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Articles 31621 - 31650 of 36832

Full-Text Articles in Engineering

Optimization And Comparison Of Broadband Monopoles, Z. N. Chen, M.Y. W. Chia, Max Ammann Jan 2003

Optimization And Comparison Of Broadband Monopoles, Z. N. Chen, M.Y. W. Chia, Max Ammann

Articles

The impedance and radiation properties of four broadband monopoles are compared and the parameters of a new roll monopole are optimised experimentally and numerically. The performances of the roll monopole with various numbers of roll turns are discussed and optimised numerically. The measurements and simulations show that, compared with conventional broadband monopoles, the roll monopole

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Design Criteria And Optical Characteristics Of One-Dimensional Photonic Crystals Based On Periodically Grooved Silicon, Vladimir Tolmachev, Tatiana Perova, Kevin Berwick Jan 2003

Design Criteria And Optical Characteristics Of One-Dimensional Photonic Crystals Based On Periodically Grooved Silicon, Vladimir Tolmachev, Tatiana Perova, Kevin Berwick

Articles

Photonic bandgap (PBG) regions have been calculated for periodically grooved Si structures, acting as a one-dimensional photonic crystal. The wavelength range of the PBG as a function of the ratio (DSi/A) is presented, where DSi is the width of the Si walls and A is the grooved silicon lattice constant. The influence of the parameter DSi, the refractive index of the space between the Si walls and the number of structure periods, m, on the forming of PBG regions is discussed. A good correlation between the calculated and the experimentally observed …

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Study Of Structure And Quality Of Different Silicon Oxides Using Ftir And Raman Microscopy, C. Moore, T. S. Perova, B. Kennedy, Kevin Berwick, I. I. Shaganov, R. A. Moore Jan 2003

Study Of Structure And Quality Of Different Silicon Oxides Using Ftir And Raman Microscopy, C. Moore, T. S. Perova, B. Kennedy, Kevin Berwick, I. I. Shaganov, R. A. Moore

Articles

In this work, SiO2 and fluorine and phosphorous doped SiO2 thin films are investigated using FTIR and Raman techniques. FTIR spectroscopy was performed at normal and oblique incidence of the probe beam in transmission and reflection modes. The effect of polarisation and angle of incidence of the probe beam is examined for the case of reflection mode. Infrared spectra taken from doped oxides show that the structure changes with the passage of time. Alternate methods to calculate the thickness of the doped film are therefore discussed. Infrared spectra of electron beam evaporated oxides give valuable information on their …

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On Stability Of Affine Blending Systems, Ruiyao Gao, Aidan O'Dwyer, Seamus Mcloone, Eugene Dermot Coyle Professor Jan 2003

On Stability Of Affine Blending Systems, Ruiyao Gao, Aidan O'Dwyer, Seamus Mcloone, Eugene Dermot Coyle Professor

Conference papers

This paper presents a novel approach to stability analysis of affine blending systems. The analysis is based on Quadratic Lyapunov functions. The approach considers the nonlinear offset term in affine blending systems as non-vanishing perturbations added to the corresponding nominal linear blending systems. The affine blending systems will be bounded if the corresponding linear blending system is exponentially stable. The bound is determined by an ultimate limit, which is proportional to the maximum of the offset terms of each affine system.

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An Outline And Further Development Of Smith Predictor Based Methods For The Compensation Of Processes With Time Delay, Pauline Sourdille, Aidan O'Dwyer Jan 2003

An Outline And Further Development Of Smith Predictor Based Methods For The Compensation Of Processes With Time Delay, Pauline Sourdille, Aidan O'Dwyer

Conference papers

An extensive literature review is presented and a new modified Smith predictor is subsequently presented.

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Pid Compensation Of Time Delayed Processes 1998-2002: A Survey, Aidan O'Dwyer Jan 2003

Pid Compensation Of Time Delayed Processes 1998-2002: A Survey, Aidan O'Dwyer

Conference papers

A time delay may be defined as the time interval between the start of an event at one point in a system and its resulting action at another point in the system. Delays are also known as transport lags or dead times; they arise in physical, chemical, biological and economic systems, as well as in the process of measurement and computation. Methods for the compensation of time delayed processes may be broadly divided into proportional integral derivative (PID) based controllers, in which the controller parameters are adapted to the controller structure, and structurally optimised controllers, in which the controller structure …

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System Identification Using Higher Order Spectra, Aidan O'Dwyer Jan 2003

System Identification Using Higher Order Spectra, Aidan O'Dwyer

Conference papers

This communication will explore the use of particular types of frequency domain concepts, labelled higher order spectra, to help determine the frequency response of a process. This will allow the identification of the parameters of a single input, single output (SISO) model for a process (which includes a time delay), in both open loop and closed loop environments.

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Query-Based Learning For Aerospace Applications, Donald C. Wunsch, Emad W. Saad, J. J. Choi, J. L. Vian Jan 2003

Query-Based Learning For Aerospace Applications, Donald C. Wunsch, Emad W. Saad, J. J. Choi, J. L. Vian

Electrical and Computer Engineering Faculty Research & Creative Works

Models of real-world applications often include a large number of parameters with a wide dynamic range, which contributes to the difficulties of neural network training. Creating the training data set for such applications becomes costly, if not impossible. In order to overcome the challenge, one can employ an active learning technique known as query-based learning (QBL) to add performance-critical data to the training set during the learning phase, thereby efficiently improving the overall learning/generalization. The performance-critical data can be obtained using an inverse mapping called network inversion (discrete network inversion and continuous network inversion) followed by oracle query. This paper …

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Smart Bridges With Fiber-Optic Sensors, Steve Eugene Watkins Jan 2003

Smart Bridges With Fiber-Optic Sensors, Steve Eugene Watkins

Electrical and Computer Engineering Faculty Research & Creative Works

This article describes an approach to bridge improvements that uses smart structures, introduces key technologies for health monitoring systems based on fiber optics and gives an overview of two instrumented bridges. A sensing system in one application monitors general performance and health of the structure, while the system in a second application interrogates the behavior of a major structural repair.

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Statistical Simulation Models For Rayleigh And Rician Fading, Chengshan Xiao, Y. Rosa Zheng, N. C. Beaulieu Jan 2003

Statistical Simulation Models For Rayleigh And Rician Fading, Chengshan Xiao, Y. Rosa Zheng, N. C. Beaulieu

Electrical and Computer Engineering Faculty Research & Creative Works

New simulation models are proposed for Rayleigh and Rician fading channels. First, the statistical properties of Clarke's fading model with a finite number of sinusoids are analyzed. An improved Clarke's model is then proposed for the simulation of Rayleigh fading channels. Based on this improved Rayleigh fading model, a novel simulation model is proposed for Rician fading channels. The new Rician fading model employs a zero-mean stochastic sinusoid as the specular (line-of-sight) component, in contrast to all existing Rician fading simulators that utilize a non-zero mean deterministic specular component. The statistical properties of the proposed Rician fading model are analyzed …

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The Development Of A Closed-Form Expression For The Input Impedance Of Power-Return Plane Structures, Minjia Xu, Todd H. Hubing Jan 2003

The Development Of A Closed-Form Expression For The Input Impedance Of Power-Return Plane Structures, Minjia Xu, Todd H. Hubing

Electrical and Computer Engineering Faculty Research & Creative Works

In multilayer printed circuit boards, the noise on the power bus is influenced by the impedance between the power and ground planes. Power-bus noise estimates require an accurate estimate of the power-bus input impedance. This paper develops a closed-form estimate of the input impedance for circular power-return plane structures. When the structure is lossy (e.g., boards employing embedded capacitance or densely populated boards), the energy reflected from the board edge does not significantly affect the input impedance. In general, the expressions developed here for circular structures can be used to estimate the impedance of lossy power-return plane structures of any …

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The Subcircuit Extraction Problem, Nian Zhang, Donald C. Wunsch, Frank Harary Jan 2003

The Subcircuit Extraction Problem, Nian Zhang, Donald C. Wunsch, Frank Harary

Electrical and Computer Engineering Faculty Research & Creative Works

The steady down scaling of CMOS device dimensions has been the main stimulus to the growth of microelectronics and computer aided very large scale integration (VLSI) design. But the more an integrated circuit (IC) is scaled, the higher its packing density becomes. The increasing size of chips, measured in either area or number of transistors, and the waste of the large capital investment involved in fabricating and testing circuits that do not work, make layout analysis and verification an important part of physical design automation. The most efficient way to overcome these difficulties is to identify a related collection of …

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A Continually Online Trained Neurocontroller For The Series Branch Control Of The Upfc, Ganesh K. Venayagamoorthy, Radha P. Kalyani Jan 2003

A Continually Online Trained Neurocontroller For The Series Branch Control Of The Upfc, Ganesh K. Venayagamoorthy, Radha P. Kalyani

Electrical and Computer Engineering Faculty Research & Creative Works

The crucial factor affecting the modern power systems today is load flow control. The Unified Power Flow Controller (UPFC) provides an effective means for controlling the power flow and improving the transient stability in a power network. The UPFC has fast complex dynamics and its conventional control is based on a linearized model of the power system. This paper presents the design of a neurocontroller that controls the power flow and regulates voltage along a transmission line. The continually online neurocontroller is used for controlling the series inverter of UPFC. Simulation results carried out in the PSCAD/EMTDC environment are presented …

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A Discrete-Time Model For Spatio-Temporally Correlated Mimo Wssus Multipath Channels, Chengshan Xiao, Jingxian Wu, Sang-Yick Leong, Y. Rosa Zheng, Khaled Ben Letaief Jan 2003

A Discrete-Time Model For Spatio-Temporally Correlated Mimo Wssus Multipath Channels, Chengshan Xiao, Jingxian Wu, Sang-Yick Leong, Y. Rosa Zheng, Khaled Ben Letaief

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a statistical discrete-time model is proposed for simulating wideband MIMO channels which experience spatially and temporally correlated, widesense stationary uncorrelated scattering (WSSUS) multipath Rayleigh fading. A new method is also presented to efficiently generate the correlated MIMO channel coefficients, which can be used for accurate simulation of physical continuous-time MIMO channel. The statistic accuracy of the discrete-time MIMO channel model is rigorously verified through theoretical analysis and extensive simulations in different criteria.

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A Dynamic Model Of Induction Generators For Wind Power Studies, Badrul H. Chowdhury, Srinivasa R. Chellapilla Jan 2003

A Dynamic Model Of Induction Generators For Wind Power Studies, Badrul H. Chowdhury, Srinivasa R. Chellapilla

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents an induction generator model that can be used for simulations to investigate and evaluate the control strategies for variable speed operation of doubly fed induction generators driven by wind turbines in transient conditions. The model makes use of rotor reference frame.

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A Nested Sensor Array Focusing On Near Field Targets, Y. Rosa Zheng, M. El-Tanany, R. A. Goubran Jan 2003

A Nested Sensor Array Focusing On Near Field Targets, Y. Rosa Zheng, M. El-Tanany, R. A. Goubran

Electrical and Computer Engineering Faculty Research & Creative Works

A nested virtual array subband beamforming system is proposed for applications where broadband signal targets are located within the near field of the array. Subband multirate processing and near field beamforming techniques are used jointly for the nested array to improve the performances and reduce the computational complexity. A new noise model, namely the broadband near field spherically isotropic noise model, is also proposed for the optimization design of near field beamformers. It is shown that near field beamforming is essential for better distance discrimination of near field targets, reduced beampattern variations for broadband signals, and stronger reverberation suppression.

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A Statistical Simulation Model For Mobile Radio Fading Channels, Chengshan Xiao, Y. Rosa Zheng Jan 2003

A Statistical Simulation Model For Mobile Radio Fading Channels, Chengshan Xiao, Y. Rosa Zheng

Electrical and Computer Engineering Faculty Research & Creative Works

Recently, a Clarke's model-based simulator was proposed for Rayleigh fading channels. However, that model, as shown in this paper, may encounter statistic deficiency. Therefore, an improved model is presented to remove the statistic deficiency. Furthermore, a new simulation model is proposed for Rician fading channels. This Rician fading simulator with finite number of sinusoids plus a zero-mean stochastic sinusoid as the specular (line-of-sight) component is different from all the existing Rician fading simulators, which have non-zero mean deterministic specular component. The statistical properties of the proposed Rayleigh and Rician fading channel models are analyzed in detail, which shows that these …

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A Study Of The Probe Induced Disturbances On The Near-Field Measurement, Jin Shi, Richard E. Dubroff, Kevin P. Slattery, Masahiro Yamaguchi, K.-I. Arai Jan 2003

A Study Of The Probe Induced Disturbances On The Near-Field Measurement, Jin Shi, Richard E. Dubroff, Kevin P. Slattery, Masahiro Yamaguchi, K.-I. Arai

Electrical and Computer Engineering Faculty Research & Creative Works

Numerical simulations were used to investigate the disturbance introduced by placing a small magnetic loop probe in the near field of a driven loop. In the absence of the loop probe, the numerical simulations were compared with an approximate closed-form analytical expression for the magnetic field produced by the driven loop. The agreement between the approximate analytical results and the simulation was good. The next set of simulations was based on a physical model that included the probe and showed that the probe does exert an effect on the field being measured. Examples of these simulations and their implications on …

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Adaptive Critic Design Based Neurocontroller For A Statcom Connected To A Power System, Salman Mohagheghi, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley Jan 2003

Adaptive Critic Design Based Neurocontroller For A Statcom Connected To A Power System, Salman Mohagheghi, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

A novel nonlinear optimal neurocontroller for a static compensator (STATCOM) connected to a power system using artificial neural networks is presented in this paper. The heuristic dynamic programming (HDP), a member of the adaptive critic designs (ACDs) family, is used for the design of the STATCOM neurocontroller. This neurocontroller provides nonlinear optimal control with better performance compared to the conventional PI controllers.

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Adaptive Critic Designs And Their Implementations On Different Neural Network Architectures, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley Jan 2003

Adaptive Critic Designs And Their Implementations On Different Neural Network Architectures, Jung-Wook Park, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

The design of nonlinear optimal neurocontrollers based on the Adaptive Critic Designs (ACDs) family of algorithms has recently attracted interest. This paper presents a summary of these algorithms, and compares their performance when implemented on two different types of artificial neural networks, namely the multilayer perceptron neural network (MLPNN) and the radial basis function neural network (RBFNN). As an example for the application of the ACDs, the control of synchronous generator on an electric power grid is considered and results are presented to compare the different ACD family members and their implementations on different neural network architectures.

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Analysis Of Simple Two-Capacitor Low-Pass Filters, Todd H. Hubing, David Pommerenke, Theodore M. Zeeff, Thomas Van Doren Jan 2003

Analysis Of Simple Two-Capacitor Low-Pass Filters, Todd H. Hubing, David Pommerenke, Theodore M. Zeeff, Thomas Van Doren

Electrical and Computer Engineering Faculty Research & Creative Works

The performance of typical low-pass capacitor filters is limited by the mutual inductance between the input and output sides of the filter. This paper describes how two appropriately spaced capacitors can be used to construct a low-pass filter with significantly better high-frequency performance than a one-capacitor filter. Laboratory measurements and numerical simulations are used to quantify the mutual inductance and compare the performance of one- and two-capacitor low-pass filters.

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A Comparison Of Dual Heuristic Programming (Dhp) And Neural Network Based Stochastic Optimization Approach On Collective Robotic Search Problem, Nian Zhang, Donald C. Wunsch Jan 2003

A Comparison Of Dual Heuristic Programming (Dhp) And Neural Network Based Stochastic Optimization Approach On Collective Robotic Search Problem, Nian Zhang, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

An important application of mobile robots is searching a region to locate the origin of a specific phenomenon. A variety of optimization algorithms can be employed to locate the target source, which has the maximum intensity of the distribution of some detected function. We propose two neural network algorithms: stochastic optimization algorithm and dual heuristic programming (DHP) to solve the collective robotic search problem. Experiments were carried out to investigate the effect of noise and the number of robots on the task performance, as well as the expenses. The experimental results showed that the performance of the dual heuristic programming …

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A Numerical Investigation Of Interior Resonances In The Hybrid Fem/Mom Method, Yun Ji, Hao Wang, Todd H. Hubing Jan 2003

A Numerical Investigation Of Interior Resonances In The Hybrid Fem/Mom Method, Yun Ji, Hao Wang, Todd H. Hubing

Electrical and Computer Engineering Faculty Research & Creative Works

The interior resonance problem that can occur when using a hybrid finite-element method/method of moments (FEM/MoM) method to model electromagnetic scattering problems is investigated. Calculations of the bistatic radar cross section of a coated dielectric sphere are presented using different formulations, solution approaches, and solvers. The solutions using the electric-field integral equation have significant errors near an interior resonance frequency. When the combined-field integral equation is employed, satisfactory solutions can be obtained that do not depend on the particular solution approach or solver.

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Fuzzy Logic In Collective Robotic Search, Nian Zhang, Donald C. Wunsch Jan 2003

Fuzzy Logic In Collective Robotic Search, Nian Zhang, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

One important application of mobile robots is searching a geographical region to locate the origin of a specific sensible phenomenon. We first propose a fuzzy logic approach using a decision table. A novel fuzzy rule based was designed. And then a fuzzy search strategy is adopted by utilizing the three tier centers of mass coordination. Experimental results show that fuzzy logic algorithm is an efficient approach for the collective robots to locate the target source. In addition, noise and the position of the target affect the searching result.

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Locating Moving Objects Over Mobile Sensor Network, Arvind Nath Rapaka, Sandeep Bogollu, Donald C. Wunsch, Ravindra Nath Jan 2003

Locating Moving Objects Over Mobile Sensor Network, Arvind Nath Rapaka, Sandeep Bogollu, Donald C. Wunsch, Ravindra Nath

Electrical and Computer Engineering Faculty Research & Creative Works

The purpose of our on going research would be to track entities, which enter their field of vision over the sensor network. Based on their sightings, they maintain a dynamic cache that can be queried by a base station- a stationary orfixed node. Since transmitting messages consumes a lot of energy, as against local processing and moreover the limited energy in sensor node does not allow heavy duty computing, we need to develop algorithms that will ensure efficient computing and minimal transmission without degradation of performance. and also data is stored locally, and memory is finite, the nodes must choose …

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Multilevel Converter-Based Dual-Frequency Induction Heating Power Supply, B. Diong, S. Basireddy, Keith Corzine Jan 2003

Multilevel Converter-Based Dual-Frequency Induction Heating Power Supply, B. Diong, S. Basireddy, Keith Corzine

Electrical and Computer Engineering Faculty Research & Creative Works

Most existing power supplies for induction heating equipment produce voltage at a single (adjustable) frequency. Recently, however, induction heating power supplies that produce voltage at two (adjustable) frequencies have been researched and even commercialized. Dual-frequency power supplies are a significant development for heat-treating workpieces with uneven geometries, such as gears, since different portions of such workpieces are heated dissimilarly at a single frequency and so require a two step process using a single-frequency power supply. On the other hand, a dual-frequency power supply can achieve the desired result for such workpieces in a one step process. However, the existing approaches …

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Multilevel Inverter-Based Dual-Frequency Power Supply, B. Diong, Keith Corzine, S. Basireddy, Shuai Lu Jan 2003

Multilevel Inverter-Based Dual-Frequency Power Supply, B. Diong, Keith Corzine, S. Basireddy, Shuai Lu

Electrical and Computer Engineering Faculty Research & Creative Works

Most existing power supplies for induction heating equipment produce voltage at a single (adjustable) frequency. Recently, however, induction heating power supplies that produce voltage at two (adjustable) frequencies simultaneously have been introduced and commercialized. These represent a significant development particularly for heat-treating workpieces with uneven geometries, such as gears. Still, the existing approaches to dual-frequency voltage generation could be improved upon to achieve better control, higher efficiency, and reduced electromagnetic interference. This letter proposes the use of multilevel inverters for providing power at two frequencies simultaneously. It describes how the stepping angles for the desired output from such inverters can …

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Pcb Emc Design Guidelines: A Brief Annotated List, Todd H. Hubing Jan 2003

Pcb Emc Design Guidelines: A Brief Annotated List, Todd H. Hubing

Electrical and Computer Engineering Faculty Research & Creative Works

Some of the worst printed circuit board design choices are made by engineers who are trying to comply with a list of EMC design guidelines. Nevertheless, a short list of design guidelines can be helpful at times. This paper reviews some of the more general EMC design guidelines for printed circuit board layout.

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Evolving Digital Circuits Using Particle Swarm, Ganesh K. Venayagamoorthy, Venu Gopal Gudise Jan 2003

Evolving Digital Circuits Using Particle Swarm, Ganesh K. Venayagamoorthy, Venu Gopal Gudise

Electrical and Computer Engineering Faculty Research & Creative Works

Particle swarm optimization (PSO) motivated by the social behavior of organisms is proposed for evolution of combinational logic circuits. Results are presented to show that PSO based evolution of digital circuits are equivalent to or even with better solutions (with minimum number of logic gates) than that of a human designer and other genetic algorithm (GA) based techniques. This PSO based approach converges faster than other approaches reported in literature using genetic algorithms and as a result the computational intensity involved in hardware evolution is reduced. Examples taken from the literature are used to evaluate the performance of the proposed …

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Fatigue Testing Of A Composite Propeller Blade Using Fiber-Optic Strain Sensors, Steve Eugene Watkins, V. E. Zetterlind Iii, M. W. Spoltman Jan 2003

Fatigue Testing Of A Composite Propeller Blade Using Fiber-Optic Strain Sensors, Steve Eugene Watkins, V. E. Zetterlind Iii, M. W. Spoltman

Electrical and Computer Engineering Faculty Research & Creative Works

The performance of surface-mounted extrinsic Fabry-Perot interferometric (EFPI) sensors during a seventeen-million-cycle, high-strain fatigue test is reported. Fiber-optic strain measurements did not degrade during the test. The sensors were applied to a composite propeller blade subject to a constant axial load and a cyclic bending load. Strain measurements were taken at four blade locations using two types of EFPI sensors and co-located electrical resistance strain gages. Static and dynamic strain measurements were taken daily during the 65 days of this standard propeller-blade test. All fiber-optic sensors survived the fatigue test while most of the resistive gages failed. The suitability of …

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