Showing papers on "Damper published in 1987"

Nonlinear Control of a Distributed System: Simulation and Experimental Results

Abstract: A nonlinear active vibration damper has been developed which uses a spatially distributed piezoelectric actuator, polyvinylidene flouride, to achieve active vibration control of a cantilever beam. The control algorithm was derived using Lyapunov’s Second Method. All modes of the beam can be controlled simultaneously if the angular velocity of the tip of the beam is known. A simulation algorithm was developed to predict the effect of the control on the free decay of a single mode. A parameter study for the first mode was performed and compared to experimental results. The active damper has been tested successfully on two different scale structures.

Method and system for controlling a single zone HVAC supplying multiple zones

Abstract: An improved monitoring and control system for a heating, ventilating and air conditioning (HVAC) unit which provides zone control in plural zones in which each zone includes a thermostat which controls a damper for its zone. One thermostat is selected and programmed to function as a monitor or master thermostat for selective actuation of the HVAC unit as well as controlling its zone damper. The other thermostats are programmed to function as slave thermostats and are interfaced with the master thermostat thereby allowing for independent zonal control in a multiple zone system which uses a single zone HVAC unit. The master thermostat may also receive control signals and data from higher intelligence such as a computer. Each thermostat is microcomputer-controlled with provision for both local and manufacturer programming via supplemental memory devices. The master thermostat contains a real time clock for time-basing the entire system with attendant advantages.

Thermostat control system

Abstract: A microcomputer-controlled thermostat for use in monitoring and controlling a single zone HVAC system which provides conditioned air to one or more zones. The thermostat can be programmed and used either as a monitor thermostat to control the HVAC unit alone and/or to control the HVAC unit and its damper in a multiple zone mode. The thermostat is also programmed as a slave thermostat in a master-slave relationship with a monitor thermostat. The microcomputer memory is supplemented with additional ROM containing control algorithms for use in system operation. Logic circuitry is used to recognize commands as being for operation of the HVAC unit, the operation of the damper, or selection of which systems sensors are to be enabled. A real time clock circuit in the monitor thermostat is used to supply data for time-based system operation.

On the Performance Capabilities of Active Automobile Suspension Systems of Limited Bandwidth

Abstract: Using methods established in earlier work, calculations are carried out to reveal the influence of actuator bandwidth on the performance capabilities of a class of active suspension system for automobiles. The suspension consists of an actuator in series with a spring, the combination being in parallel with a passive damper, and the system is modelled as a single wheel station traversing a random road. The results indicate that a system with a 3 Hz bandwidth actuator and variable damping will have excellent ride performance qualities over a wide range of road roughness conditions. Since such a system can be expected to be easily adaptable to the running conditions, to provide good static and dynamic attitude control, to be capable of contributing to good steering control responses and to be inexpensive in terms of capital and energy consumption costs compared with most of the active systems which have previously been discussed, it is suggested that it is a prime candidate for further study and pr...

Zone control apparatus for central heating and/or cooling systems

Abstract: An improved zone control apparatus having mode selectors which allow a user to select any one of a variety of operating modes for individual fluidically actuated flow control devices. The invention further provides for a smoke damper which upon automatic or manual activation causes all of the flow control devices to restrict flow of conditioned fluid through respective ducts or pipes so as to help minimize smoke contamination and the formation of a "chimney" effect. The invention further provides for the utilization of vibration type diaphragm pumps to create a source of pressure and vacuum, a pressure test device to quickly check the pressure in the apparatus, and a flow indicator for determining the location of leaks in the apparatus.

Performance of Viscoelastic Dampers in World Trade Center Towers

Abstract: The viscoelastic damper was conceived and developed as a part of the structural design for the Twin Towers of the World Trade Center, New York. They are an integral and an essential part of the structural system, being designed to assist the tubular steel frame in limiting wind-induced building oscillation to levels below human perception. The selection, quality, shape and location of the dampers was based on the dynamic analysis of the towers (computer modeling, wind tunnel, etc. ), and of the damping acquired to achieve performance standards. This paper presents information from the dynamic monitoring program, reports on the methods used to evaluate the effectiveness of the dampers, and compares overall structure damping with that calculated during structural design.

Bypass controller and bypass system

Abstract: A microcomputer-controlled bypass controller for use in maintaining a minimum airflow through a heating/cooling unit and limit the static pressure in the supply air truck duct. The bypass controller functions to control the operation of a bypass damper which regulates the airflow through a duct that bypasses air from the supply truck duct to the return. The bypass controller also measures the air flow via an air flow sensor and communicates with a microcomputer-controlled thermostat to coordinate transitions between heating and cooling cycles in association with a second sensor which monitors the duct temperature.

Effect of Fluid Inertia on Squeeze-Film Damper Forces for Small-Amplitude Circular-Centered Motions

Abstract: Fluid-film forces generated by squeeze-film dampers (SFD) in response to small-amplitude centered motions are of special interest for stability analyses of rotating machinery employing SFDs with strong centering springs. They form the basis for calculation of linearized damping and inertia force coefficients obtained by subjecting the journal center to very small perturbations in velocity and acceleration. The analysis considers the fluid flow in an open-ends SFD due to small-amplitude circular-centered motions. Simplified governing equations are derived; and regarding the flow to be stable and laminar, the linear flow equations are solved exactly for arbitrary values of the Reynolds number. Exact damping and inertia force coefficient are then derived for open ends SFDs with arbitrary L/D ratios. Presented at the 41st Annual Meeting in Toronto, Ontario, Canada May 12–15, 1986

Duct type air conditioning system

Abstract: An air conditioning system provided with a variable capability blower and heat source unit is configured such that individual room dampers 9 and controllers 14 can be subsequently added to a central control device as options to convert from an all room simultaneous air conditioning mode to a variable air volume mode with separate temperature control for each room. The utilization of existing power lines to transmit the various information and control signals simplifies the conversion and reduces its cost.

Experimental Measurement of the Dynamic Pressure Distribution in a Squeeze-Film Bearing Damper Executing Circular-Centered Orbit

Abstract: A review of previous experimental measurements of squeeze film damper (SFD) forces is given. Measurements by the authors of SFD pressure fields and force coefficients, for circular centered orbits with epsilon = 0.5, are described and compared with computer predictions. For Reynolds numbers over the range 2-6, the effect of fluid inertia on the pressure fields and forces is found to be significant.

Method of controlling damping force of damper

Abstract: The damping force of a damper on a motor vehicle is automatically controlled dependent on the running condition of the motor vehicle and the road condition in which the motor vehicle travels. An acceleration of vertical vibration of the motor vehicle body is detected by a sensor, and a binary pulse signal indicative of a variation in the acceleration is produced. Then, a first signal is generated on the basis of whether the pulse duration of the binary pulse signal is at least a prescribed value or smaller than the prescribed value. Thereafter, a second signal is produced indicating the magnitude of the absolute value of the acceleration. Finally, the damping force of the damper is selectively adjusted to hard, normal, and soft settings based on a combination of the first and second signals.

Time‐domain analysis of infinite fluid vibration

Abstract: A damper technique is proposed to model the effects of radiation damping in the finite element analysis of hydrodynamic pressures generated due to the vibration of a structure submerged in a compressible fluid. The proposed damper is suitable for a time-domain analysis. It is assumed that the fluid is inviscid and its vibration is of small amplitude. The structure–fluid system is assumed to be two-dimensional, and the fluid domain is considered to be unbounded along the direction of structural vibration. In the finite element analysis, pressure is assumed to be the nodal unknown, and the discretized equations of motion are solved by using a direct integration procedure. As a result of the analysis of several cases, the proposed damper is found to be very effective and efficient for a wide range of the period of excitation. The only exception is the case when the period of excitation is near the natural period of vibration of the fluid domain. For this case, the pressure becomes infinitely large and there is no requirement for any damper. The implementation of the proposed damper in the finite element analysis requires practically no extra computational effort. With the use of the suggested technique, an unbounded fluid domain may be truncated at a relatively very short distance from the structure, as compared to the distance required when the Sommerfeld damper is used. As a result of these advantages of the proposed technique, the cost of computation is greatly reduced.

Performance and Design Considerations for Dissipative Semi-Active Suspension Systems for Automobiles

Abstract: Following previous work aimed at determining the relative performances of automobile suspension systems of passive, active and semi-active types by calculation, similar theoretical methods are applied here to evaluate a class of semi-active system that contains a passive spring of fixed stifness in parallel with the active damper. The static attitude control of the vehicle derives from the springs and in the cases considered the spring stiffness is adequate from this point of view. Systems based on two alternative forms of control law are studied. Results which show the best systems to offer particularly good performance for rough road conditions are presented. By adaptation of the damper control law using continuously updated information some capacity to obtain good performance under moderate conditions is shown to exist, but performance comparable with that obtainable from a purpose designed or fully adaptive system on average main road and motorway conditions is not possible.

Hydraulic vibration damper having adjustable damping valve

Abstract: An adjustable damping valve for use on a hydraulic vibration damper, gas pressure damper or hydropneumatic suspension, which regulates the damping force, regardless of the orientation, and is variable in the regulation of the throughput, thereby providing a rapid switching frequency response. The damping valve has at least one electromagnet. In the preferred embodiment, each electromagnet can be controlled individually. Further, each electromagnet has a coil body with a winding and an armature. The armature is immersed in a fluid in the flow connection during operation. The armatures of the electromagnets interrupt and open directly the flow connection variably and quickly between an upper damping chamber of the vibration damper and a pressure equalization chamber. In one embodiment, there are a number of individual flow connections with corresponding electromagnets distributed over the circumference for fast action.

Rear axle torque rod damper

Abstract: A damper member is disclosed for retaining a torsion rod within cross-beam inverted channel-shaped rear axle. The damper member is normally U-shaped in cross-section having an upwardly opening central bore defined by vertically extending leg portions and a base portion. Upon the damper member being compressed into a D-shaped clearance between the channel and the rod its section is transformed for a U-shape to a C-shape. The unique design of the damper member enables it to be lockingly retained under pressure in the D-shaped clearance.

Active Suspensions Based on Fast Load Levelers

Abstract: SUMMARY A class of active suspensions is presented which provides near optimum isolation of base motion as well as zero static deflection for force disturbances using a simple type of feedback. The load leveling effect is rapid with the system stabilized using isolated mass velocity feedback both for a semi-active damper and for the load leveler. The system can be made energy conservative and fail safe since the system reverts to a reasonable passive isolator if the load leveling effect and even if the active damping effect is switched off. The system could be incorporated in automotive vehicles with some extension of the feedback control to account for several aspects of body motion.

Assembly for damping torsional vibrations

Abstract: An assembly for damping torsional vibrations in the power train between the crankshaft of the engine and the input shaft of the change-speed transmission in a motor vehicle has two flywheels which are rotatable relative to each other against the opposition of a damper system which is at least partially confined in an annular chamber containing a supply of viscous fluid. One flywheel is connected to the crankshaft and the other flywheel is connectable with the input shaft of the transmission by a friction clutch. The damper system can include a hydraulic damper, a mechanical damper and one or more friction generating devices.

Ridge vent with shape-memory actuated heat valve

Abstract: An improved actuator for the damper of a ridge vent. The actuator includes coil springs constructed from a shape-memory alloy. The springs are contracted below a selected temperature at which the damper is to open, and the contracted springs maintain the damper closed on its seat. Above the transformation temperature of the springs, they expand and raise the damper off of its seat to an open position for venting of air through the ridge vent.

Experimental Observation of Cavitating Squeeze-Film Dampers

Abstract: This paper presents the results of an experimental investigation intended to observe cavitation in squeeze-film bearing dampers representative of those commonly found in aircraft gas turbine engines. Two different squeeze-film damper geometries were tested with both high-speed motion pictures and stroboscopic video recordings acquired at speeds up to 20,000 r/min. The results presented are limited to 8000 r/min due to the increased clarity of the photos acquired at the lower speeds and the similarity of trends at the higher speeds. Comparisons are also made with analysis formulated to handle the dynamics of the film rupture for the “short” damper case. The test results confirmed several of the commonly held “short” bearing assumptions (i.e., predominant axial flow and the effect of supply pressure and eccentricity on the cavitation zone). However, the test results demonstrated that significant flow reversals and film rupture were experienced in the feed/drain grooves in contradiction to the assumed boundary conditions. While agreement between analysis and test is of the right order of magnitude in predicting the cavitation zone shape and circumferential extent, current analyses do not adequately account for the observed variations in the boundaries and change in shape of the cavitation zone.

Force Coefficients for Open-Ended Squeeze-Film Dampers Executing Small-Amplitude Motions About an Off-Center Equilibrium Position

Abstract: Fluid-film forces generated by squeeze-film dampers (SFD) in response to small-amplitude motions about an off-center equilibrium configuration are of considerable importance for stability analyses of rotating machinery employing SFDs with weak or no centering springs. This approach is the basis for calculation of linearized force coefficients obtained by subjecting the journal to small perturbations in velocity and acceleration. The analysis considers the fluid flow in an open-ended SFD due to small-amplitude motions of the journal center about the static equilibrium configuration. Simplified governing equations are derived from the full Navier-Stokes equations by order of magnitude tests. Approximate damping and inertia force coefficients for finite-length SFDs are derived by implementing a correction factor to the long SFD model solution. This finite-length correction is of extreme simplicity and shows excellent agreement with a numerical solution to the differential equations for the pressure including...

Automatically flow controlled continuous heat treating furnace

Abstract: A continuous heat treating furnace is equipped with an automatic flow control system and contains a high-temperture treating zone internally provided with a plurality of burners, a pre-heating zone connectively disposed at one end of the high-temperature treating zone and a cooling zone connectively disposed at its other end, the pre-heating and cooling zones being partitioned into a plurality of compartments each provided on its ceiling portion with a convection fan The automatic flow control system includes a first duct for communicating a terminal compartment of the pre-heating zone and a first compartment of the cooling zone, a second duct for communicating a terminal compartment of the cooling zone and a first compartment of the pre-heating zone, a first flow regulating damper disposed in the course of the first duct to regulate a flow rate of atmosphere gas flowing in the first duct, and a second flow regulating damper disposed in the course of the second duct to regulate the flow rate of the atmosphere gas flowing in the second duct By such an arrangement, the flow rate of the atmosphere gas introduced into the pre-heating zone and that introduced into the cooling zone are automatically regulated to coincide with each other

Torsional vibration damper with a V-belt pulley connected thereto

Abstract: A torsional vibration damper with a V-belt pulley unit (Front power take-off) attached to the primary part of the damper. In order to increase the service life of the damper and to improve the level of loading in the front PTO, the V-belt pulley is mounted radially and axially on a support element that is connected to the primary part of the damper. A specially designed coupling element, which contains an elastomer that has a high degree of torsional elasticity, is used in conjunction with the axial bearing. In this way, a supercritical adjustment is attained for the vibration system of the PTO, the vibration damper itself being used only for damping the torsional vibrations of the engine crankshaft.

Apparatus for reducing stress on component elements during extension and contraction of motor-driven antenna apparatus for vehicles

Abstract: An antenna rod, which is extendible and retractable, is moved up and down by a cable with a rack, and the cable is moved with rotation of a pinion gear. The rotational force of a DC motor is transferred to the pinion gear by a route of a worm, a worm wheel, gears, a damper gear, and a damper. The damper is a coil of resilient metal wire, and both ends of the coiled wire, respectively, engage stopping members, which are provided at the center portions of the damper gear and the pinion gear. When the pinion gear is at a standstill, the rotational energy of the damper gear is accumulated in the damper. The motor is rotated under control of a control circuit in response to the operation of a switch. The drive current for the motor is shut off by a detecting signal from a lock detector during the course of accumulating the rotational energy by the damper. The lead angle of the teeth of the worm is large so that the rotational energy stored in the damper is transferred to the motor.

Unbalance correction mechansm in a lock-up damper

Abstract: A drive ring (13) is fixed to a clutch plate (11) of a lock-up clutch. The ring (13) is provided with rims (13a) and support walls (17), which radially hold damper springs (15 and 16), as well as spring receiver projections (21A and 21B) and claws (23) aligned to each other. A spring seat (24), which have legs (24a) fitted into the damper spring, for correcting the unbalance is attached at each end of the damper spring.

Suppression of Machine Tool Chatter Using a Viscoelastic Dynamic Damper

Abstract: Optimization procedures to install a viscoelastic dynamic damper into a single degree of freedom primary system is briefly reviewed. Excitation methods are shown to identify elastic modulus and loss factor of a viscoelastic material at given prestrain, which are needed in the optimum design of the damper. An optimum-designed damper is attached on the toolpost of a lathe and its excellent chatter-suppressing effects are observed under six cutting conditions in terms of integrated power of the accelerations around the chatter frequency. Because one of the resonance frequencies responsible for the chatter varies depending upon the location of the carriage on the sliding surface, the prestrain of the viscoelastic element, which is initially optimum-tuned and damped at a location of the carriage, is readjusted for optimum tuning at the other locations. The effects of the readjustment are discussed in terms of the reduction of structural compliances and magnitudes of chatter vibrations.

Arrangement for controlled damping of pivoting movements in an articulated bus

Abstract: The invention relates to an arrangement for controlled damping of pivoting movements, preferably in an articulated bus The arrangement comprises hydraulic dampers arranged between the vehicle units, a hydraulic control system which connects the dampers with each other, and an electrical control system which activates electrically operated valves in the hydraulic control system The invention is characterized essentially in that it comprises devices which allows the electrical control system, in response to sensors which sense the pivot angle and the vehicle speed, to connect various throttles in the connecting lines between the dampers, to thereby control the damping level of the dampers