteworthy point is the as- sessment of the asymptotic efficiency of the maximum likelihood estimator for a linear regression model with mixed parameter vectors and known noise covariance matrix, thus complementing the rather rich literature on that topic. A representative carrier-phase based precise positioning example is provided to support the discussion and show the usefulness of the proposed lower bound
Intérêt de l'utilisation des tubes ThromboExact® pour limiter la présence d'agrégats plaquettaires lors d'analyse hématologique chez le chat
Get PDFLa présence d’agrégats plaquettaires est l’un des principaux obstacles à l’obtention d’un spécimen de bonne qualité pour une analyse hématologique dans l’espèce féline. De nombreuses observations d’agrégats avec ou sans pseudothrombopénie associée sont rapportées avec l’utilisation d’EDTA chez le chat avec une prévalence supérieure à 50 %. Plusieurs anticoagulants ont déjà été testés avec des résultats satisfaisant comme le CTAD ou l’Iloprost mais sont difficilement utilisables en routine. Par ailleurs, le tube ThromboExact®, Sarstedt ; à base de MgSO4 a montré des résultats très satisfaisants sur la prévention d’agrégats plaquettaires chez l’Homme atteint de pseudothrombopénie induite par les anticoagulants. L’objectif de ce travail est d’étudier l’intérêt de l’utilisation du tube ThromboExact® dans l’espèce féline pour limiter la présence d’agrégats plaquettaires en vue d’une potentielle utilisation en médecine vétérinaire de routine. La première partie de cette thèse est une étude bibliographique sur les propriétés antiagrégantes du sulfate de magnésium et l’utilisation du tube ThromboExact® chez l’Homme notamment en cas de pseudothrombopénie induite pat les anticoagulants. La deuxième partie correspond à l’étude expérimentale réalisée entre juillet et octobre 2020 à partir de spécimens sanguins récoltés sur des chats présentés aux cliniques de l’ENVT. Les résultats obtenus ne montrent pas de différence significative au niveau de la présence d’agrégats plaquettaires entre l’utilisation du tube ThromboExact® et d’un tube K3-EDTA. Par ailleurs de nombreux agrégats leuco-plaquettaires ont été observés avec l’utilisation du tube ThromboExact®. L’utilisation de ce tube en hématologie féline n’a donc pas d’intérêt
Can Proactive Obsolescence Management and Innovation go hand in hand during the Conceptual Design Phase of Complex Systems?
No full textInnovation is a vital element in the dynamic world we live in, aiming at add-ing value to developing new systems. Obsolescence on the other hand com-prehends the deterioration of the system or component capacity to operate when it is no longer suitable to fulfil the required function, even if it still operates and can be manufactured and supported. As innovative and obsolete products can be seen as opposites, the proactive management of obsoles-cence encompasses the principles of innovation. Obsolescence has so far been mainly addressed from a reactive point of view. Realizing the impact of the conceptual design phase on a system’s life-cycle cost, this paper presents how a model-based system engineering approach, proactively assessing obso-lescence risks, leverages with innovation considerations. In doing so, the pa-per builds on technology readiness levels (TRL) to identify critical compo-nents and innovation considerations. With clearly identified risks, designers can knowingly decide whether to improve a design, by making it robust and resilient, or to accept the risks and develop an obsolescence management plan. The paper is illustrated with an example from the automotive industry
Design Structure Matrix Generation from Open-source MBSE Tools
Get PDFThe usage of Design Structure Matrices is widely
applied to represent, cluster, and partition complex systems
information for different purposes, one of them being systems
design. Nevertheless, open-source software for their automatic
creation is rare. This leads to manual workshop sessions for
subject matter experts to fill in the design structure matrices,
a practice that is very tedious and time consuming. The importance
and application of Model Based System Engineering has
increased over the years. Nowadays, there are several open-source
MBSE software such as StarUML, Papyrus, TTool, Modelio,
Capella. This paper describes a novel approach to generate design
structure matrices and extract information automatically from
xml and xmi formats used widely in open-source Model Based
System Engineering tools. This work presents the algorithm and
a tool to extract data from the output model files, in order
to automatically create a Design Structure Matrix (DSM) of
modeled systems
Bases éthologiques et problèmes comportementaux de deux psittacidés en captivité
Get PDFLes perroquets sont des animaux sauvages non domestiqués dont les besoins en relation avec leur bien-être sont méconnus et difficiles à satisfaire en captivité. Pour les comprendre il est nécessaire de connaitre l’éthologie des espèces intéressées. L’amazone et le gris du Gabon sont des oiseaux sociaux doués d’une grande capacité cognitive. Détenus dans des conditions appauvries, ces perroquets sont sujets à développer des troubles du comportement. Les stéréotypies, le sur-toilettage, les troubles du comportement reproducteur, les fortes vocalisations, phobies, et enfin les comportements d’agressivité sont les troubles les plus souvent rapportés par les propriétaires et les vétérinaires. Il est possible de les prendre en charge par le biais d’enrichissements de l’environnement physiques, nutritionnels et sensoriels. La prévention de ces troubles est nécessaire à leur bien être en captivité
Complexity analysis for recent ALOHA random access techniques in satellite communications
Get PDFIn this paper we study the the complexity of packet localization at reception, for recent synchronous Random Access (RA) techniques based on the protocol ALOHA for satellite communications. The promising CRDSA (Contention Resolution Diversity Slotted ALOHA) offers better throughput, in comparison to the traditional slotted ALOHA protocols, thanks to the use of Successive Interference Cancellation (SIC) along with multireplica transmission. MARSALA (Multi-replicA decoding using corRelation baSed locALizAtion) is one of the many variants and enhancement schemes of CRDSA that have been proposed in the literature. It is applied to CRDSA each time a decoding deadlock situation is reached (when no packets can be retrieved by CRDSA). MARSALA first localizes the replicas of collided packets on a chosen reference time slot using correlations. Then it performs coherent signal combination of packet replicas prior to decoding. However, despite the good performance offered by MARSALA, its localization process adds a significant complexity to the receiver in terms of correlation operations. R-SPOTiT (Random Shared POsition Technique for Interfered random Transmissions) mitigates this complexity by introducing a shared information between the receiver and each of the transmitters, about all potential packets' locations on the frame, without any additional signaling overhead. We focus in this paper on the analysis of the total number of correlations which are needed to localize packets' replicas for both MARSALA and R-SPOTiT, with a single or with multiple Gold preambles. This should include preamble detection operations that are performed at CRDSA with a coarse and fine tracking. The results show that the most suitable system to use is the multi-preamble R-SPOTiT with two preambles
Reviewing the thermo-chemical recycling of waste polyurethane foam
Get PDFThe worldwide production of polymeric foam materials is growing due to their advantageous properties of light weight, high thermal insulation, good strength, resistance and rigidity. Society creates ever increasing amounts of poly-urethane (PU) waste. A major part of this waste can be recycled or recovered in order to be put into further use. The PU industry is committed to assist and play its part in the process. The recycling and recovery of PU foam cover a range of mechanical, physical, chemical and thermo-chemical processes. In addition to the well- documented mechanical and chemical processing options, thermo-chemical treatments are important either as ultimate disposal (incineration) or towards feedstock recovery, leading to different products according to the thermal conditions of the treatment. The review focuses on these thermo-chemical and thermal processes. As far as pyrolysis is concerned, TDI and mostly polyol can be recovered. The highest recovery yields of TDI and polyols occur at low temperatures (150–200 ◦C). It is however clear from literature that pure feedstock will not be produced, and that a further upgrading of the condensate will be needed, together with a thermal or alternative treatment of the non-condensables. Gasification towards syngas has been studied on a larger and industrial scale. Its application would need the location of the PU treatment plant close to a chemical plant, if the syngas is to be valorized or considered in conjunction with a gas-fired CHP plant. Incineration has been studied mostly in a co- firing scheme. Potentially toxic emissions from PU combustion can be catered for by the common flue gas cleaning behind the incineration itself, making this solution less evident as a stand-alone option: the combination with other wastes (such as municipal solid waste) in MSWI′s seems the indicated route to go