69,122 research outputs found
Ad Hoc Microphone Array Calibration: Euclidean Distance Matrix Completion Algorithm and Theoretical Guarantees
This paper addresses the problem of ad hoc microphone array calibration where
only partial information about the distances between microphones is available.
We construct a matrix consisting of the pairwise distances and propose to
estimate the missing entries based on a novel Euclidean distance matrix
completion algorithm by alternative low-rank matrix completion and projection
onto the Euclidean distance space. This approach confines the recovered matrix
to the EDM cone at each iteration of the matrix completion algorithm. The
theoretical guarantees of the calibration performance are obtained considering
the random and locally structured missing entries as well as the measurement
noise on the known distances. This study elucidates the links between the
calibration error and the number of microphones along with the noise level and
the ratio of missing distances. Thorough experiments on real data recordings
and simulated setups are conducted to demonstrate these theoretical insights. A
significant improvement is achieved by the proposed Euclidean distance matrix
completion algorithm over the state-of-the-art techniques for ad hoc microphone
array calibration.Comment: In Press, available online, August 1, 2014.
http://www.sciencedirect.com/science/article/pii/S0165168414003508, Signal
Processing, 201
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Research progress on coal mine laser methane sensor
This paper discusses the research progress of low-power technology of laser methane sensors for coal mine. On the basis of environment of coal mines, such as ultra-long-distance transmission and high stability, a series of studies have been carried out. The preliminary results have been achieved in the research of low power consumption, temperature and pressure compensation and reliability design. The technology is applied to various products in coal mines, and achieves high stability and high reliability in products such as laser methane sensor, laser methane detection alarm device, wireless laser methane detection alarm device, and optic fiber multichannel laser methane sensor. Experimental testing and analysis of the characteristics of laser methane sensors, combined with the actual application
Teaching old sensors New tricks: archetypes of intelligence
In this paper a generic intelligent sensor software architecture is described which builds upon the basic requirements of related industry standards (IEEE 1451 and SEVA BS- 7986). It incorporates specific functionalities such as real-time fault detection, drift compensation, adaptation to environmental changes and autonomous reconfiguration. The modular based structure of the intelligent sensor architecture provides enhanced flexibility in regard to the choice of specific algorithmic realizations. In this context, the particular aspects of fault detection and drift estimation are discussed. A mixed indicative/corrective fault detection approach is proposed while it is demonstrated that reversible/irreversible state dependent drift can be estimated using generic algorithms such as the EKF or on-line density estimators. Finally, a parsimonious density estimator is presented and validated through simulated and real data for use in an operating regime dependent fault detection framework
Development and testing of a dual accelerometer vector sensor for AUV acoustic surveys
This paper presents the design, manufacturing and testing of a Dual Accelerometer Vector Sensor (DAVS). The device was built within the activities of theWiMUST project, supported under the Horizon 2020 Framework Programme, which aims to improve the efficiency of the methodologies used to perform geophysical acoustic surveys at sea by the use of Autonomous Underwater Vehicles (AUVs). The DAVS has the potential to contribute to this aim in various ways, for example, owing to its spatial filtering capability, it may reduce the amount of post processing by discriminating the bottom from the surface reflections. Additionally, its compact size allows easier integration with AUVs and hence facilitates the vehicle manoeuvrability compared to the classical towed arrays. The present paper is focused on results related to acoustic wave azimuth estimation as an example of its spatial filtering capabilities. The DAVS device consists of two tri-axial accelerometers and one hydrophone moulded in one unit. Sensitivity and directionality of these three sensors were measured in a tank, whilst the direction estimation capabilities of the accelerometers paired with the hydrophone, forming a vector sensor, were evaluated on a Medusa Class AUV, which was sailing around a deployed sound source. Results of these measurements are presented in this paper.European Union [645141]info:eu-repo/semantics/publishedVersio
Photon-number statistics with Silicon photomultipliers
We present a description of the operation of a multi-pixel detector in the
presence of non-negligible dark-count and cross-talk effects. We apply the
model to devise self-consistent calibration strategies to be performed on the
very light under investigation
The self-coherent camera as a focal plane fine phasing sensor
Direct imaging of Earth-like exoplanets requires high contrast imaging
capability and high angular resolution. Primary mirror segmentation is a key
technological solution for large-aperture telescopes because it opens the path
toward significantly increasing the angular resolution. The segments are kept
aligned by an active optics system that must reduce segment misalignments below
tens of nm RMS to achieve the high optical quality required for astronomical
science programs. The development of cophasing techniques is mandatory for the
next generation of space- and ground-based segmented telescopes, which both
share the need for increasing spatial resolution. We propose a new focal plane
cophasing sensor that exploits the scientific image of a coronagraphic
instrument to retrieve simultaneously piston and tip-tilt misalignments. The
self-coherent camera phasing sensor (SCC-PS) adequately combines the SCC
properties to segmented telescope architectures with adapted segment
misalignment estimators and image processing. An overview of the system
architecture, and a thorough performance and sensitivity analysis, including a
closed-loop efficiency, are presented by means of numerical simulations. The
SCC-PS estimates simultaneously piston and tip-tilt misalignments and corrects
them in closed-loop operation. The SCC-PS does not require any a priori on the
signal at the segment boundaries or any dedicated optical path. It has a
moderate sensitivity to misalignments, virtually none to pupil shear, and is
insensitive to segment gaps and edge effects. Primary mirror phasing can be
achieved with bright natural guide star. The SCC-PS is a noninvasive concept
and an efficient phasing sensor from the image domain. It is an attractive
candidate for segment cophasing at the instrument level or alternatively at the
telescope level, as usually envisioned in current space- and ground-based
observatories.Comment: 10 pages. 9 figures. Accepted for publication in Astronomy &
Astrophysic
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