Etude et développement d'un noeud piézoélectrique intégré dans un micro-système reconfigurable: applications à la surveillance "de santé" de structures aéronautiques

Structural health monitoring is certainly one of the key technologies required to provide the safety and the reliability of future aviation. Based on non-destructive testing, current on the ground periodical structural integrity inspections showed their limit as evidenced by the Columbia tragedy. For the time being, structural health monitoring technology has reached a good technology readiness level (TRL), but the integration of these solutions into future aerospace vehicle will require advanced system architecture. Further, improved SHM techniques and alleged assessment algorithm will be necessary to ensure an embedded integration, as well as to fully exploit their sensing capability. For now, most of high critical embedded systems are based on federate architectures, where each integrated calculator is dedicated to a specific function and to a unique kind of sensor. By consequence, the integration on the field of such solutions is highly difficult in aerospace industries due to the scale and the weight of the global electronics systems. Based on fully reconfigurable hardware, combined with versatile Input output interfaces, we propose a novel approach inspired from IMA (Integrated Modular Avionics) topologies. Signal amplification, conditioning and acquisition combined with digital calculation usually requires the use of multiple chips specialised whether in analog or in digital processing. Programmable digital electronics is not a challenge anymore, thanks to the widespread PLD and PGA's technologies. On the other hand, programmable analog electronics has much more of a challenge. Nowadays, programmable analog electronics can essentially be found in FPAA and some SoC such as Actel Smart-Fusion or Cypress PSoC. To understand the flexibility that such solutions could bring, two examples of embedded systems will be exposed: * Static embedded system based on a central CPU developed in accordance to the conventional V-model. The system is intended to monitor the integrity of a rotator Air blade and is currently integrated into A400M Aircrafts. * Dynamic and reconfigurable embedded system developed using "model based approach". In this module, multi diagnostic techniques based on PZT sensors are instrumented using a unique programmable SoC (System on Chip) which includes an ARM Cortex M3 32 bits CPU, analog and Digital CPLD. Damage assessments algorithms are therefore managed by the calculator, the sensor interface is performed through a charge amplifier inside the SoC and the data are transmitted by an Ethernet controller. To cover large areas, the system is fully scalable and accepts a hardware upgrade. Based on guided waves or electromechanical impedance analysis, the presented solutions are capable to detect different kinds of events such as impacts or flaws such as corrosion, cracks or delaminations ; no matter if the probed structure was made of composite or metallic alloy.Dans une aviation où la sécurité des vols est au cœur des préoccupations des constructeurs, le contrôle de santé des structures est l'un des nouveaux pôles majeurs de recherche et développement engagé par la communauté aéronautique depuis ces dix dernières années. Un système SHM (structural Heath monitoring) intégré aux structures avioniques (tels que le sont déjà les systèmes de monitoring des moteurs) permettrait de : * rendre l'aviation plus sûre et éviterait certains des accidents aériens ; * réduire les coûts de maintenance ; * alléger, à terme, le poids total car cela permettrait de d'éviter les sur-renforcements structuraux actuels. Le travail développé durant cette thèse, dans le cadre d'un projet industriel, concerne le développement de solutions exploitant l'utilisation de nœuds piezoélectriques au sein de microsystèmes reconfigurables dédiés à la détection de défauts dans des éléments de structure d'avion. L'exploitation de données issues de la génération/capture d'ondes de Lamb ainsi que des techniques se basant sur l'étude de l'impédance électromécanique du capteur ont été développées et étudiées sur différents types de défauts identifiés tels que cracks, corrosion etc... La méthode proposée repose sur la comparaison et l'évolution dans le temps de signatures de réseaux de capteurs utilisant l'effet piezoélectrique et placés sur des éléments choisis de structures avioniques. L'interface capteur-matériau a été spécialement étudiée afin de garantir le couplage le plus efficace possible. Les techniques de " monitoring " ainsi développées ont été testées sur des structures aéronautiques extraites d'ATR72 et des structures sandwichs en matériaux composites. Différentes solutions d'intégration de ces capteurs et nœuds ont été passées en revue et une démarche a été proposée, allant de l'architecture des effecteurs au conditionnement et à la transmission des signaux et informations d'intéret. Une nouvelle vision de l'électronique de détection de défauts, permettant de développer une instrumentation " universelle " de capteurs à travers une combinaison de circuits numériques/analogiques reconfigurables à entrées/sorties versatiles, a été implémentée et testée avec succès

Study and development of a smart piezoelectric network node integrated into a reconfigurable microsystem : application to aircraft structural health monitoring

Dans une aviation où la sécurité des vols est au cœur des préoccupations des constructeurs, le contrôle de santé des structures est l'un des nouveaux pôles majeurs de recherche et développement engagé par la communauté aéronautique depuis ces dix dernières années. Un système SHM (structural Heath monitoring) intégré aux structures avioniques (tels que le sont déjà les systèmes de monitoring des moteurs) permettrait de : - rendre l’aviation plus sûre et éviterait certains des accidents aériens ; - réduire les coûts de maintenance ; - alléger, à terme, le poids total car cela permettrait de d’éviter les sur-renforcements structuraux actuels. Le travail développé durant cette thèse, dans le cadre d'un projet industriel, concerne le développement de solutions exploitant l'utilisation de nœuds piezoélectriques au sein de microsystèmes reconfigurables dédiés à la détection de défauts dans des éléments de structure d'avion. L'exploitation de données issues de la génération/capture d'ondes de Lamb ainsi que des techniques se basant sur l'étude de l'impédance électromécanique du capteur ont été développées et étudiées sur différents types de défauts identifiés tels que cracks, corrosion, délaminages etc... La méthode proposée repose sur la comparaison et l'évolution dans le temps de signatures de réseaux de capteurs utilisant l’effet piezoélectrique et placés sur des éléments choisis de structures avions. L'interface capteur-matériau a été spécialement étudiée afin de garantir le couplage le plus efficace possible. Les techniques de « monitoring » ainsi développées ont été testées sur des structures aéronautiques métalliques et des structures en matériaux composites simples/sandwichs extraites d’avions Airbus et ATR. Différentes solutions d’intégration de ces capteurs et nœuds ont été passées en revue et une démarche a été proposée, allant de l’architecture des effecteurs au conditionnement et à la transmission des signaux et informations d’intéret. Une nouvelle vision de l’électronique de détection de défauts, permettant de développer une instrumentation « universelle » de capteurs à travers une combinaison de circuits numériques/analogiques reconfigurables à entrées/sorties versatiles, a été implémentée et testée avec succèsStructural health monitoring (SHM) is certainly one of the key technologies required to provide the safety and the reliability of future aviation. Based on non-destructive testing, current on the ground periodical structural integrity inspections showed their limit as evidenced by the Columbia tragedy. For the time being, structural health monitoring technology has reached a good technology readiness level (TRL). However, the integration of these solutions into future aerospace vehicle will require advanced and innovative system architecture. Further, improved SHM techniques and alleged assessment algorithm will be necessary to ensure an embedded integration, as well as to fully exploit their sensing capability. For now, most of high critical embedded systems are based on federate architectures, where each calculator is dedicated to a specific function and to a unique kind of sensor. By consequence, the integration on the field of conventional SHM solutions is highly difficult due to the scale and the weight of the global electronics systems. Based on a fully reconfigurable micro-system, I propose in this thesis, a novel SHM approach that combines into a unique System on Chip: • Sensors instrumentation and interfacing using reconfigurable analog circuits• Signal management and conditioning using reconfigurable digital electronics • Heath diagnostic assessment algorithms using an embedded CPUBased on elastic guided waves and electromechanical impedance analysis, the presented solution is capable through piezoelectric sensors to detect different kinds of abnormal events such as impacts. Moreover, using advanced wavelet transform and signature comparison algorithms, the system is also capable to detect mechanical damages such as corrosion, cracks or delaminations ; no matter if the probed structure is in simple composite, honeycomb composite or metallic alloy. The feasibility was proven using multiples specimens directly extracted from Airbus and ATR airplanes. To cover large areas, the system is fully scalable and accepts a hardware upgrade through multiple communication ports and protocols. Moreover, the versatility of inputs/outputs interface allows the exploitation of multiple sensors in order to locate and triangulate flaw

Semi-formal Reformulation of Requirements for Formal Property Verification

Ambiguously specified requirements can be a source of risk for safety-critical electronic designs. Requirement specifications in natural language are subject to misinterpretation. A method is proposed that reduces the risk of misinterpretations. Requirements are reformulated into semi-formal properties, which we call Natural Language Properties (NLPs). These statements are composed of natural language patterns which are then translated into SystemVerilog for formal verification. This reformulation is done by an independent verification engineer and then reviewed by the requirements engineer. Applying this technique for the verification of the CERN RadiatiOn Monitoring Electronics (CROME) led to the discovery of a safety-critical fault

Wavelet-based Noise Extraction for Anomaly Detection Applied to Safety-critical Electronics at CERN

Due to the possible damage caused by unforeseen failures of safety-critical systems, it is crucial to maintain these systems appropriately to ensure high reliability and availability. If numerous units of a system are installed in various areas and permanent access is not guaranteed, remote, data-driven condition monitoring methods can be used to schedule maintenance actions and to prevent unexpected failures. Thereby, failure precursors identified by unsupervised anomaly detection algorithms can be used to detect system malfunctions or to assess the systems condition. The anomaly detection process presented in this paper proposes a novel integrative combination of noise extraction using wavelet transforms and unsupervised algorithms to improve the detectability of a broad variety of anomalies for safety-critical electronics. Here, the performance of this modular process is demonstrated by identifying outlying data samples in datasets generated by the CERN Radiation Monitoring Electronics (CROME) system

RomLibEmu: Network Interface Stress Tests for the CERN Radiation Monitoring Electronics (CROME)

The CERN RadiatiOn Monitoring Electronics are a modular safety system for radiation monitoring that is remotely configurable through a supervisory system via a custom protocol on top of a TCP/IP connection. The configuration parameters influence the safety decisions taken by the system. An independent test library has been developed in Python in order to test the system’s reaction to misconfigurations. It is further used to stress test the application’s network interface and the robustness of the software. The library is capable of creating packets with default values, autocompleting packets according to the protocol and it allows the construction of packets from raw data. Malformed packets can be intentionally crafted and the response of the application under test is checked for protocol conformance. New test cases can be added to the test case dictionary. Each time before a new version of the communication library is released, the Python test library is used for regression testing. The current test suite consists of 251 automated test cases. Many application bugs could be found and solved, which improved the reliability and availability of the system

Comparative Analysis of Ultra-Low Current Measurement Topologies With Implementation in 130 nm Technology

Radiation detectors need front-end electronics capable of measuring currents over a large dynamic range with femtoampere sensitivity. The goal of this work is to find an alternative to the legacy systems implemented using discrete components or technology nodes of 350 nm or higher. The 130 nm technology is evaluated on its leakage current performance to assess its employability in such applications. A comparative analysis of three low current measurement topologies, namely the charge balancing, reset counting, and direct slope measurement methods, is carried out and their performance in different current ranges is evaluated. The charge balancing method was found to provide a better dynamic range with greater accuracy. However, in the lower current range, the direct slope measurement method was found to give faster results than the other two methods with comparable accuracy. Also, an application-specific integrated circuit implementing the charge balancing method was found to be linear throughout the dynamic range of −1 fA to −1 μA and could measure currents with an accuracy of ±7%. This achievement in the 130 nm technology opens the way to using the high-speed digital cells offered by this technology in conjunction with the low-leakage transistors to design a high-speed accurate current measurement system

Toward Smart Aerospace Structures: Design of a Piezoelectric Sensor and Its Analog Interface for Flaw Detection

International audienceStructural health monitoring using noninvasive methods is one of the major challenges that aerospace manufacturers face in this decade. Our work in this field focuses on the development and the system integration of millimetric piezoelectric sensors/ actuators to generate and measure specific guided waves. The aim of the application is to detect mechanical flaws on complex composite and alloy structures to quantify efficiently the global structures’ reliability. The study begins by a physical and analytical analysis of a piezoelectric patch. To preserve the structure’s integrity, the transducers are directly pasted onto the surface which leads to a critical issue concerning the interfacing layer. In order to improve the reliability and mitigate the influence of the interfacing layer, the global equations of piezoelectricity are coupled with a load transfer model. Thus we can determine precisely the shear strain developed on the surface of the structure. To exploit the generated signal, a high precision analog charge amplifier coupled to a double T notch filter were designed and scaled. Finally, a novel joined time-frequency analysis based on a wavelet decomposition algorithm is used to extract relevant structures signatures. Finally, this paper provides examples of application on aircraft structure specimens and the feasibility of the system is thus demonstrated

ROMULUSLib: An Autonomous, TCP/IP-Based, Multi-Architecture C Networking Library for DAQ and Control Applications

The new generation of Radiation Monitoring electronics developed at CERN, called the CERN RadiatiOn Monitoring Electronics (CROME), is a Zynq-7000 SoC-based Data Acquisition and Control system that replaces the previous generation to offer a higher safety standard, flexible integration and parallel communication with devices installed throughout the CERN complex. A TCP/IP protocol based C networking library, ROMULUSlib, was developed that forms the interface between CROME and the SCADA supervision software through the ROMULUS protocol. ROMULUSlib encapsulates Real-Time and Historical data, parameters and acknowledgement data in TCP/IP frames that offers high reliability and flexibility, full-duplex communication with the CROME devices and supports multi-architecture development by utilization of the POSIX standard. ROMULUSlib is autonomous as it works as a standalone library that can support integration with supervision applications by addition or modification of parameters of the data frame. This paper discusses the ROMULUS protocol, the ROMULUS Data frame and the complete set of commands and parameters implemented in the ROMULUSlib for CROME supervision