Extra Damping Research Articles

A parametric study on the effect of ring damper on wheel damping

Ring dampers have been widely applied to control vibration of, and noise from, train wheels due to the simple structure, negligible impact on operational safety and potential in vibration and noise reduction. Yet, parameters affecting the vibro-acoustic performance of a ring-damped wheel are not adequately studied. In this paper, the apparent modal damping ratios of a ring-damped wheel are studied numerically using a finite element model allowing for frictional nonlinearity. Studied parameters include the impact force used to excite the wheel, the preload in the ring, the friction coefficient of the interface between the ring and the wheel, and the number of rings installed. Several findings can be drawn from the study. Installation of one or two rings to the wheel does not change the resonance frequencies (they are also termed the modal frequencies of the ring-damped wheel) but reduces the resonance responses by generating extra damping to the modes. The ring is more effective for radial excitation than for axial excitation. At most modal frequencies, damping with double rings is higher than with a single ring. Although there are few modal frequencies at which the modal damping ratios are reduced by installing the second ring, the average damping ratio with two rings is much higher, by a factor of 2.37 for axial excitation and 1.73 for radial excitation, than that with a single ring. The apparent damping of the ring-damped wheel increases with the level of the impact force, especially for radial excitation. There is an optimal combination of the preload in the ring and the frictional coefficient with which damping induced by the ring is the highest. Besides, the average damping ratios of the modes above 2000 Hz are proposed to be an indicator of the effectiveness of the performance of a ring-damped wheel in noise reduction.

Theoretical and experimental research on vibration control of the tuned liquid damper with damping net and sloped-bottom

A novel tuned liquid damper with a damping net and a sloped-bottom (DNS-TLD) is proposed as an alternative to traditional tuned liquid damper (TLD), which has limitations such as low damping efficiency and high water consumption. By combining a sloped-bottom TLD with a damping net, the DNS-TLD can increase liquid sloshing within the tank, providing a greater extra damping ratio while using less water. To demonstrate its seismic reduction process, a controlled structure equipped with a DNS-TLD mechanics model is developed. A simple method is proposed for estimating the total equivalent damping ratio of DNS-TLD. The damping performance of the structure equipped with DNS-TLD is compared and analyzed with other types of TLD using single-frame shaking table tests. Experimental findings are compared with numerical simulation results to substantiate the DNS-TLD damping law and the accuracy of the total equivalent damping ratio calculation approach. Subsequently, seismic dynamic time analysis of a multi-story structure equipped with DNS-TLD is carried out to verify its effectiveness in actual structural seismic reduction control. Both shaking table tests and numerical simulation results demonstrate that DNS-TLD is superior to other types of TLD in terms of damping performance, efficiency, robustness, and engineering applicability by effectively combining the advantages of a sloped-bottom TLD and a damping net.

The Use of Bracing Dampers in Steel Buildings under Seismic Loading

This study focuses on the modeling of manufactured damper when used in steel buildings. The main aim of the manufactured dampers is to protect the steel buildings from the damaging effects that may result due to earthquakes by introducing an extra damping in addition to the traditional damping.Only Pure Manufactured Dampers, has been considered in this study. Viscous modeling of damping is generally preferred in structural engineering as it leads to a linear model then it has been used during this study to simulate the behavior of the Pure Manufactured Damper. After definition of structural parameters of a manufactured damper (its stiffness and its damping) it can be used as a structural element that can be added to a mathematical model of the structure. As the damping of manufactured dampers is generally greater than the damping of traditional materials, then the resulting damping matrix for the whole structure will be classified as a nonclassical damping. As most of literature on earthquake engineering have been written in terms of terminology related to mode superposition method and as this method is applicable to classical damping only. Then, this study tried to check the accuracy of the mode superposition method when applied to a structure with manufactured dampers. In this checking, approximated results of mode superposition method have been compared with more accurate results of direct integration method. From this comparison, it has been noted that the mode superposition method has different levels of accuracy depending on the relation between the fundamental frequency of the structure and the dominate frequency of the earthmotion. If the frequency of the structure is approaching to a dominate frequency of the earthmotion, then the damping effect will be important and the difference between the direct integration method and the model superposition method is increasing and vice versa

Sensitive analysis on added damping of shunted piezoceramic damping: cantilever and simply supported beam

The current research investigates the prediction of piezoelectric damping of resistively shunted beams caused by resistors via joule heating. In order to maximize the extra damping of the piezoelectric shunted beam system, a sensitivity analysis was done. The geometrical impacts on the maximum additional damping simulation are investigated for different length and thickness ratios with the position of the PZT-5H from the base of the cantilever and simply supported beams. Prior to doing sensitivity analysis, a mathematical model for estimating extra damping from voltage produced. Validation experiments are also carried out.

On the positive and negative damping effect of piezoelectric structure using switched-mode bidirectional energy conversion circuit

The introduction of a switched-mode bidirectional energy conversion circuit (BECC) facilitates the development of piezoelectric devices toward integrated and energy-efficient multi-functional designs. These new designs realize the organic combinations of two or more functions among energy harvesting (EH), vibration excitation (VE), and dynamic sensing. Yet, the structural effect after applying the BECC was not comprehensively investigated and strictly quantified. This letter analyzes the electromechanical joint dynamics of a piezoelectric structure using the BECC, which was developed after the synchronized triple bias-flip (S3BF) technique, under different EH and VE operation modes. It shows that the EH modes electrically induce an extra positive damping effect, while the VE modes induce a negative one. A lumped model and impedance analysis are used to evaluate the electrically induced damping and the energy conversion efficiency by the BECC. The closed-form expression of the vibration displacement under different operation modes is derived. Experiments are carried out under different operation modes and frequencies. The theoretical and experimental results show good agreement. They validate the damping tuning capability of BECC in either positive or negative damping directions. This switched-mode interface circuit offers a promising solution for building an adaptive dynamic control of piezoelectric structures with high energy efficiency.

The Effect of Porous Media on Wave-Induced Sloshing in a Floating Tank

Placing porous media in a water tank can change the dynamic characteristics of the sloshing fluid. Its extra damping effect can mitigate sloshing and, thereby, protect the integrity of a liquefied natural gas tank. In addition, the out-of-phase sloshing force enables the water tank to serve as a dynamic vibration absorber for floating structures in the ocean environment. The influence of porous media on wave-induced sloshing fluid in a floating tank and the associated interaction with the substructure in the ambient wave field are the focus of this study. The numerical coupling algorithm includes the potential-based Eulerian–Lagrangian method for fluid simulation and the Newmark time-integration method for rigid-body dynamics. An equivalent mechanical model for the sloshing fluid in a rectangular tank subject to pitch motion is proposed and validated. In this approach, the degrees of freedom modeling of the sloshing fluid can be reduced so the numerical computation is fast and inexpensive. The results of the linear mechanical model and the nonlinear Eulerian–Lagrangian method are correlated. The dynamic interaction between the sloshing fluid and floating body is characterized. The effectiveness of the added porous media in controlling the vibration and mitigating the sloshing response is confirmed through frequency response analysis.

Port-Hamiltonian Control of Nuclear Reactors

The port-Hamiltonian form (PHF) of nuclear reactor dynamics is first given with the corresponding Hamiltonian function determined by the shifted-ectropies of neutron kinetics and reactor thermal-hydraulics. Then, a passivity-based control (PBC) is proposed by adding extra damping injections to the PHF, and it is shown by theoretical analysis that satisfactory closed-loop stability can be guaranteed. The newly designed control law is applied to a nuclear heating reactor, and the simulation results not only verify the theoretical analysis but also show the satisfactory reactor power-level control performance.

Numerical study of cosmic ray confinement through dust resonant drag instabilities

ABSTRACT We investigate the possibility of cosmic ray (CR) confinement by charged dust grains through resonant drag instabilities (RDIs). We perform magnetohydrodynamic particle-in-cell simulations of magnetized gas mixed with charged dust and cosmic rays, with the gyro-radii of dust and GeV CRs on ∼au scales fully resolved. As a first study, we focus on one type of RDI wherein charged grains drift super-Alfvénically, with Lorentz forces strongly dominating over drag forces. Dust grains are unstable to the RDIs and form concentrated columns and sheets, whose scale grows until saturating at the simulation box size. Initially perfectly streaming CRs are strongly scattered by RDI-excited Alfvén waves, with the growth rate of the CR perpendicular velocity components equaling the growth rate of magnetic field perturbations. These rates are well-predicted by analytic linear theory. CRs finally become isotropized and drift at least at ∼vA by unidirectional Alfvén waves excited by the RDIs, with a uniform distribution of the pitch angle cosine μ and a flat profile of the CR pitch angle diffusion coefficient Dμμ around μ = 0, without the ‘90○ pitch angle problem.’ With CR feedback on the gas included, Dμμ decreases by a factor of a few, indicating a lower CR scattering rate, because the backreaction on the RDI from the CR pressure adds extra wave damping, leading to lower quasi-steady-state scattering rates. Our study demonstrates that the dust-induced CR confinement can be very important under certain conditions, e.g. the dusty circumgalactic medium around quasars or superluminous galaxies.

Digital Current Controller With a Novel Active Damping Design for IPMSM

Internal model control gets wide attentions in electric drives for its outstanding robustness. Underdamped oscillations however, always can be seen in the synchronous <i>d</i>- and <i>q</i>- axis components of the stator currents if without proper extra damping elements included, especially under the low sampling to fundamental frequency ratios. The reasons for these oscillations are analyzed in the discrete-time domain other than as usually done in the continuous-time domain. Following that, a distinctive active damping matrix is proposed for the current closed-loop control of interior permanent magnet synchronous motors (IPMSMs). As a result, the anti-disturbance capability is enhanced, allowing the oscillations, often seen in the <i>d</i>- and <i>q</i>-axis current components, suppressed very well. Compared with other damping methods, the typical PI structure is still retained, which is desired on the point of engineering view. At last, the analysis as well as the damping effectiveness is validated through experiments.

Universal simplified spectral models and closed form solutions to the wind-induced responses for high-rise structures

High-rise structures are characterized as wind-sensitive vertical structures, estimating the wind-induced vibration response is a key to the structural design procedure. This study presented universal wind load spectral models for high-rise structures, including tri-para and κ model for along-wind load characterized by power dissipating with frequency and analog filter model for cross-wind load dominant by power concentration induced by vortex excitation. The spectral models appear to provide good agreement with wind tunnel data of buildings with various configurations. With analog filter approach, the along-wind spectra can be approximated by a linear filter polynomial and the cross-wind spectra is expressed by a quadratic filter polynomial. Thus forming a simple differential equation for the along- and cross-wind excitation based on a pseudo idea white noise. The closed form solutions to the wind-induced responses are derived based on analog filter approach. The Lyapunov equations are also provided in the state-space for high-rise structures with and without extra damping devices. The presented closed form solutions can provide a powerful tool in codification and vibration control optimization.

Modeling the Impact on Wheel Sensor Readouts by Eddy Current Brakes Installed in High-Speed Trains

This paper presents a model to anticipate the impact of Eddy Current Brakes (ECBs) installed in high-speed trains on the readouts of rail-side wheel sensors. The purpose is to anticipate false positive readouts of train wheels when traversing, one of the main obstacles for full ECB deployment. The ECB type EWB 154 from Knorr-Bremse and Wheel Sensor types RSR180 and RSR123 from Frauscher Sensor Technology are represented in a comprehensive model, integrating LTSpice and CST Microwave Studio. The wheel sensor predicted readout error is 4% compared to measurements when DC current is not applied to the ECB (passive case). It is demonstrated that the RSR180 is not compatible with ECBs, whereas the RSR123 is. The impact of active (DC current fed) brakes is analyzed when performing running tests with a high-speed ICE 3 train equipped with ECBs. The model is adjusted to study the saturation of the rail and ECB pole cores. The extra damping of the wheel sensor fingerprint is modeled by an extra 6% drop that may well be applicable to passive tests in a laboratory setting to shift to active tests without actually performing them. In this way, cost and time would be saved. Based on the model outcomes, a test bench is recommended for laboratory tests to emulate active behavior.

Effects of Interfacial Oxidization on Magnetic Damping and Spin-Orbit Torques.

We investigate the effects of interfacial oxidation on the perpendicular magnetic anisotropy, magnetic damping, and spin-orbit torques in heavy-metal (Pt)/ferromagnet (Co or NiFe)/capping (MgO/Ta, HfOx, or TaN) structures. At room temperature, the capping materials influence the effective surface magnetic anisotropy energy density, which is associated with the formation of interfacial magnetic oxides. The magnetic damping parameter of Co is considerably influenced by the capping material (especially MgO) while that of NiFe is not. This is possibly due to extra magnetic damping via spin-pumping process across the Co/CoO interface and incoherent magnon generation (spin fluctuation) developed in the antiferromagnetic CoO. It is also observed that both antidamping and field-like spin-orbit torque efficiencies vary with the capping material in the thickness ranges we examined. Our results reveal the crucial role of interfacial oxides on the perpendicular magnetic anisotropy, magnetic damping, and spin-orbit torques.

Effect of Ni&lt;sub&gt;3&lt;/sub&gt;Al Coating on Vibration Suppression of Beams of Various Thicknesses

High cycle fatigue (HCF) caused by the vibratory stresses is the main cause of failure in many machine components, e.g. aircraft engine and gas turbine components, which has caused loss of many lives and billions of dollars. To avoid these kind of failures, vibratory stresses should be attenuated to an acceptable level, especially at resonant frequencies. A lot of previous studies have shown that thin coatings of different materials significantly reduced these vibratory stresses by adding extra damping to the system. These include viscoelastic materials, plasma graded coatings, piezoelectric materials, and magneto-mechanical damping material coatings, but some of these had applicability and performance issues. Among these thin coatings, magneto-mechanical materials are very effective in reducing these vibratory stresses significantly.In this study, the effect of different beam structure thicknesses under same magneto-mechanical coating of 0.2mm was studied. For this purpose, Ni3Al was applied as magneto-mechanical coating. The natural frequencies, damping ratios and displacements of beams were calculated before and after applying magneto-mechanical coatings using forced response analysis and hammer tests. The results indicated a sharp change in vibration characteristics i.e. natural frequency, damping ratio and beam deflections, of all the beams used. The results showed that the magneto-mechanical coatings were more effective when applied to thin structures as compared to thick structures, because thin structures have higher strains, which enabled magneto-mechanical coatings to dissipate larger amounts of energy of applied loadings, because performance of these coatings is strain dependent.

Influence of core stiffness on the behavior of tall timber buildings subjected to wind loads

This study analyzes the feasibility of the use of cross-laminated timber (CLT) as a load-bearing structural element in a 40-story building based on Chinese design requirements. The proposed design of the high-rise concrete—CLT building utilizes the core—outrigger system. Concrete is used for the central core and outriggers, and CLT is used for the rest of the structure of the building. Finite element models with different types of connections were developed using SAP2000 to analyze the lateral behavior of the building under wind action. The finite element models with rigid connections deduce the wind load distributions on individual structural elements, which determine the total number and the stiffness of fasteners of the CLT panels. Accordingly, spring links with equivalent stiffness that simulate the mechanical fasteners were employed in SAP2000. The results indicate that CLT increases the lateral flexibility of the building. A closed concrete core was substituted by two half cores to measure the requirement of the maximum lateral deflection. However, the acceleration at the building top still exceeded the limitation prescribed in Chinese Code JGJ 3–2010 owing to the lightweight of CLT and decreased stiffness of the hybrid building. To restrict this top acceleration within the limit, further approaches to increase the stiffness in the weak direction of the building are required. Methods such as the modification of the floor layout, increase in the thickness of walls, and addition of extra damping capacity should be considered and verified in the future.

Large Damping Enhancement in Dirac‐Semimetal–Ferromagnetic‐Metal Layered Structures Caused by Topological Surface States

AbstractThis article reports damping enhancement in a ferromagnetic NiFe thin film due to an adjacent α‐Sn thin film. Ferromagnetic resonance studies show that an α‐Sn film separated from a NiFe film by an ultrathin Ag spacer can cause an extra damping in the NiFe film that is three times bigger than the intrinsic damping of the NiFe film. Such an extra damping is absent in structures where the α‐Sn film interfaces directly with a NiFe film, or is replaced by a β‐Sn film. The data suggest that the extra damping is associated with topologically nontrivial surface states in the topological Dirac semimetal phase of the α‐Sn film. This work suggests that, like topological insulators, topological Dirac semimetal α‐Sn may have promising applications in spintronics.

Validation of Novel PLL-driven PI Control Schemes on Supporting VSIs in Weak AC-Connections

The integration of distributed energy resources (DERs) in modern power systems has substantially changed the local control capabilities of the grid since the majority of DERs are connected through a controlled dc/ac inverter interface. Such long-distance located DER installations, usually represented by current regulated dc sources, can inject large amounts of power into the main ac grid at points where the strength of the ac connection is low. The efficient and stable performance of such a power scheme is related to the capability of the control applied to retain the power extraction close to the maximum and simultaneously to regulate the dc-side voltage as well as the ac-side voltage magnitude at the weak ac connection point. This is implemented by designing the controllers of the voltage source inverters (VSIs) in a manner that reliably satisfies the above tasks. To this end, decentralized cascaded control schemes, driven by novel, locally implemented phase locked loops (PLLs), suitable to work in weak ac connections, are proposed for the VSI performance regulation by using new fast inner-loop proportional-integral (PI) current controllers. A decisive innovation is proposed by inserting an extra damping term in the inner-loop controllers to guarantee stability and convergence to the desired equilibrium. This is analytically proven by a rigorous analysis based on the entire nonlinear system model, where advanced Lyapunov-based methods are deployed in detail. As a good transient response of the VSI interface is indeed critical for the energy and grid system management, the conducted simulation and experimental results confirm that the proposed scheme efficiently supports the ac- and dc-side voltages of the VSI under different varying conditions in the power production or any voltage changes of the main grid.

Extra transient block for virtual synchronous machine with better performance

An extra transient block (ETB) for virtual synchronous machine (VSM) that is able to provide extra transient damping and adjust transient inertial to better stabilise the frequency of the VSM in a shorter time during transient period without altering the steady-state performance is proposed in this study. The ETB uses extra parallel series lead-lag blocks to get the transient frequency output to make the stability of the VSM less intensive to the parameter design of the virtual inertial and damping coefficient so that an easier parameter design method can be used. In other words, this method helps to solve the contradiction between dynamic response and stable performance, especially when the damping coefficient cannot be freely modified to increase damping for a large inertial value because of the mutual dependence between damping coefficient and droop coefficient caused by the use of inner reference frequency. Moreover, a simplified method for the parameter design of the ETB is proposed and the small-signal model of the ETB-based VSM is also derived. After that, the power coupling situation is analysed and comparisons with other control strategies are presented. Furthermore, time-domain simulation results are demonstrated to verify the effectiveness of the proposed method.

Ground-state cooling of a magnomechanical resonator induced by magnetic damping

Quantum manipulation of mechanical resonators has been widely applied in fundamental physics and quantum information processing. Among them, cooling a mechanical system to its quantum ground state is regarded as a key step. In this work, we propose a scheme that can realize ground-state cooling of the resonator in a cavity magnomechanical system. The system consists of a microwave cavity and a small ferromagnetic sphere, in which phonon–magnon coupling and cavity photon–magnon coupling can be achieved via magnetostrictive interaction and magnetic dipole interaction, respectively. Within experimentally feasible parameters, we demonstrate that the extra magnetic damping can be utilized to achieve ground-state cooling of the magnomechanical resonator via an effective dark-mode interaction. The magnomechanical cooling mainly comes from the magnon–phonon interaction terms. We further illustrate that optimal cooling can be obtained by adjusting the external magnetic field.

Passivity-based decoupling control strategy of single-phase LCL-type VSRs for harmonics suppression in railway power systems

High-frequency harmonics, produced by traditional single-phase voltage source rectifiers (VSRs), frequently lead to high-frequency resonances in railway power systems. The LCL-type filter is well-suited for suppressing such harmonics. To improve the performance of single-phase LCL-type VSR systems, this paper proposes a nonlinear passivity-based decoupling (PBD) control strategy, which improves the power quality of grid-connected systems and is highly robust. The Euler-Lagrange (EL) mathematical model of the single-phase LCL-type VSR system is established in a synchronously rotating frame, decoupling the active- and reactive-power controls. Based on this model, the passivity of the single-phase LCL-type VSR system can be analyzed, and the AC current of the system can be regulated by the proposed PBD controller by adding extra damping terms. A proportional-integral (PI) regulator is used to eliminate static errors in the dc-link voltage. By using the proposed control strategy, the single-phase LCL-type VSR system can have an improved quality of current injected into the traction power grid, a better dynamic performance, and a larger stability margin. The advantages of the proposed control strategy are demonstrated by simulations and experiments.

Integrations of Neural Networks and Transient Energy Functions for Designing Supplementary Damping Control of UPFC

This article presents an integrated scheme for supplementary damping control of unified power flow controllers (UPFCs) in order to mitigate low-frequency oscillations in power systems. The entire control system consists of the primary control and the supplementary control. In the primary control, the passivity-based control is considered in the current control loop of two converters for achieving more prompt and accurate dynamical responses. In the supplementary control, the transient energy function (TEF) approach will be explored first for designing the damping control of UPFCs. This control action can be considered as an extension of droop control used in the synchronous generator. In order to further cope with unmodeled dynamics of power systems and provide the online dynamic adaptation ability, neural networks approximated control actions are designated for online weight adjustments of the TEF-based supplementary control. Numerical simulations on three benchmark systems have been performed to validate the proposed control method for providing the extra damping and suppressing power swings even under severe operating conditions.