Showing papers on "Damper published in 2014"

An Active Damper for Stabilizing Power-Electronics-Based AC Systems

Abstract: The interactions among the parallel grid-connected converters coupled through the grid impedance tend to result in stability and power quality problems. To address them, this paper proposes an active damper based on a high bandwidth power electronics converter. The general idea behind this proposal is to dynamically reshape the grid impedance profile seen from the point of common coupling of the converters, such that the potential oscillations and resonance propagation in the parallel grid-connected converters can be mitigated. To validate the effectiveness of the active damper, simulations and experimental tests on a three-converter-based setup are carried out. The results show that the active damper can become a promising way to stabilize the power-electronics-based ac power systems.

Seismic response control using electromagnetic inertial mass dampers

Abstract: SUMMARY This paper presents a new type of electromagnetic damper with rotating inertial mass that has been developed to control the vibrations of structures subjected to earthquakes. The electromagnetic inertial mass damper (EIMD) consists of a ball screw that converts axial oscillation of the rod end into rotational motion of the internal flywheel and an electric generator that is turned by the rotation of the inner rod. The EIMD is able to generate a large inertial force created by the rotating flywheel and a variable damping force developed by the electric generator. Device performance tests of reduced-scale and full-scale EIMDs were undertaken to verify the basic characteristics of the damper and the validity of the derived theoretical formulae. Shaking table tests of a three-story structure with EIMDs and earthquake response analyses of a building with EIMDs were conducted to demonstrate the seismic response control performance of the EIMD. The EIMD is able to reduce story drifts as well as accelerations and surpasses conventional types of dampers in reducing acceleration responses. Copyright © 2013 John Wiley & Sons, Ltd.

Lockup device for torque converter

Abstract: An output rotary member is coupled to a turbine and rotatable relatively to a clutch portion. First elastic members elastically and rotation-directionally couple the clutch portion and the output rotary member. A dynamic damper device is coupled to any of members forming a power transmission path from the clutch portion to the output rotary member and includes a damper plate having a plurality of circumferentially extending first openings and to be rotated together with the output rotary member. The dynamic damper device also includes inertia members disposed on both axial sides of the damper plate and rotatable relatively to the damper plate, each of the inertia members having circumferentially extending second openings located to oppose the first openings. The dynamic damper device further includes second elastic members accommodated in the first openings and the second openings, the second elastic members elastically coupling the damper plate and the inertia members.

Energy-harvesting linear MR damper: prototyping and testing

Abstract: The present study is concerned with an energy-harvesting linear MR (EH-LMR) damper which is able to recover energy from external excitations using an electromagnetic energy extractor, and to adjust itself to excitations by varying the damping characteristics. The device has three main components: an MR part having a damper piston assembly movable in relation to the damper cylinder under an external excitation, a power generator to produce electrical power according to the relative movement between the damper piston and the cylinder assembly, and a conditioning electronics unit to interface directly with the generator and the MR damper. The EH-LMR damper integrates energy harvesting, dynamic sensor and MR damping technologies in a single device.The objective of the study is to get a better insight into the structure of EH-LMR damper components, to investigate the performance of each component and a device as a whole, and to compare results of experimental study against numerical data obtained in simulations conducted at the design stage. The research work demonstrates that the proposed EH-LMR damper provides a smart and compact solution with the potential of application to vibration isolation. The advantage of the device is its adaptability to external excitations and the fact that it does not need any extra power supply unit or sensor on account of its self-powered and self-sensing capabilities.

A low sedimentation magnetorheological fluid based on plate-like iron particles, and verification using a damper test

Abstract: This study presents a new kind of low sedimentation magnetorheological fluid (MRF). Its salient properties are evaluated using a small-sized damper. The proposed MRF is characterized to investigate the effect of plate-like iron particles on rheological properties such as yield stress and flow behavior. Plate-like micron size iron particles play an important role in improving stability against rapid sedimentation as well as in enhancing the value of the yield stress. This study also considers a bidisperse MRF because this can produce a higher yield stress compared with a monodisperse suspension. Since the field-dependent yield stress is the key factor in mechanical applications, the physical properties of the MRF proposed in this work are evaluated and applied to the design of a small-sized damper which can be used for vibration control in washing machines. In order to verify the smaller effect on the damping force due to the particle sedimentation, the field-dependent damping forces are measured under two different operating conditions; one is just after filling the MRF and another after operating for 48 h. The proposed MRF is shown to be very effective in reducing adverse effects due to particle sedimentation.

Energy Regenerative Suspension Using an Algebraic Screw Linkage Mechanism

Abstract: This paper presents the development of a novel energy-regenerative suspension mechanism. The system consists of a mass-spring unit coupled with an algebraic screw kinematic pair, a rotary permanent magnet synchronous generator (PMSG), and a three-phase boost charger connected to a battery. The algebraic screw converts the translational vibration into a reciprocating rotary motion which drives the PMSG through a planetary gearhead. A pulse-width-modulated three-phase boost converter is then used to convert the energy generated by the rotary machine into battery charge. To this end, a control and switching algorithm is utilized that makes the battery appear as a pseudo-resistor across the terminals of the rotary machine. Introducing this pseudo-resistive characteristic across the machine produces the same effect as mechanical damping with an energy regenerative function. The design and analysis of the regenerative suspension mechanism are presented by considering the dynamics of the electromechanical device, parameters of the suspension system, and the base excitation input profile. Experimental results are presented that evaluate performance of the proposed regenerative damper on a small-scale suspension system, which demonstrate the feasibility of building energy-regenerative dampers.

Nonlinear Identification of a Magneto‐Rheological Damper Based on Dynamic Neural Networks

Abstract: Semi-active control of dynamic response of civil structures with magneto-rheological (MR) fluid dampers has emerged as a novel revolutionary technology in recent years for designing “smart structures.” A small-scale MR damper model with the valve mode mechanism has been examined in this research using dynamic recurrent neural network modeling approach to reproduce its hysteretic nonlinear behavior. Modified Bouc–Wen model based on nonlinear differential equations has not only been employed as the reference model to provide a comprehensive training data for the neural network but also for comparison purposes. A novel frequency and amplitude varying displacement input signal (modulated chirp signal) associated with a random supply voltage has been introduced for persistent excitation of the damper in such a way to cover almost all of its operating conditions. Finally a series of validation tests were conducted on the proposed model which proved the appropriate performance of the model in terms of accuracy and capability for realization.

Heat recovery and demand ventilation system

Abstract: A ventilation system for an air conditioning system includes dampers, a heat exchange unit, and a control unit. One damper controls the flow of ambient air into the system. The other damper controls the flow of relief/exhaust air that is cannibalized from return air from a room or space being cooled (or heated) by the air conditioning system. The ventilation system utilizes a control algorithm in the control unit to calculate, at stepped spaced apart increasing room ventilation rates, increasing CO2 concentrations in the air in the room that are below a maximum desired CO2 concentration in a room. The control algorithm permits a control unit in the ventilation system to open and close the dampers to maintain a CO2 concentration in the room that is below the desired CO2 concentration level.

An optimised tuned mass damper/harvester device

Abstract: SUMMARY Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure Traditionally, this energy is dissipated through the devices as heat In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated The energy-dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy That gives the possibility of controlled damping force whilst generating useful electrical energy Both analytical and experimental results from an adaptive and a semi-active tuned mass damper/harvester are presented The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression Copyright © 2014 John Wiley & Sons, Ltd

Precise stiffness and damping emulation with MR dampers and its application to semi-active tuned mass dampers of Wolgograd Bridge

Abstract: This paper investigates precise stiffness and damping emulation with MR dampers when clipping and a residual MR damper force constrain the desired control force. It is shown that these force constraints lead to smaller equivalent stiffness and greater equivalent damping of the constrained MR damper force than desired. Compensation methods for precise stiffness and damping emulations are derived for harmonic excitation of the MR damper. The numerical validation of both compensation methods confirms their efficacy. The precise stiffness emulation approach is experimentally validated with the MR damper based semi-active tuned mass damper (MR-STMD) concept of the Wolgograd Bridge . The experimental results reveal that the precise stiffness emulation approach enhances the efficiency of the MR-STMD significantly when the MR-STMD is operated at reduced desired damping, where the impact of control force constraints becomes significant.

Optimal control of gun recoil in direct fire using magnetorheological absorbers

Abstract: Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using a nonlinear Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with low or high recoil loads imply low or high rate of fire, respectively. The gun recoil absorber performance is also analyzed for perturbations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery position (ready to reload and fire) without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.

Modeling and Measurements on a Finite Rectangular Conducting Plate in an Eddy Current Damper

Abstract: This paper concerns the modeling of an eddy current damper with a finite conducting plate. In the eddy current damper, a finite rectangular conducting plate is moving between cuboidal magnets. The first step of the modeling method is based on an infinite conducting plate. For this infinite conducting plate, the eddy current density is derived using two different methods, the scalar potential method and the vector potential method. The finite boundaries of the conducting plate are included by means of the method of images in two dimensions and, therewith, complete the model. By applying the method of images, the accuracy of the models for calculating the damping coefficient is significantly improved. The assumption of an infinite conducting plate gives less than 15% error for a conducting plate with at least twice the dimensions of the permanent magnet. Applying the method of images reduces the modeling error for a conducting plate with two times the permanent-magnet dimensions to less than 3% in respect to a finite-element model. For the verification of the semianalytical model, measurements are performed. For a variation of the plate width, the presented semianalytical model has less than 5% discrepancy with respect to the measurements.

Optimal design of magnetorheological fluid-based dampers for front-loaded washing machines

Abstract: In this research, a magnetorheological fluid-based damper to attenuate vibration due to unbalanced laundry mass from a front-loaded washing machine is proposed and optimally designed with experimental validation. First, rigid vibration mode of the washing machine due to an unbalanced mass is analyzed, and an optimal positioning of the suppression system for the washing machine is figured out. In order to attenuate vibration from the washing machine, several configurations of magnetorheological damper are proposed considering available space and the required damping force of the system. Based on the Bingham rheological model of magnetorheological fluid, damping force of the proposed magnetorheological dampers is then derived. An optimal design problem for the proposed magnetorheological damper is constructed considering its zero-field friction force and the maximum damping force. The optimization objective is to minimize the zero-field friction force of the magnetorheological damper while the maximum value...

Analysis of a high-rise steel structure with viscous damped outriggers

Abstract: SUMMARY Damped outriggers for tall buildings draw increasingly attentions to engineers. With a shaking table test, two models of a high-rise steel column-tube structure are established, one with outriggers fixed to the core and hinged at the columns, whereas the other's cantilevering outriggers are connected to columns by viscous dampers. According to their dynamic properties, five earthquake waves are selected from the Ground Motion Database of Pacific Earthquake Engineering Research Center (PEER), and two artificial waves are generated by software SIMQKE_GR. Under various peak ground accelerations (PGAs), nonlinear time-history analysis is applied to compare structural elastic seismic responses, including accelerations, inter-story drifts, base shear force, damper's response and additional damping ratios. It is concluded that under minor earthquakes, accelerations, inter-story drifts and base shear force of structure with damped outriggers are larger than or nearly equal to those of the one with fixed outriggers, and the viscous dampers hardly work. But as PGA increases, the contrary situation happens, and the effect of viscous dampers is enhanced as well. The additional damping ratio reaches around 4% under mega earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.

Simultaneous topology and sizing optimization of viscous dampers in seismic retrofitting of 3D irregular frame structures

Abstract: SUMMARY A new methodology for performance-based optimal seismic retrofitting using a limited number of size groups of viscous dampers is presented. The damping coefficient of each size group of dampers is taken as a continuous variable and is determined by the optimization algorithm. Furthermore, for each potential location, a damper of a single size group is optimally assigned, if any. Hence, the formulation presents a large step forward towards practical optimal design of dampers. The key for achieving an efficient optimization scheme is the incorporation of material interpolation techniques that were successfully applied in other structural optimization problems of discrete nature. This results in a very effective optimization methodology that is expected to be very efficient for large-scale structures. The proposed approach is demonstrated on several example problems of 3D irregular frame structures. Copyright © 2014 John Wiley & Sons, Ltd.

Discrete element method simulation and experimental validation of particle damper system

Abstract: Purpose – The particle damper is an efficient vibration control device and is widely used in engineering projects; however, the performance of such a system is very complicated and highly nonlinear. The purpose of this paper is to accurately simulate the particle damper system properly, and help to understand the underlying physical mechanics. Design/methodology/approach – A high-fidelity simulation process is well established to account for all significant interactions among the particles and with the host structure system, including sliding friction, gravitational forces, and oblique impacts, based on the modified discrete element method. In this process, a suitable particle damper system is modeled, reaction forces between particle aggregates and the primary structure are incorporated, a reasonable contact force model and time step are determined, and an efficient contact detection algorithm is adopted. Findings – The numerical results are further validated by both special computational tests and shaki...