Variable Friction Damper Research Articles

Variable stiffness friction damper for dual-state isolation of flywheel on satellite

Variable stiffness friction damper for dual-state isolation of flywheel on satellite

Steady-State Response and Damping Control Effect of Reid-TMD

A passive tuned mass damper (TMD) fabricated using the Reid damping, referred to as the Reid-TMD, is proposed. First, the characteristics of the Reid damping model are introduced, followed by the presentation of a passive variable friction damper to achieve this model. Next, the steady-state response of single-degree-of-freedom structures with the Reid-TMD under a harmonic load is solved by the harmonic balance method (HBM), together with an error analysis of the results. Subsequently, the optimization and control effect of the Reid-TMD damping system are analyzed and compared with the traditional viscous damping TMD. The results show that under the action of a harmonic load or seismic load, the vibration suppression effect of the Reid-TMD with the same mass ratio is essentially equivalent to the traditional viscous damping TMD. In addition, the damping control effect increases with the increase in mass ratio. When the mass ratio is less than 0.05, the energy dissipation coefficient is less than 0.5 and the frequency ratio is less than 0.95. For parameters within this range, the steady-state response of the seismic reduction structure with the Reid-TMD is solved by the HBM. If the parameters of the Reid-TMD are outside this range, the error of the HBM becomes large, and recourse should be changed to general numerical methods. The optimum parameters of the Reid-TMD are determined through an optimization analysis for the mass ratio in the range of 0.005–0.1. While using the Reid-TMD for the vibration absorption design, the optimum parameters can be acquired directly by using the established tables. Because the passive variable friction damper has good durability and economy, the application of the Reid-TMD is beneficial to shock absorption technology.

Online tuning of fractional order fuzzy PID controller in smart seismic isolated structures

This paper aims at designing an adaptive fractional order fuzzy proportional–integral-derivative controller for seismic control of smart base-isolated structure by means of variable friction dampers (VFD). One main challenge occurs when large displacement of the isolator happens due to near-field motions. To overcome this challenge, a solution is to use VFDs. However, the floor accelerations of the superstructure can increase because of sudden changes in the damper friction force of VFDs. Therefore, a suitable control strategy is desired to handle the displacement of isolator without any increase in superstructure acceleration responses during both far-field and near-field earthquakes. First, a sub-level fractional order fuzzy PID (FOFPID) controller is designed to reduce the isolator displacement without significant increase in roof acceleration based on a multi-objective optimization algorithm. Using an adaptive strategy, the fuzzy rule weights of the FOFPID controller are then tuned on-line based on information sensed from both the earthquake and the building responses. Considering nine important performance criteria and several real-data earthquakes, numerical studies are carried out for a benchmark base-isolated structure equipped with VFDs. Simulation results show the superior performance of the proposed controller in mitigation of seismic responses of base-isolated structure against various types of earthquakes in comparison with other controllers presented in previous researches.

Invited Review: Recent developments in vibration control of building and bridge structures

This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber.

Numerical analysis using state space method for vibration control of car seat by employing passive and semi active dampers

In passenger cars the vibrations developed at the ground are transmitted to the passengers through seats. Due to vibrations discomfort is experienced by the passengers. Dampers are being successfully utilized to reduce the vibrations in civil engineering structures. Few dampers are used in passenger cars as well. In the present study viscous dampers and semi-active variable friction dampers are used in passenger cars. The car and car seat are modeled together as two degrees of freedom system. The study is carried out for two cases namely car moving on sagged bridges and car moving on road humps. The paper also presents the comparison of performance of both the dampers for the two cases. State space method has been employed for the numerical analysis of the study. It is found that the amplitude of displacements is reduced considerably by the employment of dampers and resonance is avoided. Performance wise viscous damper is found to be slightly better than semi-active variable friction damper.Keywords: Car seat, viscous damper, semi-active variable friction damper, two degrees of freedom, state space method

A new lever-type variable friction damper for freight bogies used in heavy haul railway

To overcome defects caused by the complex structure and unstable damping performance of the wedge-type damper, a new lever-type friction damper has been developed for use in freight bogies; the design allows the advantages of traditional three-piece bogies to be retained. A detailed description of the structure and mechanism of the lever-type damper is provided, followed by a stress analysis using the finite element method. Dynamic performance characteristics of the lever-type damper and the wedge-type damper are compared in terms of the nonlinear critical speed, riding index, and curve negotiation. The results indicate that the maximum stress of the lever remains below its yield limit. The lever-type car has higher running performance reliability, and achieves similar nonlinear critical speed, riding index, and curve negotiation when compared with the wedge-type car.

High capacity variable friction damper based on band brake technology

Implementation of high performance controllable damping devices can ameliorate cost-effectiveness of structural systems for mitigation of natural hazards. However, the applications of these damping systems are limited due to a lack of (1) mechanical robustness; (2) electrical reliability; and (3) large resisting force capability. To broaden the implementation of modern damping systems, a novel semi-active damping device is proposed. The device, termed Banded Rotary Friction Device (BRFD), has enhanced applicability compared to other proposed damping systems due to its cost-effectiveness, high damping performance, mechanical robustness, and technological simplicity. Its mechanical principle is based on a band brake, which results in a high amplification of the applied force while enabling a variable control force. The theoretical model of the BRFD is presented and experimentally verified by subjecting a prototype to various harmonic loads. Results show that the prototype BRFD is capable of a maximum force of 45kN (10kips) using only a 267N (60lb) actuation force, therefore providing a mechanical advantage of 169. A 3-stage dynamic model previously developed by the authors can successfully be used to model the dynamic behavior of the BRFD.

Semi-active friction tendons for vibration control of space structures

Semi-active vibration control systems are becoming popular because they offer both the reliability of passive systems and the versatility of active control without high power demands. In this work, a new semi-active control system is proposed and studied numerically. The system consists of variable-friction dampers linked to the structure through cables. Auxiliary soft springs in parallel with these friction dampers allow them to return to their initial pre-tensioned state. Using cables makes the system suitable for deployable, flexible and lightweight structures, such as space structures (spacecraft). A control system with three control laws applied to a single-degree-of-freedom structure is studied. Two of these laws are derived by using Lyapunov theory, whereas the third one is developed heuristically. In order to assess the performance of the control system, a parametric study is carried out through numerical simulations. An application of the proposed method to multi-degree-of-freedom structures is also presented and demonstrated through a numerical example. The system in semi-active mode is more effective than in passive mode and its effectiveness is less sensitive to loss of pre-tension.

J1010505 救急車搬送ベッド用の加速度低減装置の研究 : 可変摩擦ダンパーの再設計と改良([J101-5]制振(1))

J1010505 救急車搬送ベッド用の加速度低減装置の研究 : 可変摩擦ダンパーの再設計と改良([J101-5]制振(1))

Response of piping system with semi-active variable friction dampers under tri-directional seismic excitation

Seismic loads on piping system due to earthquakes can cause excessive vibrations, which can lead to serious instability resulting in damage or complete failure. In this paper, semi-active variable friction dampers (SAVFDs) have been studied to mitigate seismic response and vibration control of piping system used in the process industries, fossil and fissile fuel power plant. A study is also conducted on the performance of control due to variation in gain multiplier (a) in the present control law, which plays an important role in the present control algorithm of the damper. The effectiveness of the SAVFD in terms of reduction in the responses, namely, displacements, accelerations and base shear of the piping system is investigated by comparing uncontrolled responses under four artificial earthquake motions with increasing amplitudes. The analytical results demonstrate that the SAVFDs under particular optimum parameters are very effective and practically implementable for the seismic response mitigation, vi...

Application of an SMA‐based hybrid control device to 20‐story nonlinear benchmark building

SUMMARYThis paper investigates the seismic response control of a 20‐story nonlinear benchmark building with a new recentering variable friction device (RVFD). The RVFD combines energy dissipation capabilities of a variable friction damper (VFD) with the recentering ability of shape memory alloy (SMA) wires. The VFD that is the first subcomponent of the hybrid device consists of a friction generation unit and piezoelectric actuators. The clamping force of the VFD can be adjusted according to the current level of ground motion by adjusting the voltage level of piezoelectric actuators. SMA wires that exhibit a unique hysteretic behavior and full shape recovery after experiencing large strains is the second subcomponent of the hybrid device. Numerical simulations of a seismically excited 20‐story benchmark building are conducted to evaluate the performance of the hybrid device. A continuous hysteretic model is used to capture frictional behavior of the VFD and a neuro‐fuzzy model is employed to describe highly nonlinear behavior of the SMA components of the hybrid device. A fuzzy logic controller is developed to adjust the voltage level of VFDs for favorable performance in an RVFD hybrid application. Results show that the RVFD modulated with a fuzzy logic control strategy can effectively reduce interstory drifts and permanent deformations without increasing acceleration response of the benchmark building for most cases. Copyright © 2012 John Wiley & Sons, Ltd.

DEVELOPMENT OF FRICTION DAMPER WITH DISPLACEMENT DEPENDENT VARIABLE DAMPING FORCE CHARACTERISTICS

A friction damper with displacement dependent variable damping force characteristics was developed. The damper was designed to decrease damping force when damper displacement exceeded a predetermined value. Therefore, the damper is ideal for aseismic retrofit of existing skyscraper buildings in preparation for long-period earthquake ground motions expected to occur in the near future. Dynamic loading tests were conducted on a full-scale steel frame with a brace-type variable friction damper to verify the damper performance. The damper exhibited on-target characteristics, stable performance, and a high endurance capacity under cyclic loadings.

Experiment of an ABS-type control strategy for semi-active friction isolation systems

Recent studies have discovered that a conventional passive isolation system may suffer from an excessive isolator displacement when subjected to a near-fault earthquake that usually has a long-period velocity pulse waveform. Semi-active isolation using variable friction dampers (VFD), which requires a suitable control law, may provide a solution to this problem. To control the VFD in a semi-active isolation system more efficiently, this paper investigates experimentally the possible use of a control law whose control logic is similar to that of the anti-lock braking systems (ABS) widely used in the automobile industry. This ABS-type controller has the advantages of being simple and easily implemented, because it only requires the measurement of the isolation-layer velocity and does not require system modeling for gain design. Most importantly, it does not interfere with the isolation period, which usually decides the isolation efficiency. In order to verify its feasibility and effectiveness, the ABS-type controller was implemented on a variable-friction isolation system whose slip force is regulated by an embedded piezoelectric actuator, and a seismic simulation test was conducted for this isolation system. The experimental results demonstrate that, as compared to a passive isolation system with various levels of added damping, the semi-active isolation system using the ABS-type controller has the better overall performance when both the far-field and the near-fault earthquakes with different PGA levels are considered.

Base‐isolated structures with selective controlled semi‐active friction dampers

AbstractThis paper investigates effectiveness of selective control strategy in hybrid base isolation systems including isolators and semi‐active variable friction (VF) dampers. According the selective control strategy, VF dampers are activated just if the displacement at the isolators exceeds the threshold value. The slip‐force control is based on the values of floors' accelerations and velocities. By controlling the slip‐force magnitude in the VF dampers, effective energy dissipation can be achieved in a seismic event. Activation of dampers according to the selective control strategy allows high‐energy dissipation by minimum energy required for adjusting the slip‐force. Performance of a multi‐storey frame with a base isolation system and VF dampers under various earthquake records was obtained numerically using originally developed MATLAB routines. Seismic response of the analysed structure with the selective controlled system was compared with that when the VF dampers were active during the whole earthquake. It is shown that adjustment of the slip‐force in a selective manner allows additional reductions in peak displacements and accelerations of the structure. The results also demonstrate that this control strategy yields reduction of the base displacement without increasing the peak base shear forces. Copyright © 2009 John Wiley & Sons, Ltd.

Adaptive control of base-isolated structures against near-field earthquakes using variable friction dampers

This paper investigates the effectiveness of two adaptive control strategies for modulating the control force of variable friction dampers (VFDs) that are employed as semi-active devices in combination with laminated rubber bearings for the seismic protection of buildings. The first controller developed in this study is an adaptive fuzzy neural controller (AFNC). It consists of a direct fuzzy controller with self-tuning scaling factors based on neural networks. A simple neural network is implemented to adjust the input and output scaling factors such that the fuzzy controller effectively determines the command voltage of the damper according to current level of ground motion. A multi-objective genetic algorithm is used to learn the shape of the activation functions of the network. The second controller is based on the simple adaptive control (SAC) method, which is a type of direct adaptive control approach. The objective of the SAC method is to make the plant, the controlled system, track the behavior of the structure with the optimum performance. Here, SAC methodology is employed to obtain the required control force which results in the optimum performance of the structure. For comparison purposes, an optimal linear quadratic Gaussian (LQG) controller is also developed and considered in the simulations together with maximum passive operation of the friction damper. The results reveal that the developed adaptive controllers can successfully improve the seismic response of base-isolated buildings against various types of earthquake.

Base Isolation Systems Employing Variable Friction Dampers Based on a STFT Controller

Conventional isolation systems may induce an excessive response in near-fault earthquakes. A new short time Fourier transformation (STFT) control algorithm for variable friction dampers (VFD) is developed to improve the performance of base isolation buildings in near-fault earthquakes. The STFT controller varies the clamping force in the VFD damper to achieve the response reduction. In addition, the STFT algorithm is implemented analytically on a multi degree of freedom system (MDOF) with laminated rubber bearings and variable friction dampers in Simulink environment. Three types of earthquakes representing a wide variety of ground motions are considered as the ground excitations in the simulation. The numerical show that, compared with conventional isolation systems, the semi-active isolation system controlled by the STFT algorithm can reduce the excessive response in near-fault earthquakes effectively.

Response of wind‐excited benchmark building installed with dampers

AbstractThe response of the benchmark building is investigated under across‐wind loads. The governing equations of motion are solved by employing state space theory. Generally, the dampers are connected to successive floors of a building (Type‐I arrangement). As the relative velocity and inter‐storey drift between the alternate floors would be larger, the performance of dampers is studied by connecting them to alternate stories with two innovative (Type‐II and Type‐III) arrangements, and the comparison of response is made with that of the conventional (Type‐I) arrangement. Optimization of location and number of dampers is also carried out with the help of a controllability index, which is obtained with the help of root‐mean‐square value of the inter‐storey drift. Further, a parametric study of semi‐active variable friction dampers and linear viscous dampers by varying gain multiplier and damping ratio, respectively, is carried out. From the numerical study, it is observed that Type‐II and Type‐III arrangements are found to be quite effective in reducing the response quantities. It is also found that a considerable amount of economy is achieved by optimization of location of dampers. Copyright © 2009 John Wiley & Sons, Ltd.

Re-centering variable friction device for vibration control of structures subjected to near-field earthquakes

This paper proposes a re-centering variable friction device (RVFD) for control of civil structures subjected to near-field earthquakes. The proposed hybrid device has two sub-components. The first sub-component of this hybrid device consists of shape memory alloy (SMA) wires that exhibit a unique hysteretic behavior and full recovery following post-transformation deformations. The second sub-component of the hybrid device consists of variable friction damper (VFD) that can be intelligently controlled for adaptive semi-active behavior via modulation of its voltage level. In general, installed SMA devices have the ability to re-center structures at the end of the motion and VFDs can increase the energy dissipation capacity of structures. The full realization of these devices into a singular, hybrid form which complements the performance of each device is investigated in this study. A neuro-fuzzy model is used to capture rate- and temperature-dependent nonlinear behavior of the SMA components of the hybrid device. An optimal fuzzy logic controller (FLC) is developed to modulate voltage level of VFDs for favorable performance in a RVFD hybrid application. To obtain optimal controllers for concurrent mitigation of displacement and acceleration responses, tuning of governing fuzzy rules is conducted by a multi-objective heuristic optimization. Then, numerical simulation of a multi-story building is conducted to evaluate the performance of the hybrid device. Results show that a re-centering variable friction device modulated with a fuzzy logic control strategy can effectively reduce structural deformations without increasing acceleration response during near-field earthquakes.

Modified friction device for control of large-scale systems

SUMMARY Semi-active control of civil structures has shown to be promising at mitigating vibrations. Those systems typically perform significantly better than passive systems, and only necessitate small power to operate. Nevertheless, semi-active control devices are not yet accepted by the construction and structural engineering communities. Among impeding factors, semi-active devices are not perceived as sufficiently reliable or robust. In this paper, a new semi-active damping device based on existing reliable technology is proposed. It is composed of a stiffness element, a viscous damper, and a braking mechanism in parallel. The device, termed the modified friction device (MFD), is essentially a variable friction damper based on vehicular braking technology, equipped with a fail-safe mechanism. The MFD is investigated as a replacement to the actual viscous damping contained in an existing structure in Boston, MA, for mitigation of accelerations caused by wind excitations. Simulations have showed that the MFD of 200 kN is capable of wind mitigation when compared with the performance of a passive viscous strategy of much larger capacity. Also, an MFD of 1350 kN capacity can perform similarly by using only a third of the number of dampers currently contained in the existing structure. Finally, the proposed device shows to be promising at mitigating inter-story displacements in the occurrence of an earthquake. Copyright © 2011 John Wiley & Sons, Ltd.

SEMI-ACTIVE PREDICTIVE CONTROL OF STRUCTURES WITH CONTROLLED STIFFNESS DEVICES AND VARIABLE FRICTION DAMPER SYSTEM

This paper presents two active control algorithms (Instantaneous Control with Displacement and Velocity Feedback (ICDVF) and Instantaneous Control with Velocity and Acceleration Feedback (ICAVF)) to control the structures eqquiped Controlled Stiffness Devices and Variable Friction Damper System. The numerical examples aim to evaluate the effect structure’s response reductions between the two algorithms as well as the principal and accessory role.