Hover Rotor Tuned Mass Absorber for Variable-Speed Vibration Control
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Solution Overview
Problem
Existing rotor systems for hover-capable aircraft, such as helicopters, face challenges in effectively attenuating vibrations transmitted to the fuselage, particularly at varying rotational speeds, leading to reduced passenger comfort and inefficiency in passive resonant absorbers.
Innovation Solution
A rotor system with a reconfigurable passive vibration attenuating device that includes a sliding mass and elastic means, adjustable to match the rotational speed of the mast, allowing it to function as a tuned mass absorber at both nominal and increased angular speeds, thereby effectively reducing axial vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive resonant absorbers are used to attenuate vibrations at nominal rotational speed, then vibration attenuation is effective at the tuned frequency, but the absorbers become inefficient when rotational speed changes
Solution Approach 1:
The patent applies the dynamics principle by making the resonant absorber system reconfigurable through variable stiffness elastic means. The stiffness of the elastic elements can be adjusted to change the natural frequency of the absorber masses, allowing the system to adapt to different rotational speeds of the mast. This enables the passive absorbers to maintain effectiveness across a range of operating conditions rather than being fixed at a single tuned frequency.
Solution Approach 2:
The patent implements parameter changes by modifying the stiffness parameter of the elastic means supporting the absorber masses. By varying the stiffness of these elastic elements, the natural frequency of the absorber system can be tuned to match different rotational speeds of the mast. This parameter adjustment allows the vibration attenuation system to remain effective whether the helicopter operates at nominal speed or increased speed, directly addressing the adaptability problem.
2Adaptability or versatility
If active attenuating devices are used to counteract vibrations, then vibration attenuation is effective across varying speeds, but device complexity increases
Solution Approach 1:
The patent applies the self-service principle by designing a passive vibration attenuation system that automatically adapts to different rotational speeds without requiring external power sources, sensors, or control systems. The reconfigurable elastic means can be adjusted through mechanical or gravitational mechanisms that self-regulate based on operating conditions, eliminating the need for complex active control systems while maintaining adaptability across speed variations.
3Productivity
If the mast rotational speed is increased to improve performance, then aircraft performance improves, but vibration frequency changes making existing absorbers ineffective
Solution Approach 1:
The patent applies dynamics by enabling the vibration absorber system to dynamically adjust its stiffness characteristics in response to changes in mast rotational speed. When the helicopter operates at increased speed for improved performance, the elastic means can be reconfigured to change the natural frequency of the absorber masses, ensuring they remain tuned to the new vibration frequency and continue to provide effective attenuation.
Solution Approach 2:
The patent implements parameter changes by adjusting the stiffness parameter of the elastic support elements based on the operational speed of the mast. This allows the system to maintain optimal vibration attenuation effectiveness whether the helicopter is operating at nominal speed for efficiency or at increased speed for enhanced performance, directly supporting the productivity improvement without sacrificing vibration control reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system efficiently attenuates vibrations at both nominal and increased rotational speeds, enhancing passenger comfort and maintaining the simplicity and cost-effectiveness of passive absorbers.
Implementation Method 1
elastic means (22) to support the mass (21) in a sliding manner along the axis (A) inside the casing (20)
Implementation Method 2
A rotor system with a reconfigurable passive vibration attenuating device that includes a sliding mass and elastic means, adjustable to match the rotational speed of the mast, allowing it to function as a tuned mass absorber
Implementation Method 3
efficiently attenuates vibrations at both nominal and increased rotational speeds, enhancing passenger comfort
Data Source
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AI summary
A rotor (3) for a hover-capable aircraft (1) is described that comprises: a hub (5) rotating about an axis (A) and, in turn, comprising a plurality of blades (9), a mast (6) connectable to a power unit of the aircraft (1) and operatively connected to the hub (5) to drive the hub (5) in rotation about said axis (A), and an attenuating device (15) to attenuate the transmission of vibrations from the mast (6) to the aircraft (1) parallel to said (A); the attenuating device (15), in turn, comprising a casing (20), a first mass (21) free to oscillate parallel to said axis (A) with respect to the casing (20) and elastically connected to the casing (20), a second mass (25) free to oscillate parallel to said axis (A), connection means (30) adapted to make the first and second masses (21, 25) integrally movable along said axis (A) when the angular speed (Ω) of the mast (6) assumes a first value (Ω1), and actuator means (35) activatable to decouple the first and second masses (21, 25) when the angular speed (Ω) of the mast (6) assumes a second value (Ω2), different from the first value (Ω1).