Application of a Combined Active Control and Fault Detection Scheme to an Active Composite Flexible Structure.

In this paper, the problem of increasing reliability of active control procedure is considered. Indeed, a design method of rejection perturbation in presence of potentially faults, on a flexible structure with integrated piezo-ceramics, is presented. The piezo-ceramics are used as actuators and sensors. A single unit based solution, which handles both control action and fault diagnosis is proposed. The algorithm uses H∞ optimization techniques. A full order model of the structure is first obtained via both finite-element (FE) approach and identification procedure. This model is then reduced in order to be used in our robust approach. By a suitable choice of weightings functions, the provided method is able to reject disturbance robustly and to estimate occurred faults. The case of sensors and actuators faults is discussed. The choice of weightings for diagnosis and control systems is also tackled. Finally, the effectiveness of this integrated method is confirmed by both simulation and experimental results

Simultaneous Detection of H and D NMR Signals in a micro-Tesla Field

We present NMR spectra of remote-magnetized deuterated water, detected in an unshielded environment by means of a differential atomic magnetometer. The measurements are performed in a $\mu$T field, while pulsed techniques are applied -following the sample displacement- in a 100~$\mu$T field, to tip both D and H nuclei by controllable amounts. The broadband nature of the detection system enables simultaneous detection of the two signals and accurate evaluation of their decay times. The outcomes of the experiment demonstrate the potential of ultra-low-field NMR spectroscopy in important applications where the correlation between proton and deuteron spin-spin relaxation rates as a function of external parameters contains significant information.Comment: 7 pages (letter, 4 pages) plus supplemental material as an appendix. This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Journal of Phys. Chem. Lett., copyright American Chemical Society after peer review. To access the final edited and published work see: pubs.acs.org/doi/abs/10.1021/acs.jpclett.7b0285

Noise Measurement Setup for Quartz Crystal Microbalance

Quartz crystal microbalance (QCM) is a high sensitive chemical sensor which has found widespread spectrum of applications. There are several mechanisms that are related to fluctuation phenomena. Since the aim of our research is oriented to study the sensitivity and influence of different kind of noises on sensor resolution, we modified an existing method to measure the small frequency fluctuation of QCM. The paper describes our measurement setup, in which a quartz crystal oscillator with coated active layers and a reference quartz oscillator are driven by two oscillator circuits. Each one regulates a frequency of a crystal at the minimum impedance which corresponds to the series resonance. A data-acquisition card triggers on the rise-edges of the output signal and stores these corresponding times on which the instantaneous frequency is estimated by own-written software. In comparison to other measurement setups, our approach can acquire immediate change of QCM frequency, thus, chemical processes can be even described on the basis of high-order statistics. The experiments were provided on quartz crystals with the sorption layer of polypyrrole, which is suitable for the construction of QCM humidity sensors

Metamaterial absorber integrated microfluidic terahertz sensors

Spatial overlap between the electromagnetic fields and the analytes is a key factor for strong light-matter interaction leading to high sensitivity for label-free refractive index sensing. Usually, the overlap and therefore the sensitivity are limited by either the localized near field of plasmonic antennas or the decayed resonant mode outside the cavity applied to monitor the refractive index variation. In this paper, by constructing a metal microstructure array-dielectric-metal (MDM) structure, a novel metamaterial absorber integrated microfluidic (MAIM) sensor is proposed and demonstrated in terahertz (THz) range, where the dielectric layer of the MDM structure is hollow and acts as the microfluidic channel. Tuning the electromagnetic parameters of metamaterial absorber, greatly confined electromagnetic fields can be obtained in the channel resulting in significantly enhanced interaction between the analytes and the THz wave. A high sensitivity of 3.5 THz/RIU is predicted. The experimental results of devices working around 1 THz agree with the simulation ones well. The proposed idea to integrate metamaterial and microfluid with a large light-matter interaction can be extended to other frequency regions and has promising applications in matter detection and biosensing

Sensorless multi-loop control of phase-controlled series-parallel resonant converter

This paper proposes a multi-loop controller for the phase-controlled series-parallel resonant converter. Output voltage is solely measured for control and inner loop is used to enhance closed loop stability and dynamic performance compared to single-loop control. No additional sensors are used for inner loop variables. These are estimated using a Kalman filter, based on a linearized converter model. The advantage of this sensorless scheme is not only reducing the number of sensors but more significantly providing an alternative to sensing high frequency resonant tank variables which require high microcontroller resolution in real time. First, the converter non-linear large signal behavior is linearized using a state feedback based scheme. Consequently, the converter preserves its large signal characteristics while modeled as a linear system. Comparison is made between the most suitable state variables for feedback, according to a stability study. Finally, simulation and experimental results are demonstrated to validate the improved system performance in contrast with single-loop control

Application of a Combined Active Control and Fault Detection Scheme to an Active Composite Flexible Structure.

In this paper, the problem of increasing reliability of active control procedure is considered. Indeed, a design method of rejection perturbation in presence of potentially faults, on a flexible structure with integrated piezo-ceramics, is presented. The piezo-ceramics are used as actuators and sensors. A single unit based solution, which handles both control action and fault diagnosis is proposed. The algorithm uses H∞ optimization techniques. A full order model of the structure is first obtained via both finite-element (FE) approach and identification procedure. This model is then reduced in order to be used in our robust approach. By a suitable choice of weightings functions, the provided method is able to reject disturbance robustly and to estimate occurred faults. The case of sensors and actuators faults is discussed. The choice of weightings for diagnosis and control systems is also tackled. Finally, the effectiveness of this integrated method is confirmed by both simulation and experimental results

Machine-learning nonstationary noise out of gravitational-wave detectors

Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation