Adaptive Tuned Mass Damper Research Articles

Experimental study on mitigating vibration of floating offshore wind turbine using tuned mass damper

Compared to the onshore wind turbine, the floating offshore wind turbine (FOWT) suffers from worse environmental loads during its operation, leading to complicated dynamic responses. Excessive vibration can be potentially harmful to the structural safety and reliability. The Tuned Mass Damper (TMD) is regarded as a promising vibration mitigation device and has been popularized in FOWTs recently. However, the TMD performance in FOWT vibration mitigation is still difficult to investigate due to the flexibility of the FOWT system and the variety of excitations. In this paper, we present an experimental study of dynamic response mitigation of an FOWT under complex environmental loads. A highly adaptive TMD is designed and constructed based on the FOWT tower vibration characteristics. The integrated FOWT-TMD test system is set up. Extensive tests are then conducted with different offshore environments and TMD operating states. The results show that TMD can effectively reduce the FOWT peak acceleration amplitude and the peak base bending moment by 7.8% and 8.8%, respectively, in the survival condition. The present work will serve to verify the effectiveness of TMD and lay the foundation for experimental techniques on advanced FOWT controllers.

Piezoelectric-shunt-based approach for multi-mode adaptive tuned mass dampers

This paper deals with the design and development of a multi-frequency adaptive tuned mass damper based on a cantilever beam equipped with shunted piezoelectric elements. It is demonstrated that the device is able to independently shift a number of eigenfrequencies equal to the number of piezoelectric elements and that the use of negative capacitances is able to strongly improve the adaptation capability of the device. Mathematical formulations are provided for linking the values of the capacitances used for shunting the piezoelectric elements and the resulting shifts of the eigenfrequencies, and vice versa. Furthermore, being the negative capacitances based on operational amplifiers, the stability of the electro-mechanical system is investigated, giving rules about the tuning of these negative capacitances. The resulting adaptive tuned mass damper can be fruitfully employed for lowering vibrations of a primary system whose eigenfrequencies undergo different frequency shifts, improving the robustness to possible mistuning of non-adaptive classical tuned mass dampers. All the theoretical outcomes are validated through an experimental campaign with a cantilever beam equipped with two piezoelectric patches.

Experimental study on adaptive-passive tuned mass damper with variable stiffness for vertical human-induced vibration control

Serviceability problem and human-induced vibration control of slender footbridges are of increasing interest to structural engineers. Passive tuned mass dampers (TMDs) have a wide range of applications in human-induced vibration control. However, a passive TMD is sensitive to the frequency deviation and, as a result a mistuned TMD will lose its control effect. An adaptive TMD can solve the mistuning problem of a passive TMD. However, there is few adaptive TMDs with variable stiffness in this issue. To fill this gap, an adaptive-passive variable stiffness TMD (APVS-TMD) is proposed in this study. The stiffness and frequency of APVS-TMD can be retuned through changing the length of free end of cantilever beam, while the damping can be retuned by adjusting the air gap between the conductor plate and magnets. As for the target natural frequency to be adjusted, the first two modal frequencies of the TMD-structure coupled system are identified under ambient excitation first, and then, the decoupled structural natural frequency is obtained according to the developed method based on the undamped 2-degree of freedom (DOF) modal analysis. By means of numerical simulation, the identification strategy is verified using a SDOF lumped mass main structure and an ideal simply supported beam model. Then, the identification and stiffness retuning operations of the APVS-TMD are further verified through a footbridge model experiment. Here, control effects of the APVS-TMD to walking- and running-induced vibrations are highlighted and compared with those of a mistuned TMD. Experimental results show that the APVS-TMD can identify the decoupled structural natural frequency from the coupled system accurately, and control human-induced vibrations effectively.

SMA-based adaptive tuned mass dampers: Analysis and comparison

Different types of adaptive tuned mass dampers have been recently proposed in the literature. One of the most promising approaches to make tuned mass dampers adaptive is the use of shape memory alloys. In this class of tuned mass dampers, different layouts have been proposed. This paper aims at comparing the two main layouts (wire-based and beam-based) in terms of adaptation capability, exerted force and electrical power consumption. To this purpose, the models of the two layouts are developed. These models minimise the number of required inputs, which basically are only related to device geometry, shape memory alloy characteristics, and vibration input. After an experimental validation, the models are employed for the mentioned comparisons between the two considered layouts.

Parametric design of boring bars with adaptive tuned mass dampers

Slender single point boring tools are damped with tuned mass dampers (TMD) to increase their resistance against chatter. A TMD with fixed parameters may weaken its effectiveness when it is coupled with spindles or bars with different lengths. This paper presents a tunable and parametric, digital design of boring bars. The large length to diameter boring bar is modeled using Timoshenko beam elements and the effects that the TMD head has on the dynamics of the assembled boring bar-TMD system is modeled using a derived analytical expression. A universal TMD head that consists of a carbide mass, oil pocket, and two rubber O rings with experimentally calibrated stiffness and damping as a function of compression is designed. The boring bar has an internal compression shaft that can be pressed against the O ring to vary its stiffness using an integrated power screw. The complete TMD boring bar system is mathematically modeled to determine the Frequency Response Function (FRF) including the required TMD natural frequency and damping ratio to maximize the chatter-free depth of cut. The digital model is verified by comparing the simulated and experimentally measured FRF of the TMD bars. The bars are also tested in boring experiments successfully. • Parametric digital design of boring bars with Tuned Mass Dampers. • Tuning of natural frequency by adjusting O ring compression. • Optimal design of tuned mass damper head with a wide length to diameter ratio (L/D). • Optimal tuning by shrinking the amplitude of the negative real part of the Frequency Response Function (FRF) at the tool locating of boring bar.

Semi-active control of walking-induced vibrations in bridges using adaptive tuned mass damper considering human-structure-interaction

Tuned mass dampers (TMDs) are used to control pedestrian induced vibrations of pedestrian bridges as traditional vibration control devices. A TMD can have a good control effect when it is tuned to the natural/vibrational frequency of the primary system. However, a traditional passive TMD is sensitive to the frequency deviation. Actual human-induced excitations can cover a wide frequency range and are stochastic virtually, which will cause a decrement in its control effect. The human-structure interaction (HSI) can also change the structural characteristic and lead to a mistuned TMD. To propose a more robust and effective TMD in solving the serviceability problem, a semi-active independent variable mass TMD (SAIVM-TMD) is introduced in this study. Wavelet transform (WT) is used to identify the structural instantaneous frequency, then, the mass of SAIVM-TMD is adjusted according to the WT - based control algorithm by actuating devices in real time. To highlight the control effect of SAIVM-TMD, a simply supported pedestrian bridge is carried out as a case study. The bridge is simplified to a Euler–Bernoulli beam according to an in-situ test and model analysis. Then, its dynamic responses under different controllers are analyzed and compared under single pedestrian periodic and stochastic walking-induced excitations. HSI is considered and a pedestrian is modulated as a moving spring-mass-damper (SMD) model. Then, a case under crowd-induced stochastic excitation is proposed. A passive TMD optimized for a pedestrian bridge under moving loads is used for comparison. Results show that SAIVM-TMD always has the best performance because it can adapt to the structural vibrational frequency changes efficiently and retune.

Adaptive tuned mass damper with shape memory alloy for seismic application

When the characteristics of the main structure are changed, tuned mass damper (TMD) is easy to meet off-tuning problem. The object of this study is to develop a TMD with shape memory alloy (SMA) to reduce the vibration caused by off-tuning under seismic excitations. By materials characterisation of SMA, when the working temperature rises from −40 °C to 65 °C, the stiffness increases and the equivalent damping ratio drops. The SMA-based TMD was installed on a steel frame and tested under earthquake loading. The results show the SMA-based TMD is able to reduce the seismic response in the range of 34.09–47.77% at the tuned condition. However, by changing the main structural mass, the TMD was easy to be off-tuned. To retune the TMD, the SMA was heated and cooled for the TMD to resonate with the natural frequency of the main structure. When the SMA is cooled, the peak and RMS accelerations can be effectively reduced by up to 23.98% and 35.51%, respectively. It was found that the SMA-based TMD performs well if the frequency change of the main structure is in the same order. But when the temperature of SMA is increased higher than 19 °C, the damping ratio of SMA decreases, which causes a less effectiveness in reducing the vibration. In the future, the combinations of multiple SMA bars in TMD should be studied, and the applications of SMAs with higher phase transformation temperature can be investigated to improve the sensitivity while heating.

A multi-modal adaptive tuned mass damper based on shape memory alloys

This article deals with the design of an innovative adaptive multi-modal tuned mass damper able to change its eigenfrequencies to recover shifts of the natural frequencies of the primary system which needs to be damped. This is accomplished using systems of shape memory alloy wires connected to a number of masses equal to the number of modes to be damped. This article presents the analytical model used to describe the behaviour of the adaptive tuned mass damper, showing which parameters can affect the performances of the device. The layout proposed for the tuned mass damper proves to be able to act on a wide frequency range and to work adaptively on at least two eigenfrequencies at the same time with a given level of independence. The last goal is accomplished, thanks to the special features of the shape memory alloys, by heating (or cooling) each wire of the device independently and allowing the exploitation of two different effects: the change of the axial load in the wires and the change of the geometry of the device. The reliability of both the design approach and the model of the new device is proved by means of an experimental campaign performed considering a random disturbance.

Adaptive tuned mass damper with variable mass for chatter avoidance

If the machine tool damping is not sufficient to reduce the vibration induced by machining, chatter can occur. This paper presents an innovative adaptive tuned mass damper (ATMD) with variable mass. The variation of the mass of the ATMD allows the adaption of its eigenfrequency to the dominant one of the machine tool, which is dependent on the axis position of the machine. The design of the ATMD and consequently its working range was optimized with a genetic algorithm. The functionality and performance of the ATMD were then validated under real cutting conditions on a machining centre.

Modelling and control of an adaptive tuned mass damper based on shape memory alloys and eddy currents

Tuned mass dampers have long since been used to attenuate vibrations. The need to make them adaptive in order to function even after changes of the dynamic characteristics of the system to be controlled has led to using many different technologies with the aim of improving adaptation performances. Shape memory alloys have already been proven to have properties suitable for creating adaptive tuned mass dampers for light structures.However, the literature has evidenced a number of issues concerning tuned mass dampers based on shape memory alloys, for instance the limited range of adaptation for the eigenfrequency of the damper.The present paper proposes a new layout for adaptive tuned mass dampers based on shape memory alloys, which allows to overcome many of the limitations and to reach a wide range of adaptation for the eigenfrequency. This layout relies on the use of shape memory alloy wires, so that the change of eigenfrequency is achieved by changing the axial load acting on these wires.The new tuned mass damper is then made fully adaptive by including a device that uses the principle of eddy currents, which allows also to change the damping of the tuned mass damper. Indeed, this new kind of damper is designed to dampen vibrations in systems excited by a random disturbance.The paper illustrates the layout and the model of the whole damper and validates it. This model moreover evidences all the advantages allowed by the new layout proposed. Finally, two different strategies to control the dynamic characteristics of the new adaptive tuned mass damper are presented and compared, both numerically as well as experimentally, so to illustrate strengths and drawbacks of each. The experiments and the simulations show that this new damper is fully capable of functioning when random excitation acts as disturbance on the system to control.

Extended Kalman filter for modal identification of structures equipped with a pendulum tuned mass damper

Pendulum tuned mass dampers (PTMDs) have been employed in several full-scale applications to attenuate excessive structural motions, which are mostly due to wind. Conducting periodic condition assessments of the devices to ascertain their health is necessary to ensure their continued optimal performance, which involves identifying the modal parameters of the underlying (bare) structure to which they are tuned to. Such an identification is also necessary for the design of control systems such as adaptive tuned mass dampers. Existing methods of arresting the motion of the damper to estimate the modal properties are expensive, time-consuming, and not suitable for online tuning. Instead, in this paper, parameter estimation using the Extended Kalman Filter (EKF) is proposed to undertake this task. The central task accomplished here is to estimate the dynamic characteristics of the bare structure (structure without the PTMD) from response measurements of the coupled main structure and PTMD system. The proposed methodology relies on ambient acceleration measurements of TMD-attenuated responses to estimate the bare structural modal frequencies, damping, and mode shapes, which can then be used either for condition assessment or for control. The application of EKF to modal parameter estimation is not new. However, a methodology to address the problem in wind engineering arising from stochastic disturbances present in both the measurement and state equations, and unknown process and noise covariances arising due to ambient excitations, is presented for the first time. Extensively studied for synthetic data, these two challenges have limited thus far the application of Kalman filtering to practical wind engineering parameter estimation problems using experimentally obtained measurements. In this paper, a detailed methodology is presented to address these challenges by using a modified form of the standard EKF equations, together with an algorithm to estimate the unknown disturbance and measurement noise covariances. Numerical simulations and an experimental study are both presented. Results demonstrate that the method proposed provides reliable estimates for the modal parameters required to perform condition assessment and control tasks for pendulum tuned mass dampers.

Adaptive length SMA pendulum smart tuned mass damper performance in the presence of real time primary system stiffness change

In a companion paper, Pasala and Nagarajaiah analytically and experimentally validate the Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) on a primary structure (2 story steel structure) whose frequencies are time invariant (Pasala and Nagarajaiah 2012). In this paper, the ALP-STMD effectiveness on a primary structure whose frequencies are time varying is studied experimentally. This study experimentally validates the ability of an ALP-STMD to adequately control a structural system in the presence of real time changes in primary stiffness that are detected by a real time observer based system identification. The experiments implement the newly developed Adaptive Length Pendulum Smart Tuned Mass Damper (ALP-STMD) which was first introduced and developed by Nagarajaiah (2009), Nagarajaiah and Pasala (2010) and Nagarajaiah et al. (2010). The ALP-STMD employs a mass pendulum of variable length which can be tuned in real time to the parameters of the system using sensor feedback. The tuning action is made possible by applying a current to a shape memory alloy wire changing the effective length that supports the damper mass assembly in real time. Once a stiffness change in the structural system is detected by an open loop observer, the ALP-STMD is re-tuned to the modified system parameters which successfully reduce the response of the primary system. Significant performance improvement is illustrated for the stiffness modified system, which undergoes the re-tuning adaptation, when compared to the stiffness modified system without adaptive re-tuning.

Dynamic characteristics of controlled MR-STMDs of Wolgograd Bridge

This paper describes the dynamic characteristics of an adaptive tuned mass damper concept that is based on a real-time semi-actively controlled MR damper (MR-STMD) and is installed in the Wolgograd Bridge. The measurements and simulations of the prototype MR-STMD on the 15.6 m Empa bridge at different disturbing force levels demonstrate that the MR-STMD can cope with the nonlinear effect by which the resonance frequency and damping ratio of the Empa bridge depend on the amplitude and thereby on the excitation level. Whereas the efficiency of the MR-STMD is hardly affected by the aforementioned nonlinear effects, the passive TMD shows strong de-tuning. The tests for fast changes in frequency and amplitude of the disturbing force show that the response of the Empa bridge with the MR-STMD is smaller both during steady state and transient conditions than with a passive TMD, and the relative motion amplitudes in the MR-STMD are smaller or equal to those in the passive TMD. The force tracking accuracies of the prototype MR-STMD and of the Wolgograd MR-STMD are shown to be accurate, which generates precise frequency tuning of the MR-STMD in real-time and thereby explains the achievements described above. The test results indicate that the real-time controlled MR-STMD is an efficient and robust tool for the mitigation of structural vibrations.

A sliding Goertzel algorithm for adaptive passive neutralizers

A common method used in tuning adaptive–passive tuned vibration neutralizers is to adjust its resonance frequency to match the excitation frequency, which has the characteristic that the phase angle between its vibrating mass and its support is −90°. A sliding-Goertzel algorithm is presented and demonstrated for extracting the vibration signals at the frequency of interest. The benefit of using the sliding Goertzel algorithm compared to other methods when used in vibration environments with multiple tones is that additional band-pass notch filtering is not required. This algorithm could also be used for adaptive tuned mass dampers, adaptive Helmholtz resonators, and adaptive quarter-wave tubes.

An adaptive tuned mass damper based on the emulation of positive and negative stiffnesswith an MR damper

This paper presents a new adaptive tuned mass damper (TMD) whose stiffness anddamping can be tuned in real-time to changing frequencies of a target structure. Theadaptive TMD consists of a tuned mass, a tuned passive spring and a magnetorheological(MR) damper. The MR damper is used to emulate controlled friction–viscous damping andcontrolled stiffness. The controlled positive or negative stiffness emulated by the MRdamper works in parallel to the stiffness of the passive TMD spring. The resulting overallTMD stiffness can therefore be varied around the passive spring stiffness using the MRdamper. Both the emulated stiffness and friction–viscous damping in the MR damper arecontrolled such that the resulting overall TMD stiffness and damping are adjustedaccording to Den Hartog’s formulae. Simulations demonstrate that the adaptive TMD witha controlled MR damper provides the same reduction of steady state vibration amplitudesin the target structure as a passive TMD if the target structure vibrates at thenominal frequency. However, if the target structure vibrates at different frequencies,e.g. due to changed service loads, the adaptive TMD with a controlled MR damperoutperforms the passive TMD by up to several 100% depending on the frequencychange.

Structural identification of a prototype pre-stressable leaf-spring based adaptive tuned mass damper: Nonlinear characterization and classification

The current paper focuses on a prototype adaptive TMD. Its design concept is based on pre-stressable leaf-springs that are controlled by piezoceramic (PZT) stack actuators. Experiments performed on the prototype showed that it is continuously tunable in a broad frequency range. Moreover, they revealed that the device exhibits structural nonlinearities. The current paper focuses on the structural identification of the prototype and attempts for the first time to characterize and classify the observed nonlinearities. Several experiments at different PZT voltage levels are performed. The results indicate PZT voltage dependent nonlinear softening and hardening stiffness. Based upon these observations, static experiments and proper data-pooling techniques, an effective “global” model for the nonlinear stiffness is derived. The estimated nonlinear model is finally validated upon static experiments as well as more realistic operational cases, that are vibrations of the prototype under typical ground excitation.

Adaptive Tuned Mass Damper for the Construction of Concrete Piers

In this paper the authors have studied and proposed a control system for an adaptive tuned mass damper (TMD) for self-climbing formworks to be used in some critical construction phases of concrete piers. This dynamic vibration absorber will move together with the formwork, and must change the tuned parameters (frequency, damping) for an optimal situation in each instant of the pier construction. With this device, the structural damping of the pier will increase and consequently personal comfort (e.g., sickness and acceleration levels) and structural security (stress level) will improve. The numerical results are based on a finite element model (FEM) for the 92 m concrete pier of La-Miel Viaduct (Nerja, Spain). This model has been adjusted by means of acceleration records obtained on the top of the pier. On the basis of this model several approaches of adaptive TMDs have been studied and finally a feasible solution has been suggested.

Adaptive Tuned Mass Damper based on Pre-stressable Leaf-springs

Lightweight bridges exhibit a high live load to dead load ratio. Thus, their resonance frequencies depend on the current loading state and can vary in quite a broad range. This behavior is a real challenge in vibration mitigation of such structures controlled by tuned mass dampers (TMDs), since the performance of single passive TMDs degrades significantly if the resonance frequency of a structure differs even slightly from design frequency. This study proposes an adaptive TMD, which continuously adapts its natural frequency to the current resonance frequency of the structure. The concept is based on pre-stressable leaf-springs that are controlled by piezoceramic stack actuators. Experiments performed on a first prototype show that the TMD is continuously tunable in a broad frequency range.

Development of Adaptive Tuned Mass Damper ATMD

A tuned mass damper is usually used to reduce wind-induced vibration of towers and high rise buildings. However it is not so effective for the structures of which the natural frequency is varied for the case of building up bridge-towers. For these structures the semi-active controlling method seems to be effective in reducing the vibration. This paper proposes a new semi-active vibration controlling method and an adaptive tuned mass damper ATMD consists of a pendulum and an analogue controlling system. In this system the tuning condition of the ATMD is realized by retaining the phase lag of the damper mass to the main structure to be 90°. The effectiveness of the proposed ATMD is evaluated analytically and experimentally.

An adaptive mass damper for self‐excited oscillations

AbstractAn adaptive tuned mass damper aiming to optimally increase the critical flow velocity of transverse galloping oscillations is presented. The structure, simply modeled as an elastically supported bluff body exposed to a steady flow, has been connected to an added mass by a spring and a dashpot varying according to an adaptive control algorithm. Based on the knowledge of a reference model, describing the optimal conditions for the system, the paper presents two procedures to design a controller that allows to identify the uncertain mechanical parameters relying on a direct and an indirect approach. In the direct case, by assuring the convergency to zero of the error between the system and the reference model variables, in the indirect case, by using a wavelet based approach for on‐line system identification. The analytical developments are validated by numerical investigations on the nonlinear system in order to assess the feasibility of the proposed control system.