Vibration Profiles Research Articles

Assessment of MEMS Vibration Energy Harvesting for High Temperature Sensing Applications

Distributed electronics for improving the accuracy of sensing in harsh high temperature environments, such as aero-engine and down-well is a growing field, where reduced power input requirements in cabling and batteries is viewed a key enabler for accelerating the adoption of high temperature electronics. Although batteries are available that can operate up to 200°C, they offer limited life at high temperatures and are bulky, increasing the costs of deployment and maintenance. Cabling also adds weight and takes up space in limited access applications. Energy harvesting in-situ offers the opportunity to make a step change in the design of high temperature electronics modules and in expanding their possible range of applications; for example, in sensor systems for combustor and turbine monitoring in aero-engines. This paper covers an assessment of MEMS vibration energy harvesting technology for high temperature sensing applications. MEMS devices based on the principle of parametric resonance, using AlN on Silicon have been designed and fabricated, along with sourcing of high temperature components for rectification, impedance matching and energy storage. The MEMS devices have been packaged into ceramic chip carriers and measured for energy output from a random vibration profile representative of an aerospace application. The measured output from the MEMS vibration energy harvester is capable of providing sufficient power to be of interest for autonomous sensing applications. This paper reports on the performance of the MEMS vibration energy harvesting devices and their associated circuitry at room temperature and at temperatures of up to 150°C. The challenges remaining to develop robust energy harvesting devices that could be applied in aero-engine, down-well and other high temperature applications are described. This work has been carried out under the Innovate UK supported project HI-VIBE, in a collaboration between GE Aviation Systems – Newmarket and the University of Cambridge.

Tunable Vibration Energy Harvester for Condition Monitoring of Maritime Gearboxes

This paper reports on a new tuning concept, which enables the operation of a vibration generator for energy autonomous condition monitoring of maritime gearboxes. The tuning concept incorporates a circular tuning magnet, which interacts with a coupling magnet attached to the active transducer element. The tuning range can be tailored to the application by careful design of the gap between tuning magnet and coupling magnet. A total rotation angle of only 180° is required for the tuning magnet in order to obtain the full frequency bandwidth. The tuning concept is successfully demonstrated by charging a 0.6 F capacitor on the basis of physical vibration profiles taken from a gearbox.

에너지 등고선을 이용한 고주파 가진 조건들에 따른 선형 시스템의 피로 손상도 분석

Vibration profiles consist of two kinds of pattern, random and harmonic, at general engineering problems and the detailed vibration test mode of a target system is decided by the spectral condition that is exposed under operation. In moving mobility, random responses come generally from road source; whereas the harmonic responses are triggered from rotating machinery parts, such as combustion engine or drive shaft. Different spectral input may accumulate different damage in frequency domain since the accumulated fatigue damage dependent on the pattern of input spectrum in high cyclic loading condition. To evaluate the sensitivity of spectral damage according to different loading conditions, a linear elastic system is introduced to conduct a uniaxial vibration testing. Measured data, acceleration and strain, is analyzed using energy isocline function and then, the calculated fatigue damage is compared by different loading cases, random and harmonic.

입력가진 조건에 따른 선형 시스템의 피로손상도 비교 평가

Vibration testing is conducted for evaluate the fatigue resistance of responsible system over excitation situations and two kinds of vibration profiles, harmonic or random, are widely used in engineering fields. Harmonic excitation profile is adequate for the rotating machinery that is primarily exposed to the orderly excited force subjected for a rotating speed; Random profile is suitable for the non-stationary vibration input, that is a ground excitation for example. Recently, the sine on random(SOR) testing method was sometimes considered to represent the real excitation conditions since the measured response signals of a target system, expecially for moving mobility, shows usually a mixture of them. So, it is important to understand the accumulated fatigue damage over different excitation patterns, harmonic and/or random, to determine the efficient vibration profile of a target system. A uniaxial vibration testing with a notched simple beam was introduced to evaluate the fatigue damage for different excitation profiles and the best choice of vibration profile was concluded from those comparison of calculated fatigue damages.

Improved noncontact optical sensor for detection of glucose concentration and indication of dehydration level.

The ability to extract different bio-medical parameters from one single wristwatch device can be very applicable. The wearable device that is presented in this paper is based on two optical approaches. The first is the extraction and separation of remote vibration sources and the second is the rotation of linearly polarized light by certain materials exposed to magnetic fields. The technique is based on tracking of temporal changes of reflected secondary speckles produced in the wrist when being illuminated by a laser beam. Change in skin's temporal vibration profile together with change in the magnetic medium that is generated by time varied glucose concentration caused these temporal changes. In this paper we present experimental tests which are the first step towards an in vivo noncontact device for detection of glucose concentration in blood. The paper also shows very preliminary results for qualitative capability for indication of dehydration.

Nonuniform elastic stagnant wave in a wedge-shaped plate

An acoustic field near the edge of an elastic wedge-shaped plate is studied. The field is represented in the form of two counterpropagating nonuniform waves. The standing vibration profiles varying with distance to the edge are constructed. A specific acoustic effect arising when the wave moves away from the wedge is revealed. Theoretical results are confirmed by measuring the standing wave amplitudes with a proprietary setup.

Selecting seats for steel industry mobile machines based on seat effective amplitude transmissibility and comfort

The purpose of this work was to help a steel industry partner select the most appropriate of three high end heavy equipment seats to retrofit a number of their heavy mobile machines used in the steel making process. The participants included 8 males (22.3 ± 2.0 yrs.) and 8 females (23.5 ± 1.8 yrs.) with no experience operating heavy mobile equipment. Previously recorded 6-DOF chassis acceleration data from a Pot Hauler (a machine which picks up and transports pots of slag) were used to extract six, 20 second representative profiles for implementation on a lab-based heavy machine simulator (6-DOF Parallel Robotics System Corporation robot). Subjects sat on three heavy equipment seats (BeGe7150, Grammar MSG 95G1721, and a 6801 Isringhausen with the seat pan cushion retrofitted with a Skydex cushion) mounted on the simulator. Each subject completed three trials for each combination of seat (n=3) and vibration profile (n=6). Chassis and operator/seat interface vibration were measured by 2, 6-DOF vibration transducers. Variables included Seat Effective Amplitude Transmissibility (SEAT) (X,Y,Z,Roll,Pitch,Yaw,6DOF Vector Sum) to determine if the seat was attenuating or amplifying the vibration, 6-degree of freedom (DOF) vibration total value weighted predicted comfort (Avc) (according to ISO 2631-1) and operator reported comfort (ORC). Factorial ANOVAs revealed significant differences (p < or = 0.05) between seats for all SEAT variables but different seats performed better than others depending on the axis. Significant differences between males and females were observed for SEAT in X,Y, and Pitch as well as for Avs. As expected there were significant differences between vibration profiles for all assessed variables. A number of interaction effects were observed, the most frequently occurring of which was between seat and vibration profile. Based upon the number of seat and vibration profile interactions, results suggest that a single seat is not suited for all tested conditions. However, SEAT values for all of the seats tested were extremely low (e.g., 6-DOF SEAT < 30%) indicating that all of the seats were capable of providing good vibration attenuation.

Combined Temperature and Vibration Testing for Wire Bond Interconnections in Harsh Environment Electronics

The performance of electronics in harsh environments is often affected by a combination of environmental factors. Qualification tests on such electronics are normally carried out by separate environmental tests such as temperature storage, temperature cycling and vibration tests. This approach may miss the effects of combined parameters, where for example, there may be degradation in a vibration environment that may be accelerated by temperature related effects on material properties. This paper presents results from a study of the combined effects of temperature and vibration on wire bonded interconnections that are used in the production of high temperature electronic components. The study is focused on the testing of electronic components under the combination of temperature exposure up to 250°C and vibration loading with a frequency range between 500 Hz and 2,000 Hz and acceleration up to 20 Grms. The study covers aspects of wire bond connections and their failure mechanisms, where the effect of wire loop height and length under separate and combined vibration and temperature tests has been investigated. The study has also assessed the effect on packaged Silicon on Insulator (SOI) devices assembled into ceramic packages under representative combined temperature and vibration profiles. The work has shown that the combined effect of temperature and vibration has increased the susceptibility of wire bond interconnections to vibration-induced failures.

Multiple Sinusoidal Vibration Test Development for Engine Mounted Components

Durability testing is required before vehicle launching to prevent failure before designed life. Limited publications were found on specifying vibration testing to validate durability and reliability of engine mounted components. These published test methods did not consider engine firing order effects and oversimplified the vibration profiles. In this paper, a new ordered multiple sinusoidal vibration test method is proposed to improve the existing procedures. The test method is designed to fulfill an infinite life durability requirement for engine mounted components subjected to a four-stroke internal combustion engine vibration. An innovative test development procedure, based on engine vibration field data, is illustrated in details in this paper. The ordered multiple sinusoidal vibration test method covers the choice of sweep type, sweep time, frequency range, vibration magnitude and profile, and test duration. Instead of obtaining the vibration magnitude directly from order analysis results, vibration magnitudes are determined by fully analyzing the vibration data in both time domain and frequency domain. Test profiles designed by enveloping method are proposed for a better represent of the engine excitations.

Variation of the vibration profile of piezoelectric resonant sensors with different electrode conductivity at high temperatures

Gas sensors for applications at elevated temperatures provide improved gas selectivity if fabricated using high-temperature stable piezoelectric resonators. The high-temperature and chemical stability of devices based on langasite coated with metal oxide films supports their application at extreme environments. The vibrational behavior of these resonators is influenced by changes in the electrical and mechanical properties of the metal oxide film.Measurements of the spatial distribution of the displacement characteristics of thickness shear mode resonators are realized using a laser Doppler interferometer at high temperatures and oxygen partial pressures (pO2) down to 10−27bar. The pO2 dependent changes of the properties of a CeO2−x sensor film and the influence on the vibration profile of the resonator are determined. At low pO2 the conductivity of the film increases. Due to the design of the device, the increase of the conductivity results in an enlargement of the effective electrode area of up to 18%. This is reflected in a broadening of the vibration profile of the resonator. Impedance spectroscopy provides comparable results for a pO2 dependent increase of the effective electrode area. The influence of the electrode thickness on the vibration profile is investigated and a decrease of the profile width of up to 11% with increasing thickness is demonstrated. The latter is attributed to an increased energy trapping.

Optical sensor for remote estimation of alcohol concentration in blood stream

The purpose of this manuscript is to validate our recently developed novel optical approach for extraction of remote vibration sources as a successful technique to estimate the alcohol concentration in blood stream. This technique is based on the tracking of temporal changes of reflected secondary speckle patterns produced in human skin when being illuminated by a laser beam. Since the skin’s vibrations profile is changed due to the alcohol in the blood stream, the extraction of the vibration profile can be translated into the corresponding alcohol concentration values by means of defining several parameters acting as indicators for the presence of alcohol in the blood stream. We have conducted several experimental tests showing a good correlation with conventional breath alcohol concentration measurement device when determining alcohol concentration in blood. The presented preliminary results validate the proposed optical sensor as a potentially useful device for measuring alcohol in blood stream with subjects that can be car drivers inspected by police authorities or medically monitored patients.

Frequency-domain methods for a vibration-fatigue-life estimation – Application to real data

The characterization of vibration-fatigue strength is one of the key parts of mechanical design. It is closely related to structural dynamics, which is generally studied in the frequency domain, particularly when working with vibratory loads. A fatigue-life estimation in the frequency domain can therefore prove advantageous with respect to a time-domain estimation, especially when taking into consideration the significant performance gains it offers, regarding numerical computations. Several frequency-domain methods for a vibration-fatigue-life estimation have been developed based on numerically simulated signals. This research focuses on a comparison of different frequency-domain methods with respect to real experiments that are typical in structural dynamics and the automotive industry. The methods researched are: Wirsching–Light, the α0.75 method, Gao–Moan, Dirlik, Zhao–Baker, Tovo–Benasciutti and Petrucci–Zuccarello. The experimental comparison researches the resistance to close-modes, to increased background noise, to the influence of spectral width, and multi-vibration-mode influences. Additionally, typical vibration profiles in the automotive industry are also researched. For the experiment an electro-dynamic shaker with a vibration controller was used. The reference-life estimation is the rainflow-counting method with the Palmgren–Miner summation rule. It was found that the Tovo–Benasciutti method gives the best estimate for the majority of experiments, the only exception being the typical automotive spectra, for which the enhanced Zhao–Baker method is best suited. This research shows that besides the Dirlik approach, the Tovo–Benasciutti and Zhao–Baker methods should be considered as the preferred methods for fatigue analysis in the frequency domain.

Semi-empirical life model of a cantilevered beam subject to random vibration

Life estimation of structures subjected to non-uniform random vibration analysis has historically been done through the use of fatigue properties. In general, evaluation of the severity of the vibration environment is performed at the initial natural frequency. It is widely known, however, that many structures will undergo a frequency change during failure. If the random vibration is non-uniform with large peaks and valleys, the frequency change will result in a changing stress state that must be accounted for. Evaluation of the accumulated damage can be done through accounting for the natural frequency change. This model uses experimental data to determine two empirical constants to predict time to failure for various complex random vibration profiles. Although the new model will utilize an experimental component in lieu of FEA, the physics of the underlying failure will be retained. Additionally the model has shown good correlation to experimental data, and improvements over existing techniques.

Quantification of 6-Degree-of-Freedom Chassis Whole-Body Vibration in Mobile Heavy Vehicles Used in the Steel Making Industry

Whole-body vibration (WBV) of mobile machines used in the steel making industry has not previously been quantified in six-degrees-of-freedom (6DOF). The purpose of this paper was to quantify 6DOF vibrations during the daily operating tasks of 5 commonly used mobile machines types used in the steel making and metal smelting industries. Vibration data were recorded from the chassis of five commonly used mobile machines using a MEMSense MAG3 triaxial accelerometer &amp; gyroscope (MEMSense, SD, USA), and analyzed using custom MatlabTM code. Elevated values were observed at the chassis for crest factors, peak running root mean squared accelerations, and vibration total values, resulting in ISO 2631–1 (1997) comfort predictions ranging from Uncomfortable to Extremely Uncomfortable. Vibration dominant frequencies were generally between 1 and 8Hz. A second peak which occurred at approximately 27 Hz was observed for each vehicle in almost all axes. Occurring at a frequency that has the potential to produce negative health effects, this second peak was probably caused by the engine idling or running at low speeds. Field vibration profiles from this study have been used as inputs to a 6DOF robot for use in a corresponding laboratory study designed to optimize seat selection thus allowing the steel making and other similar industries to select operator seats based on industry specific field vibration characteristics.

Use of PC mouse components for continuous measuring of human heartbeat

A new technology for remote measuring of vibration sources was recently developed for industrial, medical, and security-related applications [Int. Appl. Patent No: PCT/IL2008/001008]. It requires relatively expensive equipment, such as high-speed complementary metal oxide semiconductor (CMOS) sensors and customized optics. In this paper, we demonstrate how the usage of a simple personal computer (PC) mouse as an optical system composed of a low-power laser and a CMOS circuitry on the same integrated circuit package, can be used to monitor heartbeat from the wrist. The method is based on modifying the mouse optical system in such a way that it will recognize temporal change in skin's vibration profile, generated due to the heart pulses, as mouse movement. The tests that were carried out show a very good correlation between the heartbeat rate measured from human skin and the reference values taken manually.

Comparison between ISO 2631–1 Comfort Prediction Equations and Self-Reported Comfort Values during Occupational Exposure to Whole-Body Vehicular Vibration

It is important to understand whole body vibration (WBV) since it affects comfort and is important in worker health and performance. Although discomfort can be subjectively evaluated, the ISO 2631–1 standard predicts discomfort based on vibration magnitudes, frequencies and durations. The objective of this study was to determine whether the ISO 2631–1 prediction method produces similar results to self-reported discomfort levels during routine heavy machinery operations in the field. While working under normal conditions, 6 df seat-pan vibration data were recorded in construction, mining, and forestry vehicles. At 5-minute intervals, operators rated their discomfort based on the preceding minute of vibration exposure. Discomfort was predicted from the vibration total value for each corresponding one-minute vibration profile. Each industry showed consistent trends between the predicted and self-reported discomfort; however, there were different relationships between industries. Construction showed a weak positive relationship ( r2=0.09) between predicted and self-reported discomfort values, whereas both forestry and mining showed no relationship. The predicted discomfort levels did not accurately represent self-reported discomfort; this is similar to some previous studies, but contrasts with other studies. This variability may be due to discrepancies with the prediction equations, or perhaps due to additional factors being incorporated into self-reported comfort measures, such as temperature, noise, and fatigue.

Synchronous imaging for rapid visualization of complex vibration profiles in electromechanical microresonators

Synchronous imaging is used for the dynamic space-domain studies of vibration profiles in capacitively driven, thin n + doped polysilicon microbridges oscillating at rf frequencies. Fast and high-resolution actuation profile measurements of micromachined resonators are useful when significant device nonlinearities are present. For example, bridges under compressive stress near the critical Euler value often reveal complex dynamics stemming from a state close to the onset of buckling. This leads to enhanced sensitivity of the vibration modes to external conditions, such as pressure, temperatures, and chemical composition, the global behavior of which can be conveniently evaluated using synchronous imaging combined with spectral measurements. We performed an experimental study of high drive amplitude and ambient pressure effect on the resonant vibration profiles in electrically driven microbridges near critical buckling. Numerical analysis of electrostatically driven post-buckled microbridges supports the richness of complex vibration dynamics that are possible in such microelectromechanical devices.

Combined Temperature and Vibration Testing for Wire Bond Interconnections in Harsh Environment Electronics

The performance of electronics located in harsh environments is often affected by a combination of environmental factors. Qualification tests on such electronics are normally carried out by separate environmental tests such as temperature storage, temperature cycling and vibration tests. This approach may mask the effects of combined parameters, where degradation in a vibration environment may be accelerated by temperature related effects on material properties, for example. This paper presents details of an initial study into the combined effects of temperature and vibration on wire bonded interconnections used in the production of high temperature electronic components. The study is focused on the testing of electronic components under the combination of temperature exposure up to 250°C and vibration loading with a frequency range between 50Hz and 2000Hz and acceleration up to 20g rms. The study covers the fundamental aspects of wire bond connections and their failure mechanisms, where the effect of wire loop height and length under separate and combined vibration and temperature tests has been investigated. The study has also assessed the effect on packaged silicon on insulator (SOI) devices assembled into ceramic packages under representative combined temperature and vibration profiles. The work has shown that the combined effect of temperature and vibration has increased the susceptibility of wire bond interconnections to vibration induced failures and vibration testing under the applied temperature is recommended for assessment of components for harsh environments.

Effects of vibration exposure on professional drivers: a field test for quantifying visual and cognitive performance

Effects of whole-body vibration (WBV) exposure on professional drivers were predicted using a 45 subjects sample of healthy volunteers from both genders. These volunteers preformed a visual/motor accuracy evaluation test, the 'omega test', inside a vehicle (van) under three different WBV exposure conditions, van halted, van performing a circuit on asphalt, and on cobblestone. WBV levels of the stated conditions were statistically different and impairment upon subjects' performance was found. The statistical significant difference encountered between the subjects performance under the two whole-body vibration profiles (asphalt and cobblestone), seems to indicate that the vibration levels also represent a variable to be taken under consideration. No gender related difference was found.

Experimental Study of Resonant Vibrations of Suspended Steel Cables Using a 3D Motion Analysis System

AbstractThis paper presents the results of an experimental study of regular resonant vibrations of steel cables using a camera-based three-dimensional (3D) motion analysis system. The cable had one fixed end, and the other end was subjected to harmonic vertical excitation. Retroreflective markers were fixed to the cable and evenly distributed along it. The 3D motion analysis system was used to obtain 3D time traces of all marker vibrations; these traces were then entered into other programs for further signal processing. Time-varying modal coordinates were extracted from the trajectories of the markers using a modal decomposition technique. The resonant vibrations observed include isolated and simultaneous 1∶1, 2∶2∶1, 1∶1∶2∶2, and 4∶2∶4∶2 internal resonances. Subharmonic and superharmonic resonances, period-doubling bifurcations, hardening nonlinearity effect, and complex traveling vibrations were observed and studied. The resonant vibrations were characterized by examining time-varying vibration profiles...