The classic ElectroDynamic (ED) vibration system has been used for many years to accelerate vibration fatigue in Accelerated Life Testing (ALT). During the Mercury, Gemini and Apollo programs, ED shakers performing random vibration were utilized, with significant success (United States Navy, 1979). Shaped random Power Spectral Density excitation (PSDs) were specified to meet specific stress goals, and they could be generated and controlled very precisely (U.S. Department of Defense, 1996). The ‘NAVMAT’ profile, shown in Figure 1, became a de facto standard for vibration screening (Ciufo, 2005).
ED shakers are familiar to virtually any engineer or technician whose work includes evaluating the ability of a product to tolerate end-use environment mechanical stresses, shipping stresses or environmental stress screening (ESS) that includes vibration stresses. The basic design and operation of ED shakers is most easily understood through the quite accurate analogy of an audio speaker and amplifier system, except on a much larger scale (Lang, 1997).