Showing papers on "Damper published in 1990"

Seismic Design Spectra for Friction‐Damped Structures

Abstract: A simplified seismic design procedure is proposed for structures equipped with an innovative friction-damping system. The system has been shown experimentally to perform very well and could represent a major new development in earthquake-resistant design. This paper first presents an efficient modeling approach for the seismic analysis and design of friction-damped structures. The hysteretic properties of the friction dampers are derived theoretically and are included in a Friction Damped Braced Frame Analysis Program (FDBFAP), which is adaptable to a microcompter environment. FDBFAP is then used to perform a parametric study of the optimum slip-load distribution for the friction dampers. The results of the study lead to the construction of a design slip-load spectrum for the rapid evaluation of the optimum slip-load distribution. The spectrum takes into account the properties of the structure and of the ground motion anticipated at the construction site. The availability of this design slip-load spectrum should lead to a greater acceptance by the engineering profession of this innovative design concept.

Design Principles for Vibration Control Systems Using Semi-Active Dampers

Abstract: Electronically controlled vibration isolation and control systems have recently reached at least the prototype phase in a number of fields of application. Of particular practical interest are semi-active systems which require very little actuator power. Semi-active dampers in the form of rapidly modulated hydraulic shock absorbers have been used for example in automobile suspensions to achieve some of the benefits of fully active servo-mechanism systems but with much reduced cost and complexity

Vibration attenuating method utilizing continuously variable semiactive damper

Abstract: Operation of a continuously variable semiactive damper of the system is modified so as to reduce generation in the system of undesirable shocks and noise. The modifications include delaying some or all of the changes in the on/off states of the damper, and/or limiting the rate and/or extent of changes in the damping coefficient of the damper at certain of the times when the damper is in an on state.

An Integrated Approach for Friction Damper Design

Abstract: A procedure is outlined for determining the optimal design of friction dampers for high speed turbomachinery blading. The procedure includes: an integration of bench test results with finite element analysis and a single mode blade model to ensure accuracy of the analytical model and improve reliability of the friction damper design; an extension of the single mode blade model to predict the engine behavior of friction dampers; and a new way of viewing analytical and experimental results to determine optimal design parameters when the levels of excitation and damping in the system are unknown. Analysis and experiments are performed on a test disk in order to demonstrate and verify the accuracy of the design procedure.

Apparatus for supporting a rotating shaft in a rotary machine

Abstract: A rotary machine 10 includes a rotor shaft 40 and a support system 63 for the shaft. The support system includes a spring 68 and viscous damper 70. Apparatus for removing oil from the damper at preselected rotor speeds is provided and in one embodiment permits operating the engine over a rotor speed range which avoids critical speeds.

Suspension control system

Abstract: In a suspension control system, accelerations detected by acceleration sensors are differentiated by a differentiator to calculate acceleration derivative values. Based on these values, a target electrical current calculating section calculates a target electrical current that is supplied to an actuator which controls a damping force of a damper. Before a rolling or pitch angle occurs in the vehicle, the change of the rolling or pitch angle is predicted to control the damping force of the damper, thereby improving the response of rolling angle and pitch angle control to achieve, simultaneously, an accurate posture control and a satisfactory riding comfort. Because the target electrical current calculating section corrects the target electrical current of the actuator based on a damper speed obtained by differentiating a damper displacement, even when a large input is applied to the damper due to an unevenness of the road surface, a proper posture control is performed.

Torsional vibration damping apparatus

Abstract: A torsional vibration damping apparatus which operates between the crankshaft of the engine and the input shaft of the transmission in a motor vehicle has two flywheels which are rotatable relative to each other against the opposition of one or more dampers installed in a fluid-containing chamber of the flywheel which is connected to the crankshaft The chamber has one or two annular compartments for the coil springs of the damper or dampers, and such coil springs are caused to store energy by a flange which is connected to the flywheel that drives the input shaft of the transmission and by integral or separately produced stops of the flywheel which is connected with the crankshaft The flange cooperates with the respective flywheel to form a flow restrictor which opposes the flow of fluid from and into the compartment or compartments of the chamber in response to expansion or contraction of the coil springs

The Effects of Bearing Misalignment on the Non-Linear Vibration of Aero-Engine Rotor–Damper Assemblies

Abstract: The occurrence of non-linear vibration phenomena in aero-engine rotor-damper assemblies can seriously degrade performance. A range of assemblies incorporating one and two squeeze-Jilm dampers (SFDs) with ~arious static misalignments is investigated. Waterfall diagrams are constructed which demonstrate the effects of such misalignments and of damper support flexibility on the nature and severity of subsynchronous resonance and jump phenomena. Vibration signatures uf similar rotor-damper assemblies are shown to contrast strongly due to diferent accumulations of tolerances during manufacture,$tting and operation.

Ground-borne noise and vibration damping

Abstract: A ground-borne noise and vibration damping system in which is a track bed formed with rails for a railway vehicle and generating noise and vibration, a structure is to be protected against the noise and vibration; and a damper for ground-borne noise and vibration is embedded vertically in the ground and interposed between the track bed and the structure. The damper has two upright rigid concrete plates defining a vertical gap between them, and an elastic mat sandwiched between the concrete plates and in contact therewith.

Liquid viscous damper

Abstract: A viscous liquid damper having a damper for developing a torsion torque in between an output-side driven plate (23) and an input-side drive plate (3), and a liquid chamber located between the drive plates (3) is partitioned into front and rear divided chamber (38 & 39) in rotation direction. In order to allow absorption of vibrations of different kinds without mutual confrontation in such a damper; an outward facing projection (41) is formed on the drive plate (3), a slider (40) is mated with the drive plate (3) in such a manner as slidable in the rotation direction, a main choke (A1) is formed between the slider (40) and the projection (41), stoppers (40a) able to mate with the projection (41) are formed on circumferential both ends of the slider (40), and a sub-choke (S2) connecting the both divided chambers (38 & 39) is formed separately from the main choke (S1).

Damper for a flapdoor using viscous fluid

Abstract: According to the invention, there is provided a damper for a flapdoor that does not show any damping effect when its movable shaft of the damper is rotated with the door in one sense whereas it effectively damps the rotary movement of the flapdoor when the movable shaft is rotated with the door in the other sense, wherein a one-way clutch for engaging or disengaging the movable shaft with a movable member depending on the sense of rotation of the movable shaft to cause a viscous shearing drag in the viscous fluid contained in the damper and a power source constitute so many integral parts of a coil spring. A damper for a flapdoor having such an arrangement can have a simplified configuration as compared with a damper provided with a separate coil spring as power source and a separate one-way clutch and therefore can be realized with reduced dimensions. Moreover, since such a one-way clutch can be prepared from a coil spring without requiring any additional processes and by simply engaging a portion of the coil spring with the movable member, the rest of the coil spring functioning as power source, the damper can be realized at a significantly reduced cost.

Cavitation Regimes in Squeeze Film Dampers and Their Effect on the Pressure Distribution

Abstract: High speed motion pictures have revealed several operating regimes in a squeeze film, damper. Pressure measurements corresponding to these distinct regimes were made to examine their effect on the performance of such dampers. Visual observation also revealed the means by which the pressure in the feed groove showed higher amplitudes than the theory predicts. Comparison between vapor and gaseous cavitation are made based on their characteristic pressure wave, and the effect this has on the resultant force in the squeeze film. Presented at the 44th Annual Meeting in Atlanta, Georgia May 1–4, 1989

Damper control mechanism

Abstract: An air control damper assembly for mounting in an air duct comprising a damper blade pivotally mounted within the air duct and means for rotating the damper blade from an open position to a close position. A drive system rotates the damper blade such that the system exerts a high torque and low speed at the beginning and end of the rotation of the blade from one position to the other and a low torque and high speed in the middle of the rotation of the blade between positions. The damper blade is locked in the open and close positions by means of a motor and gear unit. Electrical switches interfacing with a drive disk in the drive system partially controls the energization of the motor.

Lock-up damper device for torque converter

Abstract: A lock-up damper device for a torque converter comprising a piston clutch plate slidable in axial direction and equipped with a friction facing pressed on a front cover and a driven plate interconnected to a turbine in between the front cover and the turbine. The piston clutch plate and the driven plate are coupled to each other, for relative rotation by torsion springs arranged longitudinal in circumferential direction of such plates. The torsion springs are installed at outer and inner peripheral parts of the plates. The torsion springs installed on the inner peripheral part of said plates is in contact at at least their radial outer peripheral, radial inner peripheral and side portions between said radial outer and inner peripheries with a wall of a concave portion formed on the piston clutch plate, and the torsion springs installed on the outer and inner peripheral parts are held by the drive plate secured to the piston clutch plate.

A magnetic damper for first-mode vibration reduction in multimass flexible rotors

Abstract: Many rotating machines such as compressors, turbines, and pumps have long thin shafts with resulting vibration problems. This paper describes an experimental test rig that was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing

Squeeze film damper fluid control

Abstract: A squeeze film damper having spaced opposite piston rings for damper fluid sealing includes a fluid plenum groove adjacent and inboard of each ring to serve as a lower pressure receiver for damper fluid and as a reservoir to receive and supply fluid during pumping action of the damper.

On/off semi-active suspension control

Abstract: A controlled suspension for a wheeled vehicle includes a damper between the vehicle body and wheel, the damper being switchable, at a frequency sufficient for the control of resonant wheel vibrations, between a first mode of operation characterized by a high damping force and a second mode of operation having a low damping force. A control repeatedly derives from sensed vehicle suspension related operating variables desired force to be applied between the body and wheel in order to produce a desired suspension behavior determines whether that force result in active or dissipative suspension power. The control further stores a threshold and controls the damper for each derivation so that (1) the damper operates in its second mode of operation when the desired force would produce active power, (2) the damper operates in its first mode of operation when the desired force exceeds the threshold and would produce dissipative power, and (3) the damper operates in its second mode of operation when the desired force is less than the threshold and would produce dissipative power.

Apparatus for use in dehumidifying and otherwise conditioning air within a room

Abstract: Apparatus for dehumidifying or otherwise conditioning the air in a room has a cabinet housing a pair of units side by side. Each unit is essentially a conventional dehumidifier but has its evaporator and evaporator fan above its condenser, compressor and condenser fan and is separated therefrom to establish an upper evaporator section and a lower condenser section. The cabinet has outside air inlet ports opening into the upper and lower sections with each controlled by adjustable dampers. The cabinet also has a port through which air is discharged to the outside by the condenser fans. Separate conditioned air outlets open from the upper section into the room. In addition, the cabinet has ports in its ends to admit air from the room into the upper and lower sections and these are also provided with adjustable dampers. The control for the apparatus is based on inputs from sensors responsive to the humidity and temperature of the inside and outside air, circulating air and discharged air and they provide outputs controlling the operation of the fans, the compressors and the adjustments of the dampers to establish and maintain suitable room humidity and temperature conditions.

Suspension system for vehicle

Abstract: Among two damping devices arranged in series between wheel side members and body side members, while in one damping device spring constant of a spring member is set low and damping coefficient of a damper member is set high, in the other damping device spring constant of a spring member is set high and damping coefficient of a damper member is set low. By this arrangement, difference in damping force between the area of low oscillation frequency and the area of high oscillation frequency can be made large, whereby running stability and comfortableness to ride in can be improved on a high level.

Cavitation and Air Entrainment Effects on the Response of Squeeze Film Supported Rotors

Abstract: This paper analyzes the effects of air entrainment and cavitation on the synchronous response of squeeze film supported rigid rotors. The fluid film force coefficients are obtained from experimental measurements corresponding to a wide spectrum of operating conditions. These conditions include regimes in which air entrainment effects are dominant. Other conditions where vapor cavitation and fluid inertial effects are dominant are included for comparison. The effects of air entrainment are shown to produce a nonlinear response representative of a softening spring effect not previously known to exist in squeeze film dampers.

Fan-powered mixing box assembly

Abstract: A fan-powered mixing box assembly through which conditioned air is supplied to a plurality of zones is controlled by a programmable fan-box monitor. The assembly comprises a mixing box, a multi-speed fan and a heating element having several stages. The monitor receives data from and transmits data to a plurality of programmable zone thermostats each of which controls a zone via a duct damper through which air enters the zone. The monitor receives data from duct temperature and duct air pressure sensors for use in controlling the fan and heating element. Also, the monitor is responsive to signals representative of the real time for operating the assembly in setback modes when the various zones are not occupied. The monitor modulates a master damper for control of supply air.

A new approach to determine transient generator winding and damper currents in case of internal and external faults and abnormal operation. III. Results

Abstract: For pt.II see IEEE Winter Meeting, New Orleans, LA, 1986. A novel method for analyzing the steady-state and transient currents in the stator, rotor, and damper windings of a large generator is discussed, and the application of the method to five classes of problems of practical importance is described. These are (1) internal phase-to-phase fault in a two-circuit machine; (2) 180 degrees out-of-phase synchronization; (3) three-phase short circuit at generator terminals; (4) clearing of a three-phase system fault; and (5) unbalanced steady-state negative phase sequence load of 6%. The authors show the individual damper bar currents and energies or electric power loadings for these cases and, for one example, the time variations of stator and damper winding currents. The investigation was conducted on a standard two-pole generator that was designed for 60 Hz operation and has a rating of 700 MW. >

Active suspension system of vehicle

Abstract: An active suspension system of an automotive vehicle having four air suspension units for four wheels has a first sensor for detecting vertical acceleration of the mass above each suspension unit spring, a second sensor for detecting the vertical relative displacement of the masses above and below each unit spring, a controller for operating in response to the output signals from the two sensors and a relative displacement velocity signal obtained by differentiation of the signal from the second sensor to generate an instruction air flow quantity signal, and a control valve operating in response to this flow quantity signal from each controller to control the charging or discharging of air into or from each unit. An auxiliary damper is provided in each unit to damp vibrations of relatively high frequencies. A low-pass filter is used to filter off a relatively high-frequency component of the output signal of at least the first sensor, whereby vibrations of relatively low frequencies are damped and absorbed by the operation of the air spring action of each unit according to the operation of the control valve.

An active suspension employing an electrohydraulic pressure control system

Abstract: An active suspension employing an electrohydraulic servosystem in which pressure control valves are applied for the first time has been developed. The suspension is controlled by a microprocessor and acceleration sensors. The authors describe the theoretical and experimental analyses that were conducted in developing this system, including the studies of the active control system, vehicle system dynamics, and transmission of vertical inputs from the road surface. This system features a skyhook damper which can reduce body vibration to less than one-half that of conventional suspensions at low frequencies by applying an active damping force to the body proportional to its absolute velocity. The hydraulic system has passive damping characteristics dependent on the frequencies of road inputs. Optimization of these characteristics results in a reduction of vibration caused by high-frequency road surface inputs. An active moment control function using lateral and longitudinal sensors which can reduce body pitching and rolling is provided. >

Semi-active suspension control

Abstract: The invention concerns a method and a device for the suspension control of vehicles, in particular motorcars and commercial vehicles, with the following steps: Sensory ascertainment of the dynamic rolling condition and processing of the established rolling condition data, to generate a control signal for a semi-active damper, preferably one allocated to each wheel of the vehicle, the damping force of which is adjustable in certain situations which are dependent on the driving condition, to as small a value as possible. It is suggested that the semi-active damper, depending on the control signal and the actual value of the damper force is set in substitution for an active damper function which though desired with regard to the prevailing operating point, is not however achievable, this substitute setting being made with maximum hardness or maximum softness.

Electric power generating system with active damping

Abstract: The problem of filtering DC power on a DC bus (46) in an electrical power generating system (10) is resolved using an active damper circuit (44). The active damper circuit (44) comprises a capacitor (CD) and a switching circuit (70) for alternately switching the capacitor (CD) into and out of parallel relationship with the DC bus (46).

Self-contained acceleration-responsive adaptive damper

Abstract: A damper for a vehicle suspension utilizes accelerometer elements for controlling damping rate in response to lateral or longitudinal ("horizontal") acceleration of the vehicle. The accelerometer can be a mass/spring assembly within the damper housing. The accelerometer is linked to at least one damping rate adjuster element, such as a variable orifice or pop-off valve, so that increasing displacement of the accelerometer, in response to increasing vehicle horizontal acceleration, varies the setting of the rate-controlling elements to modify the damping rate. The horizontal acceleration/damping curve can be "tuned," and can be varied in X and Y axes, by selecting various accelerometer weights and springs, or by utilizing multiple accelerometers.