Showing papers on "Damper published in 2003"

Thermostat having modulated and non-modulated provisions

Abstract: A thermostat providing modulated or analog control of valves or dampers of an air management system. This permits operating a single cooling or heating stage with partially open valves or dampers as needed, since one full stage that is either fully on or off may not be easy to manage for effective air management of a particular type of building, zone or facility. The thermostat may also provide non-modulated control of multi-stage cooling and heating systems. The thermostat may even be used to control a modulated system having more than one stage of cooling or heating.

PDA configuration of thermostats

Abstract: A device and method that may be used at nearly any place to set and adjust a control system such as a thermostat, controller or computer having numerous parameters and options that may be selected for desired operation of an air management system. One may remotely, via a personal digital assistant, configure, commission, select, set or adjust the parameters and options of a control system, which may include, but not be limited to, temperatures, humidity, sensors, volume of air movement, fan or air mover behavior, the percentage of added fresh air, modulated and non-modulated control of valves and dampers, stages of cooling and heating at various zones, control of heat pumps, heaters and air conditioners, modes of occupied, unoccupied or standby of respective spaces in a building, for day and night, at selected times, on certain days, for specific buildings at particular locations.

Skyhook and H8 Control of Semi-active Suspensions: Some Practical Aspects

Abstract: Summary This paper deals with single-wheel suspension car model. We aim to prove the benefits of controlled semi-active suspensions compared to passive ones. The contribution relies on H 8 control design to improve comfort and road holding of the car under industrial specifications, and on control validation through simulation on an exact nonlinear model of the suspension. Note that we define semi-active suspensions as control systems incorporating a parallel spring and an electronically controlled damper. However, the type of damper used in automotive industry can only dissipate energy. No additional force can be generated using external energy. The control issue is then to change, in an accurate way, the damping (friction) coefficient in real-time. This is what we call semi-active suspension. For this purpose, two control methodologies, H 8 and Skyhook control approaches, are developed, using a linear model of the suspension, and compared in terms of performances using industrial specifications. The per...

Semi-active control of structures incorporated with magnetorheological dampers using neural networks

Abstract: Semi-active control of buildings and structures with magnetorheological (MR) dampers for earthquake hazard mitigation represents a relatively new research area. In this paper, the Bingham model of MR damper is introduced, and the formula relating the yielding shear stress and the control current of MR dampers is put forward that matches the experimental data. Then an on-line real-time control method for semi-active control of structures with MR dampers is proposed. This method considers the time-delay problem of semi-active control, which can solve distortion of the responses of structures. Finally, through a numerical example of a three-storey reinforced concrete structure, a comparison is made between controlled structure and uncontrolled structure. The calculated results show that MR dampers can reduce the seismic responses of structures effectively. Moreover, the on-line real-time control method is compared with the traditional elastoplastic time-history analysis method, and the efficacy of the on-line real-time control method is demonstrated. In addition, the Levenberg–Marquardt algorithm is used to train the on-line control neural network, and studies show that the algorithm has a very fast convergence rate.

Scissor-Jack-Damper Energy Dissipation System

Abstract: Installation of damping devices has been limited to diagonal or chevron brace configurations until the recent development of the toggle-brace configurations. These configurations magnify the effect of damping devices, thus facilitating their use in stiff framing systems. This paper introduces the scissor-jack-damper system that was developed as a variant of the togglebrace-damper systems, with the added advantage of compactness. The effectiveness of the scissor-jack configuration is demonstrated through testing of a large-scale steel-framed model structure on an earthquake simulator. Experiments showed that despite the small size of the damping device considered, the scissor-jack system provided a significant amount of damping and substantially reduced the seismic response of the tested structure. Response history and simplified analyses produce results that are consistent with the experimental results. [DOI: 10.1193/1.1540999]

Control of seismically excited cable-stayed bridge employing magnetorheological fluid dampers

Abstract: This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semiactive control strategy focusing on inclusion of effects of control-structure interaction. The subject of the ASCE benchmark problem is a cable-stayed bridge in Cape Girardeau, Missouri, for which construction is expected to be completed in 2003. The goal of the benchmark study is to provide a \Itestbed\N structure on which researchers can systematically compare and evaluate the relative merits of proposed structural protection for cable stayed-bridges. In this paper, magnetorheological (MR) fluid dampers, which belong to the class of controllable fluid dampers, are proposed for use in a control strategy for protecting the bridge. A clipped-optimal control algorithm, shown to perform well in previous studies involving MR fluid dampers, is employed. A comprehensive study of the adequacy of various types of dynamic models for MR fluid dampers, such as a Bingham model, a Bouc-Wen model, and a modified Bouc-Wen model, is provided. In contrast to previous studies, models considered in this study are based on experimental data for a full-scale MR fluid damper. Because the MR fluid damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results considering several historical earthquakes scaled to various magnitudes show that the proposed semiactive control strategy using MR fluid dampers is the promising one of the applicable control methods to reduce seismic responses of cable-stayed bridges.

Design of yielding metallic and friction dampers for optimal seismic performance

Abstract: This paper deals with the optimal design of yielding metallic dampers and friction dampers together as they both have similar design characteristics and parameters. Ample tests and analytical studies have confirmed the effectiveness of these energy dissipation devices for seismic response control and protection of building structures. Since these devices are strongly non-linear with several parameters controlling their behaviour, their current design procedures are usually cumbersome and not optimal. In this paper, a methodology is presented to determine the optimal design parameters for the devices installed at different locations in a building for a desired performance objective. For a yielding metallic damper, the design parameters of interest are the device yield level, device stiffness, and brace stiffness. For a friction device, the parameters are the slip load level and brace stiffness. Since the devices and the structures installed with these devices behave in a highly non-linearly manner, and thus must be evaluated by a step-by-step time history approach, the genetic algorithm is used to obtain the globally optimal solution. This optimal search approach allows an unusual flexibility in the choice of performance objectives. For demonstration purposes, several sets of numerical examples of optimal damper designs with different performance objectives are presented. Copyright © 2003 John Wiley & Sons, Ltd.

Semiactive damping of cables with sag

Abstract: The steel cables used in cable-stayed bridges and suspension bridges have low inherent damping and are therefore prone to vibration. Transversely attached passive viscous dampers have been implemented on some cables to dampen vibration, but for long cables, passive dampers may provide insufficient supplemental damping to eliminate vibration problems. This paper extends previous work by the authors that demonstrated that "smart" semiactive dampers can provide superior supplemental damping for a cable modeled as a taut string. In the current paper, sag, inclination and longitudinal flexibility are added to the dynamic model of transverse in-plane cable vibration. The equations of motion are given and a new control-oriented model is developed for cables with sag. Passive, active and smart (semiactive) dampers are incorporated into the model. For the general case where a node does not occur at the damper location, semiactive dampers are found to provide improved damping compared to the optimal passive viscous damper, with a 30-40% reduction in root mean square or peak response.

Semiactive Vibration Control of Train Suspension Systems via Magnetorheological Dampers

Abstract: This paper is aimed to show the feasibility for improving the ride quality of railway vehicles with semiactive secondary suspension systems using magnetorheological (MR) dampers. A nine degree-of-freedom railway vehicle model, which includes a car body, two trucks and four wheelsets, is proposed to cope with vertical, pitch and roll motions of the car body and trucks. The governing equations of the railway vehicle suspension systems integrated with MR dampers are developed. To illustrate the feasibility and effectiveness of the controlled MR dampers on railway vehicle suspension systems, the LQG control law using the acceleration feedback is adopted as the system controller, in which the state variables are estimated from the measurable accelerations with the Kalman estimator. In order to make the MR dampers track the optimal damping forces, a damper controller to command the voltage to the current drivers for the MR dampers is proposed. The acceleration responses of the car body of the train vehicle with semiactive secondary suspension system integrated with MR dampers are evaluated under random and periodical track irregularities. This semiactive controlled system is also compared to the conventional passive suspension system using viscous dampers without MR dampers, and the secondary suspension system integrated with MR dampers in passive on and passive off modes. The simulation results show that the vibration control of the train suspension system with semiactive controlled MR dampers is feasible and effective.

Semi-active control of automotive suspension systems with magneto-rheological dampers

Abstract: This paper is aimed to develop semi-active control for automotive suspension systems with magneto-rheological (MR) fluid dampers. A two degree-of-freedom quarter car model is considered. A mathematical model of MR fluid damper is adopted. In this study, there are two nested controllers including system controller and damper controller. For the system controller, a model-reference sliding mode controller is developed for considering loading uncertainty to result in a robust control system. In order to choose a good reference model, the single-degree-of-freedom skyhook system is analysed. For the damper controller, the continuous-state control is used to track the actual damping force to the desired damping force. The transmissibilities of the MR suspension system are investigated. The performances of the MR suspension systems are evaluated by computer simulation with bump and random excitations. The effectiveness of the MR suspension system is also demonstrated via hardware-in-the-loop simulation (HILS) with sinusoidal excitation.

Structural vibration control by shape memory alloy damper

Abstract: A damper device based on shape memory alloy (SMA) wires is developed for structural control implementation. The design procedures of the SMA damper are presented. As a case study, eight such SMA dampers are installed in a frame structure to verify the effectiveness of the damper devices. Experimental results show that vibration decay of the SMA damper controlled frame is much faster than that of the uncontrolled frame. The finite-element method is adopted to conduct the free and forced vibration analysis of the controlled and uncontrolled frame. The experimental and numerical results illustrate that the developed SMA dampers are very effective in reducing structural response and have great potential for use as efficient energy dissipation devices with the advantages of good control of force and no lifetime limits, etc.

Novel Semiactive Friction Controller for Linear Structures against Earthquakes

Abstract: Semiactive friction dampers (SAFD) have been shown to be more effective than passive friction dampers in reducing structural response due to earthquakes. The effectiveness of SAFD, however, depends on the control strategy used. Because of the nonlinear nature of friction dampers, the establishment of an effective control strategy is a challenging effort. The motion of friction dampers, either passive or semiactive, involves sticking and slipping phases. The idea for increasing the performance of SAFD is to maintain its motion in the slipping phase as much as possible, as energy is dissipated during the slipping phase rather than the sticking phase. In this paper, the authors propose control strategies which are capable of: 1) maintaining the motion of SAFD in the slipping phase as much as possible; and 2) eliminating the undesirable acceleration spikes by introducing an appropriate boundary layer in the control strategy. Two structures, a 6-story base-isolated structure and a 3-story fixed base building model, were used to demonstrate the performance of the proposed control strategies using different far-field and near-field earthquakes. Further, the performances of various combinations of passive and semiactive energy dissipation devices have been evaluated and compared. Based on numerical simulation results, it is demonstrated that the proposed semiactive friction control strategies are very effective.

Magnetorheological Damper System

Abstract: A magnetorheological damper system comprising a reservoir in communication with a damper. The damper comprises a damper cylinder defining a damper chamber, wherein the damper chamber contains a magnetorheological fluid and a movable damper piston. The damper piston comprises at least two coil windings on the outer surface of the damper piston, wherein the damper piston is capable of generating a magnetic field between the damper piston and a wall of the damper cylinder. The reservoir comprises a reservoir cylinder defining a passageway, wherein the reservoir includes a magnetorheological electromagnet capable of generating a magnetic field between the magnetorheological piston and a wall of the passageway. The combination of the an MR reservoir and MR damper leads to a damping system capable of damping a wide range of extreme forces.

Application of pseudo-negative stiffness control to the benchmark cable-stayed bridge

Abstract: The effectiveness of a variable damper employing pseudo-negative stiffness control on benchmark cable-stayed bridges was studied. Combination of a pseudo-negative stiffness hysteretic loop produced by the variable damper plus elastic stiffness of the deck-tower connections produces a hysteretic loop that approaches rigid perfectly plastic force–deformation characteristics with a large damping ratio. The advantage is that sensors are required only at damper connections to measure relative displacements. Moreover, the small amount of sensors and simple algorithm reduce the source of errors and uncertainties. Comparisons are made between passive, pseudo-negative stiffness, and active control for the phase II benchmark bridge. The results of pseudo-negative stiffness control are significantly better than those of passive control and comparable to those of active control. Copyright © 2003 John Wiley & Sons, Ltd.

Experimental Seismic Study of Adjacent Buildings with Fluid Dampers

Abstract: A comprehensive experimental investigation on the dynamic characteristic and seismic response of adjacent buildings linked by fluid dampers is carried out using a 4 m4 m seismic simulator. Two buil...

Semiactive Tuned Liquid Column Dampers: Experimental Study

Abstract: A tuned liquid column damper ~TLCD! is a special type of auxiliary damping device which relies on the inertia of a liquid column in a U-tube to counteract the forces acting on the structure. Damping in the TLCD is introduced as a result of headloss experienced by the liquid column moving through an orifice. The primary objective of this paper was to examine the performance of a prototype semiactive TLCD. Experiments were conducted to determine the dynamic characteristics of a coupled structure-TLCD system. The experimental setup included a prototype TLCD attached to a model of a single-degree-of-freedom structure which was mounted on a shaking table. The prototype TLCD was equipped with an electropneumatic valve to provide optimal damping at a wide range of structural motion amplitudes. The optimum absorber parameters, i.e., the optimal tuning ratio and damping ratio, were determined experimentally and compared to the analytical results obtained previously reported by the writers. A control strategy based on gain scheduling was utilized, which was designed to maintain the optimal damping based on a prescribed look-up table. This scheme was experimentally validated. It was noted that the semiactive system provided an additional 15-25% reduction in response over a passive system. Finally, a design example was presented to demonstrate the application of semiactive TLCDs to tall buildings under wind loads. The response of uncontrolled structure, braced structure, and structure with a passive damper, and semiactive damping system using numerical simulations were compared. The semiactive TLCD reduced the RMS acceleration at the building top by 45% at all wind speeds.

Neural network-based modeling and parameter identification of switched reluctance motors

Abstract: Phase windings of switched reluctance machines are modeled by a nonlinear inductance and a resistance that can be estimated from standstill test data. During online operation, the model structures and parameters of SRMs may differ from the standstill ones because of saturation and losses, especially at high current. To model this effect, a damper winding is added into the model structure. This paper proposes an application of artificial neural network to identify the nonlinear model of SRMs from operating data. A two-layer recurrent neural network has been adopted here to estimate the damper currents from phase voltage, phase current, rotor position, and rotor speed. Then, the damper parameters can be identified using maximum likelihood estimation techniques. Finally, the new model and parameters are validated from operating data.

Applications of some semiactive control systems to benchmark cable-stayed bridge

Abstract: Recently, a benchmark cable-stayed bridge model was developed for the control community as a test bed to evaluate the performance of various strategies for the control of cable-stayed bridges during earthquakes. In this paper, the effectiveness and performances of some semiactive and passive control systems for this benchmark cable-stayed bridge are evaluated and presented. The semiactive control systems considered include the semiactive stiffness damper and the semiactive friction damper. Cases of passive linear and nonlinear viscous fluid dampers are also investigated and presented. The performances of semiactive control systems are evaluated using effective control strategies and compared with that of the sample active control system using actuators. Simulation results clearly indicate that the displacement of the bridge deck as well as the shear and moment at the base of the towers can be reduced substantially by installing these passive and semiactive protective devices. It is shown that semiactive a...

On the Frictional Damping Characterization of Compliant Bump Foils

Abstract: High-speed rotor systems use either fluid film or rolling element bearing supports, depending upon their design and operating constraints. Regardless of bearing type used, these systems require specific bearing and support stiffness and damping characteristics to achieve the desired stable and low vibration operation. Building upon the technology of thin metallic corrugated bump foils presently used in a particular class of film riding hydrodynamic bearings, a novel corrugated bump foil damped mount is introduced which provides stiffness and clamping for application with rolling element bearings. These damping elements are capable of operating at elevated temperatures where implementation of conventional squeeze film dampers is ruled out. The frictional damping results from micro-slip motions between the bump foils and the mating surfaces. A semi-empirical model, based on a one degree of freedom model was developed in which damping is replaced by an equivalent frictional force in order to gain insight into the dynamic friction coefficient of the individual damping element interfaces. Experimental results, obtained in the form of hysteresis loops were compared to the developed model with good agreement. The variation in damping and dynamic coefficient of friction was found to be dependent primarily upon three factors : vibration frequency. amplitude of motion and applied static load. These parameters were tested within the range of 50-1400 Hz, 2.54-12.7 micron and 45-135 N, respectively. The tests were conducted at room and 538°C ambient temperatures under both dry and vapor phase lubricated conditions. Using the resulting empirical data, several bearing dampers were designed, built and tested in a small, high-speed gas turbine engine simulator. The tested novel foil dampers were capable of operating reliably under extremely high levels of shaft imbalance (i.e., 320 times greater than the air bearing supported with specification of 0.0002 oz-in) even while operating at temperatures to 560°C. These results show the great potential for wide application of these dampers on gas turbine engines and high-speed rotating machinery.

Fluid viscous dampers for high‐rise buildings

Abstract: Using supplemental fluid viscous dampers to dissipate energy and reduce building response to dynamic inputs is gaining worldwide acceptance. The concept of supplemental dampers added to a structure is that they absorb much of the energy input to the structure from a transient, not by the structure itself, but rather by supplemental damping elements. This paper presents an application of fluid viscous dampers in a high-rise structure to suppress the anticipated wind-induced accelerations. The description of the damping system, the design criteria and cost data are discussed. The viscous damper system proves to be a very cost-effective method to reduce wind motions. Copyright © 2003 John Wiley & Sons, Ltd.

Performance-based design of added viscous dampers using capacity spectrum method

Abstract: The conventional practice of carrying out a series of trial and error process for design of supplemental dampers requires a lot of computation time and labour. In this study a straightforward design procedure for viscous dampers was developed based on capacity spectrum method in the context of performance based seismic design. The required amount of viscous damping to satisfy given performance acceptance criteria was evaluated from the difference between the overall demand for effective damping and the inherent damping plus the equivalent damping capacity of the structure originated from plastic deformation of each structural member. The proposed method was applied to single-degree-of-freedom systems with various design parameters such as natural period, yield strength, and the stiffness after the first yield. The procedure was also implemented to 10- and 20-storey steel frames for verification of the proposed method. According to the earthquake time history analysis results, the maximum displacements of ...

Skyhook and h(infinity) control of semi-active suspensions: some practical aspects

Abstract: This paper deals with single-wheel suspension car model. We aim to prove the benefits of controlled semi-active suspensions compared to passive ones. The contribution relies on H(infinity) control design to improve comfort and road holding of the car under industrial specifications, and on control validation through simulation on an exact nonlinear model of the suspension. Note that we define semi-active suspensions as control systems incorporating a parallel spring and an electronically controlled damper. However, the type of damper used in automotive industry can only dissipate energy. No additional force can be generated using external energy. The control issue is then to change, in an accurate way, the damping (friction) coefficient in real-time. This is what we call semi-active suspension. For this purpose, two control methodologies, H(infinity) and Skyhook control approaches, are developed, using a linear model of the suspension, and compared in terms of performances using industrial specifications. The performance analysis is done using the control-oriented linear model first, and then using an exact nonlinear model of the suspension incorporating the nonlinear characteristics of the suspension spring and damper. (A)

Regenerative damping method and apparatus

Abstract: A regenerative damper and method for regenerative damping are disclosed. The regenerative damper uses the kinetic energy of undesirable vehicle motion to generate electrical current in a circuit. The electricity is generated by a power screw that operates like an alternator. Vehicle energy efficiency is increased by using the electrical current to charge a battery. The regenerative damper can be semi-active or passive. The semi-active embodiment is able to adapt to operating conditions to improve vehicle ride and handling, whereas the passive embodiment has a fixed response, regardless of operating conditions.