Andrew Swartz

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Hybrid wireless hull monitoring system for naval combat vessels

Structure and Infrastructure Engineering, 2012

There is increasing interest by the naval engineering community in permanent monitoring systems t... more There is increasing interest by the naval engineering community in permanent monitoring systems that can monitor the structural behaviour of ships during their operation at sea. This study seeks to reduce the cost and installation complexity of hull monitoring systems by introducing wireless sensors into their architectural designs. Wireless sensor networks also provide other advantages over their cable-based counterparts such as adaptability, redundancy, and weight savings. While wireless sensors can enhance functionality and reduce cost, the compartmentalised layout of most ships requires some wired networking to communicate data globally throughout the ship. In this study, 20 wireless sensing nodes are connected to a ship-wide fibre-optic data network to serve as a hybrid wireless hull monitoring system on a high-speed littoral combat vessel (FSF-1 Sea Fighter). The wireless hull monitoring system is used to collect acceleration and strain data during unattended operation during a one-month period at sea. The key findings of this study include that wireless sensors can be effectively used for reliable and accurate hull monitoring. Furthermore, the fact that they are low-cost can lead to higher sensor densities in a hull monitoring system thereby allowing properties, such as hull mode shapes, to be accurately calculated.

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Investigation of Time Series Representations and Similarity Measures for Structural Damage Pattern Recognition

The Scientific World Journal, 2013

Automated Modal Parameter Estimation by Parallel Processing within Wireless Monitoring Systems

Journal of Infrastructure Systems, 2008

With recent advances in low-cost wireless sensing and data acquisition technology, it has become ... more With recent advances in low-cost wireless sensing and data acquisition technology, it has become feasible to instrument a large structure with a dense array of wireless sensors. Furthermore, analog-to-digital conversion and data processing capabilities of current wireless sensor prototypes offer the ability to efficiently distribute data processing tasks across a large network of wireless sensing nodes. For decades, the structural engineering community has been adapting input-output modal identification techniques for use in large-scale civil structures. However, unlike in mechanical or aerospace engineering, it is often difficult to excite a large civil structure in a controlled manner. Thus, additional emphasis has been placed on developing a number of output-only modal identification methods for use in structural engineering applications. In this paper, three of these output-only methods ͑peak picking, random decrement, and frequency domain decomposition͒ are modified for implementation in a distributed array of processors embedded within a network of wireless sensor prototypes. The software architecture proposed emphasizes parallel data processing and minimal communication so as to ensure scalability and power efficiency. Using the balcony of a historic theater in metropolitan Detroit as a testbed, this network of wireless sensors is allowed to collect and process acceleration response data during a set of vibration tests. The embedded algorithms proposed in this study are used to autonomously determine the balcony's modal properties with network-derived results found to be comparable to those derived from traditional offline techniques.

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Rapid-to-deploy reconfigurable wireless structural monitoring systems using extended-range wireless sensors

Smart Structures and Systems, 2010

Wireless structural monitoring systems consist of networks of wireless sensors installed to recor... more Wireless structural monitoring systems consist of networks of wireless sensors installed to record the loading environment and corresponding response of large-scale civil structures. Wireless monitoring systems are desirable because they eliminate the need for costly and labor intensive installation of coaxial wiring in a structure. However, another advantageous characteristic of wireless sensors is their installation modularity. For example, wireless sensors can be easily and rapidly removed and reinstalled in new locations on a structure if the need arises. In this study, the reconfiguration of a rapid-to-deploy wireless structural monitoring system is proposed for monitoring short-and medium-span highway bridges. Narada wireless sensor nodes using power amplified radios are adopted to achieve long communication ranges. A network of twenty Narada wireless sensors is installed on the Yeondae Bridge (Korea) to measure the global response of the bridge to controlled truck loadings. To attain acceleration measurements in a large number of locations on the bridge, the wireless monitoring system is installed three times, with each installation concentrating sensors in one localized area of the bridge. Analysis of measurement data after installation of the three monitoring system configurations leads to reliable estimation of the bridge modal properties, including mode shapes.

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Critical insights for advanced bridge scour detection using the natural frequency

Journal of Sound and Vibration, 2017

Scour around bridge foundations is regarded as one of the predominant causes of bridge failures. ... more Scour around bridge foundations is regarded as one of the predominant causes of bridge failures. The concept of vibration-based real-time bridge scour detection has been explored in recent years by investigating the change in the natural frequency spectrum of a bridge or a bridge component with respect to the scour depth. Despite the progress, significant issues still remain unsolved in the application of this concept. This paper investigates three unsolved issues in the current framework of scour detection using the natural frequency spectrum: the physical meaning of the measured predominant natural frequency, the location of sensor installation, and the influence of the shape of scour holes, which are easily neglected but critical to the further implementations of the natural frequency spectrum-based bridge scour detection. Firstly, in-depth discussions of these three major issues were made separately by numerically modeling the scour progression of a typical and documented laboratory test. Laboratory tests were then performed to validate the conclusions made in the discussions. It was found that for an eigenproblem of the system with soil-structure interaction, the physical meaning of the natural frequency obtained from modal analysis can be understood by comparing the modal natural frequency with the natural frequency calculated from the dynamic response of the test component in that system. The results also verified that the obtained predominant natural frequency of the pier body greatly varies with the location of the pier body where a sensor is mounted for signal pickup. The shape of the scour hole affects the predominant natural frequency of the pier, causing difficulties in practical measurements. To address such a Contents lists available at ScienceDirect

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Wireless feedback structural control with embedded computing

SPIE Proceedings, 2006

In recent years, substantial research has been conducted to advance structural control as a direc... more In recent years, substantial research has been conducted to advance structural control as a direct means of mitigating the dynamic response of civil structures. In parallel to these efforts, the structural engineering field is currently exploring low-cost wireless sensors for use in structural monitoring systems. To reduce the labor and costs associated with installing extensive lengths of coaxial wires in today's structural control systems, wireless sensors are being considered as building blocks of future systems. In the proposed system, wireless sensors are designed to perform three major tasks in the control system; wireless sensors are responsible for the collection of structural response data, calculation of control forces, and issuing commands to actuators. In this study, a wireless sensor is designed to fulfill these tasks explicitly. However, the demands of the control system, namely the need to respond in real-time, push the limits of current wireless sensor technology. The wireless channel can introduce delay in the communication of data between wireless sensors; in some rare instances, outright data loss can be experienced. Such issues are considered an intricate part of this feasibility study. A prototype Wireless Structural Sensing and Control (WiSSCon) system is presented herein. To validate the performance of this prototype system, shaking table experiments are carried out on a half-scale three story steel structure in which a magnetorheological (MR) damper is installed for real-time control. In comparison to a cable-based control system installed in the same structure, the performance of the WiSSCon system is shown to be effective and reliable.

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A Framework for Embedded Load Estimation from Structural Response of Wind Turbines

Conference Proceedings of the Society for Experimental Mechanics Series, 2011

... R. Andrew Swartz, Assistant Professor, Department of Civil and Environmental Engineering, Mic... more

Probabilistic characterization of wind turbine blades via aeroelasticity and spinning finite element formulation

Proceedings of SPIE - The International Society for Optical Engineering, 2012

Wind energy is an increasingly important component of this nation's renewable energy portfol... more

Cover page Title: Distributed Data Processing Architectures for Structural Monitoring Systems Implemented on Wireless Sensor Networks for Proceedings of the Fourth European Workshop on Structural Health Monitoring 2008

Over the past decade, a variety of information technologies have emerged from the computer scienc... more Over the past decade, a variety of information technologies have emerged from the computer science and electrical engineering fields that are transforming how we monitor and manage complex civil infrastructure systems. The end result are safer structures that are easier and more economical to manage over their operational lives. Foremost among the emerging new information technologies are wireless sensors. Wireless sensors are low-cost data acquisition nodes that integrate communication and computing functionality with a sensor. Low-cost structural monitoring systems defined by high nodal densities can be designed using wireless sensors. To offer a scalable approach to management of the large data sets possible in wireless monitoring systems, in-network computing by the wireless sensor network is a powerful approach to automation of interrogation of structural response data for signs of structural distress. This paper will present the authors' experiences with the research and d...

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Rethinking Bridge Scour Detection Using the Natural Frequency: Numerical Insights

Scour around bridge foundations is regarded as one of the predominant causes of bridge failures, ... more Scour around bridge foundations is regarded as one of the predominant causes of bridge failures, which seriously threat the service to road users. The concept of vibration-based bridge scour detection has been explored in recent years by investigating the change in the natural frequency of the bridge/bridge components with respect to scour depth. Despite the progress, significant issues still remain unsolved in the application of this concept. This study investigates three unsolved issues, which are critical to the bridge scour detection based on frequencies. A numerical model was proposed and validated against existing laboratory studies. Numerical studies were carried out to advance the topic by providing insights into these three major issues: physical meaning of measured frequencies, locations for sensor installation, and influence of scour shapes.

Automated identification of modal properties in a steel bridge instrumented with a dense wireless sensor network

Bridge Maintenance, Safety Management, Health Monitoring and Informatics - IABMAS '08

Wireless sensing technology has made it possible to instrument large civil structures, such as br... more Wireless sensing technology has made it possible to instrument large civil structures, such as bridges, with dense networks of wireless sensors. Because many wireless sensing platforms integrate data processing capabilities with high-precision analog-to-digital converters, it is possible to autonomously process sensor data without the need for a central data server. By employing parallel processing techniques on typically serial modal analysis methods, a network of sensors can be used to autonomously determine modal properties (modal frequencies, damping ratios, and mode shapes). In this study, distributed versions of three output-only modal identification techniques (peak picking, random decrement, and frequency domain decomposition) are modified for implementation within a wireless sensing platform designed for bridge monitoring. A network of wireless sensors are deployed on 30m long pedestrian bridge; this wireless monitoring system is used to autonomously determine the bridge's modal properties.

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Experimental Validation of Market-Based Control Using Wireless Sensor and Actuator Networks

Structural control is a powerful tool that can ef fectively limit the undesired responses of civi... more Structural control is a powerful tool that can ef fectively limit the undesired responses of civil st ruc ures resulting from base motion occurring during a major seismic event. In particular, low cost semi-activ e control devices (such as varying dampers) are gaining popularity be cause they accomplish their control objectives by s trategically changing the properties of the structure under low po er requirements. However, these devices are lim ited in the amount of force that they can deliver compared to l arger (and more costly) active control devices. As a result, high actuator densities are often required to achieve ad equate control of a large structure using semi-acti ve control devices. This dense actuator network, coupled with sensors a nd the structure itself, represents a complex dynam ic system that is best controlled through a decentralized approach. In this study, a decentralized market-based control (MBC) solution is adopted for controlling tall buildings that employ ...

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The 2016 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems: Symposium on structural health monitoring

Journal of Intelligent Material Systems and Structures

Low-force magneto-rheological damper design for small-scale structural control

Structural Control and Health Monitoring

Decentralized civil structural control using real-time wireless sensing and embedded computing

Smart Structures and Systems

Structural control technologies have attracted great interest from the earthquake engineering com... more Structural control technologies have attracted great interest from the earthquake engineering community over the last few decades as an effective method of reducing undesired structural responses. Traditional structural control systems employ large quantities of cables to connect structural sensors, actuators, and controllers into one integrated system. To reduce the high-costs associated with labor-intensive installations, wireless communication can serve as an alternative real-time communication link between the nodes of a control system. A prototype wireless structural sensing and control system has been physically implemented and its performance verified in large-scale shake table tests. This paper introduces the design of this prototype system and investigates the feasibility of employing decentralized and partially decentralized control strategies to mitigate the challenge of communication latencies associated with wireless sensor networks. Closed-loop feedback control algorithms are embedded within the wireless sensor prototypes allowing them to serve as controllers in the control system. To validate the embedment of control algorithms, a 3-story half-scale steel structure is employed with magnetorheological (MR) dampers installed on each floor. Both numerical simulation and experimental results show that decentralized control solutions can be very effective in attaining the optimal performance of the wireless control system.

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Special Issue: ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS), Symposium on Structural Health Monitoring/NDE

Journal of Intelligent Material Systems and Structures

Output-only cyclo-stationary linear-parameter time-varying stochastic subspace identification method for rotating machinery and spinning structures

Journal of Sound and Vibration, 2015

ABSTRACT Economical maintenance and operation are critical issues for rotating machinery and spin... more ABSTRACT Economical maintenance and operation are critical issues for rotating machinery and spinning structures containing blade elements, especially large slender dynamic beams (e.g., wind turbines). Structural health monitoring systems represent promising instruments to assure reliability and good performance from the dynamics of the mechanical systems. However, such devices have not been completely perfected for spinning structures. These sensing technologies are typically informed by both mechanistic models coupled with data-driven identification techniques in the time and/or frequency domain. Frequency response functions are popular but are difficult to realize autonomously for structures of higher order, especially when overlapping frequency content is present. Instead, time-domain techniques have shown to possess powerful advantages from a practical point of view (i.e. low-order computational effort suitable for real-time or embedded algorithms) and also are more suitable to differentiate closely-related modes. Customarily, time-varying effects are often neglected or dismissed to simplify this analysis, but such cannot be the case for sinusoidally loaded structures containing spinning multi-bodies. A more complex scenario is constituted when dealing with both periodic mechanisms responsible for the vibration shaft of the rotor-blade system and the interaction of the supporting substructure. Transformations of the cyclic effects on the vibrational data can be applied to isolate inertial quantities that are different from rotation-generated forces that are typically non-stationary in nature. After applying these transformations, structural identification can be carried out by stationary techniques via data-correlated eigensystem realizations. In this paper, an exploration of a periodic stationary or cyclo-stationary subspace identification technique is presented here for spinning multi-blade systems by means of a modified Eigensystem Realization Algorithm (ERA) via stochastic subspace identification (SSI) and linear parameter time-varying (LPTV) techniques. Structural response is assumed to be stationary ambient excitation produced by a Gaussian (white) noise within the operative range bandwidth of the machinery or structure in study. ERA-OKID analysis is driven by correlation-function matrices from the stationary ambient response aiming to reduce noise effects. Singular value decomposition (SVD) and eigenvalue analysis are computed in a last stage to identify frequencies and complex-valued mode shapes. Proposed assumptions are carefully weighted to account for the uncertainty of the environment. A numerical example is carried out based a spinning finite element (SFE) model, and verified using ANSYS® Ver. 12. Finally, comments and observations are provided on how this subspace realization technique can be extended to the problem of modal-parameter identification using only ambient vibration data.

Decentralized Algorithms for SHM over Wireless and Distributed Smart Sensor Networks

Springer Environmental Science and Engineering, 2012

Effective structural health monitoring (SHM) of civil structures typically requires information d... more Effective structural health monitoring (SHM) of civil structures typically requires information derived from many spatially distributed locations throughout large infrastructure assets. Consolidating this information in a centralized location can often be difficult and costly. Collocation of sensing and computational abilities in a smart wireless sensor unit (WSU) can help to address this challenge. Embedded data processing at the sensor level can help to reduce communication burdens within sensor networks. Furthermore, embedded data processing is inherently automated, eliminating repositories of unprocessed and unused conditional data. However, to understand the global condition of a structure and to leverage spatial information, some data consolidation is necessary. This chapter will present some of the challenges inherent in decentralized data processing for SHM of seismically excited civil structures and will discuss some of the approaches that are available to leverage distributed computing in order to overcome these challenges.

Wireless sensing and vibration control of civil structures

2010 IEEE International Conference on Wireless Information Technology and Systems, 2010

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Gyroscopic Effects of Horizontal Axis Wind Turbines Using Stochastic Aeroelasticity via Spinning Finite Elements

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring, 2012

Horizontal axis wind turbine (HAWTs) structures, throughout the years, have presumed to be of rel... more Horizontal axis wind turbine (HAWTs) structures, throughout the years, have presumed to be of relatively simple construction, but wind-induced aerodynamic vibrations, wind-field conditions, and power requirements tend to lead to the need for increasingly complicated designs. One phenomenon that requires special attention is the gyroscopic or Coriolis effect. In general, blades design codes are written to optimize for lightness and slenderness, but also to withstand excitations at high frequency. As a result, gyroscopic motion derives as a nonlinear dynamic condition in the out-of-plane direction that is difficult to characterize by means of the well-known vibrational theory that has been established for their design and analysis. The present study develops and presents a probabilistic analysis of the precession — gyroscopic — effects of a wind turbine model developed for tapered-swept cross-sections of nt degree with nonlinear variations of mass and geometry along the body of the bl...

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