Semi-active Vibration Absorber Research Articles

Broadening Bandwidth in a Semi-Active Vibration Absorption System Utilizing Stacked Polyvinyl Chloride Gel Actuators.

Plasticized polyvinyl chloride (PVC) gel is a new soft and smart material, whose potential in electroactive variable stiffness can be used for vibration control in soft robotic systems. In this paper, a new semi-active vibration absorber is developed by stacking PVC gel actuator units. The absorption bandwidth of a single PVC gel absorber covers the range of three natural frequencies (76.5 Hz, 95 Hz, 124 Hz) of a rectangular steel plate in vibration attenuation. The maximum reduction percentage in acceleration amplitude is 63%. With stacked PVC gel actuator units, the absorption bandwidth can be shifted and obviously broadened.

Design and Experimental Study of a Multiple-Degree-of-Freedom Vibration Absorber by Using an Inertial Actuator

It is well known that the inertial actuator can be used as the passive vibration absorber if the natural frequency of the inertial actuator is closed to the targeted structural resonance frequency. Typically, the inertial actuator as a passive or semi-active vibration absorber can only control a single structural resonance at a time. In this study, a simple and practical multiple-degree-of-freedom (MDOF) vibration absorber, which is based on a single inertial actuator and a parallel connection of multiple low-pass filters as controller, is proposed to damp multiple structural resonances simultaneously. The control performance of the proposed MDOF vibration absorber is the combined control effects for both passive absorber and active absorber. It means that the multiple-mode structural vibration can be reduced effectively by using a single inertial actuator. Additionally, the proposed controller can be designed by low-cost analogue circuit and allows directly using acceleration feedback. The performance of the MDOF vibration absorber is first analyzed both numerically and experimentally. Then the proposed MDOF vibration absorber is applied to control the vibration of multiple resonances of a cantilever beam. The experimental results show that multimodal damping can be generated by the proposed MDOF vibration absorber.

Modelling of a semi-active vibration absorber featuring variable stiffness and variable damping using magnetorheological materials

This study focuses on vibration control and presents an innovative hybrid shock absorber with variable damping and stiffness. The simultaneous control over damping and stiffness is achieved using the Magnetorheological (MR) fluid and MR elastomer, respectively. A mathematical and Simulink model is developed by adding the four-parametric fluid model with the Bouc-Wen model. Two different road profiles, circular bump road and trapezoidal bump road profiles, are considered to analyze the performance of vibration absorbers. The compared results show the superiority of the proposed isolator over the passive system and reveal that the vehicle stability is improved by 87.5% to 92% and ride comfort is improved by 84.85% to 85.99% for circular and trapezoidal bump road profiles, respectively.

Smart hybrid VIV control of a linearly sprung cylinder using an internal semi-active NES-based vibration absorber coupled with two active rotating wake-control rods

Extensive two dimensional CFD simulations were carried out to investigate the hybrid active/semi-active cross-flow vortex induced vibration (VIV) suppression of a flexibly-mounted circular cylinder. The cylinder is equipped with two smart actively rotating control rods that are symmetrically oriented 120° apart in the near-wake region in real-time collaboration with an internally-fitted semi-active NES-based vibration absorber in the low Reynolds number flow regime (Re=100) over a typical range of lock-in reduced flow velocities (3≤U∗≤10). The control rods function as flow control actuators by enforcing the desired momentum injection into the near-wake region, while the semi-active structural control is realized by switching the nonlinear absorber force between some minimum and maximum values consistent with certain control logics. Selected multi-input-multi-output (MIMO) feedback control laws are introduced into the coupled transient dynamic simulation framework through a manually hooked user defined function (UDF) subroutine. The modified active rotating rod control system equipped with passive NES is found to be fairly successful in overall mitigation of the time response amplitudes (i.e., up to 56% reduction in the cylinder displacements, 78% reduction in the lift amplitudes, and 8% reduction in the drag coefficients as compared to the hybrid passive system). Similarly, notable reductions are obtained when a modified continuous feedback control strategy is directly applied in the NES-based semi-active vibration absorber (i.e., up to 55% in the displacements, and up to 11% in the drag coefficients). Moreover, the superior performance of proposed smart hybrid active/semi-active VIV control system in comparison to the hybrid passive system is demonstrated (i.e., up to 68% reduction in the displacements, 61% in the lift amplitudes, and 12% in the drag coefficient). Lastly, the key novelties, advantages, practical limitations, and trade-offs of the proposed numerical model are briefly pointed out in regard to the real-world marine/offshore applications and forthcoming investigations.

Online Frequency Estimation on a Building-like Structure Using a Nonlinear Flexible Dynamic Vibration Absorber

The online frequency estimation of forced harmonic vibrations on a building-like structure, using a nonlinear flexible vibration absorber in a cantilever beam configuration, is addressed in this article. Algebraic formulae to compute online the harmonic excitation frequency on the nonlinear vibrating mechanical system using solely available measurement signals of position, velocity, or acceleration are presented. Fast algebraic frequency estimation can, thus, be implemented to tune online a semi-active dynamic vibration absorber to obtain a high attenuation level of undesirable vibrations affecting the main mechanical system. A semi-active vibration absorber can be tuned for application where variations of the excitation frequency can be expected. Adaptive vibration absorption for forced harmonic vibration suppression for operational scenarios with variable excitation frequency can be then performed. Analytical, numerical, and experimental results to demonstrate the effectiveness and efficiency of the operating frequency estimation, as well as the acceptable attenuation level achieved by the tunable flexible vibration absorber, are presented. The algebraic parametric estimation approach can be extended to add capabilities of variable frequency vibration suppression for several configurations of dynamic vibration absorbers.

Design and Experimental Implementation of a Passive Dynamic Vibration Absorber to Attenuate Broadband Vibration

The challenge of designing an effective vibration absorber for any mechanical or mechatronic system is formidable. A good vibration absorber must provide broadband vibration reduction yet still keep in lightweight and size to minimize space requirements and maximize equipment accessibility. Broadband vibration is usually attenuated by using an active or semi-active vibration absorber. However, these methods are relatively costly and complicated compared with a passive vibration absorber. Moreover, passive vibration absorber often limited to narrowband frequency reduction since, in the past, it is usually tuned to the targeted frequency or optimum damping and optimum tuning ratio. This paper demonstrated that a passive vibration absorber could be implemented to reduce the broadband vibration of a system, considering the effect of the parameter of passive vibration absorber, the location attachment of the absorber, and the targeted mode shape. The result shows that a properly tuned passive vibration absorber can reduce the root mean square amplitude vibration by 60.91%, covering the first four vibration modes (0 to 300Hz).

Optimization of the semi-active vibration absorbers

In this paper, an efficient numerical approach is proposed to maximize the minimal damping of modes in a prescribed frequency range for general viscous tuned-mass systems. Methods of decomposition and numerical synthesis are considered on the basis of the adaptive schemes. The influence of dynamic vibration absorbers and basic design elastic and damping properties is under discussion. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in sinusoidal and impact forced system. One task of this work is to analyze parameters identification of the dynamic vibration absorber and the basic structure. The questions of robustness at optimization of DVA are considered. Different types of control management for semi-active DVA’s are applied. Examples of DVA’s practical implementation are presented.

A new magnetorheological elastomer torsional vibration absorber: structural design and performance test

Abstract. The semi-active torsional vibration absorber can effectively reduce the torsional vibration of the power-train system. In this paper, a new type of variable stiffness torsional vibration absorber with a magnetorheological elastomer (MRE) as an intelligent controlling element is designed, and the modal analysis, frequency-tracking scheme, and damping effects have been studied. A transient dynamic simulation is utilized to validate the rationality of the mechanical structure, the magnetic field parameters of the absorber are matched, and the magnetic circuit simulation analysis and the magnetic field supply analysis are carried out to verify the closed magnetic circuit. The principle prototype of the innovative vibration absorber is manufactured, the magnetic field strength of the absorber is tested by a Gauss meter, and the results show the efficacy of magnetizing the vibration absorber with a conductive slip ring by solving the magnetizing problem of the rotating parts of the vibration absorber. A special-purpose test rig with a torsional vibration exciter as a power source has been implemented. A comparative experiment has been carried out to test the frequency shift characteristics and authenticate the vibration-reduction effect of the new MRE torsional vibration absorber.

Research on vibration reduction performance of dynamic vibration absorber based on damping characteristic of a new material

The absorbing effect of traditional dynamic vibration absorber (TDVA) is satisfactory only when the natural frequency is close to the excitation frequency. For this defect, a semi-active vibration absorber is designed with magnetorheological elastomer (MRE) as a stiffness element, that its stiffness can be controlled by magnetic field, to widen the frequency band of the absorber. Theory and experiments show that reducing the damp of the absorber can improve the performance of the absorber at the anti-resonance point, but it will cause the vibration of the controlled system at the new resonance point, which caused by the addition of a DVA, to be more intense. For this problem, the compatibilizer: silane coupling agent KH570, is added to the preparation of MRE to reduce material damping, at the same time, the stiffness control strategy is used to eliminate the resonance of the controlled system caused by the addition of DVA. The final experimental results show that the frequency band of vibration reduction has been broadened effectively and the vibration reduction performance has been improved considerably. Moreover, the resonance has been eliminated very well.

Design of the frequency tuning scheme for a semi-active vibration absorber

Vibration absorbers have the capacity to significantly reduce local and global system vibrations under both resonant and forced vibration conditions. The subset absorbers known as semi-active vibration absorbers are characterized by the ability to reduce vibrations across a range of resonance and forced vibration conditions. Achieving an optimal tuning scheme for these vibration absorbers under a variable frequency external excitation is critical for realising maximum performance of the system. In this paper according to the dynamic tuned vibration absorption principle, an innovative magnetorheological elastomer torsional vibration absorber is proposed and installed in the torsional vibration system. Through the proposed absorber tuning process, the change in each order of natural vibration of the torsional vibration system is thoroughly analysed. The analysis results are used to optimize the frequency tuning scheme and modify the structural design scheme of the torsional vibration absorber. The effectiveness and reliability of the improved frequency tuning scheme and the structural design scheme are verified by simulation results.

Efficacy of Semi-active Absorber for Controlling Self-excited Vibration

It is shown that a passive vibration absorber can completely quench the self-excited vibration only for certain parameter values, like the strength of instability in the primary system. The present paper numerically explores the performance of semi-active vibration absorber in controlling self-excited vibration. In the proposed semi-active scheme, the damping force of the absorber is switched between the maximum and the minimum values according to certain control logics. Four different control strategies are considered—these are on–off velocity-based ground-hook control (VBG), on–off displacement-based ground-hook control (DBG), continuous VBG and continuous DBG. Numerical simulations are performed in the MATLAB Simulink to explore the efficacy of the control strategies. It is shown that the on–off DBG control is superior to all other control strategies.

Semi-active vibration absorbers for the high-rise objects

Semi-active vibration absorbers for the high-rise objects

Payload oscillations control in harbor cranes via semi-active vibration absorbers: modeling, simulations and experimental results

Semi-active vibration absorbers (SAVAs) are proposed to suppress large amplitude oscillations in container cranes during maneu-vers and wind forcing. The SAVA design and optimization are achieved via suitable nonlinear models, numerical simulations, and laboratory as well as full-scale tests. A comprehensive nonlinear modelling, featuring a full three-dimensional crane model and the adaptive vibration control architecture, is devised. The container is modeled as a rigid body elastically suspended from the trolley traveling along the crane boom. Two identical SAVAs are studied coupling their equations of motion - which include the impact against rubberized end stops - with the container crane dynamics. Suitable parametric analyses are carried out to investigate and optimize the control devices. Full-scale experiments are performed to validate the semi-active control architecture which proves to be a feasible approach.

MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations

This paper describes a semi-active vibration absorber (SVA) concept based on a real-time controlled magnetorheological damper (MR-SVA) for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD). Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.

Optimal semi-active vibration absorber for harmonic excitation based on controlled semi-active damper

The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper.

Efficient Vibration Control with a Semi-Active Vibration Absorber in a Semiconductor Fab

In this paper a new type of semi-active vibration absorber has been developed. The vibration absorber consists of mass block, cantilever beam, magnet lock system, vibration and distance sensors, controller and servo motor. The mass block is fixed on the tip of cantilever beam, and the control process is driven by a servo motor and a transmit gears. Portion of cantilever was cut in form of gear tracks, which can be driven by servo motor through transmit gear to regulate the length of the cantilever beam, and the natural frequency of absorber will also be regulated. After the mass locates in right position (i.e. the natural frequency of absorber is in assigned condition), the magnetic lock will clamp the cantilever beam. The design has the benefit of simplified control system, and extra unknown vibration modes will be averted. A fabrication prototype of the proposed semi-active vibration absorber is constructed and tested to demonstrate the application and modeling of the new cantilever beam damper. By performing the experimental work, the semi-active vibration control system is designed not only for reduce vibration level in resonant condition, but also considered for vibration attenuation in non-resonant conditions.

Semi-active vibration absorber based on real-time controlled MR damper

A semi-active vibration absorber with real-time controlled magnetorheological damper (MR-SVA) for the mitigation of harmonic structural vibrations is presented. The MR damper force targets to realize the frequency and damping adaptations to the actual structural frequency according to the principle of the undamped vibration absorber. The relative motion constraint of the MR-SVA is taken into account by an adaptive nonlinear control of the internal damping of the MR-SVA. The MR-SVA is numerically and experimentally validated for harmonic excitation of the primary structure when the natural frequency of the passive mass spring system of the MR-SVA is correctly tuned to the targeted structural resonance frequency and when de-tuning is present. The results demonstrate that the MR-SVA outperforms the passive TMD at structural resonance frequency by at least 12.4% and up to 60.0%.

Development of a Semi-Active Electromagnetic Vibration Absorber and Its Experimental Study

In this work, a semiactive electromagnetic vibration absorber has been developed based on a proposed electromagnetic stiffness adjustable spring model, which presents a new solution for adjusting stiffness in the field of vibration absorber devices. Simulation study on the electromagnetic spring has been performed to determine the structural parameter of the semiactive vibration absorber. An experimental rig is also built up to investigate its practical vibration control effectiveness. Firstly, the finite element model of the test bench is used to analyze its vibration characteristics. Then, the vibration reduction effect is predicted through the simulation analysis, from which the optimal control positions are found. Finally, the experimental studies are also conducted, and the results show that this semiactive electromagnetic vibration absorber has a frequency adjustment range from 21 Hz to 25 Hz, in which considerable vibration reduction from 5 dB to 10 dB can be achieved.

Development and Characterization of Isotropic Magnetorheological Elastomer

Magneto rheological elastomer (MRE) is a new kind of smart materials. Its dynamic mechanical performances can be controlled by controlling an applied magnetic field. MRE is usually used as stiffness - changeable spring in the semi-active vibration absorber. In order to get perfect vibration control effect, low dynamic damping of MRE is needed. This paper presents a new method of fabricating isotropic MREs under normal temperature and pressure conditions. In the absence of a magnetic field, a variety of MR elastomer samples were prepared using Sylard’s184 silicone elastomer along with un-annealed electrolytic iron power 500 mesh and 15 micron size. Their dynamic characteristics like fractional change in resonant frequency and fractional change in have been studied. The effects of iron particles and the applied magnetic field were investigated. This study is also expected to provide a good guide for designing and preparing new MR elastomers.

Integrated Dynamic Characteristics and Application in Semi-Active Dynamic Absorber of Magneto-Rheological Fluids

As a new type of controllable rheological smart material, Magneto-rheological Fluids (MRF) are widely used in the field of vibration control. This article investigated their integrated dynamic characteristics in squeeze mode and shear mode. Two prototypes were designed and fabricated. The dynamic test for the two prototypes was performed on a simply supported beam vibrating device with the methods of drop-hammering and sweep-frequency measuring. The experimental results demonstrate that the damping ratio of the prototype in squeeze effect presents linearly and widely controllable from 0.0948 to 0.2268 with the increase of the coils’ excitation current, behaving as a variable MR damper. However, its natural frequency remains unchanged. It is also shown that the natural frequency of the prototype in shear effect increases significantly from 18Hz to 24 Hz, acting as a semi-active dynamic vibration (SDVA) absorber with broadband vibration absorption for the maximum attenuation of up to 74.3%. This study provides guidance for engineering applications of MRF.