Hughes Aircraft Company

Richard L Baker

Robert H Weinmann, Jr

James M Kallis

Charles F Talbott, Jr

Dennis B Page

Henry T Abstein, Jr

A shaker table (10) includes a table base (12) mounted upon isolating supports (32) and vibrated by vibrators (34, 36). The vibration is conveyed through and damped in a flexure member (16) comprising pairs (26, 28) of honeycomb layers (18, 20, 22, 24) joined and bonded together by sheets (42) utilizing beads of elastomeric adhesive which space the honeycomb layers apart. A segmented top plate (14) is secured to the topmost honeycomb layer and is divided into a plurality of sections or segments (68-82) for separate resonances. In this way, highly damped vibrational resonances of table top plate (14) are obtained.

Shaker table

A low-cost, multi-axis, quasi-random vibration system includes pneumatically driven vibrators coupled to a resonating, self-attenuating shaker structure 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 shaker structure consists of flexible interconnected structures whose primary or driving structure acts to mechanically process the vibratory input of the coupled vibrators and whose supporting or driven structure supplies a further vibrational processing to supply the test item with multi-axis multimodal input. Automatic control and pseudo-random modulation of air pressure of the pneumatic vibrators provide closed-loop broadband acceleration-spectrum control and spectrum smearing to enhance frequency content and to prevent the shaker from locking onto any particular vibration frequency, especially a natural frequency of the shaker. Control is achieved in and about three orthogonal axes simultaneously, thus affording a realistic simulation of operational environments. The vibrators' vibration frequency is modulated by means of a variable-area orifice in the pneumatic line located between the air supply and the pneumatic vibrators. A pseudo-random change in the orifice area is made automatically, for example, every 2 to 3 seconds, by a preprogrammed microprocessor-controlled flow control mechanism.

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Rancho Palos Verdes, CA, United States of America

Richard L Baker