Vibrations aboard the shuttle tend to be random. The square of the acceleration versus frequency has a simple functional form known as the power spectral density. The active vibration control group is concerned with the problem of reducing the amplitude of these random vibrations encountered by certain critical experiments aboard the space shuttle to minute fractions of the vibrations typical of the environment during orbit. Our problem is complicated by the fact that, in any direction, the displacement of the isolated experiment relative to the shuttle cannot exceed a predetermined value.A certain degree of isolation and displacement minimization can be achieved by using passive mechanical couplers, such as foams, gels and elastomers. Indeed, if all electronic components had mechanic al analogs, controlling a mechanical system electronically would be pointless. Clearly, though, the transistor has no simple mechanical analog. Arrays of transistors can produce any signal having frequency components less than half of 2 pi divided by the response time. Thus, the response of active (i.e., electronically-controlled, externally-powered) materials is more flexible than that of passive mechanical materials. We hope to achieve optimal mechanical coupling for the particular power spectral density function characteristic of the shuttle by designing a highly compliant piezoelectric material and by choosing an appropriate algorithm for the bias voltage.
Our work so far has consisted of searching for the optimal electronic control function and determining some of the practical problems arising from a simple apparatus consisting of ceramic piezoelectric spherical segments.
For more information, visit the Advanced Materials site.
| Mail: | Dr. V. Hugo Schmidt |
|
Department of Physics |
| Montana State University | |
| Bozeman, MT 59717 |
| E-mail: | schmidt@physics.montana.edu |
| Phone: | (406) 994-6173 |
| FAX: | (406) 994-4452 |
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