Vibration Resonant Frequencies Research Articles

Tacsac: A Wearable Haptic Device with Capacitive Touch-Sensing Capability for Tactile Display

This paper presents a dual-function wearable device (Tacsac) with capacitive tactile sensing and integrated tactile feedback capability to enable communication among deafblind people. Tacsac has a skin contactor which enhances localized vibrotactile stimulation of the skin as a means of feedback to the user. It comprises two main modules—the touch-sensing module and the vibrotactile module; both stacked and integrated as a single device. The vibrotactile module is an electromagnetic actuator that employs a flexible coil and a permanent magnet assembled in soft poly (dimethylsiloxane) (PDMS), while the touch-sensing module is a planar capacitive metal-insulator-metal (MIM) structure. The flexible coil was fabricated on a 50 µm polyimide (PI) sheet using Lithographie Galvanoformung Abformung (LIGA) micromoulding technique. The Tacsac device has been tested for independent sensing and actuation as well as dual sensing-actuation mode. The measured vibration profiles of the actuator showed a synchronous response to external stimulus for a wide range of frequencies (10 Hz to 200 Hz) within the perceivable tactile frequency thresholds of the human hand. The resonance vibration frequency of the actuator is in the range of 60–70 Hz with an observed maximum off-plane displacement of 0.377 mm at coil current of 180 mA. The capacitive touch-sensitive layer was able to respond to touch with minimal noise both when actuator vibration is ON and OFF. A mobile application was also developed to demonstrate the application of Tacsac for communication between deafblind person wearing the device and a mobile phone user who is not deafblind. This advances existing tactile displays by providing efficient two-way communication through the use of a single device for both localized haptic feedback and touch-sensing.

Nonlinear Ultrasonic Second Harmonic Assessment of Concrete Defects Based on Embedded Piezoelectric Sensors

ABSTRACT In this work, the second harmonic generation (SHG) technique based on embedded piezoelectric (PZT) sensors is developed for the defect assessment of concrete samples. Three different imperfection forms of concrete including internal capillary void during the curing process, cracking damage due to compression, and bending loads are examined and analyzed. Clear second harmonics are observed by Fourier transform of time domain signal, and the square of fundamental signal amplitude shows a linear relation with the second harmonic amplitude as theoretically expected. The nonlinear parameter presents a good distinction for samples in different states of three cases, indicating the well-round feasibility of SHG technique based on embedded sensors. In addition, the nonlinear parameter presents an excellent correlation with the variation of internal capillary void and cracks in concrete. The high sensitivity of the developed SHG technique is further validated through a comparison between the nonlinear parameter and two traditional linear parameters, namely the phase velocity of Rayleigh wave and the resonance frequency of vibrations. Experimental results in this study demonstrate that the embedded sensors are promising for the nonlinear ultrasonic nondestructive evaluation of concrete structures, particularly as a low-cost alternative of commercial ultrasonic transducers.

Assessment of the vibrational resonant frequency of anisotropic black phosphorus nanoribbon

Black phosphorus (BP) has been enjoying popularity in mechanical and optoelectronic devices due to its superior anisotropic puckered structure. However, the vibrational properties of BP remain unexplored which greatly limits its wide applications in resonance-based nano electromechanical system (NEMS) devices. Therefore, in order to design mechanically reliable ultra-sensitive nanosensors, molecular dynamics simulations are utilized to explore the vibrational properties of monolayer BP. We have systematically assessed the effects of the initial actuation amplitude, internal vacancy density and mechanical strain on the vibrational properties of monolayer BP along the armchair and zigzag directions. It is found that the pristine monolayer BP exhibits lower energy disspation and smaller dominant resonant frequency during free vibration along the armchair direction than along the zigzag direction, indicating the anisotropic mechanical vibrational properties of monolayer BP, which further result in anisotropic multimode resonant characteristics in the vibration frequency spectrum. Additionally, the dominant frequency monotonically decreases gradually with increment of the internal vacancy density, while increasing with increment of the initial actuation amplitude and the mechanical strain. The energy dissipation increases gradually with increment of the initial actuation amplitude and internal vacancy density, but decreases under mechanical strain. Overall, these findings provide a fundamental understanding of the resonant properties of monolayer anisotropic BP that sheds light on its applications in micro- or nano-resonator-based devices.

Coriolis meter density errors induced by ambient air and fluid temperature differentials

Coriolis metering technology is widely applied throughout industry. In addition to the mass flow rate, a Coriolis meter can measure fluid density based on the resonant frequency of the flow tube vibration. There is currently increasing interest in utilising this density measurement capability as the primary process value in applications such as precision control for fluid property conditioning, and fluid contamination monitoring.However, within these applications, ambient temperature variation can be significant.This paper details research data obtained using NEL's ‘Very Low Flow’ single-phase facility. The rig was modified to include a programmable temperature enclosure in which a Coriolis meter was installed. Two commercial meter models from the same manufacturer were tested. Both meters showed fluid density errors when subjected to fluctuations in the surrounding ambient air temperature. The fluid properties of the test medium were confirmed to be stable using NEL's UKAS standard reference instrumentation.Previous temperature effects research for Coriolis meters have focussed on the process fluid temperature and there is little published data on the effects of ambient temperature.

Experimental and analytical investigations on nonlinear dynamic response of caisson-pile foundations under horizontal excitation

As a deep-water foundation, composite caisson-pile foundation (CCPF) is usually subjected to horizontal dynamic loads and moments due to the complicated marine environment. In this study, model tests were performed on three different types of deep-water foundation, including caisson, caisson with four piles and eight piles to investigate their lateral nonlinear dynamic characteristics under various excitation forces. Meanwhile, the effect of scour depth on the dynamic response of the foundations were also studies. The test results indicate that the excitation force and scour depth significantly affect the vibration amplitude and resonant frequency of the foundations with an obvious nonlinear behavior. Compared with the caisson, adding piles beneath the caisson results in a decrease of the vibration amplitude and an increase of resonant frequency, and the configuration of the pile also has an influence. The experimental results are compared with the results obtained by a simplified dynamic Winkler analysis model proposed here. Despite its simplicity, a reasonable agreement between the experimental and the calculated responses was observed. Moreover, scaling laws have been applied in the CCPF model to discuss the dynamic behavior of the prototype foundation.

Generation of macroscopic entangled cat states in a longitudinally coupled cavity-QED model

Macroscopic entangled cat states not only are significant in the demonstration of the fundamentals of quantum physics, but also have wide applications in modern quantum technologies such as continuous-variable quantum information processing and quantum metrology. Here we propose a scheme for generation of macroscopic entangled cat states in a molecular cavity-QED system, which is composed of an organic molecule (including electronic and vibrational states) coupled to a single-mode cavity field. By simultaneously modulating the resonance frequencies of the molecular vibration and the cavity field, the molecular vibrational displacement can be enhanced significantly and hence macroscopic entangled cat states between the molecular vibrational mode and the cavity mode can be created. We also study quantum coherence effects in the generated states by calculating the joint Wigner function and the degree of entanglement. The dissipation effects are included by considering the state generation in the open-system case. Our results will pave the way to the study of quantum physics and quantum chemistry in molecular cavity-QED systems.

Resonant frequencies analysis and vibration control of fluid in three-dimensional (3D) moonpool: Analytical modeling and experimental study

Moonpool widely exists in the fields of offshore oil and gas resources drilling, marine energy development and so on, and also has important applications in special ships and surface ships. The aim of this paper is to present an accurate three-dimensional modeling method and analyze resonant frequencies of fluid in three-dimensional moonpool. Based on the three-dimensional potential flow theory, the governing equations and boundary conditions of the fluid in the three-dimensional moonpool are established. According to the characteristics of the governing equations and boundary conditions of the fluid in the moonpool, the velocity potential of the fluid in the moonpool is expanded into the form of the sum of three-dimensional Fourier series and smooth auxiliary functions. Then, the velocity function is introduced into the governing equations and boundary conditions, so that the complex partial differential equations can be transformed into a set of simple linear equations, and the resonance frequency of the fluid vibration in the moonpool can be obtained by solving the linear equations. In order to verify the validity of the three-dimensional accurate model proposed in this paper, numerical examples and experimental verification are carried out, and then the numerical and experimental results show that the proposed solution has good convergence accuracy and calculation accuracy. On this basis, the effects of the length, width and water depth of the moonpool on the resonant frequencies and modes are discussed, and the natural vibration behavior control of the fluid in the three-dimensional moonpool are analyzed in detail. In this work, the three-dimensional analytical solution is proposed for the first time to study the natural vibration characteristics of the fluid in the three-dimensional moonpool, and its correctness is verified by the model experiment. At the same time, some bright research results are also given, which is of great engineering significance for understanding the resonant frequencies and modes of the fluid in the complex moonpool structure.

Effects of electrical properties on vibrations via electromechanical coupling in triboelectric energy harvesting

Vibration energy harvesting has been a popular research topic in recent years and is a promising technology in the development of the Internet of Things. Triboelectric energy harvesting, as a relatively new energy harvesting technique, is drawing attention. However, relevant studies from the perspective of structural dynamics are rare, and a study on how the electrical properties of triboelectric energy harvesters (TEHs) affect their vibration is still missing. In this paper, we perform such a study for TEHs that use the two most common working modes—namely the lateral sliding mode and the vertical contact-separation mode. In the first part of the paper, the coupled electromechanical model of a sliding mode TEH—based on a cantilever beam system involving friction—is established. The effects of the tribo-charge surface density and the load resistance on the vibration of the harvester are investigated. It is found that the effects of the tribo-charge surface density on vibrations are similar to those of mechanical damping, while the load resistance can result in an interesting resistive shunt damping phenomenon which is distinct from the one found in piezoelectric energy harvesters. In the second part, the modelling of a vertical contact-separation mode TEH is established based on a single-degree-of-freedom vibro-impact oscillator, and the effects of the same electrical properties on vibrations are studied. The variation of the tribo-charge surface density can result in both vibration amplitude attenuation and resonance frequency shifting, while the change of the load resistance can influence vibrations only in the case of large tribo-charge surface densities. This study further unveils the electromechanical coupling mechanisms in TEHs and sheds some light on achieving desirable dynamic responses of TEHs via tuning their electrical properties.

Hearing distributed mass in nanobeam resonators

One-dimensional vibrating nanostructures show remarkable performance in detecting small adherent masses added to a referential configuration. The mass sensing principle is based on measuring the resonant frequency shifts caused by the unknown attached masses. In spite of its important application in several fields, few studies have been devoted to this inverse eigenvalue problem. In this paper we have developed a distributed mass reconstruction method for initially uniform nanobeams based on measurements of the first lower resonant frequencies of the free bending vibration. Two main inverse problems are addressed. In the first problem, the mass variation is determined by using the first lower eigenfrequencies of a supported nanobeam, under the a priori assumption that the mass variation has support contained in half of the axis interval. In the second problem, we show that the a priori assumption can be removed, provided that the spectral input data include an additional set of first lower eigenfrequencies belonging to a second spectrum associated to different end conditions. The nanobeam is modelled using the modified strain gradient elasticity accounting for size effects. The reconstruction is based on an iterative procedure which takes advantage of a closed-form solution when the mass change is small, and shows to be convergent under this assumption and for smooth mass variation. The accuracy of the reconstruction deteriorates in presence of discontinuous mass variation. For these cases, a constrained least-squares optimization filtering shows to be very effective to reduce the spurious oscillations around the target coefficient. Numerical simulations show that the identification method performs well even for not necessarily small mass changes and it is stable in presence of errors on the data. An experimental validation of the method has provided encouraging results, despite the fact that only the first four eigenfrequencies under cantilever end conditions were used.

CONTROL OF VIBRATIONS OF ELASTICALLY FIXED OBJECTS USING ANALYSIS OF EIGENFREQUENCIES

In this paper, a mathematical model of a controlled system is investigated, created on the basis of a fourth-order differential equation widely used in various fields of science and technology. The problem of managing the behavior of structural elements has been solved. The mechanism of transition from one system to another is considered using the analysis of natural frequencies. The rod can be fixed in different ways (termination, hinge locking, elastic termination, floating termination, free end) [1]. If the ends of the rod are fixed so that resonant vibration frequencies are generated, then the question arises: is it possible to change the fastening of the rod so as to indicate a safe range for controlling the natural frequencies. The question posed by us gives rise to many others, more specific. For example, is it possible to determine how the ends of the bar are fixed by the natural vibration frequencies of the bar? Are they springs, sealed or loose? Such applications are very important especially when the first natural frequency generates a resonance situation. It is necessary to control the natural frequencies so that the system does not receive the first natural frequency for safe operation. The main result is formulated as a theorem. The stress-strain state (SSS) control has been developed for rods with elastic fastening on the left and hinged on the right. The uniqueness theorem for boundary conditions is proved using the analysis of natural frequencies.

Flexible pulse shaping for sum frequency microspectroscopies

The complexity of experimental schemes still challenges the broad application of multimodal microscopy beyond fundamental research. Pulse shaping has been a promising candidate to assist in the implementation of flexible and compact schemes. In this work, its application is demonstrated for vibrational resonant sum frequency (SF) spectroscopy in a nonlinear Raman microscope. The mixing of an ultrabroadband NIR laser pulse with a difference-frequency-generated MIR spectrum provides spectral access from 1750 c m − 1 to beyond 3000 c m − 1 via two shaping methods: (i) homodyne MIR scanning and (ii) heterodyne multiplex. The versatility of shaper-based SF is demonstrated in the spectroscopy and microscopy of crystalline cholesterol and cysteine.

타이어 저압감지를 위한 타이어 공진 주파수 추정

Indirect tire pressure monitoring system(i-TPMS) monitors the inflation pressures in pneumatic tires by using wheel speed signals acquired from the anti-lock braking system(ABS). Frequency analysis and wheel radius analysis are performed at the same time in order to monitor the tire pressures indirectly. The resonance frequency of the tire torsional vibration decreases as the tire pressure decreases. It is necessary to estimate the resonance frequency in order to detect a reduction in tire pressure. This paper discusses the method of estimating the resonance frequency with the rotational wheel speed signal. First, the toothed wheel error of the wheel speed sensor and the wheel speed corrected with the toothed wheel error are calculated from the wheel speed signals. The engine noise caused by the explosion in the four-stroke of engine is eliminated by the notch filter, which is designed by using the engine rotational speed. Finally, the resonance frequency is evaluated via model parameter estimation based on the autoregressive(AR) model. Vehicle tests have been conducted in order to evaluate the proposed estimation method of resonance frequency. The findings of the vehicle test have shown that the proposed method provides satisfactory performance for the warning indication of tire pressure loss.

The vibration behavior of submicron gas vesicles in response to acoustic excitation as determined via laser doppler vibrometry

Gas vesicles (GVs) are remarkably stable nano-sized gas-filled protein shells proven effective in ultrasonic imaging. The many potential benefits of GVs arise from their strong gas equilibrium at a submicron size as produced by bacteria or algae, producing significant contrast in ultrasound imaging. The actual vibration behavior of GVs, including buckling and collapse, is poorly understood since the GVs are too small for observation methods of sufficient speed to produce details of the GV deformation during exposure to ultrasound. Traditional optical or acoustic microscopy methods are, in any case, not useful, and ex-situtransmission electron microscopy produces useful images but without sufficient time resolution. We propose to instead use laser Doppler vibrometry (LDV) to observe the vibration behavior of GVs. Employing interferometry, LDV offers a far better spatiotemporal resolution. While the typical GV is smaller than 1 μm, an agglomeration of GVs may be used with the LDV to produce a measurable displacement response from a controlled, acoustically delivered pressure. In this talk, we report the fundamental and first harmonic resonance frequencies of GVs and vibration to buckling and collapse at the clinically relevant frequency of 6.5 MHz. We also compare these results with predictions from classic theories of bubble and particle oscillations and finite difference-based computations.

Identification of general added mass distribution in nanorods from two-spectra finite data

Abstract Nanomechanical resonators consisting in one-dimensional vibrating structures have remarkable performance in detecting small adherent masses. The mass sensing principle is based on the use of the resonant frequency shifts caused by unknown attached masses. In spite of its importance in applications, few studies are available on this inverse problem. Dilena et al. (2019) presented a method for reconstructing a small mass distribution by using the first N resonant frequencies of the free axial vibration of a nanorod under clamped end conditions. In order to avoid trivial non-uniqueness when spectral data belonging to a single spectrum are used, the mass variation was supposed to be supported in half of the axis interval. In this paper, we remove this a priori assumption on the mass support, and we show how to extend the method to reconstruct a general mass distribution by adding to the input data the first N lower eigenvalues of the nanorod under clamped-free end conditions. The nanobeam is modelled using the modified strain gradient theory to account for the microstructure and size effects. The reconstruction is based on an iterative procedure which takes advantage of the closed-form solution available when the mass change is small, and turns out to be convergent under this assumption. The results of an extended series of numerical simulations support the theoretical results.

Determination of torsional resonant frequencies of a tree

This paper discusses the applgication of vibration, in particular torsional vibrations in the creation of machines for the uprooting of entire trees with the root system. However, the use of vibration can be effective only if the correct frequency response is selected depending on the frequency characteristics of the tree and the mechanism. On the basis of the created mathematical model, the spectrum of resonance frequencies of torsional vibrations of the tree is determined. The obtained results make it possible to select the frequency characteristics of the vibration device depending on the parameters of the tree.

Experimental Analysis of Continuous Vibrations in Dielectric Elastomer Membrane Actuators via Three-Dimensional Laser Vibrometry

Dielectric elastomer (DE) membrane transducers are well known for exhibiting large deformations when subject to high voltage. Furthermore, DEs are characterized by an actuation bandwidth of several kilohertz, which allows their use in high-frequency applications, e.g., acoustic ones. The frequency response of DE membranes depends on many parameters such as geometry, pre-stress, and electrode pattern. By properly designing such parameters, it is possible to control vibration modes and resonance frequencies of the membrane, opening up a number of application scenarios. Motivated by this fact, this work presents the first experimental study of continuous vibrations generated in DE membranes via high-voltage excitation. The system under investigation consists of a squared DE membrane with a circular electrode, preloaded out of plane with a linear spring. Vibrations are generated by applying a broadband high-voltage signal to the DE membrane. A 3D laser vibrometer is used to reconstruct the three-dimensional oscillations of scanning points on the membrane surface. Experimental investigations are performed to study the effects of DE geometry and pre-stress on the membrane motion, in terms of resulting frequency spectrum and vibration modes.

Quick Suppression of Vibration of Robot via Hybrid Input Shaping Control Strategy

When the vibration amplitude and resonant frequency bandwidth of each mode are different in the multiple-modal system, the response time of a system is increased but the residual vibration is effectively reduced by the positive impulses multiple-modal input shapers. However, a negative impulses hybrid multiple-modal input shaping method can solve those problems. The basic principle of this control strategy and a 3-DOF parallel robot were introduced. Six negative impulses hybrid input shapers to reduce vibration of the first two modes were constructed based on the robot. Using simulation methods, the response time and vibration suppression abilities of various negative impulses hybrid two-modal input shapers (NHTIS) were obtained by analyzing the vibration response curves of these input shapers, and comparing with positive and negative impulses two-modal input shapers, respectively. The results show that the NHTIS can improve the response speed of the system while significantly reducing the multiple-modal residual vibration.

Damage assessment of concrete using a non-contact nonlinear wave modulation technique

This paper presents the development of a nonlinear vibro-acoustic modulation technique based on non-contact piezoelectric sensors to detect the crack progression of concrete subjected to both mechanical and thermal load. Two types of crack are investigated in the work including the isolated single crack induced by the three point bending test and distributed mapping cracks caused by heating treatment. Experimental results show that the damage index defined in the air-coupled wave modulation method – ultrasonic nonlinear parameter presents a positive correlation with the growth of single crack in bending test and the accumulation of mapping crack in thermal test. The sensitivity of developed method is validated through a comparison between the ultrasonic nonlinear parameter and two traditional linear parameters namely the phase velocity of Rayleigh wave and resonance frequency of vibrations. X-ray Computed Tomography (CT) technique and three-dimensional (3D) image reconstruction method are used to visualize microstructure of thermal damage. The CT images show that proposed nonlinear parameter is reliable and well correlated with the microstructural defects of concrete specimen. The repeatability of the air-coupled method is better than the contact method because the coefficient of variation of non-contact measurements is averagely about 43.2% of the contact measurements. Due to the advantage of removable characteristic of non-contact ultrasonic measurements, the developed air-coupled nonlinear wave modulation method could be promising for fast damage assessment of concrete structures in engineering practice.

Prototyping of a High Frequency Phased Array Ultrasound Transducer on a Piezoelectric Thick Film

A process including virtual prototyping of a high frequency phased array ultrasound transducer on a piezoelectric thick film using a finite element method (FEM) is shown. Generated FEM models were based on PMN-PT (Pb(Mg1/3Nb2/3)O3-PbTiO3) thick films, made by sol-gel technique, with the thickness vibrational mode resonant frequency of each film being close to 28.5MHz. Ultrasound transducers with such characteristics, due to their size and high frequency, are suitable for use in small medical diagnostic tools intended for use in delicate and sensitive areas (for example in ophthalmology and dermatology). With respect to their size, the transducers should retain very good focusing, beam steering and other advantages that phased array layout offers. To ensure an optimal performance of the phased array ultrasound transducer on such a piezoelectric thick film, several electrode patterns were used and tested in FEM simulations with the end goal of getting best performance from the PMN-PT thick films. A 64-element configuration was shown to be a promising technological solution for ophthalmological ultrasound diagnostics.

Study on Radial Vibration of Circular Piezoelectric Ceramic

The core component of the piezoelectric transducer is piezoelectric ceramic oscillator. The vibration of the piezoelectric ceramic oscillator is affected by piezoelectric ceramics. In this paper, the radial vibration is analyzed by using ANSYS. The variation of voltage and strain displacement, poisson’s ratio and resonance frequency are similar, and they are approximately linear. Moreover, the normalized resonant frequency gradually decreases with the thickness diameter ratio of t>=1 and t<=1. The accuracy of ANSYS to solve the resonance frequency of the radial vibration of piezoelectric ceramics is proved by experiment, theoretical calculation and ANSYS simulation results.