Search Results (755)

Metamaterials are pushing the limits of traditional materials and are fascinating frontiers in scientific innovation. Mechanical metamaterials (MMs) are a category of metamaterials that display properties and performances that cannot be realized in conventional materials. Exploring the mechanical properties and various aspects of vibration and damping control is becoming a crucial research area. Their geometries have intricate features inspired by nature, which make them challenging to model and fabricate. The fabrication of MMs has become possible because of the emergence of additive manufacturing (AM) technology. Mechanical vibrations in engineering applications are common and depend on inertia, stiffness, damping, and external excitation. Vibration and damping control are important aspects of MM in vibrational environments and need to be enhanced and explored. This comprehensive review covers different vibration and damping control aspects of MMs fabricated using polymers and other engineering materials. Different morphological configurations of MMs are critically reviewed, covering crucial vibration aspects, including bandgap formation, energy absorption, and damping control to suppress, attenuate, isolate, and absorb vibrations. Bandgap formation using different MM configurations is presented and reviewed. Furthermore, studies on the energy dissipation and absorption of MMs are briefly discussed. In addition, the vibration damping of various lattice structures is reviewed along with their analytical modeling and experimental measurements. Finally, possible research gaps are highlighted, and a general systematic procedure to address these areas is suggested for future research. This review paper may lay a foundation for young researchers intending to start and pursue research on additive-manufactured MM lattice structures for vibration control applications. Full article

This paper proposes a distributed passivity-based control scheme for the consensus and vibration suppression of multiple space manipulators holding flexible beams. A space manipulator holding a flexible beam is essentially a rigid–flexible underactuated system. The bending deformation of the flexible beam is discretized by employing the assumed modes method. Based on Lagrange’s equations of the second kind, the dynamics model of each manipulator holding a flexible beam is established. By connecting such underactuated systems with the auxiliary Euler–Lagrange systems, a distributed passivity-based controller is designed under undirected communication graphs. To suppress flexible vibration effectively, a distributed controller with the feedback of the velocity of deflection at the free end of the flexible beam is proposed to achieve the manipulator synchronization and vibration suppression simultaneously. The stability of the proposed controller is analyzed with LaSalle’s invariance principle. Numerical simulations and experiments are conducted to show the effectiveness of the designed controllers. Full article

The vibration suppression of flexible robotic arms is challenging due to their nonlinear spatiotemporal dynamics. This paper presents a novel physics-informed neural network (PINN)-based input-shaping method for the vibration suppression problem. Through a two-phase training process of a neural network based on a loss function that follows both the physical model constraints and the vibration modal conditions, we identify optimal input-shaping parameters to minimize residual vibration. With the use of powerful computational resources to handle multimode information about the vibration, the PINN-based approach outperforms traditional input-shaping methods in terms of computational efficiency and performance. Extensive simulations are carried out to validate the effectiveness of the method and highlight its potential for complex control tasks in flexible robotic systems. Full article

In the space environment, the elastic vibrations of satellite solar panels are caused by various factors that disturb satellite missions. Therefore, we propose a multi-layered high-damping yoke structure based on a passive control method. To optimize the proposed yoke structure, we performed a free vibration test on various multi-layered blade specimens and designed a yoke structure with the maximum damping performance based on the test results. This high-damping yoke structure was mounted on a dummy solar panel with flexible mode (0.79 Hz) and basic characteristic tests were performed to validate the effectiveness of the solar panel vibration suppression. The test results demonstrated that the proposed multi-layered high-damping yoke is effective in suppressing the vibrations of the first and second modes. In addition, a thermal vacuum test was performed to investigate the delamination between multi-layered structures, and the test results proved the applicability of the proposed yoke structure in an actual space environment. Full article

Industrial robots are widely used in welding operations because of their high production efficiency. The structure of the robot and the complex stress conditions during welding operations lead to the vibration of the end of robot, which leads to welding defects. However, current vibration suppression techniques for welding robots usually only consider the robotic performance while overlooking their impact on the welding metal forming process. Therefore, based on the influence of robot vibration on welding pool stability during the welding process, a new welding robot vibration suppression method is proposed in this paper, along with the establishment of a welding pool stability assessment model. The proposed vibration suppression algorithm is based on the optimization of the welding trajectory. To enhance the performance of the method, the Particle Swarm Optimization (PSO) algorithm is applied to optimize the joint angular velocity and angular acceleration. Finally, robot welding experiments are designed and conducted. By comparing vibration measurement data and welding quality before and after the vibration suppression, the effectiveness and stability of the proposed method are validated. Full article

Air compressors play an important role in energy, mining, civil engineering, and transportation engineering. However, the abnormal vibration and noise of air compressors may pose a serious threat to the structural stability and smooth operation of these types of engineering equipment. To address the broadband noise and vibration problems of a new oil-free piston air compressor, we developed a hybrid optimization method that combines experimental testing, theoretical evaluation, and numerical simulation. Firstly, we conduct noise experiment testing, identify the frequency band of aerodynamic noise using a coherence analysis method, and design orthogonal experiments to further optimize pipeline noise. Then, the vibration characteristics were discussed from both theoretical and simulation perspectives. The dynamic balance has been redesigned on the spindle counterweight plate to reduce the force on the bearings, and a multi-body dynamics model has been constructed to demonstrate the effectiveness of the optimization. Subsequently, a finite element model of the compressor housing was established to analyze the radiation noise characteristics. Finally, three weak points in the structure were selected as key objects, and the structural stiffness was increased to improve vibration stability. The simulation results of radiated noise show that the proposed design scheme can effectively reduce vibration and noise, with a maximum noise reduction rate of 7.45%. Full article

The flywheel energy storage system (FESS) of a mechanical bearing is utilized in electric vehicles, railways, power grid frequency modulation, due to its high instantaneous power and fast response. However, the lifetime of FESS is limited because of significant frictional losses in mechanical bearings and challenges associated with passing the critical speed. To suppress the unbalanced response of FESS at critical speed, a damping ring (DR) device is designed for a hybrid supported FESS with mechanical bearing and axial active magnetic bearing (AMB). Initially, the dynamic model of the FESS with DR is established using Lagrange’s equation. Moreover, the dynamic parameters of the DR are obtained by experimental measurements using the method of free vibration attenuation. Finally, the influence of the DR device on the critical speed and unbalanced response of FESS is analyzed. The results show that the designed DR device can effectively reduce the critical speed of FESS, and increase the first and second mode damping ratio. The critical speed is reduced from 13,860 rpm to 5280 rpm. Compared with FESS of the mechanical bearing, the unbalanced response amplitude of the FESS with DR is reduced by more than 87.8%, offering promising technical support for the design of active and passive control systems in FESS. Full article

This paper proposes a nonlinear dynamic modeling method based on the lumped mass approach to address the challenge of modeling the vibrations of the output external gear and internal gear plate in an aerospace three-ring gear reducer. A vibration model of bending–torsion coupling with 12 degrees of freedom was established by comprehensively considering factors such as the time-varying meshing stiffness, gear transmission error, tooth side clearance, bearing support stiffness, and damping. Finite element modal analysis and vibration test results verified the vibration model’s accuracy and applicability, indicating that the model is both precise and valid. The vibration model was solved using the fourth-order, five-level Runge–Kutta method. The results show that the symmetrical arrangement design of the internal gear plate cancels the vibrations in all directions and suppresses the vibration displacement response on the output shaft. Full article

Gear modification, which involves the removal of material from the theoretical surface to improve the contact characteristics of the gear face, is widely applied in gear vibration reduction and noise optimization design. This paper establishes a dynamic model of the straight bevel gear (SBG) transmission system to accurately and efficiently evaluate the effects of different modification strategies on the vibrational characteristics of SBGs. Initially, the time-varying meshing stiffness (TVMS) of standard SBGs was calculated, and methods such as the slicing method and deformation coordination equations were used to calculate the TVMS under tooth profile modification (TPM), Lead crown relief (LCR), and comprehensive modification (CM), which were then validated against finite element method (FEM) calculations. Subsequently, taking into account the impact of time-varying meshing point vectors and the degree of contact overlap, a finite element node dynamic model of the SBG transmission system was established. Finally, by comparing the dynamic characteristics under different modification conditions, the study further elucidates that selecting the appropriate modification method and amount according to different service scenarios is an effective means to suppress gear transmission vibration. This research provides a theoretical basis for the design of gear modification and vibration control for SBGs. Full article

This paper presents a novel power electronic module (PEM) for chassis-by-wire in passenger cars. The PEM is supposed to be installed in a close-to-wheel position, which provides electrical interfaces with a power harness and signal harness. When the vehicle is driving, the PEM works as a dynamic vibration absorber (DVA) to diminish the negative effects of un-sprung mass. Based on the vibration system model, the mechanical principles are analyzed and the design parameters are mathematically optimized. For a comparison of different configuration schemes with an in-wheel motor (IWM), we take the condition of a vehicle driving at a speed of 15 m/s on a C-class road to examine indicators of vehicle body acceleration, wheel dynamic load, and suspension dynamic deflection. The calculation results prove that the system has advantages in ride comfort and wheel grounding characteristics. For the detailed design of the machine, we build a digital virtual prototype for simulation. Compared to the initial state, the optimized DVA configuration has obvious suppression in component vibration, including the vehicle body, the IWM, and the PEM. The frequency sweep analysis proves a robust result, which ensures that the frequency and amplitude are both within the vibration tolerance range of PEM operations. Full article

To suppress large vibrations of the cable in cable-stayed bridges, it is common to install transverse dampers near the end of the cable. This paper focuses on the cable-damper system; based on the dynamic stiffness method, an accurate dynamic analysis method considering cable parameters, damper parameters, and cable forces is proposed. First, a mechanical analysis model is established which is closer to the cable with a transverse damper installed in the bridge. The model considers the cable bending stiffness, sag, inclination angle, cable force, damper stiffness, damping coefficient, and damper installation height. Then, the characteristic frequency equation of the cable-damper system is established, and a solution method that combines the initial value method and Newton–Raphson method is proposed. This method is confirmed to provide more accurate frequency analysis for the cable-damper system. Finally, using this method, the effect of the damper parameters on the dynamic characteristics of the system is investigated. Full article

The analysis conducted herein has shown that the efficiency of smoke precipitation can be improved by additionally making smoke particles interact with ultrasonic (US) oscillations. Because the efficiency of US coagulation lowers when small particles assemble into agglomerates, the authors of this work have suggested studying how smoke particles interact with complex sound fields. The fields are formed by at least two US transducers which work at a similar frequency or on frequencies with small deviations. To form these fields, high-efficiency bending wave ultrasonic transducers have been developed and suggested. It has been shown that a complex ultrasonic field significantly enhances smoke precipitation. The field in question was constructed by simultaneously emitting 22 kHz US oscillations with a sound pressure level no lower than 140 dB at a distance of 1 m. The difference in US oscillations’ frequencies was no more than 300 Hz. Due to the effect of multi-frequency ultrasonic oscillations induced in the experimental smoke chamber, it was possible to provide a transmissivity value of 0.8 at a distance of 1 m from the transducers and 0.9 at a distance of 2 m. Thus, the uniform visibility improvement and complete suppression of incoming smoke was achieved. At the same time, the dual-frequency effect does not require an increase in ultrasonic energy for smoke due to the agglomeration of small particles under the influence of high-frequency ultrasonic vibrations and the further aggregation of the formed agglomerates by creating conditions for the additional rotational movement of the agglomerates due to low-frequency vibrations. Full article

The stability of the damping pad floating slab track (DPFST) plays a critical role in the operational safety and passenger comfort of urban rail transit systems and represents a significant technical challenge. This paper introduces a novel harmonic frequency damping device (HFDD) with preload characteristics to enhance DPFST stability. First, the rubber damping pad’s constitutive relationship is determined using uniaxial tensile tests and the Mooney–Rivlin model. Next, a vehicle–track coupled dynamic model and a finite element model of the DPFST with HFDD are developed. Finally, the effects of HFDD installation and parameter adjustments on the DPFS’s modal and dynamic responses are examined. Results show that the HFDD effectively adjusts the DPFS’s natural frequency and suppresses its acceleration and displacement. Increasing HFDD stiffness from 0 to 10 kN/mm raises the DPFS’s natural frequency by up to 7.58 Hz. Within the stiffness and damping ranges of 0–20 kN/mm and 0–100 kN·s/m, respectively, the HFDD significantly reduces DPFS vibration, with maximum reductions in acceleration of 45.64% and 64.24% and in displacement of 47.55% and 39.06%. However, beyond these ranges, further increases in stiffness and damping substantially reduce the HFDD’s vibration suppression effectiveness and excessively high values are impractical for engineering use. Full article

The microphonic noise induced by the vibration from cryocoolers has been found to cause energy resolution degradation in vibration-sensitive instruments. In this paper, theoretical and experimental research on the vibration generation mechanism of an aerospace-grade coaxial pulse-tube cryocooler (CPTC) is presented. Accordingly, suggestions for suppressing the vibration of the pulse-tube cryocooler are provided. A vibration model for the Oxford-type dual-opposed linear compressor is established, and the mechanism of vibration induced by the compressor is theoretically analyzed. A numerical simulation indicates that deviations in the compressor’s inductance coefficient, electromagnetic force coefficient, and flexure spring stiffness coefficient significantly affect the axial vibration of the compressor. The theoretical and experimental studies show that the high-order harmonic vibrations of the compressor are determined by both the resonance of the flexure springs and the high-order harmonics of the driving power supply. Through experiments and simulations, it is revealed that the dynamic gas pressure only induces vibration axially at the cold tip, while the radial vibration at the cold tip is determined by the heat head ‘s vibration and the structural response characteristics of the cold finger. Full article

Among all the existing possibilities within the renewable energies field, wind energy stands out due to the significant expansion of offshore turbines installed in coastal and deep-sea areas. Although the latter represent considerable energy generation potential due to their larger size and location in areas of strong winds, they are exposed to harsh environmental disturbances, particularly waves, causing these structures to experience vibrations, increasing in this way fatigue, reducing efficiency, and leading to higher maintenance and operational costs. In this work, vibration reduction is achieved using two structural control systems for a 5 MW barge-type floating offshore wind turbine (FOWT), tuned via a metaheuristic method, with genetic algorithms (GAs). Firstly, the standard deviation of the Top Tower Displacement (TTD) is used as a cost function in the GA to optimize a passive Tuned Mass Damper (TMD), resulting in a vibration suppression rate of 34.9% compared to a reference standard TMD. Additionally, two semi-active structural control systems based on a gain scheduling approach are proposed. In one of the approaches, the TMD parameters are optimized based on the amplitude of oscillations, achieving a suppression rate of 45.4%. In the second approach, the TMD parameters are optimized in real time for the identified wave frequencies, demonstrating superior performance for medium-high frequencies compared to the other TMDs. Full article