The evaluation, health monitoring and response prediction of soil and soil-structure systems during construction and
due to extreme hazard conditions are on the verge of a significant paradigm shift. New and less expensive sensing
technologies have enabled the development of innovative instrumentation and advanced interactive modeling tools.
These tools, combined with recent advances in information technology including wireless sensor networking, data
mining, visualization and system identification, promise significant improvements in real time monitoring during
construction, sensor-assisted design and early warning of impending failure. This paper presents the newly
developed Wireless Shape-Acceleration Array (WSAA) sensor that measures multi-dimensional acceleration and
deformation profiles and constitutes a major step toward autonomous monitoring technology for soil and soil-structure
systems. The Wireless Shape-Acceleration Array (WSAA) sensor employs micro-machined
electromechanical sensors (MEMS), which have enabled gravity-based shape calculation along a sensorized
substrate. The method is an extension of technologies that use fiber optic orientation sensing to calculate 3D
polylines representing the shape of a sensor array. WSAA uses MEMS accelerometers in a pre-calibrated,
geometrically constrained array to provide long-term stability previously unattainable with fiber optic methods. This
sensor array is capable of measuring 2D soil acceleration and 3D permanent ground deformations to a depth of one
hundred meters. Each sensor array is connected to a wireless earth station to enable real time monitoring of a wide
range of soil and soil-structure systems as well as remote sensor configuration. This paper presents the evolving
design of this new sensor array as well as lessons learned from two field installations of this sensor.
This paper describes SHAPE TAPE, a thin array of fiber optic curvature sensor laminated on a ribbon substrate, arranged to sense bend and twist. The resulting signals are used to build a 3D computer model containing six degrees of freedom position and orientation information for any location along the ribbon. The tape can be used to derive dynamic or static shape information from objects to which it is attached or scanned over. This is particularly useful where attachment is only partial, since shape tape 'knows where it is' relative to a starting location. Measurements can be performed where cameras cannot see, without the use of magnetic fields. Applications include simulation, film animation, computer aided design, robotics, biomechanics, and crash testing.
This talk describes the development and evaluation of bi- directional fiber-optic based low airflow sensors for use in solvent containing elevated temperature manufacturing process environments. The sensors developed are based on Measureand Inc. cantilever beam optical fiber bend sensors. Customized paddles are added to match sensor output to the range of airflows under investigation. This talk discuses the sensor requirements, sensors' design, calibration, manufacturing process installation and testing process worthy prototypes in an elevated temperature solvent containing environment.
BEAM sensors include treated loops of optical fiber that modulate optical throughput with great sensitivity and linearity, in response to curvature of the loop out of its plane. This paper describes BEAM sensors that have two loops treated in opposed fashion, hermetically sealed in flexible laminations. The sensors include an integrated optoelectronics package that extracts curvature information from the treated portion of the loops while rejecting common mode errors. The laminated structure is used to sense various parameters including displacement, force, pressure, flow, and acceleration.
Bend enhanced fiber (BEF) sensors are curvature-measuring optical analogs of elongation- measuring resistance strain gauges. They are made by treating optical fibers to have an optically absorptive zone along a thin axial stripe a few millimeters long. Light transmission through the fiber past this zone then becomes a robust function of curvature, three orders of magnitude more sensitive to bending than in the untreated fiber. Directionality and polarity of curvature are preserved in the light transmission function, over a linear range covering five orders of magnitude, centered about zero curvature. This paper describes a project in which BEF sensors were used to improve teleoperation of a small mobile robot, by instrumenting joint angles, an extension, and four forces. The operator, who formerly had only a televised view from a camera on the robot, now has additional information on a computer screen showing these parameters in graphical form. This information, provided entirely from fiber optic sensors, makes it considerably easier to manipulate the robot. The project also included demonstrations of a multiplexing system for larger BEF arrays, use of BEF sensors in prosthetics, and plasma enhanced chemical vapor deposition of a light absorptive coating on BEF sensors.
This paper describes novel bend enhanced fiber (BEF) sensors used to make continuous, linear, real-time measurements of curvatures, which often relate more directly than strains to the control of vibration and position. BEF sensors are made by treating optical fibers to have an optically absorptive zone along a thin axial stripe a few millimeters long. Light transmission through the fiber past this zone then becomes a robust function of curvature, three orders of magnitude more sensitive to bending than in the untreated fiber. Directionality and polarity of curvature are preserved in the transmission function, over a linear range covering five orders of magnitude, centered about zero curvature. Thus, BEF sensors are curvature-measuring optical analogs of elongation-measuring resistance strain gauges, with similar sensitivity. BEF sensors add little or no thickness to the fiber, can be instrumented with simple analog electronics, and have been successfully embedded in composites. Results of dynamic curvature measurements are included, along with characterization data for BEF sensors made with plastic and silica fibers as small as 125 microns.
Continuous and discrete liquid level measurements made with fiber optic sensors generally depend on refraction of light in the liquid to be measured. Problems, including erratic or incorrect readings, arise when the index of refraction of the liquid is near that of the outer surface of the optical probe. This is often the case for common optical probe materials and many organic compounds including fuels and lubricants. This paper describes a continuous liquid level sensor which operates over a wide range of indices. The lower limit of the range is determined by an intermediate optical material in the probe, rather than the material of the outer surface; there is no upper limit. The liquid being measured may have any index equal to or greater than that of the intermediate material. Water is used as the intermediate material in the sensor to be described; it surrounds a lambertian fiber optic emitter and detector pair. The sensor is linear within +/- 5 percent over a five-inch measurement span, for liquids of any index equal to or greater than 1.33, even though the outer surface of the probe is fused quartz, with an index of 1.46. Since most liquids have an index greater than that of water, and many liquids of interest have an index near that of quartz or glasses, this method greatly extends the range of liquids that can be measured with a given sensor.
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