Showing papers on "Dynamic Vibration Absorber published in 1996"

Principles of vibration

Abstract: Free vibration of single degree of freedom systems translational vibrations - undamped rotational vibrations - undamped viscous damping Lagrange's equations homework problems forced vibration of single degree-of-freedom systems seismic excitation direct force excitation transfer functions viscous damping complex representations damped seismic motion rotating imbalance identification of damping and natural frequency other types of damping accelerometers and seismometers homework problems non-sinusoidal excitations Fourier series analysis forced response via the convolution integral shock response homework problems vibrations involving more than one degree of freedom free response - undamped system forced response vibration absorbers without damping real behaviour of a vibration absorber zeros in a forced response putting problems into normal form orthogonality of system eigenvectors more on normal forms linear damping comparison of damped eigensolutions forced response of damped systems symmetry of mass and stiffness matrices repeated frequencies and zero frequencies influence coefficients problems distributed systems free vibration of a bar (rod, string, etc.) free vibration of a beam continuous systems - forced vibration orthogonality of eigenfunctions approximate solutions methods lumped approximations Rayleigh's quotient Rayleigh-Ritz method: discrete systems Rayleigh-Ritz Method: continuous problems assumed modes method seat of the pants engineering getting approximate results limiting cases verifying your analyses random vibrations and modal analysis signal descriptions Fourier transform analysis spectral analyses noise sensors and actuators nonlinear effects four continuous systems lumped spring constants Assorted material constants elementary matrix relations vibration texts.

Controlled Semiactive Hydraulic Vibration Absorber for Bridges

Abstract: Heavy truck traffic on highway bridges is known to produce impact loads that cause large vibrations. This phenomenon can reduce the expected service life of many highway bridges. A means to mitigating those deleterious vibrations using an automatic control system that requires no pumps or line power is proposed. A semiactive hydraulic bridge vibration absorber that can be retrofitted to an existing bridge is described. The bridge/vehicle system is modeled, and a practical feedback control that uses either strain-gauge or accelerometer readings to sense the state of the system is synthesized. The results of an experimental test of the new system indicates reductions of peak amplitudes of 65–70%.

Pendulum as Vibration Absorber for Flexible Structures: Experiments and Theory

Abstract: The dynamic response ofa beam-tip mass-pendulum system subjected to a sinusoidal excitation is investigated. A simple pendulum mounted to a tip mass of a beam is used as a vibration absorber. The nonlinear equations of motion are developed to investigate the autoparametric interaction between the first two modes of the system. The nonlinear terms appear due to the curvature of the beam and the coupling effect between the beam and pendulum. Complete energy transfer between modes is shown to occur when the beam frequency is twice the pendulum frequency. Experimental results are compared with a theoretical solution obtained using numerical integration. The experimental results are in qualitative agreement with the theory.

Active vibration-absorber

Abstract: The active vibration-absorber is, in particular, an engine mount for motor vehicles. A magnet system has a magnet casing which receives a permanent magnet and which is guided in the assembly so as to be capable of movement in the axial direction. An electrical moving coil projects perpendicularly from a carrier plate and moves into the magnet casing. The carrier plate can be connected to a vibrating machine part, such as between the engine and the vehicle frame. The magnet system is held, in the axial direction, by a magnetic leakage field which is present between the magnet system and stationary ferromagnet.

An experimental comparison of piezoelectric and constrained layer damping

Abstract: A qualitative comparison between a piezoelectric vibration absorber and a constrained layer damping treatment is presented. Piezoelectric materials convert mechanical strains into electrical charge. Dissipation of the charge results in attenuation of vibration. The damping is concentrated to a single mode by constructing a piezoelectric absorber. The damped vibration absorber is comprised of the piezoelectric material and a passive electronic shunt. Previous research has applied the piezoelectric absorber to one-dimensional structures. This paper applies the absorber to a two-dimensional planar problem. The simple mathematical description of the absorber is modified for the two-dimensional problem. An analytical means of estimating the effectiveness of the piezoelectric absorber is derived. The effectiveness is estimated for an electronics chassis box subjected to random excitation. A typical constrained layer damping treatment is also analytically designed for the problem. The piezoelectric absorber and the constrained layer damping treatment are experimentally applied to identical boxes. Results show that the piezoelectric absorber can provide vibration suppression comparable to that obtained by the constrained layer damping treatment.

Nonlinear piezoelectric vibration absorbers

Abstract: The effect nonlinear electrical shunts on the performance of piezoelectric vibration absorbers for linear systems is presented. The equations of motion are derived in a format suitable for perturbation analysis. An electrical shunt containing cubic and quadratic elements is coupled to the structure via the piezoelectric effect. Nonlinearities are introduced as a combination of the square and/or cube of the charge flowing in the linear inductive - resistive (LR) shunt. Turning the shunt near a structural mode causes mechanical energy to be transformed to electric energy and dissipated by the resistive element in the shunt in a manner analogous to a damped vibration absorber. Analysis is carried out using the method of multiple scales. Simulation results are also presented.

Mass Measurement Using a Dynamic Vibration Absorber under Weightless Conditions

Abstract: A new type of mass-measurement system under weightless conditions is proposed which uses a dynamic vibration absorber as a measuring device. In this system, an object to be measured is fixed to a rotating table (rotor) at a distance from the rotation axis. Since it makes the rotor unbalanced, a centrifugal force whose amplitude is proportional to the mass is generated during rotation. It works as a harmonic excitation and forces a structure supporting the table to vibrate. However, a dynamic vibration absorber attached to the structure is tuned or controlled to reduce the vibration to zero. When the structure does not move at all, the absorber mass vibrates in such a way that the product of the mass and the displacement amplitude is equal to the amount of unbalance, that is, the product of the mass to be measured and its distance from the rotation axis. Therefore, the mass of the object is determined by measuring the displacement amplitude of the absorber mass. In this study, the principles and features of the proposed mass-measurement system are clarified. Experiments are carried out with a developed apparatus having an active dynamic vibration absorber. This apparatus can perform measurement at various rotational speeds because the absorber’s natural frequency can be tuned by a feedback parameter. Experimental results demonstrate the feasibility of the proposed mass-measurement system.

Spring-mass vibration absorber

Abstract: A spring-mass vibration absorber for absorbing vibration in a structure. The vibration absorber comprising a baseplate having a first surface and a second surface, and a plurality of recurved springs connecting the baseplate to the structure. Each of the recurved springs is fixedly connected to the first surface of the baseplate at a baseplate connection point, and fixedly connected to the structure at a structure connection point.

Tuned broadband particulate vibration absorber

Abstract: Broadband particulate absorbers include a suspended container for containing particulate beads that absorb vibration energy over a broad bandwidth so reduce coupled vibrations of mechanical systems over the broad bandwidth. The absorbers preferably include two opposing aluminum containers for containing particulate teflon beads. The aluminum containers are suspended and separated by aluminum I-beams attached to stringers of a rocket subjected during lift off to atmospheric pressure vibrations exerted on the vehicular skin coupling vibration through the stringers to trusses supporting sensitive inertial navigation payloads. The absorbers can be finely tuned using variably thick mass or various amounts of beads for reducing peak vibrations coupled into the payloads.

Optimal design method for multi dynamic absorber

Abstract: In order to improve the robustness of conventional dynamic absorbers, we propose the multi dynamic absorber and its optimum design method. Although the design method for single and dual types of dynamic absorbers has already been established, their vibration control effects are very sensitive to changes of parameters such as the natural frequency of the controlled object and the damping coefficient of the absorber itself. The quadruple and sextuple types of dynamic absorbers designed by the proposed method are demonstrated. They are effective in controlling the vibration of the controlled object under changes of these parameters and maintain stable damping performance.

Anti-rolling device

Abstract: PROBLEM TO BE SOLVED: To change the damping factor of a magnetic damper along the orbit of movable mass in the dynamic vibration absorber type anti-rolling device. SOLUTION: The magnetic damper includes a belt shaped conductive member 30 and permanent magnets 32, and the conductive member 30 is changed in shape along an orbit. For example, the conductive member 30 is changed in width, and the size or density of each hole provided for the conductive member 3O is changed. Furthermore, one out of the two permanent magnets 32 can be relatively moved with respect to the other one. Magnetic fields or magnetic fluxes can be changed by changing the relative position of the two permanent magnets 32, so that damping force can thereby be changed. COPYRIGHT: (C)1998,JPO

Method for compensating a control signal for a shock absorber of a motor vehicle

Abstract: A method is shown for determining an operating temperature of a continuously variable hydraulic shock absorber and compensating a control signal therefore. A solenoid 62 provides continuous variability in the damping level a shock absorber produces. The solenoid includes a coil 70 which may be used to determine the temperature of the hydraulic fluid in the shock absorber. An electronic controller 68 uses the temperature to compensate a desired damping signal to account for temperature variations. This allows the shock absorber to provide consistent damping levels for the vehicle throughout a broad temperature range, thereby improving the noise, vibration and harshness characteristics of the vehicle.

Parallel displacement single axis vibration isolator

Abstract: Disclosed is a vibration isolator which is comprised of parallel flexible beams of rectangular cross sections connected between parallel mounting plates to permit parallel translation of the mounting plates in substantially one parallel direction only thereby permitting the vibration absorber to absorb relative induced motion or vibration in one preferred direction only while retaining relative stiffness for control in the remaining two coordinate directions as well as restraining torsional twist.

Light scanning device

Abstract: A light scanning device includes: a light deflector deflecting and scanning light modulated by an image signal, and a member to which the light deflector is connected, wherein a portion of the member has an elastically deformable portion, a mass body is mounted to the elastically deformable portion, and a dynamic vibration absorber is formed by the elastically deformable portion and the mass body. Vibrations of the light scanning device can be reduced by the dynamic vibration absorber formed by the elastically deformable portion and the mass body. Image imperfections caused by the vibrations can be prevented.

Tunable vibration absorber

Abstract: A vibration absorbing device for a speaker enclosure is tuned upon installation to the speaker enclosure to achieve maximum attenuation of vibrations in a selected frequency range. The vibration absorber, which includes a series of vibration damping plates separated by spacers, is positioned at varying degrees of overhang on a mounting plate on a panel of the enclosure until attenuation of the desired frequency band is maximized. Then the absorber is secured to the speaker enclosure with an appropriately sized permanent mounting plate.

Apparatus and method for proctecting building from earthquakes

Abstract: Building walls are mounted to the frame of a building by using a plurality vibration absorbers, and therefore vibrations to the building are barely transmitted to the walls. The occurrence of cracks and breaks in external walls due to vibrations can be suppressed as much as possible, especially because the second vibration-absorbing material of the vibration absorber which is inserted into the mounting holes of the top and bottom mounting fixtures in the frame, and the first vibration-absorbing material which makes contact with the surface of external walls both have seismic isolation functions against vibrations from all directions such as horizontal, vertical, and diagonal. Secondary injury to persons and damage to objects due to breaks, and falling pieces, in external walls can be reduced. An independent seismic isolation function to each external wall mounted in each space of a frame is created. Therefore, even if an abnormal load is applied to one wall, this abnormal load is not transmitted to other walls.

Development of Antiresonance Enforced Active Vibration Absorber System

Abstract: We propose an antiresonance enforced active vibration absorber system, in which the passive dynamic vibration absorber is weakly damped and tuned to the peak frequency of the vibration of the main mass and the optimally designed active control system with frequency shaped cost functional is added to enforce the antiresonance. This system is a variation of a hybrid vibration absorber but is more effective than the conventional one, particularly when the external exciting force is a harmonic wave or has a sharp peak in the spectrum. By means of a cross-correlation function, the system can automatically tune the antiresonant frequency to the peak frequency, and reduce the vibration effectively even when the peak frequency of the external exciting force changes. Also, we discuss the theoretical analysis of the system, including the digital realization and control stability. Finally, experimental results are given which show the effectiveness of the mechanism.

Golf club head of iron

Abstract: PROBLEM TO BE SOLVED: To improve a ball fitting feel by using a vibration absorber and to prevent the dislodgment of this vibration absorber at the time of preventing the transmission of impact to the elbow at the time of hitting the ball and to prevent the distortion of a head body at the time of hitting the ball. SOLUTION: A reinforcing body 37 is installed between the peripheral edges 33 across the recessed part 35 of the golf club head 41 of the iron formed with the recessed part 35 exclusive the peripheral edges 33 of the back part of a head body made of metal. The vibration absorber 39 is clamped between this reinforcing body 37 and the bottom of the recessed part. The vibration absorber 39 is press bonded between the reinforcing body 37 and the bottom of the recessed part 35 of the golf club head 41.

Time Varying Passive Vibration Absorption for Flexible Structures

Abstract: A time varying extension of the passive vibration absorber is described, which increases the effectiveness of a small number of passive vibration absorbers on large or changing flexible structures. Initially, the extended absorber is targeted on a subset of the modes of the flexible structure. A stable switching scheme is described, which allows the absorber to target different subsets of modes, or to adapt to changes in the flexible structure. Computer simulation and experimental work are given which demonstrate the effectiveness of the extended absorber.

Envelope of green's function for structural response with slightly detuned vibration absorbers

Abstract: Explicit forms of the modal parameters and the envelope of the Green's function for transient response of main structures equipped with vibration absorbers are derived using a perturbation technique and assuming that the natural frequency of the absorber is slightly detuned from that of the main structure Applying these perturbation solutions, the influence of the absorber parameters on the dynamic response of main structures is investigated and the ratio of the envelope for the main mass with absorber to that without absorber is constructed to provide insight to evaluate the effectiveness of the absorber to diminish the vibrations of main structures

H∞ Robust Control of Flexible Beam Vibration by Using a Hybrid Damper

Abstract: A new hybrid damper is proposed to suppress the vibration of a flexible cantilever beam at its free end. It consists of an active piezoelectric-type servo-damper and a passive damped vibration absorber to effectively suppress both the small and large amplitude vibrations. The H∞ control scheme is successfully applied to a laboratory test rig equipped with the hybrid damper when its overhung length is continually changed.

Low noise gear

Abstract: PROBLEM TO BE SOLVED: To lower noise by a simple structure and effectively by providing a plurality of through holes in a rib part formed between a gear part and a boss part of a gear, and holding an inertial unit in these through holes through a vibration absorber consisting of elastic material. SOLUTION: A low noise gear 11 has a ring-shaped gear part 12 in a peripheral part, between this gear part 12 and a cylindrical boss part 13 provided in a center part of this gear part, a rib part 14 connecting the gear part 12 and the boss part 13 is provided. This rib part 14 is formed in a disk shape, in through holes 15... formed with an almost equal space along a peripheral direction of the gear part 12, a cylindrical vibration absorber 16 consisting of elastic material of rubber or the like is respectively provided. In the inside of the vibration absorber 16..., a columnar inertial unit 17 is inserted, also both ends of the through hole 15... are coated with a ring-shaped cover member 18a, 18b consisting of elastic material of rubber or the like bonded to a surface part 14a, 14b of the rib part 14. COPYRIGHT: (C)1997,JPO

Generation Mechanism of Unusual Noise in the Laser-Beam Printer.

Abstract: Based on the investigation of the generation mechanism of the unusual noise generated from a laser-beam printer, it has become clear that self-excited vibration is produced due to the friction between the photosensitive drum and the cleaner blade, and the noise is its vibration noise. The vibration system is that of the tortional vibration of the drum, and the vibration mode is secondary. The self-excited vibration in the secondary vibration mode is caused by the drum structure and the friction force applied to the drum. This drum is made of a thin-walled cylinder having inertia on both ends. The friction force is applied uniformly and axially to the cylinder surface. In this case, the energy can be applied to the tortional vibration of the secondary vibration mode in the drum, and the existence of negative damping friction force results in the generation of the self-excited vibration. Since the vibration frequency is the audio frequency of 10.65kHz, it lies in the audible range. To prevent the vibration and the noise without affecting the function, appropriate and positive damping needs to be applied to the vibration system. Also, the method using friction loss is investigated and verified to evaluate its effect. This method proved to be effective, and it is confirmed that self-excited vibration is discarded, and the generation of unusual noise is completely eliminated. The generation pattern of vibration and noise described in this paper is not limited only to the laser-beam printer. In equipment such as plain paper copiers, liquid crystal printers and so on in which the same mechanical structure is required, the same phenomenon can occur. The cause and the countermeasure described in this paper are expected to be practically useful for development and design.

An Adaptive Fuzzy Control Algorithm for Model-Independent Active Vibration Damping of Flexible Beam-Like Structures

Abstract: The present study deals with an AFCA (Adaptive Fuzzy Control Algorithm) for an Euler-Bemoulli approximation of a two-dimensional version of a cantilever beam-like orthogonal tetrahedral space truss. Transient disturbances, modeled as a unit impulse, excite all the modes of the beam. The resulting transverse displacement at the free end of the beam and its corresponding rate are observed by sensors placed there, and active control of the beam is provided by a collocated force actuator.A design methodology, based on fuzzy logic which assumes no a priori knowledge of plant dynamics, for the closed-loop control algorithm results in relatively quick settling times, low overshoots and dying out of vibration within a few seconds. The control algorithm is enhanced and made much faster by eliminating the need of repeatedly solving the set of differential equations of motion of an emulated dynamic vibration absorber. When the control force is turned off after a mere 15 seconds, almost all the vibrational energy is ...