Showing papers on "Dynamic Vibration Absorber published in 1989"

On the response of the non-linear vibration absorber

Abstract: The steady state vibrations of a non-linear dynamic vibration absorber are studied using the method of multiple scales, in conjunction with digital simulations. The main results are concerned with certain dynamic instabilities which can occur if the absorber is designed such that the desired operating frequency is approximately the mean of the two linearized natural frequencies of the system. A combination resonance can occur in this case, resulting in large amplitude almost-periodic vibrations. This motion destroys the effectiveness of the absorber and can coexist with the desired low-amplitude periodic response, which leads to initial condition dependent dynamics.

Optimal dynamic vibration absorber for multi-degree-of-freedom systems. (Theoretical consideration in the case of random input).

Abstract: This study deals with the optimization problem of a dynamic vibration absorber (DVA) for multi-degree-of-freedom systems subjected to random input with a dominant frequency. A new design method, which optimizes the parameter of DVA composed of such passive elements as a spring and a damper, is proposed. In this method, a suboptimization method based on the optimal control theory is applied for the optimization problem with control structure constraints due to passive elements. This method can consider the input information and the constraints on the stroke of DVAs. The vibration control performance of this method is investigated and is compared with the previous method, in numerical calculations. As a result, the usefulness of the present method is verified.

Spring suspension of a motor vehicle wheel

Abstract: Wheel suspensions are known in which the body oscillations and the comparatively higher wheel oscillations are damped separately from one another, that is by a hydraulic telescopic shock absorber, arranged between wheel carrier (stub axle) and vehicle body, on the one hand, which shock absorber is preferably part of a spring strut, and by a vibration absorber on the other. The new wheel suspension is intended to allow such a combination of conventional telescopic shock absorber and vibration absorber to be also used in modern spring strut or damper strut axles, in which the spaces close to the centre of gravity of the unsprung masses, that is the wheels, are generally very restricted. In order to obtain an especially compact, space-saving construction, the vibration absorber is fixed on the damper or cylinder tube of the telescopic shock absorber in such a way that its absorber mass encloses at least a part of the shock absorber tube circumference with clearance.

Method and apparatus for cancelling vibrations

Abstract: A dynamic vibration absorber for reducing vibrations of a platform (19) induced by an oscillating mass (17) mounted thereon is provided by mounting a mass (12) of equal mechanical resonant frequency as that of the oscillating mass and oscillating this mass in a manner to establish an equal and opposite vibration of the platform (19), thereby cancelling the vibrations induced by the oscillating mass (17). In one embodiment, a signal from the oscillating mass (12) representative of the frequency and amplitude of its mechanical oscillation is phase shifted and utilised as a driving signal to the drive motor of the absorber mass. In another embodiment, electrical signals representative of the platform vibra­tions are detected to provide phase and amplitude vibra­tion error signals. These error signals are applied to a reference signal coupled to the drive motor of the canceller mass causing the oscillations of the canceller mass to induce vibrations in the platform which counter the vibrations induced by the oscillating mass.

Development of a Centrifugal Pendulum Absorber for Reducing Ship Superstructure Vibration

Abstract: A vibration absorber (designated as the Super Dynamic Damper) for installation on ship superstructures, based on a tuned centrifugal pendulum concept, was developed through theoretical analyses followed by tests on units mounted on a vibrating platform and on actual ships. The tests confirmed the analytically estimated performance, and demonstrated that the vibrating amplitude would be reduced, to limit it to a constant low level independent of imparted exciting force. Results of analysis indicate the most important quality demanded of a tuned absorber to be the tuning accuracy. The tolerance permissible for the tuning accuracy is determined by the mass ratio: A smaller mass ratio calls for correspondingly higher tuning accuracy. The centrifugal pendulums are governed by Coulomb damping, which results in a damping behavior distinct from normal viscous damping. Both analysis and measurements attested to the importance of accurately controlling the absorber rotating speed, short of which the absorber risked becoming a vibration amplifier.

Optimal Active Dynamic Vibration Absorber for Multi-Degree-of-Freedom Systems (Feedback and Feedforward Control Using a Kalman Filter)

Abstract: This study presents a feedforward control design method of an active dynamic vibration absorber for multi-degree-of-freedom systems. The feedforward control, obtained by assuming that the shaping filter possesses the same natural frequency as primary structure in the frequency range of input disturbance. Furthermore, to improve reliability, a digital control system consisting of a reduced order feedback control and the feedforward control, using kalman filter, is synthesized. By carrying out numerical calculations and experiments, it is demonstrated that active DVA, which is optimized by the present design method, is useful for not only stationary random inputs but also nonstationary random inputs.

Vibration Reduction of a Railway Wheel by Cantilever-Type Dynamic Absorbers : Optimal Adjustment of Absorbers and Experiment

Abstract: In this paper, the optimal tuning of the natural frequency and the optimal damping parameter of a cantilever-type dynamic vibration absorber attached to a railway wheel are derived. An index, the equivalent mass ratio, with which the effectiveness of absorbers can be estimated and evaluated easily, is defined. It is found that the cantilever-type absorber can be more effective than the conventional mass-spring absorber. When N absorbers are attached to a wheel and N/2 is different form the number of nodal diameters, the effectiveness of the vibration reduction does not decrease, even though the wheel is rotating.

Rubber-based vibration absorber and antiearthquake absorber structure

Abstract: The absorber consists at least partially of a very slightly crosslinked rubber formed by crosslinking a rubber mix in which a crosslinking agent has been incorporated in a proportion ranging from 1 to 70 % by weight of the minimum proportion of crosslinking agent in common practice, the very slightly crosslinked rubber having a hysteresis ratio h50 of 0.25 and higher, measured for a tensile deformation of 50 % at 25 DEG C. Absorber structure in which the absorber 30 is placed in the centre of the antiearthquake rubber support made up of rigid layers 21 and of flexible layers 22, and the whole structure is maintained between the upper and lower plates 23.

Vibration control in piping system by dual dynamic absorber. 3-Dimensional vibration analysis and absorber design using transfer matrix method.

Abstract: This paper deals with the application of dual dynamic absorbers to nuclear piping systems to accomplish a high damping value and reduce seismic response at resonance frequencies. The transfer matrix method is used for design of the dual dynamic absorbers as well as for determination of the optimum mounting location. The effectiveness of the dynamic absorber is demonstrated by suppressing the first three resonance peaks in the 3-dimensional model piping system.

Mounting device encapsulated with electric viscous fluid

Abstract: PURPOSE:To meet required characteristics by coupling and supporting a pair of electrodes respectively to/on first and second supporting members and placing an elastic rubber coupling body at a joint to an electrode on at least one supporting member at vibration input side CONSTITUTION:A first electrode 36 is fixed through an elastic rubber coupling body 68 to an upper side supporting metal 10 at vibration input side to constitute a sub-vibration system (vibration absorber) for the supporting metal 10 In other word, the electrode 36 constitute a mass member together with fixing metals 62, 64 and a guide tube 50 so as to constitute a vibration system where the elastic rubber coupling body 68 is employed as a spring and fixed to the upper side supporting metal 10 When inherent vibration in expanding/shrinking direction of the elastic rubber body 68 is tuned to a vibration frequency zone desired for isolation of vibration, vibration in a specific frequency zone in the direction of mounting shaft can be absorbed and suppressed effectively through such dynamic vibration absorber

Ultrasonic motor and manufacture thereof

Abstract: PURPOSE:To suppress the generation of an audible sound by composing a vibration absorber layer between a moving element and a frictional material. CONSTITUTION:The vibrator of an ultrasonic motor is formed by adhering fixedly a vibrating element 2 of resilient material, such as metal or the like to the surface of a piezoelectric element 1. The moving element of the vibrator is formed by securing a frictional material 4 made of engineering plastic to the surface of a moving element 3 as a body through a vibration absorber layer 5, and bringing the surface of the material 4 into pressure contact with the surface of the element 2. Thus, a high frequency electric field of a resonance frequency is applied to the element 1 to generate a traveling wave of ultrasonic wave vibration at the elements 1 and 2. In this case, the moving element made of the material 4, the layer 5 and the element 3 in contact with each other at the traveling wave head of the element 2 is integrally driven by the frictional force with the element 2. An unnecessary vibration generated at the material 4 is absorbed by the layer 5, thereby suppressing the generation of an audible sound.

Vibration control mechanism for vibration equipment

Abstract: PURPOSE:To substitute vibration of a mass material for shock and vibration at the time of working by forming a hollow section in a part of a base section or a handle section of a vibration equipment, separating the same from a partition constituting the hollow section and providing a given mass material therein. CONSTITUTION:Part of a core cylindrical shaft 4 is formed as a hollow section 41, in which a mass material 5 is provided. A piano wire 6 is overhung with a cantilever from one side to the other against the center of the core cylindrical shaft, and a base of the piano wire 6 is fixed to the core cylindrical shaft at its root, while the piano wire 6 runs through the mass material 5 which is supported by the piano wire 6. A gellike material 7 is disposed cylindrically in a manner that the same surrounds said mass material 5 and the other side of the same is in contact with the inner side wall of the cylindrical shaft. Shocks and vibration waves from the base section 1 are transmitted to the mass material 5 through the piano wire 6. When the weight of the mass material 5, the spring constant of the music piano 6, damping force generated by the gellike material 7 and the like at that time match with the weight of a vibration equipment and a handle section and the like and inherent vibration numbers and the like, the vibration of the mass material 5 transmitting to human body is minimized by the action of the constitution in the hollow section 41 of the core cylindrical shaft 4 in which the mass material 5 is provided working as a dynamic vibration absorber.

Variable stabilizing device linked with plural parts of vibration absorbers

Abstract: PURPOSE:To enable the control of rolling rigidity and the control of the height of a vehicle by providing vibration absorbers in parallel so as to be interlockedly expanded/contracted together with wheel suspending springs and linking fluid pressurizing reserve tanks to the vibration absorbers respectively. CONSTITUTION:Vibration absorbers 1-4 are installed in parallel so as to be interlockedly expanded/contracted together with wheel suspension springs. And, a fluid pressurizing reserve tank 5 is linked to a pipe between lower liquid chamber of the vibration absorber 1 and the upper liquid chamber of the vibration absorber 2. Similarly, other fluid pressurizing reserve tanks 6-8 are liked to the pipes between the vibration absorbers 1-4 respectively, while the air chambers 16-16c of the tanks 5-8 are linked to compressor-cum-air pressure regulator devices via solenoid valves 9, respectively. Thereby, the control of height can be performed by varying the pressure of the air chambers. Also, by increasing the pressure of the air chambers, interaction between each suspension device can be made higher preventing the rolling of a vehicle body.

Elastomer-spring shock absorber

Abstract: The elastomer-spring shock absorber for which a patent has been applied for is intended, in particular, for vehicles with a high vibration level, because the spring system and damping system form a single unit and the piston rod is the only moving part. The spring force and the damping are provided by the compressible fluid elastomer.

Electric hammer with frequency following damping system

Abstract: The utility model relates to an electric hammer with a frequency following system. The utility model is used for the electric drill hole in the building engineering of houses, bridges, culverts, mines, etc. The common electric hammer is additionally provided with a frequency following damping system. The fundamental frequency of the vibration absorber automatically regulates along the working objects and the different sizes of the load application. The utility model effectively eliminates the vibration of the machine body of the electric hammer, improves the labor condition of the worker, and improves the operation service life of the electric hammer.

Oil-filled electric apparatus

Abstract: PURPOSE:To absorb vibration by the elastic face of a vibration absorber for an oil-filled electric device and to reduce the transmission of the vibration from insulating oil to an outer box by providing the absorber inside the box CONSTITUTION:A vibration absorber made of synthetic resin such as synthetic rubber or the like is so mounted over the whole periphery of the inner wall of an outer box 1 as not to transmit the dynamic pressure of insulating oil 5 due to the vibration of a device body 4 Thus, when the dynamic pressure of the oil 5 due to the vibration of the body 4 is transmitted to a vibration absorber 9, numerous small bubbles 10 are respectively contracted to absorb the dynamic pressure thereby to reduce the transmission of the oil 5 to the box 1, thereby decreasing vibration and noise to the periphery of the box 1 Since the absorber 9 has high strength and flexibility, even if the box 1 becomes vacuum, its shape is constant, the bubbles 10 are not damaged, and it can prevent a large quantity of gas from being discharged to the oil 5 even when pinholes are generated in the absorber 9 due to its ageing deterioration

Control of a flexible planar truss using proof mass actuators

Abstract: A flexible structure was modeled and actively controlled by using a single space realizable linear proof mass actuator. The NASA/UVA/UB actuator was attached to a flexible planar truss structure at an optimal location and it was considered as both passive and active device. The placement of the actuator was specified by examining the eigenvalues of the modified model that included the actuator dynamics, and the frequency response functions of the modified system. The electronic stiffness of the actuator was specified, such that the proof mass actuator system was tuned to the fourth structural mode of the truss by using traditional vibration absorber design. The active control law was limited to velocity feedback by integrating of the signals of two accelerometers attached to the structure. The two lower modes of the closed-loop structure were placed further in the LHS of the complex plane. The theoretically predicted passive and active control law was experimentally verified.

Vibration attenuator for rotary compressor

Abstract: PURPOSE:To sufficiently attenuate each vibration component by setting an installation position of a dynamic vibration absorber at a position not on a rotating body where difference in phases of respective vibration components in a radial direction and a rotating direction in a compressor is + or -90 deg. or less. CONSTITUTION:When coolant is compressed in a cylinder 7, a pressure in a compression chamber fluctuates as well as a fluctuation in an angle speed occurs in a rotation of a crank shaft 5, so that a sealed case 2 is vibrated. In this case an inertial body 21 and a tightening fixing part of a dynamic vibration absorber 20 placed in the sealed case 2 vibrate in reverse phases to a vibration and a reverse vibration of the sealed case 2 and reacting torque is applied to the sealed case 2 via a coupling 22 and a fixing jig 23 so that the vibration of the sealed case 2 is attenuated. Since a fixing position of the fixing jig 23 is specified to a position where a vibration in a rotation direction being main vibration is in the same phase as a vibration in a radial direction being sub vibration, the vibration in the radial direction can be attenuated as well as the vibration in the rotation direction.