Determination Of Impact Location Research Articles

Multichannel Real-Time Electronics Platform for the Estimation of the Error in Impact Localization with Different Piezoelectric Sensor Densities

The work presents a structural health monitoring (SHM) electronic system with real-time acquisition and processing for the determination of impact location in laminate. The novelty of this work is the quantitative evaluation of impact location errors using the Lamb wave guided mode S0, captured and processed in real-time by up to eight piezoelectric sensors. The differential time of arrival is used to minimize an error function for the position estimation. The impact energy is correlated to the amplitudes of the antisymmetric (A0) mode and the electronic design is described to avoid saturation for signal acquisition. The same electronic system is designed to acquire symmetric (S0) low level signals by adequate gain, bandwidth, and signal-to-noise ratio. Such signals propagate into a 1.4 mm thick aluminum laminate at the group velocity of 5150 m/s with frequency components above 270 kHz, and can be discriminated from the A0 mode to calculate accurately the differential arrival time. The results show that the localization error stabilizes at a value comparable with the wavelength of the S0 mode by increasing the number of sensors up to six, and then remains constant at up to eight sensors. This suggests that a compromise can be found between sensor density and localization error.

Predicting golf ball launch characteristics using iron clubhead presentation variables and the influence of mishits

In golf, it is well understood that the interaction between the clubhead and ball determines the initial ball launch conditions. Specific knowledge regarding these relationships for iron clubs, particularly when clubhead and turf interactions are considered, would be both novel and of benefit to practitioners. Linear regression analysis was used to determine relationships between selected clubhead presentation and shot outcome variables for a sample of 1127 ‘5-iron’ shots hit from natural turf by 96 golfers. As expected, clubhead speed was the most significant predictor of ball speed, with obliquity of impact and eccentricity of the impact location making smaller, yet statistically significant contributions. Marginally ‘fat’ strikes, whereby the leading edge of the clubhead was only slightly beneath the ground at impact, appeared to have a lesser effect than expected in terms of ball speed. Effective loft was found to be the strongest predictor of vertical launch angle, whilst clubhead speed and spin loft had the greatest influence in the model for predicting total spin; inclusion of ‘thin’ strikes (i.e. those struck with the leading edge) appeared to create a non-linear element to these models and consequently overestimated the influence of vertical impact location in both cases. These findings suggest that determination of impact location, particularly for instances whereby ball contact is not wholly on the club face, is critical in research concerning irons. Overall, this study makes an original contribution to the understanding of 5-iron shot outcomes based on clubhead presentation characteristics.

Pipeline two-dimensional impact location determination using time of arrival with instant phase (TOAIP) with piezoceramic transducer array

An impact event on a pipeline generates stress waves that travel along the pipeline, and the traveling stress waves can be easily detected by distributed piezoceramic transducers. To pinpoint impact location on a pipeline, the time of arrival (TOA) is commonly used and the envelope calculated by the Hilbert transform is an effective method to determine the TOA. However, the envelope used to extract the TOA depends on the manual selection of the trigger threshold. In fact, the instant phase, that changes regularly from -pi to pi as the stress wave travels, is an important characteristic parameter of the signal, and the TOA can be determined by the periodicity of the instant phase. However, this fact has been overlooked in calculating TOA in the literature. In this paper, a new method, time of arrival with instant phase (TOAIP), is developed to calculate the TOA without the need of manual selection of the threshold. Taking into account the non-stationarity of the signal and noise interference, short time window Fourier transform and band-pass filter are utilized to extract the useful signal, the TOA is then determined by using the instant phase which is based both the first zero-crossing point of signal and the periodicity of the phase. In general, most of the pipeline impact localization realize one-dimensional positioning along its length direction. Another novelty of this paper is the development of the two-dimensional impact location (TDIL) that can estimate the impact location information along both length and circumferential directions. Experimental studies based on pipeline with distributed lead zirconate titanate (PZT) transducers mounted on the surface of the pipeline are carried out in this research. Both of physical measurements and inversion results have verified the accuracy and reliability of TOAIP and TDIL on the pipeline.

Impact location determination on thin laminated composite plates using an NIR-FBG sensor system

An integration of Structural Health Monitoring (SHM) into composite structures contribute towards the development of smart composites structure. Smart-structure offers an ability have a continuous and real-time information of its circumstances under critical loading applications. One of the main objectives in this research study was the development of the Fiber Bragg grating (FBG) sensor system for SHM of thin composite laminates. Not only that, this work has been utilizing the FBG sensors in the Near Infra-red (NIR) range; ∼830nm, as an alternative to the applications of the conventional 1550nm FBG sensors. The capability of this sensor system was validated with the impact location determination test on a thin composite plate. It showed a very promising result whereby the relative error falls below 10%.

Augmented Reality to Support On-Field Post-Impact Maintenance Operations on Thin Structures

This paper proposes an augmented reality (AR) strategy in which a Lamb waves based impact detection methodology dynamically interacts with a head portable visualization device allowing the inspector to see the estimated impact position (with its uncertainty) and impact energy directly on the plate-like structure. The impact detection methodology uses a network of piezosensors bonded on the structure to be monitored and a signal processing algorithm (the Warped Frequency Transform) able to compensate for dispersion the acquired waveforms. The compensated waveforms yield to a robust estimation of Lamb waves difference in distance of propagation (DDOP), used to feed hyperbolic algorithms for impact location determination, and allow an estimation of the uncertainty of the impact positioning as well as of the impact energy. The outputs of the impact methodology are passed to a visualization technology that yielding their representation in Augmented Reality (AR) is meant to support the inspector during the on-field inspection/diagnosis as well as the maintenance operations. The inspector, in fact, can see interactively in real time the impact data directly on the surface of the structure. To validate the proposed approach, tests on an aluminum plate are presented. Results confirm the feasibility of the method and its exploitability in maintenance practice.

Localizations and force reconstruction of low-velocity impact in a composite panel using optical fiber sensors

A new approach of monitoring low-velocity impact events on composite structures was presented and experimentally evaluated. In this approach, impact strain histories of a composite plate were measured with optical fiber sensors. The recorded signals were used to estimate locations and forces of low-velocity impact events. For experimental validation, four-sensor heads were surface mounted at the four corners of a composite panel. The optical sensors caught dynamic strain due to impacts on the panel, and the optical cables transmitted wavelength changes of the sensors. The multiplexed wavelength changes were measured using a high-speed fiber Bragg grating interrogator for the determination of impact location. The locations of impact events were estimated using a neural network program and measured signals. The estimated locations and converted strain signals were taken as the inputs to the process of reconstructing impact forces. Even though the current study is an initial investigation on a simple impact problem, the result shows the possibility that the proposed technique can be applied to low-velocity impact monitoring of general composite structures.

Determination of impact location on composite stiffened panels

In this work a methodology for impact identification on composite stiffened panels using piezoceramic sensors has been presented. A large number of impacts covering a wide range of energies (corresponding to small and large mass impacts) at various locations of a composite stiffened panel have been simulated using the finite element (FE) method. To predict the impact location, artificial neural networks have been established using the data generated from FE analyses. A number of sensor signal features have been examined as inputs to the neural network and the effect of noise on the predictions has been investigated. The results of the study show that the trained network is capable of locating impacts with different energies at different locations (e.g. in the bay, over/under the stringer and on the foot of the stringer) in a complicated structure such as a composite stiffened panel.

An Early Warning System for Asteroid Impact

ABSTRACTEarth is bombarded by meteors, occasionally by one large enough to cause a significant explosion and possible loss of life. It is not possible to detect all hazardous asteroids, and the efforts to detect them years before they strike are only advancing slowly. Similarly, ideas for mitigation of the danger from an impact by moving the asteroid are in their infancy. Although the odds of a deadly asteroid strike in the next century are low, the most likely impact is by a relatively small asteroid, and we suggest that the best mitigation strategy in the near term is simply to move people out of the way. With enough warning, a small asteroid impact should not cause loss of life, and even portable property might be preserved. We describe an early warning system that could provide a week’s notice of most sizeable asteroids or comets on track to hit the Earth. This may be all the mitigation needed or desired for small asteroids, and it can be implemented immediately for relatively low cost. This system, dubbed Asteroid Terrestrial-Impact Last Alert System (ATLAS), comprises two observatories separated by about 100 km that simultaneously scan the visible sky twice a night. Software automatically registers a comparison with the unchanging sky and identifies everything that has moved or changed. Communications between the observatories lock down the orbits of anything approaching the Earth, within one night if its arrival is less than a week. The sensitivity of the system permits detection of 140 m asteroids (100 Mton impact energy) three weeks before impact and 50 m asteroids a week before arrival. An ATLAS alarm, augmented by other observations, should result in a determination of impact location and time that is accurate to a few kilometers and a few seconds. In addition to detecting and warning of approaching asteroids, ATLAS will continuously monitor the changing universe around us: most of the variable stars in our Galaxy, many microlensing events from stellar alignments, luminous stars and novae in nearby galaxies, thousands of supernovae, nearly a million quasars and active galactic nuclei, tens of millions of galaxies, and a billion stars. With two views per day ATLAS will make the variable universe as familiar to us as the sunrise and sunset.