Resonance Frequency Of System Research Articles

Integrated analytical, experimental, and numerical study of vibrational response in clamped circular plates with pressurised air cavities

This paper presents a comprehensive investigation, comprised of analytical, experimental and numerical approaches, into the interaction between the sound field produced within a pressurised air-filled back cavity and the vibration of a thin clamped circular plate subjected to its pressure. Previous investigations into the interaction of sound fields with vibrating boundaries have primarily been restricted to non-pressurised cavities. We extend the application of the weak modal coupling method to derive a solution for this unexplored physical problem by utilising classic plate theory, Fourier-Bessel series formulation and the uncoupled solutions for a pressurised cylindrical sound field and a thin clamped circular plate with uniform radial tension. We describe the vibration response of the coupled system in terms of the uncoupled cavity and plate modes. Using a set of geometric and physical properties for the system, the resonance frequencies and response functions are calculated and the coupling between the sound field and the plate is investigated as a function of cavity pressure, providing novel fundamental insights into the physical system. We construct an experimental rig to embody the conditions of the analytical investigation for the purpose of validation. Finite element analysis (FEA), employing modal analysis and transient dynamic analysis, is used to further validate and extend the analytical insights while more accurately mirroring the experimental conditions. The response functions, mode shapes, resonance frequencies and their dependence on the cavity pressure were experimentally measured and numerically simulated, with direct comparisons made with the analytical model. A high degree of accuracy for the analytical model is validated along with its ability to describe the underlying physical phenomena. The validated analytical model is then leveraged to perform fundamental explorations into the modal contributions as a function of cavity pressure and a parametric sensitivity analysis on the effects of plate radii and plate thickness on the coupled system resonance frequencies.

A Kriging Surrogate Model for Ball Grid Array Electronic Packaging With Stochastic Material and Geometrical Parameters

Abstract Ball grid arrays (BGAs) offer significant advantages in the automotive industry, such as their small size and high integration density, making them a promising electronic packaging approach. However, the operating environment of automobiles is more complex compared to other applications, primarily due to vibrations generated by power engines and oscillations caused by pavement roughness. The resonant frequencies of electronic packaging structures play a crucial role in system reliability and safety. However, accurately describing the implicit relationship between system resonant frequencies and material and geometrical parameters can be challenging. A Kriging surrogate model (KSM) is proposed by the combination of the Latin Hypercube stochastic sampling with finite element computation. Four different BGA configurations are established with either the initial values in the deterministic model or the specified sampling interval ranges in the stochastic model. The results of the finite element model (FEM) for BGA electronic packaging are validated and demonstrate qualitative agreement with published literature. The impacts of material and geometrical parameters on the resonant frequencies are investigated and compared. The mean, maximum, minimum, and variance are recorded based on a large database of stochastic samples. The feasibility of KSM for the resonant frequency prediction of BGA is confirmed by its satisfactory accuracy and computational efficiency.

Improved Position Sensorless Resonant Frequency Tracking Control Method for Linear Oscillatory Machine

To improve the reliability of control system and obtain the maximum output efficiency, it is very necessary to carry out the position sensorless piston stroke control and the resonance frequency tracking control for linear oscillatory machine (LOM) at the same time. The conventional resonant frequency tracking control method based on model reference adaptive system (MRAS) has the problem of low estimation accuracy caused by inaccurate model parameters. In order to obtain more accurate resonant frequency, an improved position sensorless resonant frequency tracking control method is proposed in this article. In this method, the adjustable model is constructed based on the mechanical dynamics equation of LOM to track the system resonant frequency. A hybrid terminal sliding-mode observer (HTSMO) is designed to replace the conventional reference model, which can obtain more accurate velocity reference signal for adjustable model by introducing the current error feedback link, thereby further improving the resonant frequency tracking accuracy. Moreover, a second-order generalized integrator (SOGI) is introduced to filter the estimated velocity signal of HTSMO. The filtered velocity signal is not only used for the adjustable model to track the resonant frequency, but also used to obtain the smooth piston stroke signal for the stroke closed-loop control. Comprehensive simulation and experimental results have proved the effectiveness and the superiority of the proposed method.

A Dual-Band Coil Array With Novel High-Order Circuit Compensation for Shielding Design in EV Wireless Charging System

For the wireless power transfer (WPT) system in electric vehicle (EV) applications, a serious concern lies in the leakage electromagnetic field (EMF) emission. In order to address this issue, this article presents a dual-band coil array (DB-CA) with novel high-order circuit (HOC) compensation. The most attractive feature of DB-CA is that both the first and third harmonics of leakage EMF can be reduced simultaneously, while the system still resonates at the same frequency. A detailed mathematical model is established to intuitively reveal the relevance between impedance design and shielding performance, as well as the constraints to achieve resonance. In addition, the novel HOC compensation is employed to decouple the shielding design at each harmonic. Both simulated and experimental results verify the effectiveness of DB-CA, and a 1-kW WPT prototype operating at 85 kHz is established. By applying DB-CA, the leakage EMF can be reduced by 3.88 dB at 85 kHz and 1.84 dB at 255 kHz, respectively. Meanwhile, the system resonant frequency still locates at 85 kHz, and the achieved zero phase angle condition is independent with load condition. It can provide significant guidance to the design of shielding configurations in EV Wireless Charging System.

The dynamic properties and performance of the bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolator

Aiming to effectively isolate disturbance vibrations for heavy machines with low frequencies, a novel bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolation (I-DAVI) isolator is proposed, which consists of a primary supporting bellows container and an additional inerter subsystem comprising horizontal bellows and inertial mass, and the incompressible oil liquid is filled in the vacuum of both bellows as the working medium. First of all, the mathematic model of the presented I-DAVI device is established, and then the vibration transmissibility for the systems under force excitation and motion excitation are derived. The relevant results indicate that the anti-resonance appears at specific frequency, creating near-zero energy transmission and significantly reducing vibration transmission to the base or machines. Through the nondimensionalization analysis, the four parameters including the inertial mass ratio, damping ratio, ratio of effective cross-section areas, and number of the inerter subsystem completely dominate the isolation characteristics of the proposed device. Subsequently, a comparison study is carried out between systems with and without inertial mass located at the end of the additional horizontal bellows, and furthermore the operating mechanism of the I-DAVI is explained clearly. It is proven that the inerter-based DAVI isolator exhibits high static and low dynamic stiffness characteristics, which cause the resonance frequency of the isolation system to shift toward lower frequency without changing the static bearing stiffness and also reduce the peak value of the transmissibility. The further numerical simulation verifies that the optimal isolation effectiveness at the anti-resonance frequency is attributed to the dynamic equilibrium between the elastic restoring force of the primary bellows and the internal hydraulic pressure. In practice, the bellows-type hydraulic inerter-based I-DAVI isolator device investigated in this study is suitable for machines with the narrowband low-frequency vibration, such as the marine turbines.

Nonlinear vibration characteristics of virtual mass systems for wind turbine blade fatigue testing

Abstract. The biaxial fatigue test of wind turbine blades is helpful to shorten the test time and is more suitable for the actual operating conditions. Adding tuning masses to the blade is a common method for blade uniaxial testing at present, and its purpose is to adjust the load distribution in one direction of the blade. However, the tuning masses on the blade will affect the load distribution in the direction of the blade flap-wise and edge-wise at the same time in the biaxial test, so the concept of “virtual masses” is proposed to realize the decoupling of the load distribution in the biaxial test. Due to the limitation of the size of the virtual mass mechanism and the complex motion trajectory of the blade, the actual inertial effect provided by the virtual masses is different from the ideal situation, which will affect the resonance characteristics of the test system and the load distribution of the blade. Therefore, in order to evaluate the effect of the nonlinear effect introduced by the virtual masses on the resonance characteristics of the test system and the blade load distribution, the equivalent dynamic model of the bladed virtual mass test system was established by using the Lagrange method. Then, the nonlinear effects of blade amplitude and virtual mass installation parameters on the test system are obtained by a numerical method. Then, based on the nonlinear vibration theory, the approximate nonlinear amplitude–frequency characteristics of the test system are obtained, that is, the resonance frequency of the test system will decrease with the increase in the blade amplitude. Through the simulation analysis of two blades over 80 m in length, the applicability of the theoretical method is verified. It can be seen from the simulation results of the simulated uniaxial test that larger amplitudes of the blade and shorter connection rods will reduce the resonance frequency of the test system. When the vibration amplitude at the excitation point is the same, a lower resonance frequency results in a smaller load distribution level, that is, the area which is actually fully tested will be reduced. In the biaxial simulation test, the resonance frequency of the test system will be further reduced because the virtual masses will be affected by the coupled motion in both directions at the same time. Furthermore, the introduction of an external mechanism of the virtual mass will also cause deformation of the envelope of the blade biaxial trajectory, which will further affect the load distribution of the blade. This work explores the nonlinear influence of virtual masses on the actual fatigue test. The theoretical analysis is helpful to provide the basis and reference for the preliminary preparation work of the test organization, including adjusting the tuning mass scheme, adjusting the load distribution and selecting the appropriate excitation equipment.

Synthesis of a zeolite@mesoporous silica composite to improve the low-frequency acoustic performance of a miniature loudspeaker system.

Herein, a zeolite@mesoporous silica composite (Z@MS) with a hierarchical porous structure was synthesized and employed as the filling material in miniature loudspeakers. The material was synthesized via a simple surfactant-directed sol-gel process in which MFI zeolites with a high silica-alumina ratio (>1000) were encapsulated in mesoporous silica with worm-like pores templated by Brij 72 under acidic conditions. Pressure spray drying technology was adopted to reassemble the intermediate slurry into hierarchical porous microspheres with large particle sizes (∼200 μm). The resonance frequency of the miniature loudspeaker system decreased by 339.77 Hz upon loading Z@MS as the filling material. The excellent acoustic performance can be considered as the result of a synergy of respective energy transmission effects among hierarchical porous structures.

A new method for reducing the number of resonance frequencies of mechanical systems within a specified frequency range with inverse structural modification and pole-zero cancellation

Resonance frequencies of a mechanical system are the most important parameters that determine the dynamic characteristics of the system. When the frequencies of the harmonic forces under the influence of the system coincide with the resonance (natural) frequencies of the system, a resonance situation occurs and the mechanical system vibrates with high amplitudes. This can cause serious damage to the system by causing effects such as break, fatigue, impact, noise on the bearings, connections and elements in the system. It is possible to eliminate some resonance frequencies of mechanical systems in an examined frequency range using pole-zero cancellation methods by shifting a resonance frequency of the system to an anti-resonance frequency or an anti-resonance frequency to a resonance frequency. Thus, a solution can be obtained for some vibration problems. In this study, a new method using the Sherman-Morrison formula is presented to eliminate some of the resonance frequencies for some FRFs (Frequency Response Functions) of mechanical systems with pole-zero cancellation. In order to eliminate a selected resonance frequency of the system in any FRF determined using the presented method, a mass (kg) and a grounded spring (N/m) modification are made and the required modification values for this are calculated by solving the obtained non-linear equation set numerically. With the proposed method, it is aimed to contribute to the literature by presenting an alternative approach for the solution of vibration problems by cancelling some selected resonance frequencies. The main highlight of the method is there is no need of a matrix inversion for calculating the required modification values. This provides a very fast solution. In addition, the proposed method uses directly the FRFs of the active coordinates (response, excitation and modification) only, which makes the method very useful for practical engineering applications.

Stiffness profile spectral composition & geometry deterioration of railway tracks

This work addresses the contribution of the wavelength composition of the spectrum of the rail support stiffness profile to the expected long-term settlement. To that aim, purely harmonic stiffness variations of different wavelength are studied. The frequency-domain model with a double periodicity level previously developed by the first and last authors is adopted to embed the stiffness profile in one of the periodicity layers. Additional resonance velocities at which the resonance frequency of the track system coincides with the support-passing frequency or its multiples are found. The susceptibility to degradation is assessed both by quantifying the mechanical energy dissipated in the substructure under a moving train axle within one wavelength of the support stiffness variation, and the work performed by the wheel-rail contact force. It is shown that shorter wavelengths and larger standard deviations of varying ballast/subgrade stiffness result in an increasing energy dissipation in the substructure, and increase the work performed by the wheel-rail contact force, therefore leading to a reduced lifetime of the track. The energetic quantities increase for lower mean values of the stiffness profile, confirming the proneness of tracks on soft soils to degradation. The influence of varying stiffness vanishes for wavelengths of approximately 16 times the sleeper span, which is equivalent to a track length of about 10 m. High railpad stiffness values result in increased energy dissipation but the influence is limited. In general, an increasing train velocity amplifies the rate of track degradation, with no stabilizing trend in the high-speed regime (300 km/h).

An Improved Active Damping Method for Enhancing Robustness of LCL-Type, Grid-Tied Inverters under Weak Grid Conditions.

The conventional proportional-gain-feedback link can only obtain the smallest effective damping region (EDR) due to the control delay among all the active damping methods regarding the capacitor current feedback. The digitally controlled system tends to be unstable when the system resonant frequency reaches the critical frequency caused by the grid impedance variation. To weaken the adverse effect on the system caused by the control delay, phase-lead feedback links are applied along the feedback path to provide phase compensation. By taking the simplicity and reliability of the feedback links into account, this paper proposes an alternative to an ideal differentiator, which consists of the Tustin discrete form of 's' and a digital low-pass filter. This proposed method has an identical phase frequency characteristic as an ideal differentiator but a better magnitude frequency characteristic, and its EDR can reach [0, fs/3]. The system stability analysis is conducted under different resonant frequencies, and under the condition of a weak grid, the co-design approach of the active damper and digital controller is presented. Finally, the experimental results are shown to verify the proposed method.

Textile Antenna Sensor in SIW Technology for Liquid Characterization.

This study showcases the creation of an innovative textile antenna sensor that utilizes a resonant cavity for the purpose of liquid characterization. The cavity is based on circular substrate integrated waveguide (SIW) technology. A hole is created in the middle of the structure where a pipe is used to inject the liquid under test. The pipe is covered by a metal sheath to enhance the electromagnetic field's penetration of the tube, thus increasing the device's sensitivity. The resonance frequency of the proposed system is altered when the liquid under test is inserted into the sensitive area of the structure. The sensing of the liquid is achieved by the measurement of its dielectric properties via the perturbation of the electric fields in the SIW configuration. The S11 measurement enables the extraction of the electromagnetic properties of the liquid injected into the pipe. Specifically, the dielectric constant of the liquid is determined by observing the resonance frequency shift relative to that of an air-filled pipe. The loss tangent of the liquid is extracted by comparing the variation in the quality factor with that of an air-filled pipe after eliminating the inherent losses of the structure. The proposed SIW antenna sensor demonstrates a high sensitivity of 0.7 GHz/Δεr corresponding to a dielectric constant range from 4 to 72. To the best of our knowledge, this article presents for the first time the ability of a fully textile SIW cavity antenna-based sensor to characterize the dielectric properties of a liquid under test and emphasizes its differentiating features compared to PCB-based designs. The unique attributes of the textile-based antenna stem from its flexibility, conformability, and compatibility with various liquids.

Research on Step-down Resonance Suppression and Filtering Device

In recent years, offshore wind farms have developed rapidly, and their installed capacity is getting bigger and bigger, and the offshore distance is getting farther and farther. In order to meet the needs of large-capacity and long-distance offshore wind power transmission, the AC submarine cable has the characteristics of long distance, high voltage and large cross-section. Along with the significantly improved transmission capacity, its equivalent capacitance is also increasing, which further reduces the resonance frequency of the offshore wind power AC transmission system. If the parallel resonance frequency of the offshore wind power transmission system is close to the main harmonic current frequency band of wind turbines, it will cause harmful system resonance and harmonic amplification, significantly increasing the harmonic current of grid-connected lines and the voltage distortion rate of nodes in nearby power grids, and seriously affect the safety of equipment and the safe and stable operation of offshore wind power transmission system. A step-down resonance suppression filtering device applied to the offshore wind power transmission system is proposed. The AC cable is connected to the low-voltage 35 kV side of the compensation winding of the centralized control center to eliminate the resonance risk of the 220 kV system and filter out the harmonic current. Compared with the existing technical scheme, the device has the advantages of simple control, reliable operation, stable resonance suppression effect, low operation loss and the like, and has great engineering popularization value.

Achieve hybrid energy harvesting based on the internal resonance of a two-degree-of-freedom cantilever beam

Taking a cantilever beam with two-degree-of-freedom (DOF) as an example, this paper studies the energy transfer mechanism between the vibration DOF and the rotation DOF, proposes a hybrid energy harvesting scheme, establishes the dynamic equation and solves it. Through the simulation of the analytical equation, it is found that under the condition of internal resonance of two DOFs, the two nonlinear peaks on the rotation DOF are very conducive to energy harvesting in the wide frequency domain. Furthermore, the influence of excitation amplitude, electromechanical coupling coefficient, time domain constant and other parameters on the resonance frequency and amplitude response of the energy harvesting system is studied.

Closed-loop Control of Biaxial Fatigue Loading of Wind Turbine Blades Based on Visual Inspection

Based on the inertial vibration excitation device, a biaxial fatigue loading system for wind turbine blades is established by using visual inspection technology and virtual spindle decoupling to control the vibration excitation motion of wind turbine blades. The image feature point tracking method is used to detect the blade vibration state. Considering the system vibration frequency characteristics, the phase difference between the exciting force and the vibration displacement is detected based on the phase detector, and the system resonance frequency is adaptively tracked to achieve accurate control of the double-free amplitude of the blade. The fatigue test shows that the control system can maintain the amplitude error of the blade, the adaptive tracking control method is reliable and effective, and the accuracy and reliability of the fatigue test are improved.

Double-Sided LCC Compensation Network and Its Tuning Method for Wireless Power Transfer for EV charging

Abstract: This research explores a double-sided LCC compensation network's utilization in an inductively coupled wireless power transfer (WPT) system for electric car charging applications and its wireless power transfer tuning procedure (WPT). A wireless power transmission system is offered with a double-sided LCC compensating network. The compensation circuit is crucial because it may be used to adjust the system's resonance frequency, lower reactive power in the power electronics converter, and boost the efficiency and capability of transferred power. The proposed architecture and its tuning technique allow the system to operate at a constant switching frequency since the resonant frequency is unaffected by the coupling coefficient between the two coils and is also independent of the load status. Also, it has been discovered that the corrected receiving coil inductance is a useful tuning parameter for ensuring the primary side zero voltage switching (ZVS) operation.

FRF Based Structural Modification of a Mechanical System by Adding Masses and Utilizing the Grey Wolf Optimization Technique

Resonance and anti-resonance frequencies are important parameters that determine the dynamic behavior of mechanical systems. Changes in these parameters, which depend on the system's physical properties such as mass and stiffness, also affect the system's dynamic behavior. Finding the necessary structural modifications to adjust the resonance and anti-resonance frequencies of a system to the desired values is a study area of inverse structural modification. In this study, an inverse structural modification method for one and multi-rank modifications is presented. With the presented method some resonance or anti-resonance frequencies of mechanical systems can be shifted to prescribed values by calculating the necessary modifications. The presented method is based on Sherman-Morrison (SM) formula and uses the frequency response functions (FRF) of the original system directly. For one modification an exact solution is obtained on the other hand for two or more modifications some nonlinear set of equations has to be solved. A meta-heuristic optimization technique known as Grey Wolf Optimizer (GWO) is applied for the solution of the nonlinear equations. The method is applied to a six-degrees-of-freedom mass-spring system. Some resonance and anti-resonance frequencies in the frequency bandwidth of the system are selected as target frequencies. The necessary modification masses are calculated to match these frequencies. After applying the calculated masses to the system the target frequencies are obtained successfully.

Evaluation of Resonance Frequency and Micromotion to Achieve Implant Stability Using Vibroacoustic Resonance Frequency Analysis: A Mathematical Model

AbstractDental implants are surgically implanted into the patient's jaw to replace a missing tooth. The implant should have adequate time to integrate with bone before being subjected to masticatory force to avoid early failure. Resonance frequency analysis (RFA) is one of the approaches for determining an implant system's primary stability in terms of micromotion. This research aims to create a two degrees-of-freedom (DOF) mathematical model for dental prostheses based on the vibroacoustic RFA approach. In vibroacoustic system, a loudspeaker or buzzer is used as an input and the displacement of implant is measured using RFA. A sinusoidal force is used which produces a combination of translational and rotational motion of the implant system. While adjusting the input frequency from 4000 to 12,000 Hz, is used with the help of matlab which later computes the implant system's subsequent micromotion and resonance frequency. matlab is used to visualize the resonance frequency, which is 6658.38 Hz in case of rotational motion and 8138 Hz in translational motion. The micromotion was 1.2692 × 10−11 m in case of translational motion and 6.91088 × 10−9 radians in case of rotational motion. When there is less micromotion, a higher resonance frequency suggests more excellent osseointegration. For the evaluation of implant stability, a mathematical model is a primary approach that can be implemented to design a stability device using vibroacoustic RFA.

A Novel Anti-Offset Interdigital Electrode Capacitive Coupler for Mobile Desktop Charging

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.

Soil resistance during vibratory driving in sand

A mechanism to explain pile shaft resistance during vibratory driving is discussed. One hypothesis is that horizontally oscillating stresses temporarily reduce shaft resistance. Vibration measurements were conducted in medium-dense to dense sand during vibratory driving. A large compaction probe was installed by a vibrator with variable frequency. The driving process and ground response were documented in detail. Geophones were installed on and below the ground surface. Horizontal ground vibrations were measured at three levels below the ground surface. The difference in vibration response of the ground during driving at a high frequency (27 Hz) and at the system resonance frequency (15 Hz) showed the effect of the vibrator operating frequency on penetration speed and emitted ground vibrations. Horizontal stress pulses are emitted along the probe shaft, which can temporarily reduce static horizontal stresses acting against it. This phenomenon can explain the temporary reduction of shaft resistance and efficiency of vibratory driving in granular soils. As a result of these pulses, the horizontal stresses are increased permanently. Using a monitoring and process control system, the system resonance frequency can be determined in the field – a critical parameter for vibratory driving resistance, emission of ground vibrations and vibratory compaction of granular soils.

Changes in Lung Volume Caused by High-Intensity Acoustic Oscillations at the Resonant Frequency of the Respiratory System

Changes in Lung Volume Caused by High-Intensity Acoustic Oscillations at the Resonant Frequency of the Respiratory System