Low-Weight, Low-Power Vibration Isolation

Montana State University-Bozeman

The objective for our flight is to test a three-degree-of-freedom (two displacement, one rotation) vibration isolation system. Our vibration isolation method uses exceptionally light-weight, low-power sensors and polymer piezoelectric actuators, as opposed to mounts using heavy electromagnets or induction devices and 35 watts (or more) of power. Our actuators are tuned for active operation in the low frequency (sub-acoustic) range and have excellent passive damping characteristics at high (acoustic range) frequencies.

The actuators are designed for the very low force requirements of the Shuttle and cannot support a substantial weight in normal earth gravity. We are now testing a one-degree of freedom prototype using a folded pendulum platform producing less than 10 micro-g restoring force over a range of +/- 3 mm. Unfortunately, no method has been found to extend the system to more than one degree of freedom. Other methods, such as airbed devices, introduce additional vibrations not characteristic of the Shuttle environment. We need to verify that the control system can maintain proper operation with multiple degrees of freedom. The extra displacement and rotation modes will introduce shear strains in the piezo actuators, which complicate the control circuitry. Ultimately, the system must deal with six degrees of freedom. Working with three degrees of freedom on the reduced gravity flight platform will provide an essential test of the control system without the cost and complexity of the final assembly.

The full system design will have a settling time of approximately twenty seconds. A scaled version will be constructed for the KC-135 flight, with a settling time of about 2 seconds. This will allow about two seconds for the attending students to retract holding pins and about 15 seconds of data collection and system performance observation near zero g.

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Last Modified: Tue May 19 1998
CSR/TSGC Team Web