Showing papers on "Dynamic Vibration Absorber published in 1988"

Theoretical and experimental investigation of space-realizable inertial actuation for passive and active structural control

Abstract: Inertial reaction devices are investigated for use as passive vibration absorbers and active control actuators for flexible space structures. Absorbers are designed for one- and two-degree-of-freedom structural representations using three parameter optimization techniques. All three yield nearly identical designs and indicate that inertial devices should be tuned to the lowest mode intended to receive increased damping. The optimal passive components of the control actuator are found to be those of the optimal passive vibration absorber. Proof-of-concept laboratory tests were performed on a quasi-free-free beam using inertial reaction devices that are space-realizable, i.e., conceptually capable of functioning in the space environment. The inertial devices were used as both passive absorbers and tuned actuators. Damping was significantly increased using both passive and passive/active techniques. Additional tests indicated the benefits and limitations of actuator tuning and the necessity of performing realistic experiments using space-realizable hardware.

Vibration absorbing apparatus

Abstract: A vibration absorbing apparatus for reducing vibrations of a vibration damping objective comprises a vibration member excited by a piezo-ceramic element. The voltage applied to the piezo-ceramic element is controlled in accordance with the vibration state of the objective.

Automatically controlled dynamic absorber

Abstract: An automatically controlled dynamic vibration absorber in which the characteristic frequency of the vibration absorber is adjusted automatically to the frequency of vibration from a vibrating source to dissipate the vibration by mating a response vibration with a forced vibration.

Active Control for Vibration Damping

Abstract: Active control laws are developed for an LSS-type structure to damp vibrations. High frequency modelling uncertainties lead to the necessity for a robust control design. The Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) control design technique is a particular robust design technique selected for use in designing a damping control system. A summary of LQG/LTR is given and numerical example using a two bay truss is presented.

Method and apparatus for countering vibrations of a platform

Abstract: A dynamic vibration absorber for reducing vibrations of a platform induced by an oscillating mass mounted thereon is provided by mounting a mass 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, thereby cancelling the vibrations induced by the oscillating mass. In one embodiment, a signal from the oscillating mass representative of the frequency and amplitude of its mechanical oscillation is phase shifted and utilized 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.

Optimal Control of Random Vibration by the Use of an Active Dynamic Vibration Absorber : Experimental Considerations on the Effect of the Control with Feedforward Link

Abstract: For the vibration control of a main structure subjected to a random input with a dominant frequency, an active dynamic vibration absorber is manufactured, which is equipped with a linear motor as an actuator and is digitally controlled by means of optimal feedback and feedforward links. First, by performing impulse excitation, the usefulness of the optimal feedback control is verified. Second, in the frequency responses obtained from a stationary random excitation, the effectiveness of the optimal feedforward link is demonstrated in comparison with a feedback link only. Further, in a nonstationary random excitation in which the same nonstationary random wave can be realized every time, it is confirmed that the active dynamic vibration absorber is useful also for a nonstationary random input.

An Optimal Active Dynamic Vibration Absorber for Multidegrees-of-Freedom Systems: (A Control Using a Reduced-Order Model and Output Feedback Controls)

Abstract: For the optimal control problem of an active dynamic vibration absorber (active DVA), this paper considers optimal control using a reduced-order model and three kinds of output feedback controls: the acceleration, velocity and displacement feedbacks of a main structure, adding together the displacement and velocity feedbacks of an active DVA. A unified approach for the optimization of the various controls of the active DVA for multidegrees-of-freedom systems is presented by identifying these as an optimization problem with control structure constraints. By carrying out numerical calculations and experiments, the characteristics of those controls were investigated and the usefulness of the present method was demonstrated.

Output Regulation in Active Dynamic Vibration Absorber Systems

Abstract: An output regulation problem of an active dynamic vibration absorber system is considered, where the object is to reject completely the effects of a sinusoidally varying external force on the main mass by manipulating the motion of a auxiliary mass in an absorber attached to the main mass. The theory of output regulation with internal stability is applied in designing the control system of an active dynamic absorber system which consists of a main mass to be regulated, an auxiliary mass generating inertial reaction, an actuator driving the auxiliary mass and sensors detecting the diplacements of the masses. A new control method is presented which is enable to remove completely the vibration of the main mass at a particular frequency and to attenuate well the vibration in a wide range of frequency as well. Moreover the obtained condition of output regulation includes the tuning condition of a passive vibration absorber without damping as a special case; that is to say, at the natural frequency of the absorber the vibration of the main mass is completely removed automatically. The effectiveness of the control method is confirmed by numerical simulation and analysis of the frequency characteristics of the designed control system.

Powder vibration absorber

Abstract: PURPOSE:To perform the braking and vibration absorption of a piston shaft linearly or rotatively moving by utilizing the phenomenon that while such object as a piston or the like moves in powder whose mobility is restricted by a cylinder or the like, the kinetic energy is absorbed. CONSTITUTION:A cylinder 2 is crammed with powder 1 which a piston 3 is placed therein. For the powder used, dried silica sand is suitable, and the specifying of the shape, quality of material, liquid content ratio, and particle diameter is not required. In case of silica sand, a particle diameter in the range of from several meshes to several hundreds meshes is suitable. When a piston rod 4 moves linearly and reciprocatively, the piston 3 directly connected to the piston rod 4 is subject to pressure drag. And the frictional force (mainly frictional drag) generated in the flow motion of the powder 1 in the space between the piston 3 and a cylinder wall is given to the piston rod 4. Therefore, since the kinetic energy of the piston rod 4 is absorbed, the effects of the braking and absorption of the vibration of the rod 4 is remarkable.

Feed screw device

Abstract: PURPOSE: To eliminate the possibility of a device being broken, to increase the speed and to make the device tall and stout by providing two vibration absorbers on the outside diameter portion of a feed screw in such a manner as to move, and screw-engaging a nut integral with a fed driven material with the feed screw between the vibration absorbers. CONSTITUTION: When a feed screw 22 is rotated, a nut 31 is fed and moved on the feed screw 22 until it contacts one vibration absorber 38b, and meanwhile, vibration generated in the feed screw 22 is absorbed by both vibration absorbers 38a, 38b. When the nut 31 is further moved on the feed screw 21, the forward end vibration absorber 38b is pushed by the nut 31 to be moved on the feed screw 22, and the base end vibration absorber 38a connected to the forward end vibration absorber 38b is also moved on the feed screw 22 in such a manner as to be pulled by the forward end vibration absorber 38b. As two vibration absorbers 38a, 38b follow up the movement of the nut 31, the vibration of the feed screw 22 caused by the movement of the nut 31 can be absorbed. COPYRIGHT: (C)1990,JPO&Japio

Vibration control in a tower structure by a two-dimensional active mass damper with an LQ control system.

Abstract: This paper proposes a two-dimensional active mass damper which is controlled by a software servo system in order to reduce the vibration of tower structures caused by strong winds or earthquake. The purpose of the two-dimensional active mass damper is to control effectively the two-dimensional 1st vibration modes of the structure. In designing the software servo system, LQ control theory is applied. The results of experirental examination on the design show that although the 1st vibration modes are well controlled, a resonance peak at the 2nd mode increases as a resonance peak at the 1st mode is decreased and runs into spillover instability. It is also shown that the spillover instability can be prevented easily by a dynamic absorber attached at the maximum amplitude point on the 2nd vibration mode.

Vibration absorber for vehicles

Abstract: A vibration absorber for vehicles consists of a receptacle which at one end has a guide and a seal for a piston rod 4 and a closure or stop cap 5. A retainer 6 welded to the cap 5 supports a member 7 which in use engages a buffer 25 to limit the return travel of the piston rod 4. Preferably the member 7 is of plastics and has a snap fit with the retainer 6, thus allowing members 7 of differing axial length to be used. In an alternative embodiment (Fig. 4) the stop cap and member form a single unit.

Adjustable vibration damper

Abstract: An adjustable vibration absorber for motor vehicles has a damping piston (5) axially movable and sealed in a damping cylinder. The damping piston (5) divides the damping cylinder filled with a damping medium into two working chambers (2, 2a) mutually linked by at least one first uncontrolled valve (8) and at least one second controllable valve (6) that have a parallel hydraulic action with respect to each other. In order to allow the effective damping power to be continuously controlled in wide ranges, at a relatively low cost, the controllable valve (6) is opened and closed in quick sucession according to timed control signals, thus regulating the damping resistance.

Adjustable vibration absorber

Abstract: An adjustable vibration absorber for motor vehicles has a damping piston (5) axially movable and sealed in a damping cylinder. The damping piston (5) divides the damping cylinder filled with a damping medium into two working chambers (2, 2a) mutually linked by at least one first uncontrolled valve (8) and at least one second controllable valve (6) that have a parallel hydraulic action with respect to each other. In order to allow the effective damping power to be continuously controlled in wide ranges, at a relatively low cost, the controllable valve (6) is opened and closed in quick sucession according to timed control signals, thus regulating the damping resistance.

코일스프링과 오일댐퍼를 가지는 동흡진기의 특성에 관한 연구

Abstract: A study on the dynamic vibration absorber with coil spring and oil damper was carried out both theoretically and experimentally. A main mass is attached to a foundation using coil spring and oil damper. A harmonic motion was applied to the foundation. The effects of the dynamic vibration absorber are theoretically summarized in graphs, and tested on a vibratory model for the isolation of actual mechanical vibration. As a result, the first resonance amplitude ratio increased and the second resonance amplitude ratio decreased as the absorber spring constant increased. When the absorber mass increase, the first resonance amplitude ratio is decreased and the second resonance amplitude ratio is increased.

Optimal Dynamic Vibration Absorber for Multi-Degree-of-Freedom Systems (Theoretical Considerations on the Case of Random Input)

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

Manufacture of vibration-absorbing base

Abstract: PURPOSE:To obtain a vibration-absorbing base having a great vibration- regulating property and having a high durability by a method in which a nonmetal or vibration absorber having a great specific damping function is buried in recessions formed in a cast iron or steel piece and covered with an other cast iron or steel piece. CONSTITUTION:One or many recessions 2 are formed in a cast iron or steel piece 1 and paced with a nonmetal substance 3 or/and a vibration absorber 4 having a great specific damping function. The cast iron or steel piece 1 is covered with an other cast iron or steel piece 5 to prevent the leak of the substance buried to the outside. The vibration-absorbing base suitable for even environments where oil and fine powdery dust are present, such as the base of machine, can thus be obtained.

Control device for dynamic vibration absorber

Abstract: PURPOSE:To obtain a vibration suppressing effect with a high degree of accuracy, by calculating a variation rate of rotational speed of a main engine, and by adding thus calculated value to a speed detection signal from the main engine to control the speed of a motor in accordance with the deviation value between thus added speed detection signal from the engine and a speed signal from the motor. CONSTITUTION:Even though the rotational speed of a main engine 10 is slightly changed, the variation rate is added to a speed detection signal from the main engine 10, and therefore, the value of the signal is such that the rotation speed of the main engine 10 is as if changed greatly. As a result, the deviation between the speed detection signal from the main engine 10 and a speed signal from a motor 5 becomes larger, and therefore, the followability of the motor 5 may be enhanced with respect to even a small change in the rotation of the main engine 10. Accordingly, it is possible to obtain a vibration suppressing effect with a high degree of accuracy.

変位で加振される動吸振器系におけるクーロン摩擦の影響 : 第3報,主系,吸振器双方にクーロン摩擦を伴う場合

Abstract: Behavior of a dynamic vibration absorber system with combined viscous and Coulomb friction both in the main system and in the absorber is investigated. In this case, the main system is subjected to harmonic base excitation. The solution for the non-stop steady motion is deduced from the equation of motion refering to the half cycle of relative motion between the main mass and the base by means of the boundary condition method. The numerical results of analytical solution coincide very well with those of digital simulation. A set of empirical formulae for calculating the optimum tuning and damping of the absorber, constructed by composing and correcting the formulae given in the previous reports, are prsented.