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A Discussion of Zero Spring Rate Mechanisms Used for the Active Isolation Mount ExperimentIn the summer of 1995 the Structural Dynamics Branch at NASA Langley Research Center set out to conceive a small, lightweight, low frequency isolation mount that could be used for spaceflight experiments. The Engineering Design Branch undertook the task of developing the isolation mount. This report describes the engineering process that led to three phases of a study entitled "Active Isolation Mounts" (AIM). A zero spring rate mechanism was used to achieve low fundamental frequencies for a payloads in the 1 to 10 pound range. It worked by balancing both a positive and a negative stiffness so that the net result was a small positive stiffness. The study demonstrated devices that could reduce the initial corner frequency by a factor of six for brief periods and a factor of two for extended periods. The designs were relatively simple and minimized weight, volume, and power. They could be scaled down and they were made of spaceflight compatible materials. All designs offered the ability to continuously vary the fundamental frequency. Yet, the goal of reducing the frequency by an order of magnitude was not achieved because the systems were too unstable at low frequencies. There was a trade between performance and stability.
Document ID
19990116712
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Teter, John E., Jr. (NASA Langley Research Center Hampton,VA United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1999
Subject Category
Mechanical Engineering
Report/Patent Number
L-17798
NASA/TM-1999-209723
NAS 1.15:209723
Funding Number(s)
PROJECT: RTOP 233-20-21-54
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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