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About this book

Sensors and Instrumentation, Volume 8. Proceedings of the 36th IMAC, A Conference and Exposition on Structural Dynamics, 2018, the eighth volume of nine from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Sensors and Instrumentation, including papers on:

Sensor Applications

Accelerometer Design

Accelerometer Calibration

Sensor Technology

Energy Harvesting Technology

Aircraft/Aerospace Technology

Table of Contents


Chapter 1. Broadband Energy Harvesting Performance of a Piezoelectrically Generated Bistable Laminate

The vibration based energy harvesting performance of a piezoelectrically generated bistable laminate consisting of only Macro Fiber Composites (MFC) is experimentally characterized. Conventionally, piezoelectric transducers are bonded onto thermally induced bistable composite laminates and exhibit broadband cross-well dynamics that are exploited for improved power generation over linear resonant harvesters. Recently, a novel method of inducing bistability was proposed by bonding two actuated MFCs in a [0MFC∕90MFC] T layup and releasing the voltage post cure to create in-plane residual stresses and yield two cylindrically stable configurations. Forward and backward frequency sweeps at multiple acceleration levels across the first two observed modes of the laminate’s two states are performed to identify all dynamic regimes and the corresponding voltages produced by each MFC. Besides single-well oscillations, snap throughs are observed in intermittencies, subharmonic, chaotic, and limit cycle oscillations across wide frequency ranges. Resistor sweeps are conducted for each regime to determine maximum power outputs, and single and multi-frequency performance metrics accounting for laminate volume, mass, input accelerations, and frequencies are evaluated for the laminate. A performance comparison with conventional bistable composite harvesters demonstrate the laminate’s viability for energy harvesting, allowing it to be multi-functional in combination with its snap through morphing capability.

Andrew J. Lee, Daniel J. Inman

Chapter 2. Performance Assessment of Several Low-Cost Consumer-Grade Analog-to-Digital Conversion Devices

The Oak Ridge National Laboratory (ORNL) has pioneered an approach where low-cost consumer-grade electronics can be used as the basis of a highly reliable data acquisition architecture. One twenty-channel system based on this approach has been operating almost 4 years at ORNL. The architecture allows a mix-and-match level of configurability so the designer can select devices that best match the desired performance trade-offs. The most important device to be selected is the analog-to-digital converter. This paper explores the performance of several candidate audio recording devices that can be used as high-speed analog-to-digital converters for such measurement systems. Various performance metrics are explored including frequency response, noise floor, and synchronous sampling. Sample rates as high as 192 KHz are supported with 16 and 24-bit resolution. While most of the devices are dual-channel, there are multi-channel devices now available that will allow modal type of synchronous sampling. One such device was tested and is discussed is this paper.

G. R. Wetherington

Chapter 3. High-g Shock Acceleration Measurement Using Martlet Wireless Sensing System

This paper reports the latest development of a wireless sensing system, named Martlet, on high-g shock acceleration measurement. The Martlet sensing node design is based on a Texas Instruments Piccolo microcontroller, with clock frequency programmable up to 90 MHz. The high clock frequency of the microcontroller enables Martlet to support high-frequency data acquisition and high-speed onboard computation. In addition, the extensible design of the Martlet node conveniently allows incorporation of multiple sensor boards. In this study, a high-g accelerometer interface board is developed to allow Martlet to work with the selected microelectromechanical system (MEMS) high-g accelerometers. Besides low-pass and high-pass filters, amplification gains are also implemented on the high-g accelerometer interface board. Laboratory impact experiments are conducted to validate the performance of the Martlet wireless sensing system with the high-g accelerometer board. The results of this study show that the performance of the wireless sensing system is comparable to the cabled system.

Xi Liu, Xinjun Dong, Yang Wang, Lauren Stewart, Jacob Dodson, Bryan Joyce

Chapter 4. Effect of Piezoelectric Material in Mitigation of Aerodynamic Forces

In this study, piezoelectric materials were used to generate perturbations on the surface. This perturbation was used to combine upward wall motion and surface curvature. For this purpose, a Macro Fiber Composite (MFC) material was mounted on the surface of a cylindrical specimen for generating perturbation in the wind tunnel. Four different perturbation frequencies (1 Hz, 2 Hz, 3 Hz and 4 Hz) as well as the baseline specimen were tested in a low-speed wind tunnel (Re = 2.8 × 104). The MFC materials were mounted in a specimen to apply a combination of upward wall motion and surface curvature on the specimen in order to their effects on the leeward flow filed. The results showed that in the leeward flow field, for all actuation frequencies flow is bounded to a narrower width. In addition, Confinement of the flow in high actuation frequencies result in more turbulence in the leeward locations. In this case, the actuation frequencies resulted in up to 27% increase in turbulence intensity in the leeward.

Gholamreza Amirinia, Sungmoon Jung, Grzegorz Kakareko

Chapter 5. A Theoretical Description of a Multi-source Energy Harvester

By harvesting energy from more than one source, it is possible to improve the power output from an energy harvester. In this paper we present an analysis that allows us to find a bound on the maximum power absorbed by a harvester from multiple sources. This is based on an extension of the analysis that was previously used to derive a power-bound for a single-source mechanical energy harvester driven by stochastic vibration. Firstly, a single-source power-bound is derived for a system with thermo-electrical coupling, driven by stochastic time-varying temperature gradients. This power-bound is verified using numerical simulations carried out using MATLAB. This analysis is then extended to a system with thermo-electro-mechanical coupling, driven by both fluctuating temperature gradients and mechanical vibration. The resulting power-bound is the sum of the theoretical bounds on the maximum power absorbed by the thermal system and mechanical system alone. As this power-bound is greater than that for a single-source system, it demonstrates that a system that harvests energy from multiple sources has the potential to achieve a greater power output than a system that only harvests energy from a single source.

J. Gosliga, D. J. Wagg

Chapter 6. Lumped Mass Model of a 1D Metastructure with Vibration Absorbers with Varying Mass

This work examines the distribution of vibration absorber mass for a lumped mass metastructure model designed to suppress vibrations in the axial direction. Metastructures, a metamaterial inspired concept, are structures with distributed vibration absorbers. In automotive and aerospace industries, it is critical to have low levels of vibrations while also using lightweight materials. Previous work has shown that this design can effectively reduce vibrations by comparing the response of the metastructure to a structure with no vibration absorbers but with equal mass. Previous work constrained the vibration absorber masses to be the same throughout the structure. This work looks at the added performance that can be realized by allowing these masses to varying throughout the length of the metastructure. Additionally, the performance of the metastructure is also compared a host structure with a single tuned mass damper to show how this new technology differs from traditional vibration suppression methods.

Katherine K. Reichl, Daniel J. Inman

Chapter 7. Dynamic Behavior and Performance Analysis of Piezoelastic Energy Harvesters Under Model and Parameter Uncertainties

The main goal of this article is to perform a comprehensive analysis of the effects of parameter and model uncertainties on the dynamic behavior of piezoelastic energy harvesters. Piezoelectric energy harvesters demand for optimized mechanical and electric models such that optimum performance can be achieved in the mechanical-to-electrical energy conversion process. The presence of uncertainties can significantly alter the dynamic response of the harvester and therefore affecting its overall performance in terms of the amount of electrical energy available in the conversion process. Euler-Bernoulli beam theory is employed in the formulation of the energy harvesting electromechanical models that account for uncertain parameters in terms of the piezoelectric, electrical, geometric and mechanical boundary condition properties. Extensive numerical analysis are performed in frequency ranges where the device under study present multiple natural frequencies. Numerically simulated results are compared to experimental data reinforcing the importance of accounting for uncertainties in the design process of piezoelectric energy harvesters.

Paulo S. Varoto

Chapter 8. Experimental Test of Spacecraft Parachute Deployment using Real-Time Hybrid Substructuring

Spacecraft are subjected to a variety of extreme loads during the course of a mission. One such demanding period during reentry is parachute deployment when a mortar on the spacecraft is used to deploy the parachute. Firing the mortar to expel the parachute imparts an impulsive force on the spacecraft and results in vibration throughout the spacecraft. Successful deployment of the parachute is critical to the success of the mission, and accurate prediction of the impulsive forces exerted on the spacecraft during deployment is paramount to the design and safety of the spacecraft. Typically the time history of the reaction force of the mortar is measured experimentally using a rigid mounting system. This approach neglects the structural compliance of the spacecraft and thus neglects the dynamic interaction between the mortar and spacecraft. This may lead to differences between the force profile observed during laboratory testing and those observed during the mission of the spacecraft.In this paper, a cyber-physical test procedure called real-time hybrid substructuring (RTHS) is proposed to test the parachute deployment of the Mars Pathfinder spacecraft. The proposed RTHS test couples, in real-time, a numerical substructure, consisting of a dynamic model of the Mars Pathfinder with a physical substructure, consisting of a mortar being fired in the Shock and Vibration Laboratory at the University of Connecticut. The proposed RTHS test will be shown to fully capture the effect of spacecraft compliance on the force profile generated during the mortar firing. The Mars Pathfinder RTHS test is used to demonstrate this new approach in aerospace testing that can allow for component testing during the design phase to provide more realistic load profiles and more certain dynamic response at critical locations throughout the spacecraft.

Michael J. Harris, Richard E. Christenson

Chapter 9. Experimental and Analytical Approaches in a Virtual Shaker Testing Simulation Environment for Numerical Prediction of a Spacecraft Vibration Test

A spacecraft is exposed to a variety of extreme dynamical loads during launch. As a result, spacecraft are tested on ground in a vibration test campaign to ensure and verify the global integrity of the structure and to screen the flight hardware for workmanship errors since safety and security are top priorities. Additionally, the gathered experimental test data can be used to validate and correlate mathematical models. During these tests especially in fixed-base sinusoidal vibration testing of large spacecraft, the dynamical interaction between the test specimen, the vibration controller and test facility is a critical issue affecting the closed-loop vibration control performance, the quality of subsequent numerical model validations or even damaging the entire testing setup. In order to assess the occurrence of such issues and to minimise their influence by adapting control parameters, virtual shaker testing intends to numerically replicate the entire vibration test chain. To successfully predict the actual experimental conditions, validated and reliable models need to be developed, replicating the control strategy as well as the shaker and test specimen dynamic behaviour as accurately as possible. In practice, such models are usually not available or accessible to the test engineer or analyst. Therefore, this paper reviews the current status of the work combining experimental and physical methodologies to numerically predict a sine vibration test. Two approaches are presented: (1) a purely experimental data driven approach based on measured data only, e.g. from system self-check data and (2) a hybrid data driven approach considering numerical shaker facility and structural dynamic test specimen models. Subsequently, the corresponding sine control closed-loop simulation results are correlated to real physical test data and consequently their advantages and disadvantages are discussed.

S. Waimer, S. Manzato, B. Peeters, M. Wagner, P. Guillaume

Chapter 10. Direct Reference-Free Dynamic Deflection Measurement of Railroad Bridge under Service Load

Today, railroads carry 40% of the US freight tonnage and this demand will double in 20 years. North American railroad infrastructure includes approximately 100,000 bridges spanning over 140,000 miles of tracks. Half of those bridges are over 100 years old. Measuring deflection time history of railroad bridges under train load can assist in quantifying the reliability and increasing the safety of railroad operations throughout the network. However, obtaining bridge deflection is often difficult to collect in the field due to the lack of fixed reference points from where to measure. Although reference-free acceleration can be used to estimate the dynamic deflection through double integration, the algorithms are difficult to develop and apply because of the complicated integration constants selected for the data post-processing. This research studies the reference-free dynamic deflection (vertical displacement) acquisition approaches, a sensing system composed of one passive-servo electro-magnetic-induction (PSEMI) velocity sensor and one built-in hardware integrator unit. This research has presented two promising reference-free dynamic deflection acquisition approaches, direct reference-free displacement measurement from a sensing system composed of one passive-servo electro-magnetic-induction (PSEMI) velocity sensor and one built-in hardware integrator unit, and a reference-free displacement estimation from accelerometer by Lee-Method, that can be used for evaluating the performance and safety of railroad bridges under service load. Using the passive-servo feedback electrical control technology, the PSEMI velocity sensor provides a low-frequency direct reference-free measurement performance with its small size and light weight. Using a finite impulse response (FIR) filtering instead of double integrating, the displacement can be estimated from acceleration without the integration errors from unknown integration constants and boundary conditions. Researchers used an ASCE steel truss bridge model and an MTS actuator to quantify the accuracy of the PSEMI sensing system. The actuator replicated various harmonic motions and real bridge vertical displacements under train-crossing events measured in the field. The direct dynamic reference-free displacements measured by PSEMI sensing system and the indirect dynamic reference-free displacements estimated by acceleration using Lee-Method were compared to reference displacements measured by LVDT. The experimental results show that the direct reference-free dynamic displacement sensing system and indirect reference-free displacement estimation method from acceleration are two promising alternatives to railroad bridge deflection under train loading, without the need to a fixed reference frame.

Bideng Liu, Ali Ozdagli, Fernando Moreu

Chapter 11. A Low-Cost Modular Impact-Based Experimental Setup for Evaluation of EMI Based Structural Health Monitoring at High Rates

This paper investigates the use of the electromechanical impedance (EMI) method for detecting changes in the dynamic state of structures by presenting a low-cost, modular, instrumented, impact-based experimental setup. This experimental setup consists of a pneumatically actuated moving impacting aluminum bar, which will be launched to collide with a static incident bar at various impact velocities. The system allows for the use of different dimensions and materials for both the impacting bar and the incident bar. The boundary conditions of the incident bar can be changed by configuring the non-impacted side of the bar as clamped or free. The velocity of the impacting bar is measured using an array of two photoelectric sensors. A piezoelectric transducer attached to the incident bar is utilized for detecting the changes in dynamic state at the interface between the two bars by utilizing the EMI method. The impedance data is acquired and processed using a custom made measurement and analysis suite at very high-rate. Preliminary measurement results are presented to demonstrate the capability of the developed system to achieve repeatable and customizable impact events and also monitor the impedance response of the piezoelectric sensor. The long-term goal of this research is the use of this impact-based experimental setup for damage detection in structures operating in highly dynamic environments. This will be done by coupling the setup with a measurement system capable of microsecond data acquisition and processing.

Ekramul Haque Ehite, Steven R. Anton

Chapter 12. Real-Time Low-Cost Wireless Reference-Free Displacement Sensing of Railroad Bridges

The U.S. freight rail network moves about 40 tons of freight per person over 225,000 km (140,000 miles) of rail track every year. The railroad infrastructure contains more than 100,000 bridges, which correspond to one bridge for every 2.25 km (1.4 miles) of track. Railroad resources and funds are limited. Consequently, railroads’ maintenance, repair, and replacement (MRR) decisions should be optimized. An objective prioritization of MRR decisions requires quantitative data that informs the structural integrity. Lateral displacement measurement of bridges is an objective and quantitative performance indicator. Traditional wired displacement measurement systems are costly, labor-intensive, and are difficult to apply on bridges due to the need of stationary reference points. This paper proposes an Arduino-based low-cost wireless sensing system to estimate bridge displacements from acceleration data. The system uses a low-cost MMA8451 accelerometer and implements a FIR-filter to convert the measurements to displacement. The data is transmitted to the base station using a XBee Series 1 module in real-time. Each sensor platform is estimated to cost about $75. To evaluate the feasibility of the proposed system, a set of laboratory experiments are conducted by placing the sensor platform on a shake table and simulating bridge displacements measured on the field during train crossing events. The proposed measurement system can have impact on many applications that need real-time displacement information including, but not limited to aerospace engineering, mechanical engineering, and wind engineering.

Ali Ozdagli, Bideng Liu, Fernando Moreu

Chapter 13. Multi-Tonal Based Impedance Measurements for Microsecond State Detection

This paper concerns the development of a system capable of microsecond state detection via the electromechanical impedance (EMI) method utilizing a novel multi-tonal excitation approach. Structures that operate in highly dynamic environments, such as aircraft and drilling equipment, can benefit from a system capable of quickly detecting changes in the structure’s dynamic state. These changes of state can occur due to phenomenon, such as high velocity impacts, and necessitate a measurement system capable of working at millisecond to microsecond timescales. Traditionally, the electrical impedance of the PZT utilized in the EMI method is measured across a broad range of frequencies using an impedance analyzer, such as an HP 4194A; however, they are heavy, slow, and limited to a small amount of data points for each measurement. These disadvantages are overcome by using an alternative measurement system using data acquisition hardware, an auxiliary measurement circuit, and a custom coded analysis system. A key part of this measurement system is the use of a customizable excitation signal to drive the PZT. Due to the small amount of time in which a microsecond state detection system has to collect and analyze data, the excitation signal should be carefully designed to minimize measurement time while retaining accuracy. The use of conventional broadband frequency sweep excitations in a short amount of time presents challenges due to the fact that the total energy available to excite the structure becomes limited. This work investigates a novel multi-tonal excitation approach where only targeted frequency bands containing relevant structural information are excited in order to reduce the excitation time. The timing advantage of the multi-tonal signal is shown by matching the frequency dependent voltage of targeted frequency bands to that of a wideband chirp signal, which results in a 36% reduction in excitation time. The accuracy of the multi-tonal signal is also demonstrated; the impedance spectrum shows good agreement with both the wideband chirp signal and the HP 4194A. Damage detection of a structure is also presented using the multi-tonal excitation signals.

Ryan A. Kettle, Steven R. Anton

Chapter 14. Design and Installation Considerations of Dynamic Strain Gages for Thermo-Acoustic Aerospace Structures Test

Traditional polyamide film strain gages designed for high temperature applications have a survivable temperature threshold of 500–600 degrees F. Free-Filament (platinum) strain gages offer dynamic strain response with a temperature threshold up to 1800 degrees F. There are challenges using free-filament strain gages including providing robust installation methods, attachment leads, and signal conditioning. These factors are often overlooked and if not correctly addressed will give poor or incorrect responses. Standard adhesives and solder used to attach the strain gage and wire attachment leads break down at similar temperatures as polyamide film gages and are not well suited to use with free-filament gages. This paper will discuss ceramic flame spraying techniques using alumina or other high temperature bonding agents providing a robust and stable attachment. In addition, the use of, Nextel insulated, Constantan wire leads to withstand the high temperatures and direct radiation in high temperature dynamic testing environments will be addressed.

Matthew S. Stefanski, William E. Boles

Chapter 15. TESS Vibration Testing: A Boundary Condition Case Study

The Transiting Exoplanet Survey Satellite (TESS) program is led by the Massachusetts Institute of Technology (MIT) Kavli Institute for Astrophysics and Space Research. The TESS payload consists of four identical cameras mounted to a composite plate and a data handling unit. Each camera consists of a detector assembly, a lens assembly, and a lens hood. TESS is currently slated to launch in March 2018 to begin a two year, all sky transit survey to detect exoplanets. MIT Lincoln Laboratory is responsible for the four cameras and the composite camera plate. As part of the environmental test campaign, Lincoln Laboratory conducted force limited proto-flight vibration testing at two distinct levels of assembly. As vibration responses were monitored at nearly identical locations during the two sub-system level tests, a variety of valuable assessments can be made regarding fixed-base vibration testing. As part of this case study, the effects of the boundary condition on the overall test article response are evaluated. This discussion addresses the effects of the boundary condition on the qualification of hardware against various failure mechanisms. Additionally, the advantages and limitations of force limited vibration testing are assessed.

Alexandra Karlicek, Allison Pinosky

Chapter 16. Performing a Large-Scale Modal Test on the B2 Stand Crane at NASA’s Stennis Space Center

A modal test of NASA’s Space Launch System (SLS) Core Stage is scheduled to occur prior to propulsion system verification testing at the Stennis Space Center B2 test stand. A derrick crane with a 180-ft long boom, located at the top of the stand, will be used to suspend the Core Stage in order to achieve defined boundary conditions. During this suspended modal test, it is expected that dynamic coupling will occur between the crane and the Core Stage. Therefore, a separate modal test was performed on the B2 crane itself, in order to evaluate the varying dynamic characteristics and correlate math models of the crane. Performing a modal test on such a massive structure was challenging and required creative test setup and procedures, including implementing both AC and DC accelerometers, and performing both classical hammer and operational modal analysis. This paper describes the logistics required to perform this large-scale test, as well as details of the test setup, the modal test methods used, and an overview of the results.

Eric C. Stasiunas, Russel A. Parks

Chapter 17. Study on the Soft Suspension Behavior for Aircraft Ground Vibration Test Set-Up

The influence of the aircraft boundary conditions when setting a Ground Vibration test is always an issue. As aircrafts designs are becoming bigger is size and weight, the challenge in developing test set-ups for a successful GVT also increases. These challenges include not only the mechanical design of test devices, but also the goal to have the test performed in a shorter time, and with limited budget. Embraer decided years ago to have reliable device, which could duplicate the aircraft boundary condition, allowing at the same time fast test set-up and fast dismount. Even though, that design was modified and some opportunities had to be evaluated. This paper shows the conclusions of some variations on actual aircraft GVT set-ups, as well as studies performed in a small aircraft- like structure.

Antonio Almeida Giacomin, Airton Nabarrete, Marcelo Camilo Alves Costa, Tatiana Chloe Digou

Chapter 18. A Review of the Vibration Environment Onboard Small Unmanned Aircraft

A review of the vibration environment onboard multiple popular small unmanned aircraft is presented. The use of small Unmanned Aircraft Systems (UAS) or drones for surveillance and image collection is becoming ever more popular. To increase the performance of the imaging systems, vibration isolation and absorption systems are needed. For the effective design of these systems accurate data on the vibrational environment of the host aircraft is essential. This review provides the data experimentally acquired from multiple airframes that are used commonly in the UAS community. Both multi-rotor and fixed wing airframes are examined for the study. The data is obtained from aircraft fully powered and airborne in a hovering or level flight configuration. This will provide payload and image system developer the information required for choosing the correct aircraft for the mission as well as the design of vibration control.

William H. Semke, Matthew D. Dunlevy
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