<title>Fin-buffet alleviation via distributed piezoelectric actuators: full-scale demonstrator tests</title>

Abstract

Structural fin or wing vibrations are observed on high performance aircraft when flying at high angles of attack. The severity of the so-called buffeting vibration depends on the aircraft configuration and aerodynamic optimization of the configuration. The vibrations are caused by flow fluctuations resulting from flow separation at wings or from bursting of wing leading edge and front fuselage vortices. The resulting dynamic loads together with manoeuvre loads lead to increased material fatigue and may require an augmented effort in aircraft maintenance.A number of different concepts have been proposed to either minimize the buffeting excitation by passive devices or to alleviate the resulting structural vibrations by active control systems. One of the most innovative suggestions has been to use piezoelectric patch actuators distributed across the surface of a vertical tail to actively induce a counter-strain into the structure. This concept promises to efficiently suppress vibrations of elastic modes with low aerodynamic damping up to high frequencies without an excessive amount of additional weight.In order to investigate the performance of such a system a collaborative research project was initiated between DaimlerChrysler Aerospace -Military Aircraft Division and DaimlerChrysler Research and Technology within the framework of the Advanced Aircraft Structures program. For this purpose a demonstrator was conceived, designed and manufactured that is dynamically equivalent to a typical fighter aircraft vertical tail and simulates its structural set-up. Custom-made actuator modules were surface-mounted onto the fin-box demonstrator in locations prescribed by a design optimization scheme to provide optimal actuation authority up to 200 Hz. A series of tests have been performed to determine the structural dynamic behaviour of the test-box and to validate the mathematical model and calculation methods. Both open and closed ioop tests show excellent agreement with the theoretical expectations and indicate the potential for significant vibration reduction for on-ground conditions and consequently might lead to buffet alleviation in flight using this technology.The effectiveness of buffeting alleviation at relevant flight conditions has to be demonstrated via total aircraft dynamic buffet response calculations and needs verification by flight test.

Active Aeroelastic Tailoring of High-Aspect-Ratio Composite Wings

“…21 Simpson and Schweiger 22 and Manser et al 23 also carried out similar studies. A program to investigate the active suppression of vertical tail buffeting vibrations in the F-18 aircraft is currently under way in a joint US/Australia/Canada effort (see, for example, Refs.…”

Review of Smart-Materials Actuation Solutions for Aeroelastic and Vibration Control

“…Simpson and Schweiger (1998) conceptualized the use of piezo-electric damping for active suppression of buffeting vibration in the vertical tail of fighter aircraft. Manser et al (1999) describe proof-of-concept experiments performed on a 2000-mm ¥ 700-mm ¥ 156-mm fin-box specimen at Daimler-Chrysler Aerospace in Germany. The fin box specimen was constructed from aluminum spars and carbon fiber composite skins of thickness varying from 14-mm at the root to 3-mm at the tip.…”

“…(Moses, 1999), (b) power spectral density of acceleration measured on the vertical tail tip near the trailing edge on F/A-18 aircraft during initial ground tests (McGowan et al, 1998) and (c) achieved reduction in rms root-bending moment during simulated ground tests for various flight speed and angle of attack (AOA) values (Moses, 1999). (Manser et al, 1999). mented with PZT wafer actuators, 14 for symmetric actuation, and 8 for anti-symmetric actuation.…”

Active-Materials Induced-Strain Actuation for Aeroelastic Vibration Control

“…Simpson and Schweiger (1998) conceptualized the use of piezo-electric damping for active suppression of buffeting vibration in the vertical tail of fighter aircraft. Manser et al (1999) describe proof-of-concept experiments performed on a 2000-mm x 700-mm x 156-mm fin-box specimen performed at Daimler-Chrysler Aerospace in Germany. The fin box specimen was constructed from aluminum spars and carbon fiber composite skins of thickness varying from 14mm at the root to 3-mm at the tip.…”