Showing papers on "Active vibration control published in 1978"
TL;DR: In this article, a vibration insulation device for a handle of a vibratory machine is described, which is characterized by a spring K adapted to be displaced in the direction of unidirectional vibration transmitted to the handle, and a dynamic vibration absorber consisting of a cantilevered spring Kd, a magnetic damper and a conductive weight plate md provided in the section m to be insulated.
Abstract: A vibration insulation device for a handle of vibratory machine, which is characterized by comprising: a spring K adapted to be displaced in the direction of unidirectional vibration transmitted to the handle, and a dynamic vibration absorber consisting of a cantilevered spring Kd, a magnetic damper cd and a conductive weight plate md provided in the section m to be insulated. In case the vibration is directional, i.e. when the vibration is caused in X and Y directions, the above described unit consisting of the spring K and the dynamic vibration absorber is disposed for respective directions of vibration.
68 citations
Patent•
19 Apr 1978
TL;DR: In this paper, the authors used pneumatically driven vibrators coupled to self-attenuating structures define a shaker which enables a test item to be vibration tested under controlled conditions of multi-frequency, multi-degree-of-freedom acceleration history, to achieve a frequency spectrum and acceleration-level control of a broadband quasi-random vibration output in the frequency range, for example, from 40 Hz to 2 kHz for vibration testing of equipment.
Abstract: Pneumatically driven vibrators coupled to resonating, self-attenuating structures define a shaker which, when included in a vibration system, enables a test item to be vibration tested under controlled conditions of multi-frequency, multi-degree-of-freedom acceleration history, to achieve a frequency spectrum and acceleration-level control of a broadband quasi-random vibration output in the frequency range, for example, from 40 Hz to 2 kHz for vibration testing of equipment. The driving set of annular structure responds to an intense vibration spectrum, created by the attached pneumatic vibrators, with multi-modal forced and resonant frequencies in limited directions. The driven set of annular structure, holding the test hardware, responds with forced and harmonic oscillations to a vibration field transmitted from the driving set of structure through a specially designed elastomeric path. Specific design of the size, mass, and resonant behavior of the driving and driven structure sets with appropriate transmissibility characteristics of the elastomeric interface results in a controlled multi-modal, uniform RMS acceleration, multi-degree-of-freedom, wide-frequency-range vibration testing method. The annular arrangement of structure takes advantage of the complex amplitude-displacement behavior of the circumference of a ring excited into multi-modal in-plane and out-of-plane bending and torsional activity by the attached vibrators. Changes in pneumatic vibrator operating pressure change vibrator frequencies and expand available modal density.
56 citations
TL;DR: In this article, a hollow tabletop is horizontally divided into four sections, each containing a number of heavy balls which roll and bounce about within the compartments in the tabletop, impacting with the floor and ceiling of the compartment and with each other in a random fashion to produce random shocks over a wide band of frequency and amplitude.
Abstract: A random vibration generator includes a hollow tabletop for supporting equipment to be subjected to vibration, and a sinusoidal reaction-type vibration machine connected to the tabletop to produce a sinusoidal vibration of adjustable frequency and amplitude. The hollow tabletop is horizontally divided into four sections, each containing a number of projectiles such as heavy balls which roll and bounce about within the compartments in the tabletop, impacting with the floor and ceiling of the compartment and with each other in a random fashion to produce random shocks over a wide band of frequency and amplitude, and subject the equipment to every possible vibration failure mode that might occur in nature.
22 citations
TL;DR: In this paper, a closed-form optimal solution for minimizing a quadratic cost functional is derived, but it is shown to be dependent on the initial conditions and produces time-varying damping coefficients.
Abstract: Structural engineers have found that passive damping can reduce the amount of active damping required to control structural vibration. Conversely, improperly designed passive damping can inadvertently increase system reaction times, reducing control effectiveness. This paper presents several techniques for blending active vibration control and passive viscous damping. A closed-form optimal solution for minimizing a quadratic cost functional is derived, but it is shown to be dependent on the initial conditions and produces time-varying damping coefficients. To eliminate the dependence on initial conditions, solution techniques for suboptimal, state independent solutions are developed. The suboptimal solutions require less computation effort, but still give good estimates of the optimal solution. The advantages and disadvantages of the different solution techniques are discussed with respect to computation requirements and robustness. Methods of comparing competing designs are also discussed. Several numerical examples illustrate the similarities and differences of the various techniques. More importantly, the examples demonstrate the significant improvements achievable by simultaneously designing passive and active damping.
12 citations
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