Abstract

Piezoceramic actuators have been utilized in many laboratory tests to provide a means of actively damping structural vibration; but have not, up till now, been applied to a high performance operational aircraft. This paper describes a program which applied a set of actuators (PZTs) to a skin panel on the aft fuselage of the B-1B aircraft. This panel is exposed to very high acoustic excitation during takeoff and to significant oscillating pressures during high speed-low altitude flight. The overall objective of this program was to demonstrate that an active vibration suppression system could reduce the vibration levels of a thick sharply-curved aircraft skin panel with PZT actuators attached only on the inner surface. This goals had to be achieved in a moderate temperature environment, with a digital processing rate of over 8000 Hz, at a low voltage, and with two relatively small hardware packages. Secondary goals included obtaining information on the durability, reliability, weight, and cost of the system. This latter information will be used to determine if the fatigue life of an aircraft type structure can be improved at a reasonable cost which is competitive with a structural beef up. The program was piggy backed on an ongoing B-1B flight test program. This allowed an actual flight test demonstration to be performed with out the costs associated with flight test support and a stand alone instrumentation system. The program was performed in three stages. The first stage included laboratory tests:

1. to determine the PZT characteristics and epoxies that will give the maximum structural response under the severe aircraft environments

2. to develop a micro-processor design that was capable of processing the control equations in a 120 microsecond time period

3. to design, build and test a structural equivalent B-1B fuselage panel with the PZT patch actuators and associated control system

4. to develop and test the hardware packages to be used for the flight tests

The second stage of the program included designing, fabricating, assembly and installing all of the equipment in the aircraft for the active vibration suppression system. This included the actuator patches on the skin panels, the installation of the power source and digital computer on the aircraft and all of the electrical wiring. The wiring supplied power to the system, connected the various parts of the system and interfaced with the aircraft test instrumentation system to get the required accelerometer feed back signals. The third stage of the program was the actual flight test of the system on the aircraft during takeoff and significant flight conditions. Vibration data collected on the aircraft was reduced and analyzed to show the panel response with and without the system operating. The system was successful in reducing the fundamental panel vibration as much as 79% for the takeoff condition and about 46% for flight conditions. The paper presents a discussion of each stage of the development of the system and the active vibration suppression system performance.

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