Measuring Relative-Story Displacement and Local Inclination Angle Using Multiple Position-Sensitive Detectors

We propose a novel sensor system for monitoring the structural health of a building. The system optically measures the relative-story displacement during earthquakes for detecting any deformations of building elements. The sensor unit is composed of three position sensitive detectors (PSDs) and lenses capable of measuring the relative-story displacement precisely, even if the PSD unit was inclined in response to the seismic vibration. For verification, laboratory tests were carried out using an Xθ-stage and a shaking table. The static experiment verified that the sensor could measure the local inclination angle as well as the lateral displacement. The dynamic experiment revealed that the accuracy of the sensor was 150 μm in the relative-displacement measurement and 100 μrad in the inclination angle measurement. These results indicate that the proposed sensor system has sufficient accuracy for the measurement of relative-story displacement in response to the seismic vibration

Jishindo ni taisuru kenchikubutsu no herusu monitaringu no tame no sokan hen\u27i keisoku ni kansuru kenkyu

制度:新 ; 報告番号:甲3342号 ; 学位の種類:博士(工学) ; 授与年月日:2011/2/25 ; 早大学位記番号:新564

The metrology and applications of PSD (position sensitive detector) sensors for microrobotics.

International audienceThe position sensitive (or sensing) detectors (PSD) are special special monolithic PIN photodiodes featuring a series of lateral electrodes in order to achieve a 1D or 2D displacement measurement of an optical spot. Compared to the discrete array sensors, the PSD have many advantages including high positioning resolution, fast response time and very simple analogue signal conditioning circuits. This paper investigates the metrology of a two-dimensional PSD working alternately in direct or indirect (reflective) mode. The possible applications consist in precise assembly of optical MEMS micromirrors or fast tracking of an object over a pneumatic smart-surface. The first results showed a good linearity and a fast response time, which successfully enable such applications for PSD sensors

Cable Tension Monitoring using Non-Contact Vision-based Techniques

In cable-stayed bridges, the structural systems of tensioned cables play a critical role in structural and functional integrity. Thereby, tensile forces in the cables become one of the essential indicators in structural health monitoring (SHM). In this thesis, a video image processing technology integrated with cable dynamic analysis is proposed as a non-contact vision-based measurement technique, which provides a user-friendly, cost-effective, and computationally efficient solution to displacement extraction, frequency identification, and cable tension monitoring. In contrast to conventional contact sensors, the vision-based system is capable of taking remote measurements of cable dynamic response while having flexible sensing capability. Since cable detection is a substantial step in displacement extraction, a comprehensive study on the feasibility of the adopted feature detector is conducted under various testing scenarios. The performance of the feature detector is quantified by developing evaluation parameters. Enhancement methods for the feature detector in cable detection are investigated as well under complex testing environments. Threshold-dependent image matching approaches, which optimize the functionality of the feature-based video image processing technology, is proposed for noise-free and noisy background scenarios. The vision-based system is validated through experimental studies of free vibration tests on a single undamped cable in laboratory settings. The maximum percentage difference of the identified cable fundamental frequency is found to be 0.74% compared with accelerometer readings, while the maximum percentage difference of the estimated cable tensile force is 4.64% compared to direct measurement by a load cell

Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

Astrometric Methods and Instrumentation to Identify and Characterize Extrasolar Planets: A Review

I present a review of astrometric techniques and instrumentation utilized to search for, detect, and characterize extra-solar planets. First, I briefly summarize the properties of the present-day sample of extrasolar planets, in connection with predictions from theoretical models of planet formation and evolution. Next, the generic approach to planet detection with astrometry is described, with significant discussion of a variety of technical, statistical, and astrophysical issues to be faced by future ground-based as well as space-borne efforts in order to achieve the required degree of measurement precision. After a brief summary of past and present efforts to detect planets via milli-arcsecond astrometry, I then discuss the planet-finding capabilities of future astrometric observatories aiming at micro-arcsecond precision. Lastly, I outline a number experiments that can be conducted by means of high-precision astrometry during the next decade, to illustrate its potential for important contributions to planetary science, in comparison with other indirect and direct methods for the detection and characterization of planetary systems.Comment: 61 pages, 8 figures, PASP, accepted (October 2005 issue

Technology Needs Assessment of an Atmospheric Observation System for Multidisciplinary Air Quality/Meteorology Missions, Part 2

The technology advancements that will be necessary to implement the atmospheric observation systems are considered. Upper and lower atmospheric air quality and meteorological parameters necessary to support the air quality investigations were included. The technology needs were found predominantly in areas related to sensors and measurements of air quality and meteorological measurements

Computer vision-based structural health monitoring and condition assessment for small to medium-span bridges

Many UK bridges are currently nearing the end of their life cycles, and therefore their maintenance and inspection routines assume a higher priority, since they become more likely to fail. Bridge maintenance routines are still predominantly based on visual inspections which are expensive, time and labour consuming and prone to human error. Structural Health Monitoring (SHM) systems, mostly utilising contact sensors have been introduced to some larger structures such as the Humber and Severn bridges to complement visual inspections. Contact sensing, however, requires access to the structure, involves working at height and is expensive. More importantly, while many larger structures have received the aid of SHM, older assets, especially small bridges with small traffic volumes still rely solely on visual inspections due to high costs associated with such SHM systems. These challenges can be circumvented by employing the fast-emerging computer-vision based structural health monitoring systems (CV-SHM), which are much more affordable, can be set up to not require working at height, nor require direct access to the structure, and which do not cause traffic disruptions. This thesis proposes an affordable and accurate CV-SHM and damage detection system to complement conventional bridge inspection routines for small to medium-size bridges. The framework comprises firstly, a computer vision (CV)-based sensing system which consist of a consumer-grade image acquisition device such as a GoPro or smartphone camera, a computer, and an image processing algorithm. This system obtains structural response without access to the structure by using image processing and feature detection techniques to analyse images of a structure captured during loading and obtain its structural response. The second part of this framework is the response analysis for damage detection and characterisation. Here, a set of data-based techniques are developed based on response information such as displacements, curvatures, inclination angles, and strains. Displacements serve as primary response obtained from the monitoring process. Others (strain, curvatures, and inclination angles) are secondary responses obtained by manipulating the primary. In this approach, response from any section of the structure can be analysed, without the requirement for further structural information, such as flexural rigidity (EI), or distance to support, unlike similar studies in literature. The condition of a structure can then be determined by comparing response measurements collected at a first inspection Others (strain, curvatures, and inclination angles) are secondary responses obtained by manipulating the primary. In this approach, response from any section of the structure can be analysed, without the requirement for further structural information, such as flexural rigidity (EI), or distance to support, unlike similar studies in literature. The condition of a structure can then be determined by comparing response measurements collected at a first inspection

Determination of optical technology experiments for a satellite

Optical technology experiments for satellite - communications, acquisition, tracking, lasers, photometry, and atmospheric