Passive Dynamic Absorber Research Articles

Unified Shear-Flexural Model for Vibration Control of Buildings Using Passive Dynamic Absorbers

A unified design model is proposed for various kinds of passive dynamic absorbers (PDAs) attached to buildings with different lateral resisting systems. A total of five different PDAs are considered in this study: (1) tuned mass damper (TMD), (2) circular tuned sloshing damper (C-TSD), (3) rectangular tuned sloshing damper (R-TSD), (4) two-way liquid damper (TWLD), and (5) pendulum tuned mass damper (PTMD). The unified model consists of a coupled shear-flexural (CSF) discrete model with equivalent tuned mass dampers (TMDs), which allows the consideration of intermediate modes of lateral deformation. By modifying the nondimensional lateral stiffness ratio, the CSF model can consider lateral deformations varying from those of a flexural cantilever beam to those of a shear cantilever beam. The unified model was applied to a 144-meter-tall building located in the Valley of Mexico, which was subjected to both seismic and along-wind loads. The building has similar fundamental periods of vibration and different nondimensional lateral stiffness ratios for both translational directions, which shows the importance of considering both bending and shear stiffness in the design of PDAs. The results show a great effectiveness of PDAs in controlling along-wind RMS accelerations of the building; on the contrary, PDAs were ineffective in controlling peak lateral displacements. For a single PDA attached at the rooftop level, the maximum possible value of the PDA mass efficiency index increases as the nondimensional lateral stiffness ratio decreases; therefore, there is an increase in the vibration control effectiveness of PDAs for lateral flexural-type deformations.

Mechatronic robot arm with active vibration absorbers

Serial robots are typically able to cover large workspace, but their mass/stiffness ratio does not allow combining high accuracy and high dynamic of the end effector operations. Widely spread usage of serial robots, even for tasks such as drilling, leads to high accuracy demands through its workspace. Absolute measurement of the end point for position feedback can be challenging due to objects or even a workpiece in the workspace. Moreover, inbuilt motors of the serial robot cannot response in the frequency range high enough as vibration of the end point. Instead, an additional spring–mass system is attached to the robot to suppress vibrations. The narrow frequency range of a passive dynamic absorber can be extended with active elements between the robot and absorber. An active approach is also necessary because of robots eigenfrequencies and eigenmodes variability. The study deals with a planar flexible robot equipped with a three-degree-of-freedom planar active absorber. The absorber is tuned passively to one value of multiple eigenfrequency. The linear-quadratic regulator control with a state observer has been designed as an active absorber control algorithm. Feedback inputs are absorber body acceleration, end effector acceleration, and relative motions in three absorber actuators realized by voice coils. The end effector vibration suppression along the robot trajectory is achieved using gain scheduling of local controller’s outputs.

Active vibration control of rotor-bearing system by virtual dynamic absorber

The main sources of the vibration in rotor dynamic systems are unbalanced masses and manufacturing defects of bearings used in the rotor system. In this study, magnetic absorber as a new method brings the rotor system out of resonance state by applying a dynamic absorber system force and creating two new natural frequencies. This study virtually reconstructed magnetic absorber controller software as a combined active and passive dynamic absorber to reduce vibration amplitude, efficiently. In this approach, combined routes are defined for the rotor frequency response, so that the optimal values of the parameters of dynamic absorber system are calculated using H∞ method and maximum damping for frequencies lower and higher than resonance frequencies, respectively. The results confirm that transient response overshoot is less, and transient response attenuation is more in maximum damping method. Hence, the controller system easily recognizes initial overshoots and determines the parameters of the dynamic absorber system in accordance with maximum damping state if it is struck at any rotor frequency and any rotation angle. It is also observed that for all rotor rotation frequencies, the system overshoot reduces in comparison with H∞ method by using this control method.

Vibration mitigation of a flexible bladed rotor dynamic system with passive dynamic absorbers

The main objective of this paper is to study the application of tuned mass damper (TMD) and nonlinear energy sink (NES) on vibration mitigation of a flexible bladed rotor system. TMD tunes to a specific frequency of the main system and reduces its amplitude only in a vicinity of that frequency. NES is another well-known passive dynamic absorber comprises a mass, nonlinear spring, and linear or nonlinear damper. The nonlinearity of this absorber allows it to reduce the vibrations of the main system in a wider frequency range. In this study to reduce the contact of flexible bladed rotor system, the mentioned passive absorbers are attached both to the disk and to the tips of the blades, such that to deactivate the effect of disk's eccentricity force and stabilizing the behavior of the system. The optimum parameters of the absorbers are obtained through optimization. The bifurcation diagrams, and Lyapunov exponent of the system are obtained with respect to different parameter and rotational speed are obtained and consequently, the efficiency of the absorbers are investigated. The obtained results show how these passive absorbers can decrease the vibration of the rotor system and remove the contact at higher clearance values between the blades and the stator; although, there are limitations in their performances at lower values of clearance.

Vibration control of imbalanced Jeffcott rotor by virtual passive dynamic absorber with optimal parameter values

Today, dynamic absorbers are widely used to control vibrations of the systems that are being excited by the harmonic forces. In this paper, the usage of the magnetic force as virtual dynamic absorber for vibration control in rotary systems is investigated. In order to examine this new method, two different types of passive dynamic absorber systems are applied to control imbalanced Jeffcott rotor vibrations. In the first type of the absorber system, damper is located between the absorber mass and the disk and in the second type, it is located between the absorber mass and the ground. Then, the optimal parameters of absorber system, stiffness and damping have been analytically achieved by using two fixed points theory. Moreover, for further reduction of the vibration amplitude, combined paths have been designed for rotor frequency response. Finally, in order to evaluate the obtained results, the experimental data of our virtual dynamic absorbers were compared with simulation results and it is found that the vibration amplitude of rotor was efficiently limited in this case. Furthermore, the second type of the absorber system with equal mass ratio to the first type of the absorber system was more efficient than the first one in reduction of the amplitude of vibrations. Our findings show that the second absorber transfer more force than the first one since the second absorber connects chasis of system with damper. Therefore, it is recommended to apply the first absorber after the first resonance.

Methodology for Tuning a Semi-Active Dynamic Vibration Absorber on a Passive Suspended Seat

The article deals about an application of two types of dynamic absorber applied on an operator’s seat. In the first case, the seat is suspended by passive elements. The passive dynamic absorber (DA) is composed from a viscous damper and a linear spring. In the second case, the semi-active damper is composed from a linear spring and a MR damper. The affectivity of the vibration reduction of the seat is observed. The parameters of the seat suspension with the passive DA were identified from multi-criterion optimization using genetic algorithms. The parameters of the semi-active DA were evaluated using information obtained from the passive DA.

Active vibration control of structures using a semi-active dynamic absorber

This study is concerned with the theory and application of a tuneable dynamic absorber. The dynamic characteristics of the tuneable dynamic absorber are discussed in terms of the mass ratio, natural frequency of the main structure, natural frequency of a dynamic absorber and excitation frequency. We proposed a semi-active dynamic absorber with a natural frequency that can change through the use of repulsive forces produced by permanent magnets and electromagnetic forces induced by current flowing through a coil. A simple active control algorithm is implemented in the LabView software and the experimental results showed that when the proposed semi-active dynamic absorber is used with the active control algorithm, the vibrations of a structure can be more effectively suppressed than when a passive dynamic absorber with a fixed natural frequency is used.

Application of a Magneto-rheological Damper and a Dynamic Absorber for a Suspension of a Working Machine Seat

The article deals with two alternatives of semi active suspensions of a seat of working machine. A magneto-rheological damper is used in the first case and in the second case the suspension of the seat is a combination of magneto-rheological damper and dynamic absorber. The dynamic absorber is composed from passive elements. In both cases, the dampers are controlled by the well known Sky hook algorithm. The dynamic analysis is focused on the influence of the applied passive dynamic absorber on the reduction of the seat displacements. The passive parameters of the seat suspension and the dynamic absorber were evaluated based on the optimization process using genetic algorithms according the defined minimization function.

A38 インピーダンスマッチング指標を用いた柔軟構造物の振動制御 : 受動ダンパと動吸振器の最適調整(振動の解析と制御)

A38 インピーダンスマッチング指標を用いた柔軟構造物の振動制御 : 受動ダンパと動吸振器の最適調整(振動の解析と制御)

Design of Passive Type Dynamic Absorber with Robust Performance by Using Control Theory

This paper proposes a design method of a passive dynamic absorber with robust performance. In this study, the dynamic absorber is designed from the view of feedback control. We consider that a extended model is constructed by two main systems which have maximum and minimum natural frequencies in the given variable domain, and the maximum value of frequency response of the extended plant is reduced by one static output feedback H∞ controller. Finally, numerical simulations show the advantage of the proposed design method.

Study on Aseismic Design Based on Semi-active Dynamic Absorber

Control algorithm based on semi-active dynamic absorber for aseismic design is investigated. The structure with joint elements is simplified by dual mass model and they are regarded as main and sub structure. Considering the sub structure and a joint element as a semi-active dynamic damper, control algorithm to reduce the seismic response of main structure is studied. This algorithm demands a damper to act as a spring which has various spring constants and the stiffness is shifted real time based on the information for the dominant frequency of input earthquakes, so as to avoid the resonance between the boiler structure and the ever-changing dominant frequencies of input earthquakes. Numerical simulation showed that the proposed method is superior to the optimally tuned passive dynamic absorber.

Vertical vibrations of a multi-span beam steel bridge induced by a superfast passenger train

Transient and quasi-steady-state vertical vibrations of a multi-span beam steel bridge located on a single-track railway line are considered, induced by a superfast passenger train, moving at speed 120-360 km/h. Matrix dynamic equations of motion of a simplified model of the system are formulated partly in the implicit form. A recurrent-iterative algorithm for solving these equations is presented. Excessive vibrations of the system in the resonant zones are reduced effectively with passive dynamic absorbers, tuned to the first mode of a single bridge span. The dynamic analysis has been performed for a series of types of bridges with span lengths of 10 to 30 m, and with parameters closed to multi-span beam railway bridges erected in the second half of the 20 th century.

Unified dynamic absorber design formulas for wind-induced vibration control of tall buildings

The objective of this paper is to establish some unified design formulas for various kinds of passive dynamic absorber for wind-induced vibration control of tall buildings. A total of five different passive dynamic absorbers (TMD, TLCD, LCVA, C-TLD and R-TLD) are considered in this study. Firstly, unified equations of motion for the building–absorber system under wind-induced excitation are presented. A set of unified formulas for the optimal properties and the equivalent damping ratios for these five dynamic absorbers are then derived analytically. The Shanghai Central Plaza, which is a thirty-nine-story reinforced-concrete building, is used as an example to demonstrate the procedure and to verify the accuracy of the unified approach. The results show that these unified formulas provide direct performance evaluation and comparison between the five dynamic absorbers for the control of wind-induced vibration of tall buildings. © 1998 John Wiley & Sons, Ltd.

Optimal passive vibration control of cutting process stability in milling

The paper proposes a design concept for an optimal passive dynamic absorber in the milling process. An investigation and analysis into the characteristics of, and interaction between, forced vibration and linear chatter in milling has been carried out by use of a two—degree—of—freedom structural model simulation. A dynamic absorber mass is then connected to the main system through passive elements (spring and damper). Optimization procedures to determine the optimum values of spring and damping coefficients for a specific mass ratio have been developed by employing the ADS optimization package. A theoretical approach for the prediction of machine tool chatter in milling including dynamic cutting forces permits calculation of borderlines of stability for a structure model with an optimal absorber. Compared with the limit of stability under no control, the stable range under optimal passive control has been improved over one hundred percent. Transient responses can also be obtained from numerical integration of the system's equation of motion in the state variable representation based on the fourth—order Runge—Kutta method. The theoretical predictions can be verified by the results of numerical simulation of transient response.

Optimal passive vibration control of cutting process stability in milling

The paper proposes a design concept for an optimal passive dynamic absorber in the milling process. An investigation and analysis into the characteristics of, and interaction between, forced vibration and linear chatter in milling has been carried out by use of a two—degree—of—freedom structural model simulation. A dynamic absorber mass is then connected to the main system through passive elements (spring and damper). Optimization procedures to determine the optimum values of spring and damping coefficients for a specific mass ratio have been developed by employing the ADS optimization package. A theoretical approach for the prediction of machine tool chatter in milling including dynamic cutting forces permits calculation of borderlines of stability for a structure model with an optimal absorber. Compared with the limit of stability under no control, the stable range under optimal passive control has been improved over one hundred percent. Transient responses can also be obtained from numerical integration of the system's equation of motion in the state variable representation based on the fourth—order Runge—Kutta method. The theoretical predictions can be verified by the results of numerical simulation of transient response.

Vibration control by a hybrid dynamic absorber.

This paper proposes a new hybrid dynamic absorber that combines an electro-magnetic actuator with a magnetic-damping-type dynamic absorber and shows its vibration controlling performances. Although the passive dynamic absorber with optimum adjustment conditions is able to control vibration well, the controlling effectiveness deteriorates markedly when these adjustment conditions fail. On the contrary, the active dynamic absorber expends a lot of energy for controlling vibration, instead of obtaining good control performance and robustness of control. In this paper, it is demonstrated theoretically and experimentally that the hybrid dynamic absorber has the advantages of both passive and active dynamic absorbers.

Optimal active suspension structures for quarter-car vehicle models

The preliminary design of active vehicle suspensions can be naturally cast into an equivalent linear-quadratic Gaussian (LQG)-optimization problem, where the performance index is an appropriate combination of ride comfort, vehicle handling and suspension design constraints. The vehicle models vary in complexity with the simplest one being the one degree-of-freedom (DOF) quarter-car model which neglects wheel dynamics. The present paper explores the connections between LQG-optimal one DOF and two DOF models. In a recent study (Hrovat, 1987), it was shown that for the optimal two DOF systems, both ride and handling can be improved by reducing the unsprung mass. The limiting one DOF case of zero unsprung mass then represented the maximum possible improvement within the constraint of a single active actuator. It is shown in the present paper that in practice these limiting benefits can be approached via passive dynamic absorbers attached to the unsprung mass. Moreover, the structural constraint of a single active actuator has been relaxed to allow for both secondary suspension and unsprung mass active actuators. Here the maximum possible ride and handling improvements for two DOF systems are obtained in the limiting case of singular control with zero penalty on unsprung actuator force. This absolutely optimal structure turns out to be yet another special one DOF system, which in practice could be approached with the help of active dynamic absorbers.

Optimal Dynamic Absorbers for Plate Vibration Control

Modern optimal control theory is used to design passive dynamic absorbers to minimize the transient vibrations of thin plates. In addition to spring and damping constants, the absorber locations on the plate are optimized. If dynamic plate loads excite certain modes of vibration, the technique can be used to select parameters such that damping of these modes will be emphasized. The numerical example used to discuss the characteristics of the optimal designs concerns a uniform rectangular plate which is simply supported at its edges, but the technique applies in all cases where the vibration can be expressed as a sum of terms in orthogonal modes of vibration.