2005 Fiscal Year Final Research Report Summary
VIBRATION SUPPRESSION OF HELICOPTER BLADES BY PENDULUM ABSORBERS
| Project/Area Number |
14550225
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Dynamics/Control
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| Research Institution | CHUBU UNIVERSITY |
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Principal Investigator |
NAGASAKA Imao CHUBU UNIVERSITY, DEPERTOMENT OF ENGINEERING, ASSOCIATE PROFESSOR, 工学部, 助教授 (60102779)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIDA Yukio NAGOYA UNIVERISYT, DEPERTMENT OF ENGINEERING, PROFESSOR, 大学院・工学研究科, 教授 (10092991)
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| Project Period (FY) |
2002 – 2005
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| Keywords | helicopter / rotor blade / dynamic damper / absorber / nonlinear forced vibration / nonlinear theoretical analysis / pendulum |
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| Research Abstract |
In general the high level of vibration occur in a helicopter, and therefore, makes the crew uncomfortable and gives rise to the metallic fatigue of the structural materials in the fuselage. Particularly the rotor blades of helicopter can be induced to oscillate violently by the vibration of main rotor and the aerodynamic force. The aerodynamic force being main source of the vibration in helicopter has integer multiple frequencies of the rotational speed of the main rotor.
A pendulum absorber is used now to suppress the vibration of the rotor blade of the helicopter. The design of the pendulum absorber is determined by the theory based on linear anti-resonance point. But few papers on the pendulum absorber analyze in detail the characteristics of its vibration, and no paper analyzes nonlinear vibration of the pendulum absorber.
In this research, we make the two-degree-of-freedom model of the rotor blade and the pendulum absorber. We provide the force with three times frequency of main-rot
… More
or rotational speed to the model by up-and-down displacement of main rotor. The responses of the blade with the pendulum for the external forces are simulated by integrating the nonlinear equations of motion, are analyzed by nonlinear theoretical analysis, and are obtained by performance in the experimental setup. The following are made clear by comparison of their results.
1.By tuning the natural frequency of the pendulum with that of the external force, the pendulum absorber is effective for vibration suppression over the wide rotational speed of the main rotor.
2.When the external forced amplitude becomes larger, the amplitude of deflection of the pendulum becomes larger. Therefore, the effect of vibration suppression is reduced. If it becomes further larger beyond a threshold, the pendulum rotates, and its effect is lost.
3.The effects of the position at that the pendulum is attached, the mass ratio of the pendulum and the blade, the damping coefficient of the pendulum, and so on, are made clear.
4.That bifurcation phenomena occur in the blade with the pendulum is confirmed by nonlinear theoretical analysis.
5.It is made clear that the pendulum absorber has the better effect by tuning the natural frequency of the pendulum with slightly lower than that of the external force. Less
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