Showing papers on "Damper published in 2018"

Particle impact dampers: Past, present, and future

Abstract: Particle damping, an effective passive vibration control technology, is developing dramatically at the present stage, especially in the aerospace and machinery fields. The aim of this paper is to provide an overview of particle damping technology, beginning with its basic concept, developmental history, and research status all over the world. Furthermore, various interpretations of the underlying damping mechanism are introduced and discussed in detail. The theoretical analysis and numerical simulation, together with their pros and cons are systematically expounded, in which a discrete element method of simulating a multi-degree-of-freedom structure with a particle damper system is illustrated. Moreover, on the basis of previous studies, a simplified method to analyze the complicated nonlinear particle damping is proposed, in which all particles are modeled as a single mass, thereby simplifying its use by practicing engineers. In order to broaden the applicability of particle dampers, it is necessary to implement the coupled algorithm of finite element method and discrete element method. In addition, the characteristics of experimental studies on particle damping are also summarized. Finally, the application of particle damping technology in the aerospace field, machinery field, lifeline engineering, and civil engineering is reviewed at length. As a new trend in structural vibration control, the application of particle damping in civil engineering is just at the beginning. The advantages and potential applications are demonstrated, whereas the difficulties and deficiencies in the present studies are also discussed. The paper concludes by suggesting future developments involving semi-active approaches that can enhance the effectiveness of particle dampers when used in conjunction with structures subjected to nonstationary excitation, such as earthquakes and similar nonstationary random excitations.

Demand-based optimal design of oscillator with parallel-layout viscous inerter damper

Abstract: Summary In this study, a demand-based optimal design method is proposed for an oscillator (a single-degree-of-freedom system) with a parallel-layout viscous inerter damper (PVID) The proposed design method overcomes some deficiencies of the existing method, which is based on the fixed-point theory and is mainly suitable for tuned mass dampers Moreover, for the fixed-point method, the inherent damping of the primary structure is neglected, and the global optimal solution cannot be obtained The proposed method can obtain a more rational and practical design for the actual design by minimizing both the response and the cost The design problem of a PVID-equipped oscillator is transformed into a multi-objective optimization problem that can be solved using the e-constraint approach, which is consistent with the concept of demand-based design The dynamic response of the oscillator and the force of the PVID (ie, the cost factor) are evaluated according to theories of random vibration to reduce the number of calculations required A computer program is developed to perform demand-based parametric design of a PVID-equipped oscillator Several design cases were examined under different excitation conditions using the computer program, and dynamic time history analyses were then conducted to verify the designs obtained The results show that the proposed optimal design method identifies satisfactory designs more effectively than the existing method by obtaining PVID design parameter values that better meet the performance demand and simultaneously minimize the cost

An Adaptive Active Damper for Improving the Stability of Grid-Connected Inverters Under Weak Grid

Abstract: When a grid-connected inverter is connected to a weak grid, the system may be unstable. An active damper can be connected to the point of common coupling (PCC), which simulates a virtual resistor to dampen the resonance and thus stabilize the system. In this paper, an adaptive tuning method of the virtual resistor is proposed, which can automatically regulate the virtual resistor to the critical value to stabilize the system, and thus reduce the power loss. Furthermore, the active damper is designed not to respond to the dominant low-frequency harmonic components in the PCC voltage introduced by the grid background harmonics, so that its power loss can be further reduced. In order to make the active damper more accurately simulate the virtual resistor in a wide frequency range, a harmonic-current-reference compensation method is proposed. The prototypes of a 6-kW grid-connected inverter and a 1-kVA active damper are built and tested to verify the effectiveness of the proposed control scheme of the active damper.

Semi-active seismic control of an 11-DOF building model with TMD+MR damper using type-1 and -2 fuzzy algorithms:

Abstract: Nowadays, vibration control of structures is considered as a challenging field among scientists and engineers. Structural damage and financial losses due to recent earthquakes in different countrie...

Reliability-based optimal design of nonlinear viscous dampers for the seismic protection of structural systems

Abstract: Viscous dampers are widely employed for enhancing the seismic performance of structural systems, and their design is often carried out using simplified approaches to account for the uncertainty in the seismic input. This paper introduces a novel and rigorous approach that allows to explicitly consider the variability of the intensity and characteristics of the seismic input in designing the optimal viscous constant and velocity exponent of the dampers based on performance-based criteria. The optimal solution permits controlling the probability of structural failure, while minimizing the damper cost, related to the sum of the damper forces. The solution to the optimization problem is efficiently sought via the constrained optimization by linear approximation (COBYLA) method, while Subset simulation together with auxiliary response method are employed for the performance assessment at each iteration of the optimization process. A 3-storey steel moment-resisting building frame is considered to illustrate the application of the proposed design methodology and to evaluate and compare the performances that can be achieved with different damper nonlinearity levels. Comparisons are also made with the results obtained by applying simplifying approaches, often employed in design practice, as those aiming to minimize the sum of the viscous damping constant and/or considering a single hazard level for the performance assessment.

Application of hybrid electromagnetic suspension in vibration energy regeneration and active control

Abstract: To improve the reliability of active electromagnetic suspension and reduce energy consumption, a hybrid electromagnetic suspension that consists of linear motor and passive damper in parallel is pr...

An Energy Saving Variable Damping Seat Suspension System With Regeneration Capability

Abstract: In this paper, an energy saving variable damping seat suspension system is designed, manufactured, modeled, and validated A continuously controllable electromagnetic damper (EMD) system, which consists of a permanent magnet synchronous motor, a three-phase rectifier, a metal–oxide–semiconductor field-effect transistor (MOSFET) switch, and an external resistor, is built and tested first Its model parameters have been identified based on the test results The EMD's damping property can be controlled by exerting pulsewidth modulation (PWM) signal with different duty cycles on the MOSFET switch The EMD is integrated with a planetary gearbox to amplify its torque output, and the formed variable damper is installed on the center of the scissors structure of a seat suspension By analyzing the EMD test results and the seat suspension's kinematic, the controllable damping of the proposed seat suspension is derived as 112 to 746 N·s/m A control method for vibration isolation is proposed based on the system model The proposed variable damping seat suspension and its controller are validated on a six-degrees-of-freedom vibration platform in both frequency domain and time domain; a well-tuned commercial passive seat suspension is also tested for comparison The test results show that the controlled variable damping seat suspension has better performance in vibration isolation than the proposed seat with highest and lowest damping, and the conventional passive one In the meantime, the RMS value of the system harvestable power is 1492 W, and the power consumption of the PWM control signal is small Therefore, this variable damping seat suspension can improve ride comfort with ignorable energy cost

Optimal design of tuned liquid column dampers for seismic response control of base-isolated structures

Abstract: In this paper, the use of a tuned liquid column damper (TLCD) as a cost-effective means to control the seismic response of a base-isolated structure is studied. A straightforward direct approach for the optimal design of such a device is proposed, considering a white noise model of the base excitation. On this base, a direct optimization procedure of the TLCD design parameters is performed and optimal design charts are presented as a ready-to-use practical design tool. Comparison with the optimal parameters obtained considering a classical iterative statistical linearization technique proves the reliability of the proposed approach. The performance of the base-isolated TLCD-controlled structure is examined and compared with that of the simple base-isolated one (without TLCD), using a set of 44 recorded ground motions as base excitation. Theoretical and numerical results show that the TLCD is rather effective in reducing the response of base-isolated structures under strong earthquakes. Therefore, considering its advantageous characteristics and its overall beneficial effects, TLCDs can be considered as practical and appealing means to control the seismic response of base-isolated structures.

Multivariable Adaptive Control of the Rewinding Process of a Roll-to-roll System Governed by Hyperbolic Partial Differential Equations

Abstract: In this paper, an active control scheme for the rewinding process of a roll-to-roll (R2R) system is investigated. The control objectives are to suppress the transverse vibration of the moving web, to track the desired velocity profile, and to keep the desired radius value of a rewind roller. The bearing coefficient in the rewind shaft is unknown and the rotating elements in the drive motor are various. The moving web is modeled as an axially moving beam system governed by hyperbolic partial differential equations (PDEs). The control scheme utilizes two control inputs: a control force exerted from a hydraulic actuator equipped with a damper, and a control torque applied to the rewind roller. Two adaptation laws are derived to estimate the unknown bearing coefficient and the bound of variations of the rotating elements. The Lyapunov method is employed to prove the robust stability of the rewind section, specifically the uniform and ultimate boundedness of all of the signals. The effectiveness of the proposed control schemes was verified by numerical simulations.

Performance-based optimisation of RC frames with friction wall dampers using a low-cost optimisation method

Abstract: Friction-based dampers can be considered as one of the suitable passive control systems for seismic strengthening and rehabilitation of existing substandard structures due to their high adjustability and good energy dissipation capability. One of the main issues in the design of these systems is to obtain the magnitude of the maximum slip force and the distribution of slip forces along the height of the building. In this study, a practical performance-based optimisation methodology is developed for seismic design of RC frame buildings with friction energy dissipation devices, which allows for an accurate solution at low computational cost. The proposed method aims at distributing the slip loads of the friction dampers to achieve a uniform distribution of damage along the height of the building. The efficiency of the method is evaluated through the optimum design of five different low to high-rise RC frames equipped with friction wall dampers under six natural and six synthetic spectrum-compatible earthquakes. Sensitivity analyses are performed to assess the reliability of the method using different initial height-wise slip load distributions, convergence parameters and earthquake records. The results indicate that optimum frames exhibit less maximum inter-storey drift (up to 43%) and global damage index (up to 75%), compared to uniform slip load distribution. The method is then developed to obtain the optimum design solution for a set of earthquakes representing a design spectrum. It is shown that the proposed method can provide an efficient tool for optimum seismic design of RC structures with friction energy dissipation devices for practical purposes.

Mitigation of nonlinear oscillations of a Jeffcott rotor System with an optimized damper and nonlinear energy sink

Abstract: Contact occurrence between disk and stator as result of undesirable vibrations produced by eccentricity of the disk is one of the most destructive and common phenomena in rotor dynamics systems. In this work, utilizing tuned mass damper (TMD) and nonlinear energy sink (NES) are suggested as a solution for preventing contact occurrence. The mass and angular position of absorbers determine their efficiency for resisting the eccentricity force produced by the disk, and their stiffness and damping coefficients determine the displacement scope of the absorber. In order to efficiently design absorbers, optimization is proposed. In this suggested optimization process, complex averaging method is used in order for deriving the equations of motion of the system in presence of dynamic absorbers at the steady state condition. Afterwards, for determining trustworthiness of each absorber’s performance, system’s behavior is studied for different values of its parameters such as rotational speed, stiffness, clearance and eccentricity in presence of each absorber. From the obtained results, it can be perceived that TMD and NES are as efficient as possible and they have exactly the same positive influence on the system’s vibrations. The reliability of the proposed optimization process can be determined by the results.