Rotor Hub Attenuator Using Variable-Radius 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, particularly at higher frequencies, and are susceptible to transients and varying dynamic characteristics, leading to inadequate performance and potential vibration amplification.
Innovation Solution
A rotorcraft hub-mounted vibration-reduction system utilizing revolving spring masses that orbit at higher frequencies than the rotor, allowing for self-positioning to counteract vibrations and providing a steady counterforce, independent of the mast's dynamic characteristics, with a control system to adjust the weight's radial position and phase for optimal vibration attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional vibration attenuation systems are used, then vibrations at specific frequencies can be reduced, but vibrations at other frequencies may be amplified and the system is susceptible to transients
Solution Approach 1:
The patent employs a spinning mass that rotates at a variable speed independent of the rotor, allowing the system to dynamically adapt to different vibration frequencies. The spinning mass can be accelerated or decelerated to match different n/rev frequencies, providing reliable vibration attenuation across varying operating conditions without being susceptible to transients that affect fixed-speed systems.
Solution Approach 2:
The system changes the rotational speed parameter of the spinning mass to optimize vibration attenuation at different frequencies. By varying the spinning speed independently from the rotor speed, the system can target specific n/rev vibrations without being constrained by the rotor's dynamic characteristics, thereby improving reliability across different flight conditions.
2Object-affected harmful factors
If UREKA device is used, then rotor imbalance at 1/rev frequency can be minimized, but other n/rev vibrations are not opposed and the device may amplify vibration if mast characteristics are not met
Solution Approach 1:
The spinning mass rotates at a variable speed that can be independently controlled from the rotor speed, enabling the system to adapt to different n/rev frequencies. This dynamic adjustment capability allows the system to oppose multiple vibration frequencies beyond just 1/rev, providing versatility across different operating conditions without being constrained by specific mast dynamic characteristics.
Solution Approach 2:
The system is designed to attenuate multiple types of vibrations (n/rev vibrations where n>1) rather than being limited to a single frequency. The spinning mass can be adjusted to target different vibration modes, making the system universally applicable to various vibration problems in tiltrotor aircraft regardless of the specific mast characteristics.
3Object-affected harmful factors
If hub shear pendulums are used, then approximately 50% of n/rev vibration can be attenuated, but the system is heavy and only effective at tuned frequency
Solution Approach 1:
The patent replaces the heavy mechanical pendulum system with a spinning mass system that uses rotational inertia and variable speed control to generate counteracting forces. This substitution reduces weight while improving effectiveness, as the spinning mass can be adjusted to optimize vibration attenuation without the inherent limitations of pendulum mechanics.
Solution Approach 2:
The system changes the rotational speed parameter of the spinning mass to optimize vibration attenuation at different frequencies. By varying the spinning speed, the system can achieve effective vibration reduction across a broader frequency range with less weight compared to fixed-frequency pendulum systems.
4Object-affected harmful factors
If conventional vibration attenuators are used, then specific point vibrations can be reduced, but vibrations are amplified in other locations on the airframe
Solution Approach 1:
The system uses sensors to detect vibrations at multiple locations on the airframe and adjusts the spinning mass speed and phase accordingly. This feedback mechanism allows the system to optimize vibration attenuation across the entire airframe, preventing localized reduction from causing amplification elsewhere by continuously adapting to the actual vibration patterns.
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 effectively attenuates vibrations across a range of frequencies, reducing the wear on aircraft components and passenger comfort, while being less susceptible to transients and not dependent on specific mast attachment dynamics, offering improved performance compared to prior art.
Implementation Method 1
The weight assembly has a spring-mass system that revolves with the proprotor and generates an oscillatory force that minimizes the vibrations
Implementation Method 2
The weight assembly has a spring-mass system that revolves with the proprotor and generates an oscillatory force... The mass moves in a circular path that varies in radius proportionally with the N/REV vibration magnitude
Data Source
AI summary
A vibration attenuator has a first spinner configured for rotation about a first axis and a first mass coupled to the first spinner for rotation therewith, the first mass being movable radially relative to the first axis between an inner position and an outer position. An actuator is coupled to the first mass for selectively controlling a radial location of the first mass relative to the axis, and a first motor is configured for driving the first spinner in rotation about the first axis.