Showing papers on "Damper published in 1994"

Intervertebral stabilization device incorporating dampers

Abstract: An intervertebral stabilization device is disclosed, made in the form of a damper adapted to resist elastically, on the one hand, an elongation and, on the other hand, an axial compression without buckling, as well as of at least two implants anchored on two adjacent vertebrae.

An impedance method for dynamic analysis of active material systems

Abstract: This paper describes a new approach to analyzing the dynamic response of active material systems with integrated induced strain actuators, including piezoelectric, electrostrictive, and magnetostrictive actuators. This approach, referred to as the impedance method, has many advantages compared with the conventional static impedance method, has many advantages compared with the conventional static approach and the dynamic finite element approach, such as pin force models and consistent beam and plate models. The impedance approach is presented and described using a simple example, a PZT actuator-driven one degree of freedom spring mass damper system

Automotive air conditioner having condenser and evaporator provided within air duct

Abstract: An automotive air conditioner which conditions air making use of radiation of heat of a condenser and absorption of heat of an evaporator effectively. The evaporator 207 and the condenser 203 are disposed in a duct 100. A bypass passageway 150 is provided sidewardly of the condenser 203 in the duct 100, and a flow rate of air bypassing the condenser 203 is controlled by pivotal motion of an air mixing damper 154. Another bypass passage is provided sidewardly of the evaporator 207 in the duct 100, and a flow rate of air bypassing the evaporator 207 is controlled by pivotal motion of a bypass damper 159. Air is conditioned to an optimum blown out air temperature by varying the cooling rate at the evaporator 207 and the heating rate at the condenser 203 and is blown out to a room of an automobile from spit holes 141, 142 and 143. An outside heat exchanger is provided outside the duct 100, and a flow of refrigerant is changed over suitably among the outside heat exchanger 202, the evaporator 207 and the condenser 203 to perform cooling operation, heating operation, dehumidifying operation, dehumidifying heating operation and defrosting operation.

Diagnostic system for use in an environment control network

Abstract: The present invention relates to a diagnostic system for use in a network control system. The diagnostic system is preferably utilized to analyze VAV box performance in an environmental control system such as a network facilities management system. The diagnostic system advantageously allows the serviceperson to perform diagnostic tests on VAV boxes from a remote location. Flat box warnings, starved box warnings, box excessive damper hysteresis warnings, oversized box warnings, damper stroke out of bounds warnings, as well as other box and damper warnings may be provided by the diagnostic system. Preferably, the diagnostic system formats the air flow data so that it can be displayed for graphing. The diagnostic system causes individual controls to adjust the damper positions. Air flow parameters for each position are communicated to the remote location.

On-line monitoring of controllers in an environment control network

Abstract: The present invention relates to a diagnostic system for use in a network control system. The diagnostic system is preferably utilized to analyze HVAC system or VAV box performance in an environmental control system such as a network facilities management system. The diagnostic system advantageously records temperature, air flow, and actuator position data in the controller associated with the VAV box and calculates an exponentially weighted moving average value. The exponentially weighted moving average value may be related to error values, process output values, change in actuator position, actuator position, duty cycle of the actuator, or starts, stops and reversals of the actuator. Such a system allows a person to analyze VAV boxes and controller performance over a particular timely period and the lifetime of the system. Box and damper warnings may be provided by the diagnostic system when the EWMA values are over or under particular threshold values. The EWMA values are advantageously calculated and stored in the individual controllers.

Controller for use in an environment control network capable of storing diagnostic information

Abstract: The present invention relates to a diagnostic system for use in a network control system. The diagnostic system is preferably utilized to analyze VAV box performance in an environmental control system such as a network facilities management system. The diagnostic system advantageously records temperature, airflow, and actuator position data in the controller associated with the VAV box. Such a system allows person to analyze VAV boxes and controller performance over a particular timely period and the lifetime of the system. Box and damper warnings may be provided by the diagnostic system when the box or damper is operating below particular performance levels. Preferably, the diagnostic system formats the air flow actuator positions and temperature data so that it can be displayed for graphing. The diagnostic data is advantageously stored in the individual controllers.

Structural stiffness and Coulomb damping in compliant foil journal bearings: Theoretical considerations

Abstract: Compliant foil bearings operate on either gas or liquid, which makes them very attractive for use in extreme environments such as in high-temperature aircraft turbine engines and cryogenic turbopumps. However, a lack of analytical models to predict the dynamic characteristics of foil bearings forces the bearing designer to rely on prototype testing, which is time-consuming and expensive. In this paper, the authors present a theoretical model to predict the structural stiffness and damping coefficients of the bump foil strip in a journal bearing or damper. Stiffness is calculated based on the perturbation of the journal center with respect to its static equilibrium position. The equivalent viscous damping coefficients are determined based on the area of a closed hysteresis loop of the journal center motion. The authors found, theoretically, that the energy dissipated from this loop was mostly contributed by the frictional motion between contact surfaces. In addition, the source and mechanism of the nonline...

Temperature effect of viscoelastic dampers during earthquakes

Abstract: Viscoelastic dampers have been adopted for improving the seismic resistance of structures. One of the major difficulties is the modeling of the temperature effect of dampers on the structural responses during earthquakes. This paper is aimed at the influence of the temperature on the energy‐absorbing features of the viscoelastic dampers. Not only the capacity of the energy dissipation but also the stiffness of the dampers are dependent on ambient temperatures. That leads to quite different behavior of the structure at different temperature levels while the viscoelastic dampers are added to the structure. In this study the behavior of a 10‐story building equipped with viscoelastic dampers is examined while it is subjected to earthquake ground motions. Numerical results show that the energy‐absorbing capacity and stiffness of the viscoelastic damper decreases with increasing the ambient temperature. The responses, including displacements and stresses, of the given examples are significantly reduced while vi...

Theoretical and experimental studies on rectangular liquid dampers under arbitrary excitations

Abstract: This paper presents a study on the behaviour of rectangular liquid dampers under a horizontal excitation of arbitrary time history. The theoretical model to predict motion of a shallow liquid in a rectangular tank is adapted from a previous researchers' model which was developed for sinusoidal excitations. The model includes an energy dissipation term arising from liquid viscosity. In the present consideration of arbitrary excitations, the energy dissipation term is derived in a straightforward way, without resorting to the equivalent linearization method or assumption of harmonic response as used by earlier researchers. The up‐crossing rate of wave height is used in furnishing the Reynolds number required for the evaluation of shear stress in the boundary layer. Since there was no known precedent study involving arbitrary excitations, experiments have been performed accordingly to verify the model. Generally, the theoretical model furnishes results which are found to be in close agreement with the experimental ones. The results also illustrate the strong dependency of liquid motion upon the natural frequency of the damper, amplitude and frequency content of the excitation spectrum. The model is then applied to study the effectiveness of tuned liquid dampers in vibration control of a single‐degree‐of‐freedom structure subjected to earthquake excitations. Significant suppression of structural vibration can be achieved using tuned liquid dampers.

Stability and Bifurcation of Unbalanced Response of a Squeeze Film Damped Flexible Rotor

Abstract: The stability and bifurcation of the unbalance response of a squeeze film damper-mounted flexible rotor are investigated based on the assumption of an incompressible lubricant together with the short bearing approximation and the “π” film cavitation model. The unbalanced rotor response is determined by the trigonometric collocation method and the stability of these solutions is then investigated using the Floquet transition matrix method. Numerical examples are given for both concentric and eccentric damper operations. Jump phenomenon, subharmonic, and quasi-periodic vibrations are predicted for a range of bearing and unbalance parameters. The predicted jump phenomenon, subharmonic and quasi-periodic vibrations are further examined by using a numerical integration scheme to predict damper trajectories, calculate Poincare maps and power spectra. It is concluded that the introduction of unpressurized squeeze film dampers may promote undesirable nonsynchronous vibrations.

Advanced 1.5 Hz Passive Viscous Isolation System

Abstract: Presented at the AIAA 35th SDM Conference Hilton Head, South Carolina April 1994 Copyright „ 1994 by Honeywell Inc. A high-performance isolator has been developed for a multiaxis isolation system for a large reaction wheel assembly. Reaction wheel assemblies are used for spacecraft attitude control. The isolator offers significant improvements over prior isolators, providing a low break frequency and featuring a tuned, three-parameter configuration that significantly outperforms the more conventional two-parameter design. A three-parameter system is one that is modeled with spring elements in series and parallel with the damper. Two-parameter systems, as modeled in most vibration texts, have a single spring element in parallel with the damper. The system is tuned by selecting three-parameter values that provide maximum damping at the fundamental frequency and reduced damping at higher frequencies. The mathematical basis for three-parameter isolators with tuning methodology is included. Physical design features of the isolator are described in addition to actual test data that confirms the fundamental performance improvement. The technique for obtaining low suspension frequencies is also discussed.

Seismic Response Control of Bridges by Variable Dampers

Abstract: This paper discusses a variable damper proposed to control bridge response against an earthquake. The variable damper changes its damping coefficient depending on the structural response so that it...

A fuzzy preview control scheme of active suspension for rough road

Abstract: A new control algorithm of active suspension is proposed for rough roads. In this study, a quarter car model is used. The large tyre deflection and the stroke limit of the actuator are taken into consideration. A virtual damper concept is proposed to attenuate the tyre deflection by feeding back the relative velocity between road and unsprung mass to the force actuator. A fuzzy preview control scheme is presented to generate a reference curve by sensing the road information ahead of the vehicle so that the actuator can operate within the stroke limit even in the rough road. Computer simulations are performed to verify the above concepts, and it is shown that satisfactory performance can be achieved by the proposed control scheme.

A preliminary parametric study of electrorheological dampers

Abstract: In approaching the design of an electrorheology-based, semi-active suspension, the electrorheological component (ER damper) can be built as either a flow-mode, shear-mode, or mixed-mode type of damper. The source of damping force in the flow-mode is exclusiuely from flow-inducedpressure drop across a value, while that in the shear-mode is purely from the shear stress on a sliding surface. The dynamics of the fluid flow are included in the derivation of the zero-field damping forces. The control effectiveness is found to be strongly related to the dynamic constant (which is proportional to the square root of the vibration frequency) and, for shearandflow-mode dampers, the ratio of the piston area to the cross-section of the ER control gap

Rotary actuator vibration damper

Abstract: A bearing assembly supports an actuator arm for rotation about an axis in a disc drive. The bearing assembly includes a shaft generally defining the axis. A plurality of bearings are disposed about the shaft. A sleeve is coupled to the bearings for rotation about the shaft, and a damper is coupled to the sleeve. The damper damps rotary actuator vibrations.

Active Chatter Suppression of Slender Boring Bar Using Piezoelectric Actuators

Abstract: The chatter suppression described in this paper is based on the application of active dampers to a slender boring bar. Chatter vibration signals detected by a pickup are fed to a computer. After calculating the chatter frequency and the corresponding phase shift parameter, the computer supplies the amplified signals to piezoelectric actuators with the same phase as that of the vibration velocity of the boring bar. As a result of this, the actuators generate damping forces ; that is, they act as active dampers. It has been confirmed in cutting tests that the active damping system adapts to change and fluctuation of the chatter frequency and suppresses chatter well. Furthermore, it has become clear that there is an optimum position of the active damper for chatter suppression.

Air quality-temperature controlled central conditioner and multi-zoned conditioning

Abstract: An air quality and temperature responsive air conditioning system wherein modules are employed to precondition the air for humidity control, to heat and cool the air, and to bypass the supply air in excess of the demand of a multiplicity of comfort zones (Z) with thermostat control (T), and featuring a bypass module (M) characterized by parallel ducting, one ducting (55) which is restricted by a damper (57) responsive to a supply air back pressure sensor (S1), and one ducting (56) which is opened by a damper (60) responsive to an air quality sensor (S2).

A fundamental study on impact dampers

Abstract: A fundamental study on impact dampers is reported in which the performance of impact dampers was investigated from free damped vibration generated when a step function input was supplied to a leaf spring with a free mass. The investigation showed that the damping capability of impact dampers results from collision between the free mass and the main mass. The frequency of the system with an impact damper varies with the natural frequency of the main vibratory system and the mass ratio. The optimum damping effect is achieved in combinations of the mass ratio and a clearance, i.e. motion extent of the free mass. The use of a free mass of only 25% of the main mass and a clearance of 0.6 mm, for example, can improve the damping capability of the main vibratory system at least 10 times or more, even though the clearance and the free mass are not adjusted to an amplitude of the main vibratory system. The critical amplitude where the impact damper does not function is determined by the natural frequency and the acceleration of gravity.

Adaptiv hydropneumatic pulsation damper

Abstract: The invention relates to an adaptive hydropneumatic pulsation damper which is especially suitable for hydraulic systems prone to pulsations and having a greatly varying operating pressure and makes possible during an effective damping action a hydraulically rigid coupling between the elements, e.g. pressure source and consumer, of a hydraulic system.

Damping configuration for improved disk drive performance

Abstract: A disk drive (10) having attenuated vibrational motion for improved disk drive performance has a first viscoelastic damper secured to top cover (18) and a second viscoelastic damper secured to the bottom of the baseplate (20) These viscoelastic dampers attenuate vibrations during rotation of the spindle (16) of the disk drive (10)

Harmonic Balance Analysis of General Squeeze Film Damped Multidegree-of-Freedom Rotor Bearing Systems

Abstract: Squeeze film dampers introduce nonlinear motion dependent damper forces into otherwise linear rotor bearing systems, thereby considerably complicating their analysis. Noncircular orbit type dampers, such as unsupported or uncentralized dampers, have generally necessitated transient solutions, which are computationally prohibitive for design studies of large order systems, particularly for systems with low damping. By utilizing harmonic balance with appropriate condensation, it is possible to considerably reduce the number of simultaneous nonlinear equations inherent to this approach

Friction device for protection of structural systems against dynamic actions

Abstract: A friction damper that is able to reduce vibrational motions in two dimensions, can be re-used, is easily adjustable and has an extremely smooth transition between sticking and sliding in particular. The friction damper features a stack of at least two friction discs and a prestressing device for this stack. Touching each other at curved contact surfaces, these friction discs are alternately joined with the first and second of two friction damper connections, respectively. The curved contact surfaces can be provided in a simple manner either by an alternate arrangement of lense-shaped and plane friction rings or by alternate arrangement of plane friction rings with convex inserts and plane friction rings.

Damper element for damping compressive oscillations and method for producing the same

Abstract: A damper element for damping compressive oscillations in the fuel circulation circuit of an internal combustion engine is situated directly in the fuel distributor. The damper element includes one or more gas-filled chambers and is manufactured from a resilient material. A bubble-type flexible cord can be used as a damper element. Because of its very simple structure and small mass, the damper element can be integrated in the fuel distributor so that no additional space is required. The damping of the compressive oscillations induced by the switching pulses of the injection valves takes place in the immediate vicinity of each individual injection valve.

Friction damper for gas turbine engine blades

Abstract: A friction damper (50) provides friction damping for gas turbine engine airfoils to reduce vibrations thereto. The friction damper (50) includes a plate (52) underlying radially outer shrouds (30) of two adjacent airfoils (20). Friction generated between an outer surface (53) of the plate (52) and undersides (42) of the adjacent shrouds (30) reduces undesirable vibrations in the airfoils (20).

Modular air conditioning system

Abstract: A heating, ventilation, and air conditioning (HVAC) system is disclosed which is capable of receiving interchangeable ventilation modules having varying degrees of air mixing abilities. A ventilation module fits inside the HVAC system and connects to a return air opening, an exhaust duct, an inlet air opening, and a supply air duct for proper routing of air to be conditioned. As ventilation needs change, a different module with appropriate ventilation characteristics can replace the existing module while keeping intact all other components of the HVAC system such as blowers, compressors, heaters, condensing coils and the like. Ventilation module functionality ranges from an economizer module which allows 100% outside air into a structure, to a motorized air damper module which can be controlled based on various factors such as room occupancy to provide a limited range of fresh and return air mixing, to a blank-off plate which completely prevents use of outdoor air thus leaving the system to condition return air only for supply to the structure. A ventilation module for efficient and economical system operation capable of energy transfer between incoming air and exhausted stale air from the structure is also provided, adaptable to various new or existing types of heating and cooling systems.

Coolable rotor assembly

Abstract: In a rotor assembly (10) having a rotor disk (12) and a plurality of outwardly extending rotor blades (16) with platform sections (20), a damper (58) engages the underside of the platform sections (20), a seal member (42) inwardly of the damper engages the damper to provide damping of vibrations in the rotor blades. Both the damper and the seal member are provided with cooling air holes (42, 74) to positively distribute cooling air collected inwardly of the damper and seal member and to direct the cooling air preferentially between the adjacent platform sections (20) of the rotor blades to effectively cool the rotor blades.

Nceer-taisei corporation research program on sliding seismic isolation systems for bridges experimental and analytical study of a system consisting of lubricated ptfe sliding bearings and mild steel dampers.

Abstract: This report describes the results of an experimental study of the behavior of a bridge seismic isolation system consisting of lubricated flat sliding bearings and mild steel dampers. Earthquake simulator tests have been performed on a model bridge structure both isolated with this system and non-isolated. The experimental results demonstrate that the system is capable of maintaining the forces transmitted to the substructure at a preset limit, however at the expense of significant permanent displacements. Analytical techniques are used to predict the dynamic response of the system and the obtained results are in good agreement with the experimental results.