Marco Mugnaini

SBT soft fault diagnosis in analog electronic circuits: a sensitivity-based approach by randomized algorithms

This paper addresses the fault diagnosis issue based on a simulation before test philosophy in analog electronic circuits. Diagnosis, obtained by comparing signatures measured at the test nodes with those contained in a fault dictionary, allows for sub-systems testing and fault isolation within the circuit. A novel method for constructing the fault dictionary under the single faulty component/unit hypothesis is proposed. The method, based on a harmonic analysis, allows for selecting the most suitable test input stimuli and nodes by means of a global sensitivity approach efficiently carried out by randomized algorithms. Applicability of the method to a wide class of circuits and its integration in diagnosis tools are granted since randomized algorithms assure that the selection problem can be effectively carried out with a poly-time algorithm independently from the fault space, structure, and complexity of the circuit.

Model and Experimental Characterization of the Dynamic Behavior of Low-Power Carbon Monoxide MOX Sensors Operated With Pulsed Temperature Profiles

Wireless sensor networks for home automation or environment monitoring require low-cost low-power sensors. Carbon monoxide (CO) metal-oxide (MOX) sensors could be suitable in terms of device cost, but they show some severe limits, such as the need to be heated, which means large power consumption and the need for complex and frequent calibration procedures, which increases the overall cost. This paper investigates the possibility to partially overcome these limits by a low-cost detection system based on a suitable commercial sensor (TGS 2442, Figaro, Inc.) and an ad hoc measurement technique exploiting specifically tailored temperature profiles. To this aim, the authors study the dynamic behavior of low-power CO MOX sensors operated with pulsed temperature profiles by means of two approaches: 1) sensor modeling and 2) experimental evaluation. To analyze how the sensor dynamic response changes as a function of the CO concentration, the authors individuate a temperature profile, which ensures satisfactory sensitivity to the target gas and very low power consumption. Moreover, some parameters describing the sensor response shape are selected, which prove to be significant in terms of both robustness to environmental conditions and calibration simplicity.

Flow cell for strain- and temperature-compensated refractive index measurements by means of cascaded optical fibre long period and Bragg gratings

An optical fibre sensing system based on a hybrid cascaded long period grating (LPG) and fibre Bragg grating configuration and a thermo-stabilized flow cell for refractometric measurements is proposed. The system makes it possible to measure, and thus to cancel, the LPG cross-sensitivities to strain, temperature and fibre bending. The experimental results show that the proposed system provides satisfactory performances as far as the refractive index sensitivity and resolution are concerned. The maximum sensor sensitivity and resolution are 3120 nm/RIU and 2 × 10−5 RIU, respectively. The whole system with its flow cell and the gratings fabrication are extensively described, together with the acquisition and data processing. The stability of the sensor for several hours was also tested. We believe that the proposed system can be successfully used for label-free chemical/biochemical sensing.

Surface State Model for Conductance Responses During Thermal-Modulation of SnO

This paper and its companion (Part I) are devoted to the development and to the experimental verification of three simple gray-box models able to predict the behavior of some commercial thick film SnO2-based sensors in presence of oxygen and a reducing gas (CO). In this paper the models developed in Part I are applied to different commercial tin oxide sensors, and experimental results are discussed in order to gain a deeper insight into the sensor behavior

_{2}

In this paper, the authors discuss a measurement method, based on the zero-crossing demodulation technique of FM signals, to estimate the angular velocity vibrations of a rotating shaft. The demodulation algorithm is applied without any filtering to the direct voltage output issued by some probes sensing the passages of arbitrarily shaped targets installed on the rotating shaft. The authors discuss a theoretical approach to analyze the measurement problem taking into account the chief nonidealities related to the measurement setup, i.e., they have investigated the effects of both the shaft side vibrations and the irregular shape of the targets. On the basis of the theoretical results, the authors propose a measurement method that can reject the effects of these mentioned nonidealities, exploiting the measurements of two or more probes properly positioned around the shaft.

-Based Thick Film Sensors: Part II—Experimental Verification

In this paper, a new version of the field-mill sensor structure for atmospheric electric field measurements is presented. Both the hardware components (i.e., the mechanical structure, the electronic front end, and the acquisition and control systems) and the data processing software are designed in order to reduce power consumption and enhance the instrument metrological performance in terms of accuracy, sensitivity, and frequency band.

Measurement of Angular Vibrations in Rotating Shafts: Effects of the Measurement Setup Nonidealities

A measurement system designed for the development of novel conductometric gas sensors and of new gas sensing materials is described. The system allows to simultaneously characterize up to 8 sensors. Prototype sensors can be easily realized thanks to an ad hoc structure based on an alumina substrate equipped with electrodes, a heater and an accurate temperature sensor, on this structure the studied material can be deposited by screen printing, spin coating or dip coating. The system is designed to study the behavior of the sensors by accurately setting the operating conditions in terms of chemical environment composition, gas flow, humidity and temperature. The system is fully programmable and it individually controls the film temperatures or measures them with a resolution lower than 0.1 °C. Both chemical transients and thermal transients can be studied. These features make the system suitable for determining the principal performance indexes of a gas sensing device (e.g., sensitivity, stability, selectivity, response/recovery times, etc.) as functions of various combinations of measurement conditions (e.g., gas concentrations, temperature, humidity, flow). The proposed measurement system will find also useful applications in sensor model validation.

Design, Modeling, and Test of a System for Atmospheric Electric Field Measurement

Abstract In modern electronics and in electrical applications design is very important to be able to predict the actual product life or, at least, to be able to provide the end user with a reasonable estimate of such parameter. It is important to be able to define the availability as a key parameter because, although other performance indicators (as the mean time before failures MTBF or mean time to failure MTTF) exist, they are often misused. To study the availability of an electrical, electronic or an electromechanical system, different methods can be used. The most common one relies on memory-less Markovian state space analysis due to the fact that a little information is needed, and under simple hypothesis, it is possible to gather some outcomes on the availability of steady state value. In this paper the authors, starting from classical approach of Markov models, introduce an extension known as Hidden Markov Models approach to overcome the limits of the previous one in estimating the system availability performance over time. Such a technique can be used to improve the logistic aspects connected with optimal maintenance planning. The provided dissertation in general can be used in different contexts without losing in generality.

Versatile measurement system for the characterization of gas sensing materials

In this paper we discuss a measurement method based on the zero-crossing demodulation method of FM signals to estimate the angular velocity vibrations of a rotating shaft. The demodulation algorithm is applied without any filtering to the direct output voltage of probes sensing the tooth passing of a geared wheel installed on a rotating shaft. The proposed method rejects the effects on the measurements due to the irregular cogwheel shape profile.

Hidden Markov Models approach used for life parameters estimations

The concern related to the design of highly reliable communication structures used in applications where safety plays a crucial role has always been under the attention of researchers due to the complexity and importance of the topic. In this paper the authors study the availability of a communication system topology exploitable in rolling stock applications comparing results for two different physical implementations, and discuss the modeling techniques exploited. The optimization of the selected architecture in terms of both availability and safety is provided under qualitative and quantitative aspects. The proposed modeling approach seems to represent a good tradeoff between complexity and adherence of results to realty. The modeling technique solution illustrated in this paper, starting from a given architecture, faces the problem of getting the desired safety degree according to IEC61508 standard through some standard approach exploiting Markov state space. The paper firstly describes the problem outline, then, it analyzes the possible architectures fitting for the solution and then describes the use of the state space techniques to address the desired availability targets to get enough confidence on the desired system robustness to random failures still keeping the requested safety integrity levels.