Rotor Hub Attenuator With Orbiting Masses for N/REV Vibration
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Solution Overview
Problem
Conventional vibration attenuation systems for rotary-wing aircraft, such as helicopters and tiltrotors, face challenges in accurately predicting and effectively reducing rotor-induced vibrations, often leading to amplified vibrations in other locations and susceptibility to transients, particularly due to their dependence on specific dynamic characteristics of the mast attachment point and limited effectiveness across varying rotor rotational speeds and gross weights.
Innovation Solution
A rotorcraft hub-mounted vibration-reduction device featuring revolving spring masses that move in a circular path proportional to N/REV vibration magnitude, counteracting hub vibrations with a centrally located mass orbiting at N/REV frequency, and a control system that adjusts the radial position and phase of weights to optimize vibration attenuation without relying on stationary frame springs, thus providing effective vibration reduction across varying flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If UREKA device is used, then rotor imbalance at 1/rev frequency can be minimized, but the device cannot oppose other rotor-induced n/rev vibrations
Solution Approach 1:
The counterbalancing masses are made dynamically adjustable rather than fixed. Each mass can be independently positioned angularly around the rotor hub, allowing the system to adapt to different vibration frequencies (n/rev where n≥1) and provide effective attenuation across multiple vibration modes, not just 1/rev imbalance.
Solution Approach 2:
The system changes the parameters of the counterbalancing masses (angular position, radial distance from hub center) based on detected vibration characteristics. This allows the masses to be optimized for different vibration frequencies and amplitudes, enabling the system to oppose various n/rev vibrations effectively.
2Object-affected harmful factors
If UREKA device is used, then vibration can be attenuated, but the device is susceptible to gusts and transients that may disturb roller position
Solution Approach 1:
Vibration sensors continuously monitor vibrations at multiple airframe locations, providing real-time feedback to the control system. This feedback allows the system to detect and correct disturbances caused by gusts and transients, maintaining reliable vibration attenuation without being susceptible to position disturbances like the UREKA rollers.
Solution Approach 2:
The system uses its own vibration sensors to detect disturbances and automatically adjusts the counterbalancing mass positions to compensate for gusts and transients. This self-correcting capability makes the system reliable and insensitive to external disturbances that would affect passive systems like UREKA.
3Object-affected harmful factors
If UREKA device is used, then vibration reduction can be achieved, but the dynamic characteristics of the mast attachment point must be specific (supercritical shaft)
Solution Approach 1:
The vibration attenuation system is designed to be universally applicable to different aircraft types and rotor configurations without requiring specific mast dynamic characteristics. Multiple independently controllable counterbalancing masses can be optimized for various vibration modes, making the system versatile for different applications including helicopters, tiltrotors, and other rotary-wing aircraft with different gross weights and operating conditions.
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 effectively attenuates rotor-induced vibrations without the need for traditional spring attachments, offering greater force output and reduced susceptibility to transients, while maintaining steady-state vibration magnitude and phase, thus enhancing aircraft component lifespan and passenger comfort.
Implementation Method 1
revolving spring masses that move in a circular path proportional to N/REV vibration magnitude
Implementation Method 2
revolving spring masses
Implementation Method 3
a centrally located mass orbiting at N/REV frequency
Implementation Method 4
creating oscillatory shear forces that oppose and attenuate rotor-induced vibrations
Data Source
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AI summary
A vibration attenuation system for attenuating vibrations in a mast of an aircraft includes a weight attached to the mast but free to orbit about the mast. The weight can be comprised of one or more weight assemblies. Embodiments can include a single weight, or plural weight assemblies wherein each weight assembly can include a mechanical interconnecting mechanism so that each weight assembly receives feedback regarding the position and movement of one or more other weight assemblies. Each weight can be associated with a spring that urges the weight towards a neutral position. Rotation of the mast can cause the weight to orbit about the mast and self-excite such that the weight acts against the urging of the spring towards an attenuating position.