Showing papers on "Dynamic Vibration Absorber published in 1992"

Vibration control of beams by beam-type dynamic vibration absorbers

Abstract: Dynamic vibration absorbers with one degree of freedom are generally applied to the passive control of beam vibration. These absorbers are useful to control a single mode of vibration under harmonic excitation. In this paper, a beam-type dynamic vibration absorber is presented and is composed of a beam (dynamic absorbing beam) under the same boundary conditions as the main beam and uniformly distributed, connecting spring and damper between the main beam and absorbing beam. Equations of motion of the system in modal coordinates of the main beam become equal to those of the two-degrees-of-freedom system with two masses and three springs. Formulas for optimum design of the beam-type dynamic vibration absorber are proposed by using the optimum design method of a dynamic absorber in two degrees of freedom, obtained by Den Hartog’s method. Numerical calculations indicated the response of the main beam without damping is reduced with the exception of the response of the second, and the one with damping is remarkably reduced.

Controllable hydraulic vibration absorber

Abstract: A controllable hydraulic vibration absorber is disclosed whose power cylinder and a tube defines a connecting duct which affords a balance of volume between both power chambers of the vibration absorber and a balancing chamber which is formed between the tube and an external tube disposed coaxially with it. The controllable vibration absorber valve affords variations of the vibration absorbing power and allows a flow through it in one direction only and is arranged between the connecting duct and the balancing chamber so as to be integrated as to its action in a valve assembly which is constituted by a non-return valve and by a switching valve. The switching valve is inserted between the second power chamber and the connecting duct.

Active vibration absorber for the CSI evolutionary model - Design and experimental results

Abstract: The development of control technology for large flexible structures must include practical demonstrations to aid in the understanding of controlled structures in space. To support this effort, a testbed facility has been developed to study practical implementation of new control technologies. The paper discusses the design of a second-order acceleration feedback controller that acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated accelerometer/actuator pairs in the absence of accelerometer/actuator dynamics and computational time delay. Experimental results in the presence of these factors are presented and discussed. The primary performance objective considered is damping augmentation of the first nine structural modes. Comparison of experimental and predicted closed-loop damping is presented, including test and simulated-time histories for open- and closed-loop cases. Although the simulation and test results are not in full agreement, robustness of this design under model uncertainty is demonstrated. The basic advantage of this second-order controller design is that the stability of the controller is model-independent for collocated accelerometers and actuators.

Electrical machine tool housing - has vibration body in clearance between overlapping edges of two sections of housing connecting sections together

Abstract: The housing includes a first housing section (1) which houses a motor. A second section (5) acts as a hand grip and consists of two shells. One edge (3) of the first section overlaps a facing edge (7) of the second section. There is a clearance between the two edges. A vibration absorbing body (10) sticks on one side to the edge of the first section and on the other side to the edge of the second section to connect the housing sections together. ADVANTAGE - Has simplified structure for housing sections and vibration absorber. Motor housing need not be enclosed by additional housing.

Belt or chain drive disc

Abstract: The disc comprises an input part (3) and an output part (4) coupled for rotation by a damping device (5( with circumferentially compressible energy accumulators, such as coil compression springs (9). The input and output parts are mounted rotatable relative to each other by a bearing (26). A vibration absorber has an absorber mass (29) connected to the same shaft as the drive disc vias a damper (28) of elastomer, connected to absorber input part (24). Absorber input part (24) may be fixed to radially inner area (22) of input part (3) either by screws or rivets. Cover cap (41) is provided to prevent dirt entering circular chamber (8) which is partially filled with a viscous medium. To prevent overheating, axial apertures (42) are provided.

Effects Of Vibration Absorbers On The Longitudinal Vibration Of A Pipe String In The Deep Sea - Part 1: In Case Of Mining Cobalt Crust

Abstract: In order to reduce the longitudinal vibration of the pipe string for mining the cobalt crust at the bottom of the deep sea, a vibration absorber, which was composed of a mass, springs and dampers, was attached to the pump module as well as the buffer. Then, the effect of the absorber on the vibration was analyzed theoretically. The results indicate that the abovementioned absorber attached to the buffer can reduce the resonance amplitudes of the buffer and pump module to almost 40% values and that larger mass of the absorber reduces those amplitudes more within the range where the mass ratio of the absorber to the buffer is small, although the effective range of the absorber is more limited. There are the optimum values for the spring constant of the absorber and the above-mentioned mass ratio to reduce the vibration of the pipe string. Furthermore, the absorber attached to the buffer causes much greater effect on the vibration of the pipe string than that attached to the pump module.

Dynamic vibration absorber

Abstract: PROBLEM TO BE SOLVED: To provide a dynamic vibration absorber which is suitable for characteristic adjustment when installed in field or readjustment after secular change. SOLUTION: The dynamic vibration absorber 1, which absorbs vibration applied to a vibration deadening object by vibrating a rod spring 3 to which a spindle 4 is attached in lower end, and damps a vibration of the rod spring 3 by a magnetic damper 14 constituted with the spindle 4, comprises a frame 2 in which a hole inserted by the rod spring 3 is arranged, an inner cylinder body 5 fixing an upper part of the rod spring 3 to the frame 2, and an outer cylinder body 6 forming a fulcrum point when the rod spring 3 vibrates by contacting the rod spring 3 so that the vibration of the rod spring 3 may be regulated in one section on the axis of the rod spring 3. Furthermore, damping property is adjusted by expanding/contracting a space between the spindle 4 and permanent magnet 8 in such a way that a fixed position B of the rod spring 3 in the frame 2 is moved vertically by rotating the inner cylinder body 5. Additionally, spring characteristic is adjusted by telescoping a distance from the fulcrum point to the spindle 4 in such a way that the fulcrum point is moved vertically by rotating the outer cylinder body 6. COPYRIGHT: (C)2010,JPO&INPIT

Hydraulic controllable vibration absorber

Abstract: A hydraulic controllable vibration absorber for an automotive vehicle has a power cylinder that is divided a vibration absorber piston into a first power chamber, which is configurated above the vibration absorber piston, and a second power chamber, which is configurated beneath the vibration absorber piston. These configurations allow both chambers to be brought into connection with a balancing chamber. The vibration absorber is equipped with a sensor arrangement which affords a recognition of the direction of movement of the vibration absorber piston. The sensor arrangement is inserted between the second power chamber and the balancing chamber.

Comparison of vibration control schemes for a smart antenna

Abstract: Two active vibration control schemes, positive position feedback (PPF) and active vibration absorber (AVA), were experimentally implemented with an eight ribbed smart antenna. Mounted on five of the eight ribs are collocated piezoceramic sensor/actuator pairs creating a multi-input multi-output (MIMO) control structure. A single-input single-output (SISO) pole zero model of one of the antenna ribs is identified. The design parameters for the AVA and PPF controllers are numerically optimized from simulations of the SISO model. The design parameters found in the SISO simulations are then implemented in the MIMO structure. Theoretical stability bounds for collocated and non-collocated control for both the PPF and AVA control schemes are also presented. >

Active dynamic vibration absorber

Abstract: PURPOSE:To provide an active dynamic vibration absorber allowing desirable vibration damping effect to be obtained in a wide frequency band with a small power consumption without causing extreme enlargement in the size of a device. CONSTITUTION:Inside a main frame body 2 fixed onto a floor 21, a movable mass 7 is supported elastically in the vertical direction by coil springs 14, 15, and vertical electromagnetic force is imparted to this movable mass 7 by an electromagnetic actuator formed of a permanent magnet 10 fixed to the movable mass 7 and an electromagnetic coil 13 fixed onto the main frame body 2 side. An adjusting mass 16 is fixed to the lower end part of a shaft 4 for guiding the vibration of the movable mass 7, and the shaft 4 is constituted in such a way as to advance/recede freely in relation to the main frame body 2 by linear bearings 5A, 5B. A disc 17 fixed to the shaft 4 can be magnetically fitted or separated to/from the movable mass 7.

Optimal active vibration absorber: Design and experimental results

Abstract: An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

Vibration absorber for windscreen frame of car - consists of mass with each end attached to tension spring

Abstract: The frame of the windscreen of a cabriolet type motor car is prevented from vibrating by a vibration absorber fitted inside the hollow upper cross member of the windscreen frame (3). The vibration absorber consists of a mass (2) which has each end attached by a tension spring (5,6) or by resilient thrust bearings to the windscreen frame. The vehicle engine generates torsional vibrations in the side members of the frame. These vibrations are damped by the damping force exerted by the absorber on the upper cross member (3). USE/ADVANTAGE - Vibration absorber for windscreen frame can be designed to suit natural frequency of the frame.

Compact proportional electromagnet mainly for vibration absorber control

Abstract: A proportional action electromagnet has a main body (1) that is cylindrical with an actuator pin of non magnetic material in the centre. This supports an armature element (6a) and moves on bearing surfaces. The armature moves in the gap (11) formed between projecting sections (14, 15) that provide magnetic flux surfaces. In comparison with a version in which the intermediate section (15) is absent, the magnetic force generated is greatly increased.

Vibration Damping Mechanisms with Gyroscopic Moment

Abstract: Damping mechanisms based on gyroscopic moments are studied and their characteristics are compared with conventional mechanisms. A generalized form of Schlick's gyroscope is theoretically analyzed, and an optimal design method is derived. The stabilizing effect is compared with the rotational dynamic vibration absorber. It turns out that the effect of the passive gyroscopic stabilizer depends on the rotating speed of the gyroscope; thus the stabilizer has no essential limitation by the inertial moment such as there is with the rotational dynamic vibration absorber. The gimbal movement of the CMG (control moment gyroscope) is directly controlled with an actuator, thus it can be used as a fully active vibration control mechanism. The single-gimbal CMG is compared with the RW (reaction wheel) with respect to the damping efficiency for impulsive disturbances. Experiments with a single-gimbal CMG for a Pendulum are carried out and the results prove the efficiency.

Damping device for structure

Abstract: PROBLEM TO BE SOLVED: To provide a damping device for structure capable of simplifying the structure of a damping device, having superior productivity and maintenability, and installable in a minimum space. SOLUTION: Four points of a weight 1 comprising TMD(tuned mass damper), or a dynamic vibration absorber for the structure, are supported by rolling pendulums 3. The rolling pendulum 3 is provided with plate rolling parts 3b and 3c forming arc projecting surfaces on the upper/lower end parts of a shaft part 3a and the upper/lower rolling parts 3b and 3c are mutually orthogonally provided so as to vibrate in an orthogonal two direction. The curvatures of the projecting surfaces of the rolling parts 3b and 3c are decided by periods (for example, period synchronized with a primary natural period of the structure) required according to a design of the TMD as the rolling pendulum 3 and designed within ranges of L

Vibration removing device

Abstract: PURPOSE:To suppress an influence of rocking vibration so as to attain also substantial space saving by dividing a mounting bed into upper and lower part stages, providing rigid connection between both the stages through a coupling pillar and arranging a dynamic vibration absorber in space between both the stages. CONSTITUTION:When vibration of acceleration character is input from a set up floor, a vibration remover 20 removes vibration by displaying insulation performance. That is, a vibratory component in a perpendicular direction is substantially reduced with a high frequency side after about 1Hz serving as the center by damping action of a vibration removing system mounting bed 24, each spring mechanism 26 and each oil damper 28 and also concentrically reducing a component of 2.5Hz by vibration absorbing action in an antiresonance point given by a dynamic vibration absorber 30. On the other hand, a component in a horizontal direction is reduced with a high frequency side after about 0.6Hz serving as the center by damping action of the mounting bed 24, spring mechanism 26 and each oil damper 28 in a vibration removing system and also concentrically reducing a component of 0.8Hz by vibration absorbing action in the antiresonance point applied by the dynamic vibration absorber 30.

Resilient towing connection

Abstract: A towing hook 34 has an attachment plate 31 attached to the mounting plate 1 of a vehicle towbar by two bolts (4 fig 3, 4), with a vibration absorber sandwiched between. The vibration absorber has a rectangular elastomeric block 21 between two bonded-on facing plates 22, 23, and can be installed/removed as a separate unit. The separation of the plates 1, 31 can be controlled by the mounting bolts which allow the plates to move together, by compression of the elastomeric block, to absorb towing shocks, but limit their separation apart.

Output Regulation in an Active Dynamic Vibration Absorber System with an Electromagnetic Servomechanism.

Abstract: The control system of an active dynamic vibration absorber with an electromagnetic servomechanism, is designed based on the theory of output regulation with internal stability. The absorber system consists of a lever generating an inertial reaction, two electromagnets driving the lever, sensors and a controller. The object of the control is twofold. First, it is to reduce the vibration of the primary system equipped with the absorber to a nonresonant level in the whole range of frequencies. Second, it is to reduce the vibration to zero at a specified frequency. It is shown that the latter property is preserved in the face of small parameter variations in the primary system, but is not preserved when the parameters in the absorber system are perturbed. Experimental results emphasize the effectiveness of the proposed control method, and support the analytical predictions well.

アクティブ動吸振器を用いた多自由度構造物のh∞制御--周波数重み関数の設計指針について

Abstract: This paper proposes a design method using H∞ control theory concerning an active dynamic vibration absorber for multi-degree-of-freedom systems In particular, the weighting functions of H∞ control are discussed as to which one is better We finally propose the best weighting functions for vibration control, robust stability and stroke limits of the dynamic vibration absorber in two cases, namely, a hybrid dynamic vibration absorber and an active dynamic vibration absorber The control object is a tower structure with four degrees of freedom, two vibration modes in the lower frequency domain as the reduced order model should be controlled, and another two higher modes as the residual model should be uncontrolled on the condition of robust stability without spillover We have confirmed the strong robustness concerning parameter variations of the spring constant and the damping constant in the case of a hybrid dynamic vibration absorber Also, it has been made clear that an active dynamic vibration absorber designed by H∞ control theory is effective against seismic disturbances such as the E] Centro earthquake

MD-80 aft cabin noise control: A case history

Abstract: The interior noise technology program to improve the noise environment in the aft cabin of the MD-80 twin jet aircraft is discussed. Two potential noise control treatments were identified: vibration absorber devices for the airframe and for the engine. A series of ground and flight tests using in-service aircraft was then conducted. These tests showed that the vibration absorbers for the airframe and engine decreased aircraft noise significantly.

Vibration isolating structure in precision equipment or the like

Abstract: PURPOSE:To sufficiently absorb vibration in horizontal and vertical directions by providing an umbrella-shaped vibration absorber between a supporting part provided in a fixed frame and a holding member provided in a mounting bed. CONSTITUTION:A connection hole 6 is provided in a mounting bed 3 on which an accurate equipment is loaded, and a holding member 9 is provided by forming a supporting surface 8 in an internal surface of a cover part 7. A fixing screw 15 is screwed by forming an internal thread hole 12 corresponding to the connection hole 6 in a chassis 4 which is a fixed frame. A vibration absorber 21 is provided between the fixed frame and the holding member 9 and connected by providing a support cylinder 13 which is a supporting member. The vibration absorber 21 is formed in an umbrella shape. Accordingly, the vibration absorber escapes to a space S1 relating to vibration in the vertical direction and to a space S2 relating to vibration in the horizontal direction. Thus, sufficient vibration absorbing action is displayed in both the horizontal and vertical directions.

Hybrid dynamic vibration absorber

Abstract: PURPOSE:To prevent spillover unstability in vibro-isolating control by setting a natural frequency of a passive dynamic vibration absorber higher than a vibration frequency of the highest mode of a building considered in the control. CONSTITUTION:A passive dynamic vibration absorber is constituted of a mov able mass ma2 horizontally movably supported onto the highest story of a build ing, spring (its rigidity constant is assumed ka2) for connecting this movable mass ma2 to the building and a damper (its damping constant is assumed Ca2). Further, an active dynamic vibration absorber is constituted of a movable mass ma1 horizontally movably supported onto the movable mass ma2 and an actuator for connecting this movable mass ma1 to the movable mass ma2 to apply con trolled horizontal driving force between both the movable masses. The constants ka2, ca2 of the spring and the damper are switched bordering a rapid brake by a stopper. Then, a large impact is applied to the building by showing maxi mum acceleration larger than in the case of no control excepting a switching type hybride dynamic vibration absorber (SHDVA).

Vibration controlling structure

Abstract: PURPOSE:To decrease the response of a building effectively in accordance with characteristics of external disturbance caused by wind, earthquakes, etc.. CONSTITUTION:An upper vibration control system A forming an active type vibration absorber is provided to the top of a building, and active type or passive type lower vibration control systems B are provided to floors from the first to the third of the lower part of the building. The upper vibration control system A regards the weight of the uppermost layer of the building as a weight, and the movement thereof is controlled with a variable damping device 1a to deal with wind vibration. Vibration control devices of a variable damping device 1b, etc., are incorporated into the lower vibration control systems B between an inverted V-shape brace 35 and a beam 34 in a column and beam framing 31, and the vibration control device is functioned to deal with an earthquake.

Optimal Repetitive Control with Preview for Active Vibration Control

Abstract: In this paper a new repetitive control scheme is presented for active vibration control of linear systems subject to periodic disturbances. The motion of the structure is controlled by momentum exchange with essentially collocated masses. Due to inherent structural limitations, performance trade-offs have to be made and perfect regulation cannot be achieved even when the disturbance is known. By combining ideas from optimal preview control, simultaneous state and input estimation, and repetitive control, a methodology is developed that allows for minimization of system vibration as defined by a quadratic performance index. The system disturbance is estimated based on the information from the most recent period and, assuming the disturbance to be repetitive, this estimate is used to compute a preview input for the consecutive cycle. Since the optimal preview control law requires a full state feedback and feedforward of a variable dependent on future inputs, an observer is required. A design procedure for a simultaneous state and disturbance observer is therefore developed. Necessary and sufficient conditions for the existence of a full order observer are formulated using straightforward matrix calculus. In principle, the system can achieve optimal performance after one cycle of operation. The proposed approach is illustrated on an example of a 2-DOF model representing a machine with an active vibration absorber.

Heat-expansible viscoelastic body and method for vibration isolation using the same

Abstract: PURPOSE:To improve vibration absorptive capacity by disposing a specific heat-expansible viscoelastic body in the space inside a tubular body, and allowing a vibration absorber obtained by heating the heat-expansible body to stick to the inner wall surface of the tubular body. CONSTITUTION:A heat-expansible viscoelastic body, which has a penetration (JIS-K-2530) of 40-300 and a volume increase rate of 20-150% based on the volume of the heat-expansible viscoelastic body prior to heat treatment when the body is heat-treated at 80-200 deg.C, is obtained by dispersing a heat--expansible agent in a viscoelastic body made of a polymer having a rubber elasticity (e.g. polyisoprene), foaming agent (e.g. NaHCO3), plasticizer (e.g. polybutene), inorganic filler, bituminous material, tackifier, etc. Then the heat-expansible viscoelastic body is arranged in the space inside a tubular body 2A and heated at 80-200 deg.C, so that the heat--expansible body is converted into a vibration absorber 1A which is stuck to the inner wall B of the tubular body 2A.

Engine vibration absorber

Abstract: PURPOSE:To prevent vibration or noise surely by correcting response delay of electrostrictive elements with regard to engine vibration absorbers to absorb engine vibration by using the electrostrictive elements. CONSTITUTION:Vibration absorbers 11-13 provided with electrostrictive elements therein are arranged in the middle of a vibration transmitting route to transmit engine vibration, and voltage changing in synchronism with the period of the engine vibration is impressed upon the electrostrictive elements, and a turning angle sensor 16, a control device 15 and a voltage impressing device 14 are arranged in engine vibration absorbers to absorb diaplacement of the vibration by means of distortion generated in the electrostrictive elements. The turning angle sensor 16 detects the number of revolutions of an engine. A relationship between the number of revolutions of the engine and timing time to impress the voltage upon the electrostrictive elements is memorized in the control device 15, and the timing time to impress the voltage upon the vibration absorbers 11-13 is determined according to the number of revolutions of the engine detected by means of the turning angle sensor 16. The voltage impressing device 14 impresses the voltage upon the vibration absorbers 11-13 according to the timing time determined by means of the control device 15.

Vibration absorber for steering wheel

Abstract: PURPOSE:To keep a mass body from coming in contact with peripheral parts and prevent the generation of noise and moreover allow various parts to be disposed around a cover body by providing a space, formed between the mass body and the cover body, with elastically deformable contact parts protruding from the cover body CONSTITUTION:A vibration absorber 35 disposed on the boss plate 18 of a steering wheel body 11 is provided with a vibration absorbing dynamic damper 36 and a cover body 37 for covering this dynamic damper 36 The dynamic damper 36 is formed of a base plate 41, rubber made supporting legs 42 rigidly fixed to four corners of the base plate 41, and a mass body 44 rigidly fixed to the supporting legs 42 The side wall part 61 of the cover body 37 surrounds the mass body 44 so as to form a space part 63, and the space part 63 is protrusively provided with contact parts 65 elastically deformable toward the recessed part 54 of the mass body 44 from the inside of the side wall part 61 In the case of the steering wheel 11 being excessively vibrated, the mass body 44 comes in elastic contact with the contact parts 65 to regulate the movement of the specified value or more, so that the mass body 44 is prevented from coming in direct contact with peripheral parts