Simulated Frequency Response Research Articles

Comparative Study on Hyperelastic Constitutive Models for the Static and Dynamic Behavior of Resilient Mounts

Resilient mounts play a vital role in anti-vibration and shock-absorption systems, making precise estimation of their static and dynamic stiffness essential for ensuring optimal mechanical performance and effective design. This study investigates the behavior of resilient mounts by analyzing their static and dynamic stiffness characteristics through the application of various hyperelastic constitutive models. Seven hyperelastic models were reviewed and systematically compared using numerical simulations, experimental data, and analytical solutions. The model parameters were calibrated and optimized based on experimental results obtained from quasi-static loading tests, including tension, compression, and shear conditions. Additionally, frequency response simulations were employed to evaluate the dynamic behavior of the resilient mounts under varying preload scenarios. The results provide practical insights into the performance of hyperelastic models and offer a comprehensive guideline for selecting suitable models for resilient mount applications, contributing to improved accuracy in both static and dynamic performance predictions.

Design of a Suspension Controller with Human Body Model for Ride Comfort Improvement and Motion Sickness Mitigation

This paper presents a method to design a suspension controller with a human body model for ride comfort improvement and motion sickness mitigation. Generally, it has been known that the vertical acceleration of a sprung mass should be reduced for ride comfort. On the other hand, recent studies have shown that, combined, the vertical acceleration and pitch rate of a sprung mass are key factors that cause motion sickness. However, those variables have been considered with respect to the center of gravity of a sprung mass. For motion sickness mitigation, the vertical acceleration of a human head should be also considered. In this paper, the vertical accelerations and pitch rates of a sprung mass and a human head are controlled by a suspension controller for ride comfort improvement and motion sickness mitigation. For the controller design, a half-car and human body models are adopted. With those models, several types of static output feedback suspension controller are designed with linear quadratic optimal control methodology. To reduce the pitch rate of the sprung mass and the vertical acceleration of the head, a filtered-X LMS algorithm is adopted as an adaptive feedforward algorithm and combined with the static output feedback controllers. A frequency response analysis and simulation are performed with the designed controllers on vehicle simulation software, CarSim®. From the simulation results, it is shown that the proposed controllers can effectively reduce the vertical accelerations and the pitch rate of the sprung mass and the human head.

Study on Dynamic Characteristics of Resilient Mount Under Preload.

Resilient mounts are essential for anti-vibration and shock absorption applications, making accurate predictions of their static and dynamic behaviors critical for effective design and mechanical performance. This study investigates static and dynamic characteristics of resilient mounts to predict their effects. Tension, compression, and shear tests were performed under quasi-static loading conditions to obtain stress-strain cycle curves. This study includes a review of the Yeoh hyperelastic model, which consists of three parameters, and discusses the calibration of these parameters to describe the hyperelastic material behavior. The parameters were validated through numerical analysis by comparing them with experimental results from quasi-static tests on the resilient mount. The dynamic behavior was further analyzed using modal analysis and frequency response simulations under various preload conditions. Results show that increasing preload significantly shifts the transmissibility curves and resonance peaks to lower frequencies. This study offers valuable insights into static and dynamic characteristics of resilient mounts, contributing to the design and optimization of vibration isolation systems for naval applications.

A tunable dual-narrowband HTS filter using coding superconducting metamaterials aided by grey wolf algorithm

Abstract The design of tunable dual-narrowband high-temperature superconducting (HTS) filter based on coding superconducting metamaterials aided by grey wolf algorithm (GWA) is proposed in this paper. By virtue of the characteristics of right/left-handed bands and scale of deep sub-wavelength, the tunable metamaterials unit loaded with varactor is designed, with coupling types of coding pairs further studied. A tunable sixth-order HTS filter circuit is then constructed, whose layout is effectively optimized by newly developed GWA method. Simulated frequency responses demonstrate that the center frequencies of dual-band respectively locate at 170.1-177.2 MHz (Band I) and 185.2-194.1 MHz (Band II), with 3-dB fractional bandwidth (FBWs) of 0.65%-0.61% and 0.62%-0.57%. The deeply miniaturized circuit size is 0.037×0.046 λ2 g, and the close-to-band rejection level reaches 80-dB. Experimental results of fabricated prototype measured at 70 K validate the feasibility of described design method for high order tunable HTS filter.

Fingertip dynamic response simulated across excitation points and frequencies

Predicting how the fingertip will mechanically respond to different stimuli can help explain human haptic perception and enable improvements to actuation approaches such as ultrasonic mid-air haptics. This study addresses this goal using high-fidelity 3D finite element analyses. We compute the deformation profiles and amplitudes caused by harmonic forces applied in the normal direction at four locations: the center of the finger pad, the side of the finger, the tip of the finger, and the oblique midpoint of these three sites. The excitation frequency is swept from 2.5 to 260 Hz. The simulated frequency response functions (FRFs) obtained for displacement demonstrate that the relative magnitudes of the deformations elicited by stimulating at each of these four locations greatly depend on whether only the excitation point or the entire finger is considered. The point force that induces the smallest local deformation can even cause the largest overall deformation at certain frequency intervals. Above 225 Hz, oblique excitation produces larger mean displacement amplitudes than the other three forces due to excitation of multiple modes involving diagonal deformation. These simulation results give novel insights into the combined influence of excitation location and frequency on the fingertip dynamic response, potentially facilitating the design of future vibration feedback devices.

Analysis of frequency characteristics of power system with wind farm-energy storage coordinated inertial control

With the increasing penetration level of wind power in the power system, the decoupling of wind turbine rotor speed and system frequency has led to the loss of the inertia of wind farms (WF), which can no longer be neglected. With the continuous development of energy storage (ES) technology, WF-ES coordinated inertial control has attracted attention as an effective means for wind turbines (WT) to participate in inertia response. How to build a WF-ES coordinated inertial control strategy and analyze system frequency characteristics has become a key research issue. In this paper, the frequency response model of a power system with WF-ES is established using the system frequency characteristic analysis method. The wind speed zones of the WF are taken into account, and different WF-ES control schemes are adopted under different wind speeds, aiming to ensure the active participation of WTs in the system frequency process across all wind speed conditions and effectively prevent frequency secondary drop. Finally, a power system frequency response simulation model is built in Matlab/Simulink to analyze the frequency characteristics of the power system with WF-ES coordinated inertial control and verify the feasibility of the proposed WF-ES coordinated inertial control strategy under various wind speeds.

Bandgap analysis of periodic composite plates considering fluid–structure coupling

This article presents a novel approach for predicting vibration bandgaps in periodic composite plates with fluid–structure interaction (FSI) using a unit cell-based finite element model. The novelty of our approach lies in the formulation of a fluid-induced added mass matrix, which integrates the Bloch periodic boundary condition, allowing for the incorporation of the fluid’s inertial effect in the context of unit cell-based bandgap analysis. We therefore construct a unit cell model comprising a composite Mindlin plate which integrates periodic FSI effects with the simultaneous application of Bloch conditions on both the structure and the fluid domains. Subsequently, we studied a set of periodic composite plates with FSI effects on one or both sides, thereby assessing the influence of the fluid properties such as density and the fluid domain dimension on the structure vibration. The bandgap prediction is compared with the frequency response simulations which involve diversified microstructure designs. The obtained results provide indications regarding the effectiveness and applicability of the proposed numerical methodology.

An applicator for high-power rock comminution using microwave technology in the megawatt range

Abstract The mining industry is heavily dependent on energy-intensive processes, such as rock breakage, which leads to significant operational costs. This paper explores microwave-assisted rock breakage as an innovative method to enhance the efficiency of comminution within the mining industry. It introduces a system that employs a Klystron microwave power source with a maximum output of 7.5 MW, using a $\mathrm{TM}_{010}$ single-mode cavity at 3 GHz, to channel energy inside a specially designed rock cavity. The paper emphasizes the importance of designing an efficient microwave cavity for this system, focusing on the cavity’s design and simulation. Through both simulated results (using HFSS software) and experimental observations, the study reveals the promising application of microwave technology in the field of mining. The simulated frequency response of the designed cavity (S11) is −22 dB, it demonstrates significant potential for reducing both energy consumption and associated costs. Additionally, the designed cavity is fabricated from aluminum and filled with polyether ether ketone material. The measured frequency response (S11) of the cavity at 3 GHz is −17 dB.

Analysis of Coupled Vibration Characteristics of Linear-Angular and Parameter Identification

Abstract A steady-state sinusoidal and distortion-free excitation source is very important for the accuracy and consistency of the calibration parameters of micro-electro-mechanical systems (MEMS) inertial sensors. To solve the problem that the current MEMS inertial measurement unit (IMU) calibration device is unable to reproduce the spatial motion of linear and angular vibration coupling, research topics on the coupling vibration characteristics and parameter identification for an electromagnetic linear-angular vibration exciter are proposed. This research paper used Ampere’s law and Lorentz force to establish the analytical expressions for the electromagnetic force and electromagnetic torque of the electromagnetic linear-angular vibration exciter. Then, the main purpose of this paper is to establish uniaxial and coupled vibration electromechanical analogy models containing mechanical parameters based on the admittance-type electromechanical analogy principle, and the parameter identification model is also obtained by combining the impedance formula with the additional mass method. Finally, the validity of the coupling vibration characteristics and the parameter identification model are verified by the frequency response simulation and the additional mass method, and the relative error of each parameter identification is within 5% in this paper.

Topological localized modes in moiré lattices of bilayer elastic plates with resonators

We investigate the existence of higher order topological localized modes in moiré lattices of bilayer elastic plates. Each plate has a hexagonal array of discrete resonators and one of the plates is rotated at an angle (21.78∘) which results in a periodic moiré lattice with the smallest area. The two plates are then coupled by inter-layer springs at discrete locations where the top and bottom plate resonators coincide. Dispersion analysis using the plane wave expansion method reveals that a bandgap opens on adding the inter-layer springs. The corresponding topological index, namely fractional corner mode, for bands below the bandgap predicts the presence of corner localized modes in a finite structure. Numerical simulations of frequency response show localization at all corners, consistent with the theoretical predictions. The considered continuous elastic bilayered moiré structures opens opportunities for novel wave phenomena, with potential applications in tunable energy localization and vibration isolation.

Effect of indented growth rings on spruce wood mechanical properties and subsequent violin dynamics

Abstract In this study, the influence of “bear claw” or indented growth ring anatomical patterns on the vibro-mechanical behavior of spruce wood have been investigated, particularly in the context of utilizing these singularities/specific features for the construction of violins. By employing vibrometry and modal analysis followed by finite element model updating, the vibro-mechanical properties (specific stiffness in longitudinal (L) and radial (R) directions and shear LR plane, and associated damping) of the indented growth rings spruce were identified and implemented in a numerical model of a violin. Results have revealed a significant increase in specific moduli in R direction and LR plane and decrease in L direction of spruce wood in the presence of indented growth rings, therefore accompanied by a reduction in anisotropic elastic properties, in comparison to spruce without these patterns. These properties led to changes in violin dynamics, globally increasing resonance frequencies and changing the shape of the vibration modes. The simulated frequency response function of the violin at the bridge suggested a global shift of the admittance of the bridge toward higher frequencies. These results suggest a potential impact of indented growth rings of spruce on the acoustic properties of instruments.

Natural frequency response simulation and mathematical modelling of nettle fibre-based composites using RSM process

Natural frequency response simulation and mathematical modelling of nettle fibre-based composites using RSM process

Natural frequency response simulation and mathematical modelling of nettle fibre-based composites using RSM process

Natural frequency response simulation and mathematical modelling of nettle fibre-based composites using RSM process

Time-Based High-Pass, Low-Pass, Shelf, and Notch Filters

This paper presents formulations for time-based first-order and second-order high-pass, shelf, and notch filters. These formulations are an extension to the existing literature where low-pass filters are already developed using a multiphase controlled oscillator in conjunction with a phase detector and charge pump. The presented high-pass filter expands the circuit by introducing a current-controlled delay line (CCDL) that provides a direct path from input to output. By combining the high-pass filter with the low-pass filter, we show that shelf and notch filters can be obtained without an increase in circuit complexity compared to the high-pass filter. The results show good matching between the ideal small signal and the simulated time-based large signal frequency response. The simulated of total harmonic distortion for the filters shows an increase in distortion due to the nonlinearities introduced by the CCDL for the high-pass, notch, and shelf filter compared to the existing low-pass filter. The derivation of the new filter types allows the creation of complex high-order time-based filters by combining multiple first- or second-order filters.

Design and Performance Analysis of Rectangular Microstrip Patch Antennas Using Different Feeding Techniques for 5G Applications

In this article, the design and performance of a novel rectangular microstrip patch antenna (RMPA) utilizing the dielectric substrate material FR4 of relative permittivity (Ԑr = 4.3) and thickness (h = 0.254 mm) is proposed to operate at (fr = 28 GHz). Three different feeding techniques (microstrip inset line, coaxial probe, and proximity coupled line) are investigated to improve the antenna radiation performance especially the antenna gain and bandwidth using Computer Simulation Technology (CST) and High Frequency Structure Simulator (HFSS). The simulated frequency responses generally reveal that the proximity-coupled fed provides extremely directive pattern and maintain higher radiation performance regardless of its antenna size which is larger than the other considered feeding ones. With the presence of the three feeding techniques, the gain is improved from 5.50 dB to 6.83 dB additionally, the antenna bandwidth is improved from 0.6 GHz to 3.60 GHz at fr = 28 GHz when the reflection coefficient S11= -10 dB. Compared to the previously designed RMPA, the proposed design has the advantages of reliable size, larger bandwidth and higher gain, which make it more suitable for many 5G application systems.

A Proposed Frequency Selective Surface (FSS) using Bio-Inspired Element for Wi-Fi 6E Applications

Recently bio-inspired elements with shapes or geometries found in nature have received special attention, both for applications in antennas and in electromagnetic filters, the unit cell of the proposed FSS consists of a modification in a bio-inspired shaped element. A single and multilayered band-stop Frequency Selective Surface (FSS), with polarization independence, is proposed to be used in frequency applications at 6.0 GHz (Wi-Fi 6E). In the industry, Wi-Fi 6E is the name that identifies those Wi-Fi devices that operate in the 6.0 GHz band, designed to improve efficiency and more capacity than previous standards. Band-stop frequency responses for the single and multilayer structures are presented. The simulated frequency responses show bandwidth values for inhibit transmission about of 1.75 GHz and 3.15 GHz, respectively for single and multilayer structures. Furthermore, good agreement between simulated and measured results is shown for the single bio-inspired FSS. The proposed FSS structure presents features that allow its use as an electromagnetic filter or its integration with microstrip antennas developed for applications in the same standard.

Multi-Body Dynamic Analysis of Hydrostatic Bearing with the MMC Material in Micro-Nano Machining.

This study focuses on the analysis of a linear hydrostatic bearing using harmonic frequency response and harmonic response simulations. The aim is to evaluate the feasibility of replacing the existing alloy steel material with a metal matrix composite (MMC) in terms of its performance and dynamic characteristics for both the base and carriage parts. The simulation results indicate that the MMC material exhibits higher resonant frequencies and improved damping capabilities compared to the structural steel material. The higher resonant frequencies observed in the MMC material are attributed to its stiffness and structural properties. These properties contribute to increased natural frequencies and improved vibration damping characteristics. This suggests that incorporating the MMC material in the bearing design could enhance motion control, improving the ability to precisely control and manipulate the movement of components or systems. In the context of ultraprecision machining applications, incorporating the MMC material in the hydrostatic bearing design can also lead to a more accurate and controlled motion, resulting in improved precision and finer machining outcomes. The displacement analysis confirms that both materials meet the specifications provided by the manufacturer, supporting the viability of using MMC as an alternative. However, further experimental validation and considerations of material feasibility, manufacturing factors, and cost-effectiveness are necessary before implementing the MMC material in practical applications. Overall, this research highlights the potential benefits of MMC in the design of linear hydrostatic bearings, paving the way for enhanced performance in ultraprecision machining processes.

System identification using Bayesian model updating with cross-signature correlations

In this paper, a novel likelihood function for Bayesian model updating algorithms is proposed, in particular for the transitional Markov chain Monte Carlo algorithm. The likelihood function is based on a measure of fit in which the prediction errors between the measured and simulated frequency response functions are evaluated using the cross-signature correlation. This formulation avoids the problem that for the commonly used modal measure of fit, the obtained results are ambiguous (i.e., correlated) when both the mass and stiffness properties are uncertain. Validation is first performed on simulated test data of cross-laminated timber structures and, in a second application, on real experimental data of a cross-laminated timber panel by performing Bayesian model updating on a finite element model of the specimen under consideration.

Metamaterial beam with dual-action absorbers for tunable and multi-band vibration absorption

This paper presents a new class of metamaterial beams of tunable and multi-band vibration absorption. The metamaterial beam is composed of uniform and periodic beam cells with locally resonant substructure called dual-action vibration absorber, DA. A DA vibration absorber comprising of three locally resonant subsystems, 3-DOF spring-mass-damper subsystems, is utilized to generate frequency stopbands to stop elastic wave propagation. The governing equations of motion for a periodic beam cell are derived. Several distinct mass and stiffness configurations for the metamaterial beam with DA vibration absorber are proposed. The dispersion relations and presence of three frequency stopbands are studied. A finite element method based on Timoshenko beam theory is used to model and analyze the introduced metamaterial beam with DA vibration absorber. The frequency response simulations agree well with the projected stopbands of the developed dispersion relations of the mass and stiffness configurations. The concept of the presented metamaterial beam with tunable and multi-stopbands is promising for wave propagation attenuation and control applications.

Small-Signal Modeling of Phase-Shifted Digital PWM in Interleaved and Multilevel Converters

In this article, small-signal modeling of digital pulsewidth modulators (DPWMs) used in multicell voltage source converters (VSCs) is addressed. In addition to sampling and computation, DPWM introduces delay, which impairs VSC's dynamic performance and robustness. In order to take into account the influence of modulation delay, an accurate small-signal representation of DPWM is necessary. Here, modeling of multisampled bipolar and unipolar phase-shifted DPWMs for single-, double-, and multi-update strategies is presented. The simplest multilevel modulation of single-cell full-bridge VSCs, unipolar DPWM, is also covered by the analysis. The derived operating-point-dependent small-signal DPWM models are verified using simulated and experimental frequency response measurements up to four times the Nyquist frequency. Comparisons are also made with the models conventionally considered in the literature. Additionally, an approximate method is presented to model the influence of dead time on DPWM's small-signal dynamics. For the purposes of showcasing the importance of the proposed DPWM models, high-frequency admittance of a VSC employing multisampled multiupdate unipolar DPWM is modeled and verified in simulations and experiments.