KEYWORDS: Solar cells, Solar energy, Resistance, Energy harvesting, Prototyping, Structural health monitoring, Sensing systems, Domes, Detection and tracking algorithms, Field effect transistors
The SCANSn is a structural health monitoring (SHM) system is being developed by Acellent Technologies to monitor
steel bridges. The required voltage of the system is 14.4 V for active scanning, and the power consumption is
approximately 8 W. The investigated energy harvesting from both solar and thermal sources to recharge the lithium-ion
battery of the system. A solar panel and a Thermal Electric Generator (TEG) are used to harvest ambient energy. The
thermoelectric device is placed in a Fresnel dome to maximize the temperature gradient of the TEG. During shading of
the solar panel, the TEG continues to supply power to the battery charger. Since the output voltages and currents of the
solar and thermal energy harvesters vary significantly, the energy harvesting module is constructed by two buck-boost
converters operating in parallel. Maximal Power Point Tracking (MPPT) is employed for the buck-boost converter for
the solar panel, while a fixed duty cycle converter is used for the TEG due to substantially lower power compared with
the solar panel. The system design and measured results of a prototype system are presented. Our prototype system
successfully demonstrates that the SCANSn system can be powered by the energy harvested from solar and thermal.
Structural health monitoring technology is perceived as a revolutionary method of determining the integrity of structures
involving the use of multidisciplinary fields including sensors, materials, system integration, signal processing and
interpretation. The core of the technology is the development of self-sufficient systems for the continuous monitoring,
inspection and damage detection of structures with minimal labor involvement. A major drawback of the existing
technology for real-time structural health monitoring is the requirement for external electrical power input. For some
applications, such as missiles or combat vehicles in the field, this factor can drastically limit the use of the technology.
Having an on-board electrical power source that is independent of the vehicle power system can greatly enhance the
SHM system and make it a completely self-contained system. In this paper, using the SMART layer technology as a
basis, an Autonomous Self-powered (ASP) Structural Health Monitoring (SHM) system has been developed to solve the
major challenge facing the transition of SHM systems into field applications. The architecture of the self-powered SHM system was first designed. There are four major components included in the SHM system: SMART Layer with sensor network, low power consumption diagnostic hardware, rechargeable battery with energy harvesting device, and host computer with supporting software. A prototype of the integrated self-powered active SHM system was built for performance and functionality testing. Results from the evaluation tests demonstrated that a fully charged battery system is capable of powering the SHM system for active scanning up to 10 hours.
KEYWORDS: Sensors, Composites, Passive remote sensing, Data modeling, Failure analysis, System integration, Inverse problems, Calibration, Structural health monitoring, Systems modeling
Next generation technology of integrated health management systems for air-transportation structures will utilize
SHM methods in combination with simulation techniques for the prediction of structural degradation induced
by adverse events such as impacts. The contribution focuses on the development of an advanced real-time
monitoring system for impact loads using passive sensing networks. Starting from the fundamental approach of
real-time monitoring based on system identification models, problems of model order, signal conditioning and
efficient model training will be addressed. Finally, the load monitoring system is interactively linked to a damage
prediction module based on numerical failure analysis employing composite failure criteria. The utilization of appropriate database techniques allows a real-time prediction of impact induced damage after detection of any adverse impact event making information available on developing degradation at the earliest possible state.
In order to take full advantages of composites and enable future composite structures to operate at their physical limits
rather than limits predetermined from computational design assumptions and safety factors, there is a need to develop an
embeddable sensing system to allow a structure to "feel" and "think" its structural state. In this paper, the concept of
multi-modal sensing capabilities using a network of multifunctional sensors integrated with a structure has been
developed. Utilizing this revolutionary concept, future structures can be designed and manufactured to provide multiple
modes of information that when synthesized together can provide capabilities for intelligent sensing, environmental
adaptation and multi-functionality. To demonstrate the feasibility of multi-modal sensing capabilities with built-in sensor
network, one single type of piezoelectric sensor was selected to perform the measurements of dynamic strain,
temperature, damage detection and impact monitoring. The uniqueness of the sensing system includes (1) Flexible,
multifunctional sensor networks for integration with any type of composite structural component, (2) Scalable sensor
network for monitoring of a large composite structure, (3) Reduced number of connecting wires for sensors, (4) Hybrid
diagnostics with multiple sensing capabilities, (5) Sensor network self-diagnostics and self-repair for damaged sensor
system.
Acellent Technologies, Inc. developed a smart structural health monitoring (SHM) sensor network that can autonomously assess in real time the structural stability of buildings. The sensor network uses piezoelectric actuators and sensors to characterize damage in, and monitor the
rigidity of components of the building primary structure. Additionally, temperature sensors are integrated into the proposed sensor network to
monitor the temperature of the structural components. Acellent's existing sensor network SMART Layer technology was used as the basis for
the proposed development. The modifications to our existing technology included a redesigned sensor/actuator arrangement, the development
of a SmartDAQ sensor package with the required sensor and electronics, and additional software that provides a map of the structural damage,
temperature and rigidity information. This will be useful to provide a real time assessment of the building structural integrity. The data will be
available for display to provide and early warning to first responders and emergency personnel to ensure their safety prior to entering the
building.
Real-time monitoring the status of in-service structures such as unmanned vehicles can provide invaluable information
to detect the damages to the structures on time. The unmanned vehicles can be maintained and repaired in time if such
damages are found. One typical cause of damages of unmanned vehicles is from impacts caused by bumping into some
obstacles or being hit by some objects such as hostile fire. This paper introduces a novel impact event sensing system
that can detect the location of the impact events and the force-time history of the impact events. The system consists of
the Piezo-electric sensor network, the hardware platform and the analysis software.
The new customized battery-powered impact event sensing system supports up to 64-channel parallel data acquisition.
It features an innovative low-power hardware trigger circuit that monitors 64 channels simultaneously. The system is in
the sleep mode most of the time. When an impact event happens, the system will wake up in micro-seconds and detect
the impact location and corresponding force-time history. The system can be combined with the SMART sensing
system to further evaluate the impact damage severity.
Structural Health Monitoring (SHM) that uses integrated sensor network to provide real-time monitoring of in-service
structures can improve the safety and reliability of the structures significantly. Acellent Technologies' SHM systems
based on SMART technology consists of the integrated sensor network, diagnosis hardware platform and the diagnosis
software. This paper introduces the latest SMART damage detection hardware platform - ScanGenie and the new
analysis software for damage detection in composite and metal structures. The ScanGenie is a portable high-performance
hardware that provides many features such as through-transmission, pulse-echo, temperature measurement,
self-diagnosis, sensor diagnosis, etc. The new analysis software is based on the ScanGenie hardware to provide
functions such as temperature compensation, auto-gain adjustment, impedance-based diagnosis and probability of
detection. The system can be used for damage detection in most composite and metal structures such as aircraft,
spacecraft and civil infrastructures.
It is essential to ensure the safety and reliability of in-service structures such as unmanned vehicles by detecting
structural cracking, corrosion, delamination, material degradation and other types of damage in time. Utilization of an
integrated sensor network system can enable automatic inspection of such damages ultimately. Using a built-in network
of actuators and sensors, Acellent is providing tools for advanced structural diagnostics. Acellent's integrated structural
health monitoring system consists of an actuator/sensor network, supporting signal generation and data acquisition
hardware, and data processing, visualization and analysis software.
This paper describes the various features of Acellent's latest SMART sensing system. The new system is USB-based
and is ultra-portable using the state-of-the-art technology, while delivering many functions such as system self-diagnosis,
sensor diagnosis, through-transmission mode and pulse-echo mode of operation and temperature
measurement. Performance of the new system was evaluated for assessment of damage in composite structures.
A novel piezoelectric/fiber-optic system is developed for long-term health monitoring of aerospace vehicles and structures. The hybrid diagnostic system uses the piezoelectric actuators to input a controlled excitation to the structure and the fiber optic sensors to capture the corresponding structural response. The aim of the system is to detect changes in structures such as those found in aerospace applications (damage, cracks, aging, etc.). This system involves the use of fiber Bragg gratings, which may be either bonded to the surface of the material or embedded within it in order to detect the linear strain component produced by the excitation waves generate by an arbitrary waveform generator. Interrogation of the Bragg gratings is carried out using a high speed fiber grating demodulation unit and a high speed data acquisition card to provide actuation input. With data collection and information processing; is able to determine the condition of the structure. The demands on a system suitable for detecting ultrasonic acoustic waves are different than for the more common strain and temperature systems. On the one hand, the frequency is much higher, with typical values for ultrasonic frequencies used in non-destructive testing ranging from 100 kHz up to several MHz. On the other hand, the related strain levels are much lower, normally in the μstrain range. Fiber-optic solutions for this problem do exist and are particularly attractive for ultrasonic sensing as the sensors offer broadband detection capability.
Currently, there exist several different types of structural health monitoring (SHM) systems that are in the stage of development and/or are being tested for use in real-world applications. For a number of years, Structural Health Monitoring (SHM) systems have demonstrated feasibility in laboratory and controlled testing environments. Acellent has been developing and testing strategies to bring the SHM field to the next level. These include issues involved with system installation, calibration, reliability and connections for structures fabricated with composite materials. Composite structures are susceptible to hidden or barely visible damage caused by impacts and/or excessive loads that if unchecked may lead to lower structural reliability, higher life-cycle costs, and loss in operational capability. Current maintenance and inspection techniques for in-service composite structures can be labor-intensive and time-consuming. Utilization of an integrated sensor network system such as that developed by Acellent can greatly reduce the inspection burden through fast in-situ data collection and processing. Using a built-in network of actuators and sensors, Acellent Technologies is providing the tools required for a practical SHM system. In this paper, key development and testing issues concerning real-world implementation of the SHM system on composite structures are presented.
The SMART Layer (reg. TM) manufactured by Acellent is a thin flexible layer with a network of miniature piezoelectric actuators
and sensors that can be embedded inside or mounted onto metal and composite structures to acquire information on
structural integrity. Currently, SMART Layers (reg. TM) are used to assess the condition of structures and to monitor impact
events. The layers can be used to perform built-in structural inspection by exciting the devices with a periodic or
transient burst controlled input and analyzing the corresponding structural response. The technology can also be applied
to areas concerned with Homeland Security. For example, the technology can be used for motion monitoring and
monitoring of structures used in defense applications. By having a network of sensors that monitor loads on a structure, it
is possible to monitor the movement of people by measuring the loads exerted by them. The SMART Layer (reg. TM) technology
can be used to enhance the readiness of structures used for homeland defense such as manned and unmanned aircraft,
missiles and radar systems. It can also be used to monitor a pipeline network for any terrorist related activity that can
potentially damage the pipe system. A brief overview of such potential applications is presented here.
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