Analysis of non ambiguous BOC signal acquisition performance Acquisition

The Binary Offset Carrier planned for future GNSS signal, including several GALILEO Signals as well as GPS M-code, presents a high degree of spectral separation from conventional signals. It also greatly improves positioning accuracy and enhances multipath rejection. However, with such a modulation, the acquisition process is made more complex. Specific techniques must be employed in order to avoid unacceptable errors. This paper assesses the performance of three method allowing to acquire and track BOC signal unambiguously : The Bump-jumping technique, The "BPSK-like" technique and the subcarrier Phase cancellation technique

Classical EIS and square pattern signals comparison based on a well-known reference impedance

International audienceElectrochemical impedance spectroscopy or ac impeda nce methods are popularly used for the diagnosis of electrochemical generators (batteries or fuel cell) . It is now possible to acquire and quantitatively interpret the experimental electrical impedances of such syst ems, whose evolutions indirectly reflect the modifications of the internal electrochemical proce ss. The scope of these measurement methods is to identify the frequency response function of the sys tem under test by applying a small signal perturbat ion to the system input, and measuring the corresponding r esponse. Once identified, and according to the application, frequency response functions can provi de useful information about the characteristics of the system. Classical EIS consists in applying a set of frequency-controlled sine waves to the input of th e system. However, the most difficult problem is the integration of this type of measuring device in embedded systems. In order to overcome this problem , we propose to apply squared pattern excitation signals to perform such impedance measurements. In this paper, we quantify and compare the performance of classical EIS and the proposed broadband identif ication method applied to a well-known impedance circuit

Optimisation d'une chaîne de réception pour signaux de radionavigation à porteuse à double décalage (BOC) retenus pour les systèmes GALILEO et GPS modernisé

Avec le développement de nombreux systèmes de navigation, la nécessité de partager efficacement la bande spectrale allouée aux nombreux signaux de ces futurs systèmes est apparue. Dans ce souci, la sous-modulation BOC a été retenue pour un grand nombre de signaux GNSS. Cette sous-modulation présente non seulement de très bonnes propriétés en terme de séparation spectrale, mais apporte aussi une meilleure précision et une robustesse accrue vis à vis des multitrajets. Néanmoins, l'utilisation de cette sous-modulation BOC rend l'acquisition des signaux plus complexe. Ce travail de thèse concerne l'optimisation d'une chaîne de réception de signaux BOC, et des signaux composites dérivés du BOC. Nous avons analysé les problèmes que pose l'utilisation de cette modulation lors de l'acquisition du signal, celle-ci étant rendue ambiguë. Plusieurs algorithmes résolvant ce problème d'ambiguïté ont été évalué. Les résultats ont été validés grâce à un simulateur de récepteur. Ensuite, l'étude s'est focalisée sur l'acquisition des signaux BOC en présence de multitrajets. Après une analyse approfondie de l'impact des multitrajets sur le traitement des signaux BOC, une étude visant à obtenir une forme optimisée du discriminateur de boucle de code a été menée. Utilisant au mieux les caractéristiques des signaux BOC, ce discriminateur a été recherché sous la contrainte de lutter le plus efficacement possible contre les multitrajets sans pour autant dégrader la robustesse face au bruit. Une autre méthode originale de réduction de l'erreur due aux multitrajets basée sur un concept différent a été proposée et analysée. Cette méthode très simple affiche de très bonnes performances.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Multi-channel extended Kalman filter for tracking BOC modulated signals in the presence of multipath

Multipath is one of the main error sources when tracking signals in the GNSS systems. The presence of reflected signals gives place to a bias when estimating the propagation delay of the direct signal. There are several ways for mitigating this multipath problem. Several solutions have already been discussed for different techniques such as Narrow Correlator, Double delta or Early1/Early2 where the key factor concerns the discriminator curve shape to be used in a conventional DLL(delay lock loop)

An enhanced correlation processing multipath mitigation technique for BOC signals

Multipath is an issue of paramount importance in the GNSS context. The presence of reflected signals gives place to a worrying bias when estimating the propagation delay of the direct signal. This paper presents the design and the evaluation of a correlation processing technique that computes an estimation of the tracking error induced by the presence of multipath. This technique is especially designed for BOC signals and attempt to exploit the particular shape of its autocorrelation function

Solving the correlation peak ambiguity of BOC signals

The Binary Offset Carrier (BOC) modulation is planned for future GNSS signal. This modulation improves positioning accuracy and enhances multipath rejection. However this modulation brings some drawbacks resulting from the representation of the autocorrelation function (ACF). The ACF presents multiple peak bringing about risk of false acquisition or false tracking, especially in a noisy environment. This paper presents a new efficient alternative technique allowing to acquire BOC signals unambiguously. It is based on a non linear quadratic operator called Teager-Kaiser (TK) operator. This TK operator has shown a high efficiency to mitigate multipath on classical C/A GPS signals and can be very simply implemented [7]. In this study, we analyze the effectiveness of this operator to exploit the structure of the correlation function between the received signal and the reference BOC signal. So it is shown that the operator can be defined as an unambiguous solution for BOC acquisition. It is also adapted for DLL loop monitoring by detecting false peak tracking

Optimal lifetime management strategy for Self-Reconfigurable Batteries

International audienceDue to factory production discrepancies and different operation conditions, cells integrated in conventional battery systems are not similar. In a static series connection, the weakest cell limits the battery pack capacity. Self-reconfigurable batteries (SRB), where semiconductor switches allow cells to be connected or bypassed dynamically, are used to by-pass the weakest cell and so use the full battery capacity at any time. The in-line configuration even allows the direct generation of AC current without any power converter. This paper proposes an optimal lifetime management strategy for SRB generating AC current. A full battery cell model including ageing mechanisms is used to perform the minimization of the SRB capacity losses with the aim of demonstrating the SRB capabilities in terms of lifetime extension. A direct multi-shooting numeric method is used to solve the minimization problem on battery partial discharge, which is often encountered, like in the electric vehicle usage. Simulation results validate the proposed method and a major lifetime extension of 54% compared to conventional battery pack has been observed

An IR-based Wireless Optical Communication System for New Generation Battery Pack

International audienceThis study shows the design of a low-cost cell-module optical wireless communication system within an electric vehicle battery pack module.The increase in the energy density of the cells is accompanied by increasing constraints on the monitoring of their state. This implies an increase in the number and type of sensors used close to the cells and therefore an increase in the number of connections between the cells' surroundings and the cell monitoring/management system at module level.Wired connections are costly and prone to failure because they are often implemented manually. Monitoring/management systems therefore use distributed sensor systems connected by an isolated wired communication bus of the Daisy Chain type, often offering data rates of up to 1 Mbits.Studies have been carried out on wireless communication systems to replace these Daisy Chains [1]. Some use radio with a simple integration of Bluetooth gateway components [2]. Radio communications can have disadvantages in terms of confidentiality of the data exchanged and resistance to attacks from outside the battery pack.Powerline communication systems have also been proposed. These are sensitive to the noise generated on the power circuit. They are also sensitive to the variation in the impedance of the battery pack, which does not allow the case of advanced battery architectures such as Self Reconfigurable Batteries [3].An optical inter-module communication solution has also been proposed by LION Smart [4]. This solution is based on the same principle as the wired Daisy Chain, i.e. messages are sent back and forth between serial and pack stages. Thus, the data rate is divided as many times as there are communication nodes (one hundred to two hundred times for the case of a battery pack). The proposed solution is based directly on the integration of discrete infrared receiver circuits which do not solve the cost and power constraints.Most of the proposed solutions do not allow the management of events in real time, such as the synchronisation of measurements.This study proposes to investigate the implementation of an optical wireless communication bus between cells and modules that integrates the space, power and cost constraints imposed by this level of integration.The communication bus is based on the principle of open air communication between cells and module by exploiting the empty spaces within the module for light propagation. The environment of a module or even a battery pack offers interesting characteristics in terms of signal-to-noise ratio for light signals. This allows the use of very small and low cost solutions which is an important criterion for cell level integration.The characteristics of the communication bus are asymmetrical in order to take into account the specific constraints of the cell nodes and the module node. In contrast to the cell nodes, the module node is less constrained in terms of compactness and even cost because there are fewer of them in the system.The complexity of receiving an optical message, and therefore its cost and space requirements, increases with the bandwidth used, while the bandwidth of the transmission stage is only slightly affected. Thus, different bandwidths are used for uplink and downlink communications. Module-to-cell downlink communication is limited to a low bandwidth, while cell-to-module communication uses a higher bandwidth.This asymmetry is compensated by another asymmetry in the communication protocols used by the upstream and downstream channels. The slow communication between the module node and the cell nodes is based on periodic broadcast communication. The fast communication between the cell nodes and the module node is based on sequenced point-to-point communication.The broadcast communications from the module node are used as a time reference for the synchronisation of the sequential cell-to-module communications, thus reducing the clock accuracy constraints applied to the cell node sufficiently to avoid the need to use expensive time references such as crystal oscillators.A higher level protocol is then developed. This protocol is based on the request and answer principle. Each request and answer consists of a frame of several bytes including addressing and integrity information (in the form of an error checking code). The module node interrogates the cell nodes with a broadcast request addressing either a specific cell node or all the cell nodes (depending on the address contained in the question frame). The nodes concerned then respond in their respective slot times according to the nature of the request.A prototype of the communication bus that meets the integration constraints of a 12-cell pouch cell battery module has been realized. This prototype consists of 12 cell communication nodes and one module-level communication node. The open air propagation channel for the optical communications is made with a cross-section of 7x21mm over a length of 200mm. Each cell node is spaced at a distance of between 12 and 17mm.The cell communication nodes are implemented with a target component cost of less than $1 per cell (including encoding, transmitting, decoding, receiving, voltage and temperature measurement stages, an MCU monitoring the cell parameters and powering all these elements). The resulting bandwidths are 115.2kbits module to cell and 1.14Mbits cell to module with a minimum request-answers period of 10 ms.Tests of a low cost reflective coating were also carried out on one side of the propagation channel with improvements of around 40% on the amplitude of the optical signal.This work is part of the European Cobra project and will be used to produce 3 automotive modules of 12 cobalt-free cells equipped with advanced near-cell sensors.References[1] S. S. W. S. Samanta, «A Survey of Wireless Battery Management System: Topology, Emerging Trends, and Challenges,» Electronics, vol. 10, n° %118, p. 2193, 2021. [2] J. F. e. al., «Wireless Battery Management System for Safe High-Capacity Energy Storage,» Materials Research Society, San Francisco, CA, United States, 2014.[3] R. T. e. al., «A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation,» World Electric Vehicle Journal, vol. 12, n° %11, p. 8, 2021. [4] Lion SMART, «NEW BATTERY CONCEPT LIGHT BATTERY MODULAR, SAFE AND WIRELESS,» 05 06 2018. [En ligne]. Available: https://lionsmart.com/en/new-battery-concept-light-battery-modular-safe-and-wireless/

An IR-based Wireless Optical Communication System for New Generation Battery Pack

International audienceThis study shows the design of a low-cost cell-module optical wireless communication system within an electric vehicle battery pack module.The increase in the energy density of the cells is accompanied by increasing constraints on the monitoring of their state. This implies an increase in the number and type of sensors used close to the cells and therefore an increase in the number of connections between the cells' surroundings and the cell monitoring/management system at module level.Wired connections are costly and prone to failure because they are often implemented manually. Monitoring/management systems therefore use distributed sensor systems connected by an isolated wired communication bus of the Daisy Chain type, often offering data rates of up to 1 Mbits.Studies have been carried out on wireless communication systems to replace these Daisy Chains [1]. Some use radio with a simple integration of Bluetooth gateway components [2]. Radio communications can have disadvantages in terms of confidentiality of the data exchanged and resistance to attacks from outside the battery pack.Powerline communication systems have also been proposed. These are sensitive to the noise generated on the power circuit. They are also sensitive to the variation in the impedance of the battery pack, which does not allow the case of advanced battery architectures such as Self Reconfigurable Batteries [3].An optical inter-module communication solution has also been proposed by LION Smart [4]. This solution is based on the same principle as the wired Daisy Chain, i.e. messages are sent back and forth between serial and pack stages. Thus, the data rate is divided as many times as there are communication nodes (one hundred to two hundred times for the case of a battery pack). The proposed solution is based directly on the integration of discrete infrared receiver circuits which do not solve the cost and power constraints.Most of the proposed solutions do not allow the management of events in real time, such as the synchronisation of measurements.This study proposes to investigate the implementation of an optical wireless communication bus between cells and modules that integrates the space, power and cost constraints imposed by this level of integration.The communication bus is based on the principle of open air communication between cells and module by exploiting the empty spaces within the module for light propagation. The environment of a module or even a battery pack offers interesting characteristics in terms of signal-to-noise ratio for light signals. This allows the use of very small and low cost solutions which is an important criterion for cell level integration.The characteristics of the communication bus are asymmetrical in order to take into account the specific constraints of the cell nodes and the module node. In contrast to the cell nodes, the module node is less constrained in terms of compactness and even cost because there are fewer of them in the system.The complexity of receiving an optical message, and therefore its cost and space requirements, increases with the bandwidth used, while the bandwidth of the transmission stage is only slightly affected. Thus, different bandwidths are used for uplink and downlink communications. Module-to-cell downlink communication is limited to a low bandwidth, while cell-to-module communication uses a higher bandwidth.This asymmetry is compensated by another asymmetry in the communication protocols used by the upstream and downstream channels. The slow communication between the module node and the cell nodes is based on periodic broadcast communication. The fast communication between the cell nodes and the module node is based on sequenced point-to-point communication.The broadcast communications from the module node are used as a time reference for the synchronisation of the sequential cell-to-module communications, thus reducing the clock accuracy constraints applied to the cell node sufficiently to avoid the need to use expensive time references such as crystal oscillators.A higher level protocol is then developed. This protocol is based on the request and answer principle. Each request and answer consists of a frame of several bytes including addressing and integrity information (in the form of an error checking code). The module node interrogates the cell nodes with a broadcast request addressing either a specific cell node or all the cell nodes (depending on the address contained in the question frame). The nodes concerned then respond in their respective slot times according to the nature of the request.A prototype of the communication bus that meets the integration constraints of a 12-cell pouch cell battery module has been realized. This prototype consists of 12 cell communication nodes and one module-level communication node. The open air propagation channel for the optical communications is made with a cross-section of 7x21mm over a length of 200mm. Each cell node is spaced at a distance of between 12 and 17mm.The cell communication nodes are implemented with a target component cost of less than $1 per cell (including encoding, transmitting, decoding, receiving, voltage and temperature measurement stages, an MCU monitoring the cell parameters and powering all these elements). The resulting bandwidths are 115.2kbits module to cell and 1.14Mbits cell to module with a minimum request-answers period of 10 ms.Tests of a low cost reflective coating were also carried out on one side of the propagation channel with improvements of around 40% on the amplitude of the optical signal.This work is part of the European Cobra project and will be used to produce 3 automotive modules of 12 cobalt-free cells equipped with advanced near-cell sensors.References[1] S. S. W. S. Samanta, «A Survey of Wireless Battery Management System: Topology, Emerging Trends, and Challenges,» Electronics, vol. 10, n° %118, p. 2193, 2021. [2] J. F. e. al., «Wireless Battery Management System for Safe High-Capacity Energy Storage,» Materials Research Society, San Francisco, CA, United States, 2014.[3] R. T. e. al., «A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation,» World Electric Vehicle Journal, vol. 12, n° %11, p. 8, 2021. [4] Lion SMART, «NEW BATTERY CONCEPT LIGHT BATTERY MODULAR, SAFE AND WIRELESS,» 05 06 2018. [En ligne]. Available: https://lionsmart.com/en/new-battery-concept-light-battery-modular-safe-and-wireless/

Self-Reconfigurable Battery Lifetime Management in EV Application

International audienceDue to factory production discrepancies and various operating conditions, cells integrated in conventional battery systems are not similar. In a static serial connection, the weakest cell always limits the battery pack capacity. Self-reconfigurable batteries (SRB), where semiconductor switches allow cells to be connected or bypassed dynamically, are used to by-pass the weakest cell and so use the full battery capacity at any time. The in-line configuration even allows direct generation of AC current without any power converter. This paper proposes a lifetime management strategy for SRB generating AC current. A full battery cell model including ageing mechanisms is used to perform the minimization of the SRB capacity losses with the aim of demonstrating the SRB capabilities in terms of lifetime extension in the EV application. The performance analysis of the strategy is achieved through simulation of the SRB using a standardized vehicle driving cycle at various Depth of Discharge and State of Heath. A whole battery life simulation allows estimating a battery lifetime extension of 40.6%