The study to reduce noise and vibration in aircraft cabin through PZT was implemented, using a semi-monocoque structure, 1.5m in diameter and 3.0m long with 2.3mm skin, which stimulates an aircraft body. We utilized PZT of 480 pieces bonded on inner surface of the structure as sensor and actuator. We applied random noise of low frequency range between 0~500Hz to the test model. We tried to reduce the vibration level of structure and internal air due to the external load by controlling the PZTs. Two control methods, gain control and feed-forward control, were tried. We measured internal sound pressure on 150 spots and compared overall values of sound pressure with gain control to them without control and evaluated its reduction capability. The tests showed 4.0dB O.A. reduction at maximum in gain control and 3.5dB O.A. reduction at maximum in feed forward control.
We are carried out the tests for the sound and vibration control of the CFRP square panel. 500Hz bandwidth noise through two speakers is applied to the CFRP panel. Our objects are to improve the structural damping of the panel and attenuate the sound power radiated from the panel using piezoelectric sensors and actuators. The dimensions of the CFRP plate are 600.0 mm x 600.0mm in area and 1.8mmt in thickness. Eighteen piezoelectric elements (40.0 x 20.0 x 0.3mmt) are bonded on the surface of the panel by epoxy adhesive. The panel is driven using some piezoelectric elements as actuators. The vibration of the panel is monitored using piezoelectric elements as sensors. We can get the strain of the panel from the voltage induced by piezoelectric elements. The signals are sent to digital signal processor (DSP) through filters and the control signal are sent to the power amplifiers. The amplified signals drive the piezoelectric actuators. The vibration and the radiated sound power of the panel are suppressed. We try to apply two methods for the control which are the gain control and the reduced LQG control. In the case of the gain control, the strain is reduced as much as 10-20 dB at some resonant peaks and the radiated sound pressure level as much as 1-15 dB. The radiated sound power is reduced by 1.59dB in the 0-500Hz frequency range. In the case of the LQG control, the strain is reduced as much as 7-10dB at some resonant peaks and the radiated sound pressure level as much as 1-7dB. The radiated sound power is reduced by 0.7dB in the 0-500Hz frequency range.
KEYWORDS: Actuators, Vibration control, Digital signal processing, Ferroelectric materials, Aluminum, Control systems, Autoregressive models, Sensors, Amplifiers, Signal processing
We carried out tests and analysis of flutter and vibration control of rectangular aluminum plate wing. The dimensions of the plate wing (420.0 X 140.0 X 1.0 mmt) were determined based on the wind tunnel size and blowing air velocity. The plate wing was driven by eight piezoceramic actuators bonded on the surfaces at the wing root part. Acceleration sensor was located at the wing tip and the signal was sent to digital signal processor through filters and control signal was sent to power amplifier. Amplified signal drove the piezoceramic actuator and suppressed vibration of the plate wing. System consist of structure, piezoceramic actuator and unsteady aerodynamic force was modeled into the standard form of modern control theory. Piezoceramic actuator's force was modeled using analogy of thermal analysis. Unsteady aerodynamic force in case of flutter control was calculated by DLM (frequency domain), then transformed to Roger's approximation for the purpose of time domain analysis. Full order control law consist of optimum regulator and Kalman's filter was reduced to low order law for practical use. First, we carried out the test for vibration control. In this case, structural damping ratio of the system increased remarkably in both case of gain control and reduced LQG control. Using gain control, that of the system increased up to 0.3. Second, we carried out the wind tunnel test of flutter control. Flutter speed at test increased about 2.9 m/s (10.8%, in calculation 12.2%) using reduced LQG controller.
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