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Shock and Vibration Application Brief

Vibration Control

The Solution


Fabreeka now uses DADiSP, the graphical display and data management software product created by DSP Development Corporation. Using DADiSP, the product management team can record site vibrations on a tape recorder and bring them back to the lab on DAT tape. The data are then Vibration Power Spectral Density analyzed in several simultaneous windows in a custom DADiSP labbook, which saves a great deal of time.

Multi-Channel Fourier Analysis


In Fabreeka's lab, collected data are downloaded to a personal computer and imported into a DADiSP worksheet. A multi-channel analysis of the recorded vibrations is generated, and the time data are translated into the frequency domain with a series of Fast Fourier Transforms (FFTs). Transfer functions are generated using FFTs of data recorded at different points simultaneously. Data are often converted to an acceleration vs. frequency format so that evaluations can be made at individual frequencies; the greatest acceleration levels in vibration-control work are usually found at moderately low frequencies, from 0 to 30 Hz. When it is necessary to know how much power these accelerations have at each frequency, Fabreeka's project team performs a Power Spectral Density (PSD) operation, yielding data in an acceleration2/frequency format. They also use DADiSP to display data in a displacement vs. frequency format, since the specifications for many sensitive machines are written this way.

Multiple Analysis Windows


"One of DADiSP's most useful aspects is its ability to display several different analyses at once," says the product management team. They use DADiSP to display data on-screen in multiple windows and to perform operations in each window. Seeing all the results together provides the team with enough information for them to decide what kind of vibration control, if any, is necessary at the sites being considered for installation of the delicate equipment in question. DADiSP allows the team to analyze data and make these decisions in a timely fashion, then generates a report that is easy to read. DADiSP also helps them to create impressive presentation materials.

Force Cancellation System


Fabreeka recently began using DADiSP in the testing phase of their projects as well as in their field work. Prior to acquiring DADiSP, they had used a two-channel vibration analyzer for research and development, but it was not capable of performing the complex analyses required for their most innovative work. DADiSP handles these analyses so well that even when the development team is testing equipment as complex as a 6-degree-of-freedom active force cancellation system, they can dependably quantify the cancellation on the second or third iteration of a testing cycle.

DADiSP, Work Guaranteed


For applications in satellites, lithography, and computer chip manufacturing, active force cancellation must bring vibration levels down to the nano-g level. Even at that level of precision, Fabreeka only guarantees their work when they use DADiSP.

The Problem