Showing papers on "Dynamic Vibration Absorber published in 1983"

Free and Forced Vibrations of Elastically Connected Double-beam Systems

Abstract: The free vibrations and forced vibrations of a system comprising two elastically-connected parallel upper and lower beams having unequal masses and unequal flexible rigidities are analysed using a generalised method of finite integral transformation and the Laplace transformation. The natural frequencies and the amplitude ratios for the normal modes of vibration are presented; it is also shown that a system comprising a lower beam and coupling springs can be used as a dynamic vibration absorber to reduce the vibrations of an upper beam that is subjected to a periodic force.

Vibration studies of a lightweight three-sided membrane suitable for space application

Abstract: Vibration studies carried out in a vacuum chamber are reported for a three-sided membrane with inwardly curved edges Uniform tension was transmitted by thin steel cables encased in the edges Variation of ambient air pressure from atmospheric to near vacuum resulted in increased response frequencies and amplitudes The first few vibration modes measured in a near vacuum are shown to be predictable by a finite element structural analysis over a range of applied tension loads The complicated vibration mode behavior observed during tests at various air pressures is studied analytically with a nonstructural effective air-mass approximation The membrane structure is a candidate for reflective surfaces in space antennas

Optimal design of a passive vibration absorber for a truss beam

Abstract: The selection of the design parameters of passive vibration absorbers attached to a long cantilevered beam is studied. This study was motivated by the need for conducting parametric analysis of dynamics and control for Space-Shuttle-attached long beams. An optimization scheme using a quadratic cost function is introduced yielding the optimal sizing of the tip vibration absorber. Analytical solutions for an optimal absorber are presented for the case of one beam vibrational mode coupled with the absorber dynamics, and results are extended to cover the multiple mode case. An algorithm is developed to make an initial estimate of optimal tuning parameters which minimize the quadratic error cost function. Examples are given to illustrate the design concept.

Dynamic vibration absorber

Abstract: PURPOSE:To absorb vibrations of an oscillating member at frequencies around the frequency intended to damp by furnishing an arm to couple the dynamic vibration absorber body with a weight, an arm deforming means, an oscillating member acceleration sensing means, a weight acceleration sensing means and a controller for said arm deforming means, and thereby seizing accurately the desired frequency even though vibrations of the oscillator range in a wide extent CONSTITUTION:A motor 5 is furnished in the case 1 of a dynamic vibration absorber installed on an oscillating member 8, to shift a lever 10 through a pinion 6, wherein a weight 9 is fixed to the lever 10 An oscillating member acceleration sensor 12 is fixed to the specified surface of said case 1 of dynamic vibration absorber, while a weight acceleration sensor 13 is fixed to the weight 9 These sensors shall sense accurately the vibratory acceleration of the oscillating member 8 and dynamic vibration absorber, and the position of weight 9 is controlled so that the phase difference between the two measurements will lie within a certain specified extent Thereby vibration of the oscillating member 9 can be absorbed at a specific frequency even though the spectrum of vibrations of the member 8 has varied

Antivibration device of electrically-operated enclosed compressor

Abstract: PURPOSE:To enable to miniaturize the compressor and at the same time reduce the vibration and noise thereof by a structure wherein leg parts fixed to the bottom part of the compression main body are supported by elastic vibration insulators and at the same time dynamic vibration absorbers comprising supporting a weight by means of an elastic support fixed onto the leg part are provided. CONSTITUTION:The compressor is rotated at a rotational frequency a little lower than the frequency of power source and large vibration is excited at said frequency. However, because the dynamic vibration absorbers 5, the primary natural resonance frequency of which is made coincide with the rotational frequency of the compressor or the frequency of power source, are installed at the leg parts 2, the dynamic vibration absorbers 5 vibrate with a phase opposite to the vibration of the compressor. Accordingly, the dynamic vibration absorbers 5 supply reaction torques to the compressor main body 1 at the installation positions of the leg parts 2 through the elastic supports 5b and the leg parts 2. As a result, the torque due to the vibration of the compressor and the torque supplied by the dynamic vibration absorber 5 deaden each other, resulting in effectively reducing the overall vibration of the compressor.

Promoting device for engine fuel vaporization

Abstract: PURPOSE:To improve fuel atomization efficiency, in a carburetor, by a sytem in which the fuel pipe supported by a vibration absorber is installed downstream from the carburetor, while the fuel pipe is vibrated by a supersonic resonator, and fuel is atomized through a porous metal plate mounted to the tip of the fuel pipe. CONSTITUTION:The porous metal plate 4 mounted to the tip of the fuel atomization nozzle 1 is supported by the vibration transmission pipe 6. The vibration transmission pipe 6 accommodates the supersonic resonator 5 to be contained in the box-type vibration absorber 8. Therefore, supersonic vibrations are prevented from being transmitted to the air-inlet manifold 10. The fuel led through the fuel pipe 7 is subjected to strong vibrations at the time of passing the porous metal plate 4 to be atomized effectively.

Vibration suppression in large space structures

Abstract: The problem of potential instability caused by actuator dynamics is examined. Two ways of overcoming it are discussed: rate feedback with compensation and position feedback with tuning filters.

Dynamics of Coupled Fluid-Structure Multiplate Systems

Abstract: A general formulation, for the study of free vibrations and frequency response of a multiplate system fully submerged in fluid contained in an enclosure, has been presented. Although the analytical formulation is suitable for a system consisting of any number of plates submerged in fluid, the present study has been carried out for two-plate systems only. The response of the system is analytically studied when a disturbing force acts on the system through one of the walls of the enclosure in the form of a harmonic wall acceleration. It has been found that the two-plate vibrating system submerged in fluid behaves like a coupled or uncoupled system, depending on the distance between the plates. The fluid coupling effect depends upon the relative positions of plates and walls. It is also observed that the response curves of the two-plate submerged system exhibit the dynamic vibration absorber effect.

Variable stabilizer including plural pairs of vibration absorbers coupled to each other

Abstract: PURPOSE:To enable the adjustment of the height of a vehicle and its rolling rigidity, by juxtaposing pairs of hydraulic cylinders as vibration absorbers alongside wheel suspension springs and coupling the upper and lower chambers of the cylinders to each other through fluid pressurizing reserve tanks connected to a compressor and air pressure adjuster CONSTITUTION:When a vibration absorber 1 is compressed, liquid 17 in its lower liquid chamber 14 moves to the upper liquid chamber 13A of another vibration absorber 2 so that it is also compressed Under similar action, the vibration absorbers 1, 2 are elongated simultaneously Another pair of vibration absorbers 3, 4 also function in the same mannr As a result, the height of a vehicle is adjusted When a compressor and air pressure adjuster interlocked with solenoid valves 9 is operated to make the pressure of air chambers 5, 7 of fluid pressurizing reserve tanks 5, 7 higher than that of air chambers 16A, 16C of other reserve tanks 6, 8, the liquid of liquid chambers 15, 15B compresses the vibration absorbers 1, 3 and elongates the other absorbers 2, 4 to adjust the rolling rigidity of the vehicle Such a variable stabilizer is provided alongside wheel suspension springs to adjust the height and rolling rigidity of the vehicle

Vibration attenuator for rotary enclosed motor compressor

Abstract: PURPOSE:To reduce the vibration in all direction of a compressor by cancelling the torque due to the vibration of the compressor and the counter-torque from a dynamic vibration absorber CONSTITUTION:In order to match with the rotary frequency of the compressor or the power source frequency, the dynamic vibration absorbers 4, 5 arranged in an enclosed container 1 will vibrate with the vibration of the compressor and the reverse phase Consequently the torque due to the vibration of the compressor and the counter-action torque to be fed from the dynamic vibration absorbers 4, 5 are cancelled to provided the nod of the vibration, thereby each dynamic vibration absorbers 4, 5 will form the nod of vibration at two different points of the compressor thus to reduce the vibration in all directions of the compressor

Vibration absorber for pipe

Abstract: PURPOSE:To provide a vibration absorber of simple structure and low cost for the pipe of a power plant or the like, by using a buffer material to absorb small vibration and by using the frictional resistance to oil to absorb large vibration. CONSTITUTION:An outer pipe 2 is provided around a pipe 1 concentrically thereto. A buffer material 8 for absorbing vibration energy is provided between the pipes 1, 2. The annular inside opening of the outer pipe 2 is divided by annular plates 3 into a plurality of small chambers 4 juxtaposed in the axial direction. Each small chamber 4 is divided into smaller chambers of sectorial cross section by a plurality of plates 5 distributed in the circumferential direction and extending radially. Oil 6 is provided in each smaller chamber so that the volume of the oil is less than that of the chamber. Small vibration is absorbed by the buffer material 8, while large vibration is absorbed by the frictional resistance to the motion of the oil 6.

Development of monofilar rotor hub vibration absorber

Abstract: A design and ground test program was conducted to study the performance of the monofilar absorber for vibration reduction on a four-bladed helicopter. A monofilar is a centrifugal tuned two degree-of-freedom rotor hub absorber that provides force attenuation at two frequencies using the same dynamic mass. Linear and non-linear analyses of the coupled monofilar/airframe system were developed to study tuning and attenuation characteristics. Based on the analysis, a design was fabricated and impact bench tests verified the calculated non-rotating natural frequencies and mode shapes. Performance characteristics were measured using a rotating absorber test facility. These tests showed significant attenuation of fixed-system 4P hub motions due to 3P inplane rotating-system hub forces. In addition, detuning effects of the 3P monofilar modal response were small due to the nonlinearities and tuning pin slippage. However, attenuation of 4P hub motions due to 5P inplane hub forces was poor. The performance of the 5P monofilar modal response was degraded by torsional motion of the dynamic mass relative to the support arm which resulted in binding of the dynamic components. Analytical design studies were performed to evaluate this torsional motion problem. An alternative design is proposed which may alleviate the torsional motion of the dynamic mass.

A Study on the Torsional Dynamic Vibration Absorber Consisting of Rare-earth Magnets

Abstract: A new torsional dynamic vibration absorber is proposed, consisting of a circular conducting plate and four cylindrical rare-earth magnets of which magnetic energy is extremely strong, and its absorbing characteristics is investigated experimentally and theoretically. First, the magnetic torsional stiffness between two magnets is analyzed theoretically, and the magnetic damping characteristics by the relative motion between the magnets and the conductor is investigated experimentally. Second, a solution of the steady-state vibration response is derived from the equation of motion with the term of the nonlinear magnetic torsional force, and the criterion of its stability is obtained. Subsequently, the experimental results about the optimum absorbing effect are presented.

Flat phonograph tone arm

Abstract: Flat tone arm (1) for phonographs with a stylus holder (C) includes an arrangement for adjustment of the vertical tracking force on the stylus and with a dynamic vibration absorber, the frequency and damping factor of which is adjustable, which tone arm is yieldable solely in the vertical direction and is provided with openings (11) for fastening and making accessible different operating elements of the phonograph and with electrically conductive connections (13, 14) between the stylus holder and the phonograph.

Positioning mechanism for rotary magnetic head of magnetic disk device

Abstract: PURPOSE:To ensure the positioning with high accuracy, by attaching a dynamic vibration absorber to a shaft and suppressing the vibration of a shaft magnetic head. CONSTITUTION:A dynamic vibration absorber 11 is attached to a shaft 2 to suppress the resonance. This absorber 11 contains a weight 12 and a viscoelastic matter 13. The resonance frequency of the absorber 11 is approximately coincident with that of the shaft 2. When the shaft 2 has resonance, the weight 12 has resonance with a larger amplitude to absorb the vibrating energy of the shaft 2. Thus the vibration of the shaft 2 is suppressed. This reduces the vibration of a magnetic head 7 to ensure the positioning with high accuracy.

Vibration absorber for enclosed rotary compressor

Abstract: PURPOSE:To provide effective vibrating absorbing effect by arranging a mounting frame formed in U-shaped opposed surface with through holes on the outer wall of an enclosed rotary compressor and mounting a wieght removable on the mounting frame through supports made of elastic material. CONSTITUTION:On the outer wall of an enclosed container 1 is fixedly mounted a mounting frame 11 formed in the generally U-shaped surfaces with through holes 12, 12 in which is removably mounted a weight 13 through supports 14, 14 of elastomer such as hard rubber. The mass of said weight 13 and the spring constant of supports 14, 14 are selected such that the characteristic frequency of vibration absorber in the rotational direction of an enclosed rotary compressor is approximately equal to the rotational frequency of the compressor. And by driving a motor is vibrated the vibration absorber in response to the produced vibration to reduce the vibration of the compressor. Since these supports 14 is of elastomer, they are strong against shock and further removably attached so that the size of packaged comressor and the volume in a transport truck which is occupied by this compressor can be reduced.

Subspan oscillation and aeolian vibration absorber for single and bundle conductors

Abstract: In a vibration absorber for use with aerially suspended conductors and cables, there is described an improved vibration absorber wherein wind or turbulence induced vibrations resulting in travelling waves on conductors cables are absorbed so as to prevent damage to or failure of conductors and related hardware due to fatigue. Known devices, particularly dampers and spacer dampers, attempt to control merely the amplitude of the waves produced on the conductor and are therefore ineffective in preventing the formation of such waves and the damage that may result. In this invention, a vibration absorber comprising a piston and cylinder device whereby a travelling wave displaces the piston or the cylinder relative to one another causing a fluid contained within the cylinder to be displaced through an orifice in the piston. The absorbing system thus defined has a mechanical dissipative impedance of value R to inhibit the reflection of a wave propagated on the conductor whereby the wave is absorbed. The value of R is in the range of to where T is the tension of the conductor and M is the mass of the conductor per unit length.

Vibration absorber for elevator

Abstract: PURPOSE: To make the vertical spring constant of rubber variable so as to facilitate adjustment of vibration absorbing frequency by forming a dynamic vibration absorber composed of elastic body rubber and a weight, into rotatable fitting structure with respect to a horizontal axis. CONSTITUTION: This dynamic vibration absorber is so constituted that both side faces of a weight 7 are held by rubber 8. The dynamic vibration absorber is fitted to a bracket, and the bracket 9 is fitted to a fitting plate 5 by a fitting bolt 10 rotatably to a horizontal axis. The horizontal spring constant of the rubber 8 is considerably smaller than the vertical spring constant. When the bracket 9 is rotated around the fitting bolt 10, the vertical combined spring constant of the rubber is changed to adjust vibration absorbing frequency easily and continuously.