The CuSum algorithm - a small review

This document is a small research report on the CuSum algorithm for on-line abrupt change detection in signals

Estimation of geometric characteristics of three-component oscillations for system monitoring

International audienceThe estimation of the geometric properties of the elliptical trajectory followed by a three-component sinusoidal signal in three-dimensional Euclidean space with the objective of system monitoring is addressed in this paper. In system monitoring problems, multicomponent signals are frequently encountered. Most physical quantities are naturally composed of three components. In this paper, a three-component sinusoidal signal is studied. Three sinusoids of the same frequency follow a trajectory in the shape of an ellipse when plotted in three- dimensional Euclidean space. It is the geometric properties of this elliptical trajectory that are estimated in this paper. The geometric properties of interest are the norm of the position vector, the binormal vector, curvature and torsion. Straightforward expressions of these quantities are given which allow the geometric properties of the ellipse to be recovered from three-component data. Definition and interpretation of the expressions are also included, followed by a step-by-step explanation of the approach used to estimate these quantities. The performance and limitations of the method with respect to various parameters such as noise, frequency of the sinusoids and ellipticity are discussed. The usefulness of this method as an informative means of describing three-component sinusoidal signals is illustrated with two applications

Method for computing efficient electrical indicators for offshore wind turbine monitoring

International audienceOffshore wind turbines availability is an important issue if such wind farms are to be considered a reliable source of renewable energy for the future. Environmental conditions and the low accessibility of such wind farms have contributed to the decrease of the availability of the wind turbines, compared to the onshore ones. In order to improve the reliability, condition monitoring systems and the implementation of scheduled maintenance strategies are a must for offshore power plants. This paper proposes a method of computing efficient electrical indicators using the available three-phase electrical quantities. These indicators are then to be used to obtain fault indicators for fault detection and diagnosis. The electrical indicators are obtained by using the instantaneous symmetrical components decomposition, a well proven method in power networks design and diagnosis. The new quantities are able to fully describe the whole electrical system and provide an effective mean to quantify the balance and unbalance in the system. The method uses the electrical three-phase quantities measured at the output of the generator in a wind turbine to obtain the indicators. The performance of this method is illustrated using both synthetic and experimental data

Mechanical Fault Detection in Induction Motor Drives through Stator Current Monitoring - Theory and Application Examples

Available from: http://sciyo.com/articles/show/title/mechanical-fault-detection-in-induction-motor-drives-through-stator-current-monitoring-theory-and-apIn a wide variety of industrial applications, an increasing demand exists to improve the reliability and availability of induction motor drives. Common failures occurring in such drives can be classified into electrical and mechanical faults (rotor eccentricity, bearing faults, shaft misalignment, load unbalance, gearbox fault or general failure in the load part of the drive). Mechanical faults are most commonly detected through vibration or noise monitoring, but stator current monitoring is an interesting alternative. Indeed, current sensors are cost-effective, easy to implement, and most drives already contain such sensors for protection and control purposes. However, the effects of mechanical faults on the stator currents are more indirect compared to vibration or noise analysis. This work focuses on various aspects of mechanical fault detection through stator current monitoring, starting from a general theoretical analysis to signal processing methods for fault detection and several application examples

Detection of RNAP-DNA complexes using solid state nanopores

International audienceTranscription is the first step in gene expression where DNA is copied into RNA. It is extensively studied at the bulk level especially the regulation mechanism, which in cancerous cells is impaired. We were interested in studying E. coli RNAP enzyme at the single-molecule level for its functional as well as molecular motor properties. With nanopore sensing, we were able to observe RNA polymerase-DNA complexes translocate through nanopores and able to distinguish between individual complexes and bare RNA polymerase. We were also able to observe orientation of RNA polymerase in the nanopore whether flow or electric field predominates. The complexity of the signals from the protein-DNA complexes experiment motivated us to develop level detection software. This software is based on a change detection method called the CUSUM algorithm. OpenNanpore software was designed to analyze in details current blockages in nanopore signals with very little prior knowledge on the signal. With this work one can separate events according to their number of levels and study those sub- populations separately

Online condition monitoring of wind turbines through three-phase electrical signature analysis

International audienceIn the context of the KAStrion European project, a complete solution was proposed in order to monitor wind turbines. The developed solution comprises both hardware and software parts of the condition monitoring system. In terms of software, modules for vibration analysis and electrical signal analysis have been developed. The current paper presents the electrical analysis solution proposed in the context of this project. The electrical module is able to detect both mechanical and electrical faults in a wind turbine system. The goal of the mechanical fault detection using electrical signals is to confirm the faults also detected by vibration analysis, while the main focus of the module remains the detection of electrical faults. Results showing the performance of mechanical fault detection are presented using electrical signals acquired on the test-bench developed for testing the KAStrion system. Moreover, results regarding the electrical unbalance are presented using signals acquired on a three-phase transformer. The final solution has been implemented on two onshore wind turbines since the end of 2014, and online condition monitoring results are presented at the end of the paper

A NEW OPTIMIZATION ALGORITHM FOR A LI-ION BATTERY EQUIVALENT ELECTRIC CIRCUIT IDENTIFICATION

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Annulation d'un signal périodique à travers une fonction de transfert périodique

Nous proposons une méthode de compensation active des vibrations d'une machine synchrone. Ceci revient à annuler un signal périodique à travers une fonction de transfert linéaire non-stationnaire périodique. Nous exprimons les coefficients de Fourier du signal de commande, préalablement montré périodique. Ces coefficients convergent vers des valeurs optimales stationnaires, malgré la non-stationnarité du transfert. Un algorithme du gradient est ensuite proposé et testé sur des signaux de vibration

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

Key parameters design for online battery electrochemical impedance tracker

International audienceNew applications in transport and energy storage require the use of Lithium-ion batteries. Advanced battery management systems including electrochemical impedance measurement are studied for the determination of the state of the battery, the prediction of the autonomy, the failure and security management. Taking into account constraints of cost and simplicity, we propose to use the existing electronics of current control and we evaluate the effect of the electronics design on the performance of a frequency evolutionary estimation of the electrochemical impedance. This recursive method relies on a wideband active approach and provides both an accurate estimate of the impedance in the frequency area and a tracking of its temporal variations. Benefits are the limitation of the data memory required and the amount of operations that can be completely carried out by a target such as a microcontroller. We propose a methodology to design the key parameters of electronics in function of the frequency band of interest and the desired accuracy. We highlighted that electronics of conventional BMS can host this tracking algorithm, with analog to digital converters of 10 bits or more, having an analog stage to adapt their dynamics, and that microcontrollers can be enough powerful to perform calculations, both in terms of number of operations and speed of execution. This design strategy has been applied to define a prototyping environment for a BMS based on an ARM microcontroller which is expected to provide the tracking impedance of a battery every 250 ms with less than 0,5 % of error