Passive Tuned Vibration Absorber Research Articles

Comparison of Floating Offshore Wind Turbine Tower Deflection Mitigation Methods Using Nonlinear Optimal-Based Reduced-Stroke Tuned Vibration Absorber

Tower fatigue and strength are crucial operational concerns of floating offshore wind turbines (FOWTs) due to the escalation of the vibration phenomena observed on these structures as compared to land-based ones. FOWT towers are excited by wave and wind polyperiodic disturbances yielding continual transient states of structural vibration that are challenging for vibration mitigation systems. Thus, the paper investigates a novel implementation of nonlinear optimal-based vibration control solutions for the full-scale, tension leg platform (TLP)-based, NREL 5MW wind turbine tower-nacelle model with a 10-ton tuned vibration absorber (TVA), equipped with a magnetorheological (MR) damper, located at the nacelle. The structure is subjected to excessive wave and wind excitations, considering floating platform motions derived from model experiments in a wave tank. The MR damper operates simultaneously with an electromagnetic force actuator (forming a hybrid TVA) or independently (a semiactive TVA). The study includes both actuators’ nonlinearities and dynamics, whereby the former are embedded in the Hamilton-principle-based nonlinear control solutions. The TVA is tuned either to the NREL 5MW tower-nacelle 1st bending mode frequency (TVA-TN) or to the TLP surge frequency (TVA-TLP). The optimal control task was redeveloped concerning the TVA stroke and transient vibration minimisation, including the implementation of the protected structure’s acceleration and relative displacement terms, as well as the nonzero velocity term in the quality index. The regarded model is embedded in a MATLAB/Simulink environment. On the basis of the obtained results, the TVA-TN solution is by far superior to the TVA-TLP one. All the regarded TVA-TN solutions provide a tower deflection safety factor of ca. 2, while reference systems without any vibration reduction solutions or with a passive TVA-TLP are at risk of tower structural failure as well as the hybrid TVA-TLP system. The obtained TVA stroke reductions of 25.7%/22.0% coincide with 3.6%/10.3% maximum tower deflection reductions for the semiactive/hybrid TVA-TN case (respectively) with regard to the previously developed approaches. Moreover, these reductions are obtained due to the sole control algorithm enhancement; thus, no additional resources are necessary, while this attainment is accompanied by a reduction in the required MR damper force. The lowest obtained TVA stroke amplitude of 1.66 m is guaranteed by the newly introduced semiactive control. Its hybrid equivalent ensures 8% lower primary structure deflection amplitude and reduced nacelle acceleration levels thanks to the utilisation of the force actuator of the relatively low power (ca. 6 kW); the trade-off is an increased TVA stroke amplitude of 2.19 m, which, however, is the lowest among all the tested hybrid solutions. The analysed reference passive TVA systems, along with a modified ground-hook hybrid solution, can hardly be implemented in the nacelle (especially along the demanding side–side direction). The latter, being the well-proven hybrid solution for steady-state tower deflection minimisation, yielded unsatisfactory results. The achievements of the study may be used for an effective design of a full-scale vibration reduction system for the TLP-based floating wind turbine structure.

Experimental Study on the Optimal-Based Vibration Control of a Wind Turbine Tower Using a Small-Scale Electric Drive with MR Damper Support

The paper presents an experimental implementation of an optimal-based vibration control for a scaled wind turbine tower-nacelle structure. A laboratory model of the approximate power scale of 340 W, equipped with a nonlinear tuned vibration absorber (TVA), is analysed. For control purposes, a combined operation of a small-scale electric servo drive and a magnetorheological (MR) damper is used in the TVA system. Nonlinearities of both the electric drive and the MR damper are intrinsic parts of the adopted nonlinear control concept. The aim of the research is the simple-hardware real-time implementation and the experimental investigation of the simultaneous actuator and damper control, including the analysis of the influence of optimal control law parameters and quality function weights on the vibration attenuation efficiency and actuator energy demand. As a reference, an optimal-based, modified ground-hook control with the single goal of the primary structure deflection minimisation is used along with the passive system with zero MR damper current and idling electric actuator, proving the advantages of the proposed method. The regarded solutions guarantee 57% maximum structure deflection reduction concerning the passive TVA configuration, using an MR damper of 32 N maximum force and an electric drive of 12.5 N nominal force and 0.76 W nominal power. An interesting alternative is the optimal control concept tuned with regard to the actuator power minimisation—it provides 30% maximum structure deflection attenuation (concerning the passive TVA configuration) while using a passive damper of 3.3 N maximum force and an actuator of 0.17 W nominal power only. It makes evident the advantage of the properly tuned optimal control algorithm over the modified ground-hook law—it requires 51% less actuator energy than the latter parametrised to exhibit the same vibration attenuation properties.

Analysis, optimization and control of an adaptive tuned vibration absorber featuring magnetoactive materials

Excessive vibration may cause premature fatigue failure on structural components if it is not properly controlled. One effective way to attenuate vibration is to attach a tuned vibration absorber to the main structural component. Passive tuned vibration absorbers are mainly effective to attenuate vibration at a specific range of frequencies and thus they become infective under varied environmental conditions which can significantly alter the tuning frequencies. The present study aims at development of a wide-bandwidth and light-weight adaptive tuned vibration absorber (ATVA) featuring a magnetorheological elastomer (MRE) which is tuned to absorb the vibrations of a flexible beam. The accelerance transfer function is derived for both beam with and without ATVA. The effectiveness of the ATVA to control vibration of the flexible beam caused by external excitation under wide range of frequencies is demonstrated. The proposed ATVA consists of C-Shape frame with winding coils, two isometric MRE specimens with 40% volume fraction, and active mass. An empirical model for the MRE has been developed through an experimental identification method in order to predict the MRE's elastic modulus under various levels of excitation frequencies and applied magnetic fields. Using MRE models and magneto-circuit analysis, the frequency bandwidth of the ATVA is analytically obtained. The analytical model is then used to develop a multidisciplinary design optimization formulation to minimize the mass and maximize the frequency bandwidth of an ATVA featuring MRE given several geometrical and physical constraints. Finally, a tuning algorithm has been presented to determine the required applied magnetic flux density to the MRE layers based on the identified phase difference between the absolute acceleration of the host and relative acceleration of the host and ATVA's resonator.

On the vibration suppression of power lines using mobile damping robots

Fixed passive tuned vibration absorbers (TVA) are ineffective in controlling wind induced vibration of continuous systems (e.g., power lines). This is because fixed passive TVAs are not only narrowband, but they are also unable to adapt to changing wind characteristics, and thus are unable to reposition themselves at antinodes of the vibrating loop. To tackle this issue, this paper proposes a mobile vibration absorber (i.e, mobile damping robot) capable of self-adjustment to antinodes. The study focuses on power lines vibration suppression, but it can be extended to other continuous systems. The mobile damping robot is connected to a single conductor that is subjected to a pretension and a wind force. The governing equations of motion are obtained using Hamilton's principle. A control force is incorporated in the mathematical formulation for driving the robot to the antinode location based on the wind excitation frequency. Also, the two-way nonlinear coupling between the robot and cable is considered. Numerical simulations indicate that the mobile damping robot significantly improves the vibration suppression of the power line. Parametric studies are carried out to determine the influence of key design parameters on the performance of the mobile damping robot.

Optimal Semiactive Damping Control for a Nonlinear Energy Sink Used to Stabilize Milling

Improving product quality of machining components has always met with problems due to the vibration of the milling machine’s spindle, which can be reduced by adding a vibration absorber. The tuned vibration absorber (TVA) has been studied extensively and found to have a narrow bandwidth, but the cutting force possesses wide bandwidth in the process of machining parts. Introducing nonlinearity into the dynamic vibration absorber can effectively increase the bandwidth of vibration suppression and can significantly improve the robustness of the vibration absorber. In addition, a semiactive TVA has proved to be more effective than a passive TVA for many applications, so the main purpose of this study is to find some appropriate semiactive control methods for a nonlinear energy sink (NES), a nonlinear vibration absorber, in structural vibration applications. Two semiactive control methods are considered in this study: continuous groundhook damping control based on velocity and on-off groundhook damping control based on velocity. To fairly compare these vibration absorbers, the optimal parameters of a passive TVA, a passive NES, and two semiactive NESs are designed using numerical optimization techniques to minimize the root-mean-square acceleration. Two cutting forces are introduced in this study, a periodic force and an aperiodic force, and the four vibration absorbers are compared. When the primary structure is excited with aperiodic cutting force, the amplitude of the primary structure decreased by 17.73% with the passive TVA, by 72.29% with the passive NES, by 73.54% with the on-off NES, and by 87.54% with the continuous NES. When the primary structure is excited with periodic cutting force, the amplitude of the primary structure decreased by 49.01% with a passive TVA, by 86.93% with a passive NES, by 96.38% with an on-off NES, and by 99.23% with a continuous NES. The results show that the passive NES is better than the passive TVA; the semiactive NES provides more effective vibration attenuation than the passive NES, and the continuous control is more effective than the on-off control.

Structural Vibration Control of NREL 5.0 MW FOWT Using Optimal-Based MR Tuned Vibration Absorber

In this work, a National Renewable Energy Laboratory (NREL) 5.0 MW floating offshore wind turbine (FOWT) model equipped with nonlinear, magnetorheological (MR) tuned vibration absorber (TVA) is analysed. Several optimal-based MR damper control solutions are regarded against passive TVA configurations and the structure without the TVA system. Tower and barge/platform angular displacement amplitude frequency responses are compared, proving the efficiency and robustness of the adopted vibration reduction solutions, as well as their capability to minimise the amplitude of the vibrating structure, the demanded actuator (e.g. MR damper) force and stroke range.

Progress in studying passive and active devices for fuselage noise reduction for next generation turboprop

Over the years, the interior noise levels have been improved, and nowadays a high acoustical comfort is of major importance for the commercial success of propeller aircraft. The use and development of high vibro-acoustic performance devices and their integration on the primary structure are, therefore, among the most critical topics in the greening of the next generation air transportation. The purpose of this research was properly focused on the analysis of a dynamic control system appointed to increase the noise attenuation transmitted in the propeller aircraft fuselage. Passive and active dynamic devices have been studied and characterized in this work. Simulations and tests performed on the first stage demonstrator structure highlighted how the passive tuned vibration absorber increases the comfort controlling the structural behaviour of the fuselage at the first blade pass frequency. Further improvements of fuselage comfort can be reached using active devices. A conceptual design of a hybrid active device able to act on the first three blade pass frequencies has been outlined. The characterization of the whole active noise control system has been described and its effect on noise reduction in fuselage of propeller aircraft has been evaluated.

Vibration Control of Slab Breaker Machine by Passive Dual Mass Tuned Vibration Absorber

Tuned Vibration Absorber (TVA) is the best solution available to control/suppress vibrations of any dynamic systems. Dual mass Tuned Vibration Absorber are designed and implemented for the vibration control. Though the slab barker machine is operating at various natural frequencies, the Dual mass TVA can be designed to mitigate the vibrations depending on the position of mass. The experiments were carried out for various locations of mass. And it is found that the vibration /shock waves of slab breaker machine are absorbed by using a passive TVA system. By keeping the operating condition same it is practically found that at the location of 4cm the optimal vibration reduction obtained and the amplitude is found to be reduced by 37 %.

Resonance reduction of primary system using variable mass tuned vibration absorber

The conventional passive tuned vibration absorber (TVA) can substantially reduce the vibration of a primary system only when it is tuned to the excitation frequency. To overcome this narrow-band problem, some adaptive tuned vibration absorbers (ATVAs) were developed in recent years. ATVAs possess natural frequencies that can usually be adjusted by altering absorber stiffness. Another problem of this device is that using the TVA can result in the resonance of a primary system since a new composite system is formed when a TVA is attached to a primary system. In this paper, a novel control strategy based on variable mass (VM) ATVA is proposed to reduce the resonance of the primary system. Unlike previous designs, the natural frequency of the VM ATVA can be adjusted by changing its mass, and the control plan can be implemented in the same manner. A numerical simulation and some experiments were conducted to test the performance of the new control plan, and the results show that the suggested plan can achieve a resonance reduction of approximately 17.6 dB in the simulation and about 11.3 dB in the experimental system. This finding implies that the VM absorber that uses the proposed control plan can effectively suppress the vibration of a primary system over a wide frequency band and effectively reduce its resonance. Moreover, the new control strategy is actually a generalizable method that can be used on other types of ATVA.

Qualitative Analysis of Magneto-Rheological Tuned Vibration Absorbers: Experimental Approach

The primary purpose of this study is to provide an experimental evaluation of some of the characteristics and benefits of magneto-rheological tuned vibration absorbers (MR TVAs). Tuned vibration absorbers (TVAs) often provide a simple and elegant solution to many vibration problems. To extend the concept of passive TVAs to MR TVAs, we discuss four different control methods, called velocity-based on—off groundhook control, velocity-based continuous groundhook control, displacement-based on—off groundhook control, and displacement-based continuous groundhook control. Using the test apparatus, a series of tests were conducted to investigate the dynamics of the MR TVA with each control policy. The performances of each of the cases were then analyzed along with the equivalent passive TVA. The performance index was the transmissibility between the input and the output displacement of the structure. The experimental results indicate that the most suitable control method for MR TVAs is the displacement-based groundhook control.

Dynamic performance analysis of non-linear tuned vibration absorbers

The main purpose of this study is to evaluate the dynamic characteristics of a damping controlled semi-active tuned vibration absorber (TVA). A base-excited, single-degree-of-freedom structure coupled with a TVA model is adopted as the baseline model for our analysis. A non-model based groundhook control (displacement-based on–off control or “on–off DBG”) was used to control the damping of the TVA. After developing numerical models of a non-linear TVA along with the on–off DBG control and a passive TVA, the optimal tuning parameters of both TVA models were obtained using an optimization routine. Using the two optimally tuned models, parametric studies were preformed by varying the values of both on and off-state damping to evaluate the dynamic performances of the TVAs using the peak transmissibility criteria. The results showed that the peak transmissibility of the semi-active TVA is nearly 21% lower than that of the passive, indicating that the semi-active TVA is more effective in reducing vibration levels. The results further showed that increases in off-state damping decreases the effectiveness of semi-active TVA in reducing maximum vibration levels.

Experimental Robustness Analysis of Magneto-Rheological Tuned Vibration Absorbers Subject to Mass Off-Tuning

This paper offers an experimental robustness analysis of a semi-active tuned vibration absorber (TVA) subject to structural mass off-tuning, which occurs frequently in practical applications of TVAs. One of the critical problems of a conventional TVA is off-tuning or miss-tuning because off-tuned TVAs may amplify the vibrations of the primary structure. This study intends to evaluate how well semi-active TVAs are able to adapt to structural mass changes (mass off-tuning) as compared with passive TVAs. To this end, a test apparatus was built to represent a two-degree-of-freedom structure model coupled with a TVA. The semi-active TVA considered in this study employed a magneto-rheological (MR) damper as its damping element to enhance overall performance. Using this test apparatus, a series of tests were conducted to identify the optimal tuning parameters of the TVAs. After obtaining each TVA’s optimal tuning parameters based on equal peak transmissibility criteria, the mass off-tuning tests were then performed on the optimally tuned TVAs. In order to off-tune the system, the mass of the primary structure varied from −19% to +19% of its nominal mass using a set of steel plates. Overall, the experimental results show that the semi-active MR TVA outperforms the passive TVA in reducing maximum vibrations. Moreover, the results show that the semi- active TVA is more robust to changes in the primary mass (mass off-tuning) The results further show that the semi-active MR TVA offers larger performance gains as the structure mass increases.

Improving Robustness of Tuned Vibration Absorbers Using Shape Memory Alloys

A conventional passive tuned vibration absorber (TVA) is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs) have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs) in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA‐TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system′s natural frequency. The simulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. Additionally, a PID controller is included for regulating the applied voltage to the SMA wires in order to maintain the desired stiffness. The robustness analysis is then performed on both the SMA‐TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by ± 30% of its nominal mass. The simulation results show that the SMA‐TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.

A qualitative analysis of groundhook tuned vibration absorbers for controlling structural vibrations

The primary purpose of this study is to investigate the dynamic characteristics of semi-active groundhook tuned vibration absorbers (TVAs), using closed-form equivalent models of such systems. Closed-form, equivalent models of groundhook TVAs are developed and compared analytically with those for passive TVAs. Additionally, closed-form solutions of groundhook equivalent TVA models are obtained and are used for a parametric study to evaluate the dynamic characteristics of such systems as various parameters change. The numerical results are compared with passive TVAs which have been studied extensively in the past. The results indicate tat groundhook TVAs, with off-state damping levels within a critical value, are capable of lowering the magnitude of resonant peaks without increasing vibration. In contrast, increasing damping in passive TVAs results in a reduction in the amplitude of resonant peaks, at the expense of increased vibrations at the tuned frequency. The results further indicate that increasing the mass ratio between the TVA and the structure increases the effectiveness of groundhook TVAs, in a manner much similar to passive TVAs. However, increasing off-state damping decreases the effectiveness of groundhook TVAs.

NON-LINEAR VIBRATION ABSORBER FOR A SYSTEM UNDER SINUSOIDAL AND RANDOM EXCITATION: EXPERIMENTS

A system consisting of a primary structure coupled with a passive tuned vibration absorber is experimentally studied. The primary structure consists of four flexible columns with a mass, while the absorber consists of a beam with a tip-mass. The system, which is a coupled non-linear oscillator, is subjected to sinusoidal and random excitation. The effects of the forcing frequency, forcing amplitude, mass ratios and frequency ratios on the displacement response of the system in the neighborhood of the autoparametric region are studied. Control parameters related to effectiveness of the absorber are determined. The objective of this study is to experimentally define an absorption region for the passive vibration absorber and to determine the parameters that influence the effectiveness of the vibration absorber.

State-Switched Absorber for Semi-Active Structural Control

A system that has the capability to make instantaneous changes in its mass, stiffness, or damping may be termed a state-switchable dynamical system. Such a system will display different dynamical responses dependent upon its current state. For example, state-switchable stiffness may be practically obtained through the control of the termination impedance of piezoelectric stiffness elements. If such a switchable stiffness element is incorporated as part of the spring element of a vibration absorber, the change in stiffness causes a change in the resonance frequencies of the system, thereby instantaneously “retuning” the state-switched absorber to a new frequency. This paper briefly develops the fundamental analysis tools for a Single-Degree-of-Freedom state-switchable device, and then considers the application of such a device for the purpose of vibration control in a 2-DOF system. Simulation results indicate that state-switched vibration absorbers may be advantageous over classical passive tuned vibration absorbers under certain conditions.

Hybrid active-passive noise and vibration control system for aircraft

A hybrid active-passive system (20) for reducing noise within a passenger compartment and vibration of a fuselage of a vehicle, such as an aircraft (turboprop, turbofan, or helicopter). The hybrid active-passive system (20) includes, in combination: an active acoustic producer such as a loudspeaker (35), Active Vibration Absorber (AVA) (34), or active absorber assembly (39) for producing antinoise within the compartment (42), and a passive resonant device, such as a passive Tuned Vibration Absorber (TVA) (36), or passive TVA assembly (37) for controlling vibration of the fuselage or structural supports interconnecting the disturbance source (e.g. power plants (26), propellers (28a), gearbox (57), main rotor (28m), tail rotor (28t)) and the fuselage wall (25).

Vibration isolation system including a passive tuned vibration absorber

An isolation system (20) including the combination of an elastomeric mount (25) for attachment between a structure (24) and a vibrating member (22) and further including at least one passive tuned vibration absorber (TVA) (32) attached in the proximity the elastomeric mount (25) but on the structure side thereof. The resonant frequency f r of the passive TVA (32) is tuned to a resonant frequency f r just below the predominant operating frequency f o of the vibrating member (22), such that the resonance of the tuned vibration absorber (32) makes the structure (24) appear dynamically stiffer. In particular the ratio of f r /f o is in the range of between about 0.90 and 0.90. In one embodiment, the passive TVA (32) attaches directly to the inner member (28) of the elastomeric mount (25) and clamps the TVA assembly (43) to the structure (24) and clamps the structure (24) to the elastomeric mount (25). In another embodiment, the passive TVA (32) is clamped to the structure (24) at a point where it cooperates with the elastomeric mount (25) to reduce transmitted vibration, preferably the TVA (32) is attached at a point within last 20% of the end of the beam-like structure (24).

Passive, Adaptive and Active Tuned Vibration Absorbers—A Survey

An overview of the recent development of tuned vibration absorbers (TVAs) for vibration and noise suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and presents some contemporary applications of passive TVAs. Furthermore, the paper also presents a brief discussion on the recent progress of adaptive and semi-active TVAs along with their on-line tuning strategies, and active and hybrid fail-safe TVAs.

Passive, Adaptive and Active Tuned Vibration Absorbers—A Survey

An overview of the recent development of tuned vibration absorbers (TVAs) for vibration and noise suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and presents some contemporary applications of passive TVAs. Furthermore, the paper also presents a brief discussion on the recent progress of adaptive and semi-active TVAs along with their on-line tuning strategies, and active and hybrid fail-safe TVAs.