Vibration Reduction System Research Articles

A Self-Adaptive Vibration Reduction Method Based on Deep Deterministic Policy Gradient (DDPG) Reinforcement Learning Algorithm

Although many adaptive techniques for active vibration reduction have been designed to achieve optimal performance in practical applications, few are related to reinforcement learning (RL). To explore the best performance of the active vibration reduction system (AVRS) without prior knowledge, a self-adaptive parameter regulation method based on the DDPG algorithm was examined in this study. The DDPG algorithm is unsuitable for a random environment and prone to reward-hacking. To solve this problem, a reward function optimization method based on the integral area of the decibel (dB) value between transfer functions was investigated. Simulation and graphical experimental results show that the optimized DDPG algorithm can automatically track and maintain optimal control performance of the AVRS.

Higher-Order Complex Periodic Motions in a Nonlinear, Electromagnetically Tuned Mass Damper System

In this paper, the existence and bifurcations of higher-order complex periodic motions in a nonlinear, electromagnetically tuned mass damper system are studied through period-3, period-9, and period-12 motions. For such a nonlinear system, there exist three branches of period-3 motions, one branch of period-9 motions, and one branch of period-12 motion. The corresponding stability and bifurcations of periodic motions are determined. The frequency-amplitude characteristics for bifurcation routes of such higher-order periodic motions are presented. Numerical illustrations are presented for complex periodic motions. Higher-order unstable and stable periodic motions exist in nonlinear systems, which are difficult to control for energy harvesting and vibration reduction. The unstable higher-order periodic motions make the system responses more complicated. The higher-order stable and unstable periodic motions have been studied comprehensively. This study on periodic motions can help people better understand the dynamical behaviors of an electromagnetically tuned mass damper system under different excitation frequencies. The study of higher-order periodic motion stability and bifurcations will also benefit the new development and design of vibration reduction and energy harvesting systems.

Vibration Reduction of a Timoshenko Beam with Multiple Parallel Nonlinear Energy Sinks

A nonlinear energy sink is a promising device to reduce structural vibrations. In this work, the vibration reduction performances of multiple parallel nonlinear energy sinks attached to a short beam are investigated based on the Timoshenko beam theory. The dynamic equations of a vibration reduction system subjected to a harmonic excitation are established. The frequency responses are analyzed based on Galerkin discretization and the harmonic balance method, and the accuracy is verified by the Runge–Kutta method. An optimization method based on the genetic algorithm is proposed for the number, location, and cubic stiffness of the nonlinear energy sinks. The study reveals that, with the same total mass, multiple parallel nonlinear energy sinks can achieve a larger vibration reduction ratio than a single nonlinear energy sink. The parameter influences of the nonlinear energy sinks are revealed, and unstable responses with large cubic stiffness are presented. The optimal locations of the multiple parallel nonlinear energy sinks are related to low-order modal shapes. A larger reduction ratio on the resonant amplitude can be achieved compared to a uniform distribution of the nonlinear energy sinks. The optimal locations and cubic stiffness are related to the number of nonlinear energy sinks. In the studied case, the optimal number of nonlinear energy sinks was two.

Study of the Dynamic Model and Vibration Performance of Pot-Shaped Metal Rubber

Metal rubber has been extensively used in recent years due to its several unique properties, especially in adverse environments. Although many experimental studies have been conducted, theoretical research on metal rubber is still in its infancy. In this work, a dynamic model for the nonlinear characteristics of pot-shaped metal rubber is established on the basis of the asymmetric dynamic model of the wire rope shock absorber and the trace method model. In addition, the corresponding parameters in the model are identified based on the parameter-separation method. The theoretical hysteresis loop obtained using the model and the measured hysteresis loop agree with each other. The results show that the asymmetric dynamic model can better describe the asymmetric dynamic characteristics of pot-shaped metal rubber. Furthermore, a pot-shaped metal rubber vibration reduction system is built to further verify the correctness of the model. This study provides an experimental reference and a theoretical basis for the practical application of pot-shaped metal rubber in the field of three-dimensional vibration reduction.

Design and characteristics analysis of a new vibration reduction system for in service long span transmission tower

The wind-induced fatigue is the main factor leading to reduction of the bearing capacity of long-span transmission towers. In order to reduce the harm of wind vibration, this paper takes the 500 kV Jiamusi region ISLSTT (in service long span transmission tower) as the research object, and a new kind of vibration reduction system is proposed based on a steel wire rope damping structure, with which the vibration characteristics of ISLSTT is analyzed. Firstly, the layout and components of the new vibration reduction system are described, and the damping performance of which is verified and analyzed by finite element method. Secondly, the nonlinear finite element dynamic simulation model of ISLSTT with the new vibration reduction system is established, and the multi-dimensional fluctuating wind speed time history satisfying Davenport wind speed spectrum is given by harmonic superposition method in the time domain. Based on the Bernoulli theorem, the corresponding time history of wind pressure is obtained, and the random wind load is applied to the finite element model to verify the feasibility and efficient of the new vibration reduction system. Finally, the aero-elastic wind tunnel test model of ISLSTT with the new vibration reduction system is built, and the time history curves of stress and acceleration at key points under different wind directions are obtained. By comparing with the un-damped system, it is demonstrated that the average damping efficiency of this method in the scale of stress and acceleration is 72.88% and 77.17%, respectively. The simulation and wind tunnel test results also demonstrate that the vibration reduction system based on wire rope damping structure can effectively reduce the vibration of ISLSTT caused by the non-uniformity of wind speed. The research results lay a solid foundation for the vibration reduction design of in service long span tower-line system in future.

Experimental study on the nonlinear vibration of a new composite magnetorheological damping system

Magnetorheological shock absorbers provide poor damping force in shearing direction. Thus, a composite magnetorheological damper composed of a rubber spring and a magnetorheological damper is proposed to withstand shear loads. A new damper tester is designed to obtain the vibration signal of this damper under external excitation. The magnetorheological vibration-reduction system is a typical nonlinear system, which has higher requirements for information extraction. To obtain the deeper correlation between crucial parameters of the damper and its performance, the autoregressive higher-order spectrum model is established. The formulas of the autoregressive trispectrum and its two-dimensional slice spectrum, diagonal slice spectrum and one-dimensional slice spectrum are derived. Then, the characteristics of the trispectrum and its slices of a magnetorheological vibration-reduction system under different loading currents, working frequencies are discussed. The experiment results show that the composite damper has good performance compared with common rubber shock absorbers, and the higher-order spectrum and its slices exhibit different the distribution density of the spectral amplitude and the distribution of spectral peaks under different working states, which are closely related to the currents and frequencies. The higher-order spectra are effective to quantificationally describe nonlinear coupling, restrain gaussian noise and reserve phase components of the vibration system.

Advanced Prototype of an Electrical Control Unit for an MR Damper Powered by Energy Harvested from Vibrations

The work deals with a newly developed prototype of an electrical control unit (ECU) for a magnetorheological (MR) damper powered by energy harvested from vibrations. The ECU, consisting of a rectifying bridge, a driver unit, a microcontroller, and an internal power supply system, is an advanced version of the specially designed processing system for energy harvested from vibrations and the use of this energy to control the MR damper. Unlike a typical MR damper control system in which electrical circuits are powered from an external energy source, the ECU is powered by a part of the energy extracted from a vibrating system using an electromagnetic harvester. However, the excess amount of energy recovered over that necessary to power the MR damper and electrical circuits can be collected in harvested energy storage. The study presents the design concept of the ECU, computer simulations of the in-built driver unit (DU), the method of connecting the ECU with the harvester, the MR damper and displacement sensors, and also describes experimental tests of the engineered unit applied in a vibration reduction system (VRS) with an energy recovery function.

New fractional-order proportional integral derivative semi-active control composite magnetorheological damping system

In this paper, semi-active control analysis and research on the vibration reduction system of vibratory roller with nonlinear stiffness and fractional damping are carried out. A two-degree-of-freedom semi-vehicle mathematical model with nonlinear stiffness and fractional damping is established, and the fractional calculus operator in the model is approximated by using the Oustaloup filter algorithm. The vibration characteristics of passive control, proportional integral derivative control, and fractional-order [Formula: see text] control on the vibration reduction system of the vibratory roller are simulated and analyzed. Results show that the vibration reduction effect of the first-stage vibration reduction device of the vibratory roller is evidently improved by using fractional-order [Formula: see text] controller. Compared with traditional passive control, the parameters are increased by about 40%, and the vibration intensity evaluation grade of the vibratory roller can be improved by about one level, which provides a new idea for the research of the vibration reduction system of the vibratory roller.

A new active anti-vibration system using a magnetostrictive bimetal actuator

This paper introduces a new vibration reduction system using a magnetostrictive (Fe-Ga alloy) bimetal actuator. The proposed method (i) uses a magnetostrictive bimetal actuator instead of prevalent single material ones that need an auxiliary temperature control system and (ii) utilises a novel disturbance rejection control scheme that eliminates an unknown disturbance, without needing knowledge of its dynamics. In experiments, the vibration source is demonstrated as an unbalanced motor attached to the tip of a cantilever beam, resembling a beam-like element subject to ambiance vibrations. In the first step, the fundamental of this anti-vibration system is introduced and described. Then, analytical and data-driven modelling for the combination of the beam, the motor, and the bimetal is reported. These follow by model validation and impulse response analysis. Then, the proposed control system is introduced in detail. Experimental results indicate that the control system results in 33.6% decrease in beam vibration amplitude. Furthermore, the presented method in this paper can be employed as a design guideline for future applications.

Investigation on Low-Frequency Micro-Vibration Model of Air Spring With Auxiliary Chamber for Steel Plate Concrete Composite Structures

Steel plate concrete composite (SPCC) structure plays an essential role in modular construction, which has been widely applied in the floating foundation vibration reduction system. This study proposed a basis for designing an SPCC floating foundation vibration reduction system with an air spring as the main vibration isolation element. Based on the engineering thermodynamics and aerodynamics theories, the non-linear state equations and dynamic equations of each component of the air spring with auxiliary chamber were established, respectively. According to the operational characteristics of the air spring, the equations were linearized by using the small deviation linearization method under the condition of small amplitude, and the linearized model of the dynamic stiffness of the air spring with an auxiliary chamber was therefore proposed. The reliability of the proposed method was proved by a floating foundation vibration test, which was performed in a solid-state quantum laboratory. The constitutive equations of an air spring model and an SPCC floating foundation model were incorporated into the STERA_3D software. The simulation results showed good agreement with the low-frequency micro-vibration region test data.

Characterization of the solid deuterium layer in the inertial confinement fusion cryogenic target without the requirement of cryocooler deactivation

For the preparation of cryogenic fuel layer in inertial confinement fusion experiments, the vibration amplitude of cryogenic target must be reduced to the order of 1 μm or less to ensure the fuel layer to be distinguished by the X-ray phase contrast imaging system. An efficient vibration-reduction system with the Gifford-McMahon cryocooler mounted at the horizontal direction is designed, which is based on a two-stage floating thermal shielding and flexible connection. The obtained lowest temperature of the sample mount is less than 10 K, the temperature stability is within ±1 mK@18 K, the cooling power is greater than 500 mW, and the corresponding vibration amplitude is less than 1 μm. With this proposed method, the X-ray phase contrast imaging of cryogenic deuterium layer can be performed successively without requirement of cryocooler deactivation. Finally, the achieved resolution of the X-ray phase contrast imaging is about 1.5 μm while the contrast of solid-gas interface is larger than 5%, which is verified by the in-situ characterization of solidification of deuterium in the cryogenic target.

A sliding mode control strategy for active horizontal seat suspension under realistic input vibration

In the paper, an innovative active control of a horizontal seat suspension system is discussed in context of realistic input vibration that occurs in the cabins of agricultural tractors. The vibration reduction system is represented by the state-space model and its numerical parameters are determined experimentally. For such a reliable mathematical representation of the system dynamics, the finite-time sliding mode controller is successfully designed for different spectral classes of the random excitation signal. A multi-objective control strategy is implemented in order to satisfy opposite requirements, that is, at the limited value of active force, a horizontal vibration of the seated human body is considerably reduced, but the suspension travel does not exceed unacceptable stroke of the system. Laboratory measurements of the seated human body have shown improved comfort of drivers under fore-and-aft vibrations.

Vibration Reduction System with a Linear Motor: Operation Modes, Dynamic Performance, Energy Consumption

The study aimed to present the features of a 2-DOF vibration reduction system (VRS) equipped with a linear electrodynamic motor in passive, semi-active and active mode. At first, the VRS model was formulated. Then, simulation tests of the VRS were conducted to distinguish its most advantageous features in each mode and to analyze dynamic performance and energy consumption. Next, the VRS was experimentally tested to evaluate its effectiveness in each mode for the assumed excitations and to compare tests results against simulation data. In active mode, a sliding mode algorithm was employed for motor control, while in semi-active mode, the equivalent damping coefficient analysis was used.

Design and Experiment of Magnetic Antenna Vibration and Noise Reduction System

The magnetic antenna can receive extremely weak underwater magnetic signals, and induce the magnetic field intensity which can reach the femto-tesla (fT) level, making it widely used in underwater electromagnetic signal detection. However, even the slightest vibration in the environment transmitted to the antenna will make it cut the geomagnetic field movement; as a result, electromagnetic-induced noise would be generated, and affect the performance of the magnetic antenna. The best method to suppress the motion induced noise is to isolate the magnetic antenna effectively from the ambient vibration. In this paper, the vibration reduction requirements of magnetic antenna are identified, and the principle of vibration absorber system of the magnetic antenna model is established. A magnetic antenna damping system, mainly focusing on low frequency, is proposed by using a silicon rubber elastic element. Based on the proposed method, a magnetic antenna damping system with an attenuation rate up to 100 times is designed, and some performance experiments are scheduled. The experiment results show that the performance of the magnetic antenna damping system meets the design requirements.

Dynamic modeling and analysis of vertical vibration reduction system for passenger train

Based on wheel-rail impact vibration and considering the body stiffness and natural damping, this paper builds a four-degree-of-freedom vibro-impact system model for passenger train’s vertical vibration reduction system. The Poincaré map of the system is determined by the analytic solution of the system derived from the motion differential equation of the multi-degree-of-freedom vibro-impact system combined with Newton's second law. It is found that the fork bifurcation, Hopf bifurcation and other dynamical behavior leading to Chaos when the system parameters are changed. On this basis, the dynamic parameters of the train are optimized to avoid chaos in the train operation, reduce the vertical vibration of the train, improve the stability and comfort of the train operation, and provide the theoretical basis for the active vibration reduction design of the train.

Design, analysis, control simulation, and experiment of novel electromagnetic hybrid vibration absorber

This paper presents a novel type of electromagnetic hybrid vibration absorber (EHVA) with a double-ring series permanent magnetic circuit applied to improve the two-stage vibration isolation system of marine power machinery. The EHVA comprises a mover with several groups of coils having a series connection, as well as a stator with internal permanent magnets and external permanent magnets, which form a novel magnetic circuit structure based on an improved Halbach array. In this magnet circuit, two adjacent groups of magnetic induction lines overlap at the coil position, thereby strengthening the magnetic field intensity. When the mover moves axially, the coil cuts the magnetic induction line to produce Lorentz force and magnetic damping force. First, the dynamic parameters of the EHVA were calculated based on multi-rigid-body dynamic theory and fixed-point theory. Second, the mechanical and electromagnetic structures of the EHVA were designed. Finally, a test stand was constructed, the system control channel was identified, and the simulation as well as experiment for vibration control using an [Formula: see text] controller were performed. Results indicated that the hybrid vibration reduction system under control reduced the acceleration amplitude by 12.3 dB at 30.6 Hz and achieved better vibration absorption effects between 27 and 33 Hz compared with the uncontrolled system.

Experimental Validation on Active Vibration Reduction System for 2.4m×2.4m Transonic Wind Tunnel Model

An active vibration reduction system has been developed to solve pitch vibration problems of the force test models in 2.4m × 2.4m transonic wind tunnel. The twin flexure hinges structure types and PD control algorithm are used in the system. The constitution of active vibration reduction system is presented. The results of Ground Tests and wind tunnel tests are given. The influence of the system on the static signal of the balance and its performance are discussed. The ground tests show that the system can increase the damping of the sting more than tenfold. It is shown that the vibration amplitude decreases by more than 70% in wind tunnel tests. The wind tunnel tests also reveal that the active vibration reduction system has relatively strong performance on the suppression of the model vibration.

Real-Time Sensing Action of the Electromagnetic Vibration-Based Energy Harvester for a Magnetorheological Damper Control

This study investigated the self-sensing mechanism in the electromagnetic vibration-based energy harvester (EV-EH) prototype specially engineered for a commercial magnetorheological (MR) damper. The objective of the work is to demonstrate that the EV-EH unit with a specific self-powered feature can also be employed as a relative velocity sensor in the system. To do this, the self-sensing action of the unit was experimentally studied over the assumed range of working conditions. The analysis of the test results and the determined self-sensing function indicated that the EV-EH has a highly accurate monitoring capability. The EV-EH self-sensing and self-powered features confirm the potentials and applicability of the unit for MR damper control in a vibration reduction system with energy regeneration.

Research on New Types of Suspension Vibration Reduction Systems (SVRSs) with Geometric Nonlinear Damping

Firstly, this paper puts forward two new types of suspension vibration reduction systems (SVRSs) with geometric nonlinear damping based on general SVRS (GSVRS), which only has geometric nonlinear stiffness. Secondly, it derives the motion differential equations for the two new types of SVRS, respectively, and discusses the similarities and differences among the two types and GSVRS through the comparison of motion differential equations. Then, it conducts dimensionless processing of the motion differential equations for the two new types of SVRS and carries out a comparative study on the vibration isolation performance of the two types of SVRS under impact excitation and random excitation, respectively. At last, it performs the optimal computation of the chosen new type of SVRS through the ergodic optimization method and studies the influence rule of SVRS parameters on vibration isolation performance so as to realize the optimization of vibration isolation performance.

Experimental Analysis of Power Flows in the Regenerative Vibration Reduction System with a Magnetorheological Damper

The aim of the work is to investigate power flows in the vibration reduction system equipped with a magnetorheological (MR) damper and energy regeneration. For this purpose, experiments were conducted in the test rig compound of the shaker and the vibration reduction system (electromagnetic harvester, MR damper, spring) which are attached to the sprung mass. The experimental data acquired under sine excitations enabled us to analyze instantaneous power fluxes, as well as a rate of inertial energy changes in the system.