Hover Rotor Vibration Attenuation With Counter-Rotating Masses
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Solution Overview
Problem
Current vibration attenuation systems for hover-capable aircraft, such as helicopters, face limitations in precision, rapid responsiveness, weight, bulk, and cost, particularly in effectively reducing vibrations transmitted to the fuselage, and they often stress transmission components like shafts and gears.
Innovation Solution
A rotor design incorporating a vibration-attenuating device with mass units rotating at specific angular speeds relative to the mast, generating centrifugal forces that counteract vibrations, and controlled by adjustable angles and phases to optimize attenuation, using a compact epicyclic train and reversible gear systems to enhance flexibility and reduce torque requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive attenuating devices are used, then the device complexity is reduced and ease of manufacture is improved, but the manufacturing precision and attenuation performance are limited
Solution Approach 1:
The patent employs dynamic balancing masses that rotate at controlled speeds to generate counter-vibrations, transforming the static passive attenuator into a dynamic system that actively adapts to vibration frequencies, thereby improving attenuation performance while maintaining manufacturing simplicity
Solution Approach 2:
The invention changes the operational parameters by introducing variable rotation speeds for the balancing masses, allowing the system to adjust its attenuation characteristics dynamically without complicating the manufacturing process
2Manufacturing precision
If active attenuating devices with high reduction ratio transmission are used, then the manufacturing precision and attenuation performance are improved, but the device complexity increases and torque requirements increase
Solution Approach 1:
The patent uses multiple balancing masses that replicate the vibration pattern with opposite phase, creating a simplified transmission system that achieves high attenuation performance without requiring complex high reduction ratio gear mechanisms
3Manufacturing precision
If active attenuating devices with high reduction ratio transmission are used, then the manufacturing precision and attenuation performance are improved, but the weight and bulk of the device increase
Solution Approach 1:
The dynamic rotation of balancing masses at variable speeds provides effective vibration attenuation without requiring heavy, bulky transmission components, thereby achieving high performance with reduced weight
4Reliability
If irreversibility coupling is used in the transmission device, then the reliability is improved by preventing backward motion, but the adaptability decreases and responsiveness to changing vibration directions is reduced
Solution Approach 1:
The patent employs dynamically controllable balancing masses that can adjust their rotation speed and phase in real-time, providing both reliability through controlled operation and high adaptability to changing vibration conditions without irreversible coupling
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 solution provides precise and rapid attenuation of vibrations, reduces stress on transmission components, and minimizes weight and bulk, while improving responsiveness to changing vibration directions, ensuring efficient vibration reduction with lower operational loads and maintenance needs.
Implementation Method 1
The masses are coupled to the rotation of the mast by a transmission device so that the masses of the first mass unit rotate eccentrically around the mast with a rotational speed with respect to the fixed system equal to N*Ω... In this way, the masses generate respective radial centrifugal forces with respect to the axis of the mast
Data Source
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AI summary
A rotor (3, 3') for an aircraft (1) is described that has a mast (50), an attenuating device (7, 7') to attenuate the transmission of vibrations from the mast (50) in a plane orthogonal to the first axis (A), and a transmission device (15) interposed between the mast (50) and the attenuating device (7, 7'); the attenuating device (7; 7') comprises a first and a second mass unit (8, 9) with a first and a second mass (10, 11) rotatable about the first axis (A) with a first and a second rotational speed ((N-1)*Ω; (N+1)*Ω), two control units (40) operable to cause an additional rotation of at least one of the first and second masses (10, 11), and a first and a second support assembly (41, 42) carrying the first and second masses (10, 11); each control unit (40) controls the angle between the first and second masses (10, 11) and comprises a set of drive gear teeth (55, 55') integral with the first support assembly (41, 42), a cogwheel (56) with a set of control gear teeth (57) meshing with the drive gear teeth (55, 55'), and an actuator (58) to cause the rotation of the cogwheel (56) about a second axis (F) and of the first mass (10, 11) about said first axis (A) .