Hover-Capable Aircraft Rotor Vibration Attenuator for Variable Speeds
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Solution Overview
Problem
Existing rotor systems for helicopters face challenges in effectively attenuating vibrations at both nominal and increased angular speeds, leading to discomfort for occupants due to inadequate performance of passive resonant absorbers when the rotor speed changes.
Innovation Solution
A rotor system with a reconfigurable passive vibration attenuating device that includes a sliding mass and elastic means, which adjusts its tuning based on the angular speed of the mast, behaving as a tuned mass absorber at both nominal and increased speeds to efficiently reduce axial vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive resonant absorbers are used to attenuate vibrations at nominal angular speed, then vibration reduction is effective at nominal speed, but vibration attenuation performance deteriorates when rotor speed increases
Solution Approach 1:
The patent applies the dynamics principle by making the vibration attenuating device reconfigurable through a control system that adjusts the stiffness of elastic elements based on detected rotor speed. The device transitions from a static passive absorber to a dynamic system that adapts its characteristics in real-time, allowing effective vibration attenuation across multiple operating speeds including both nominal and increased angular speeds
2Reliability
If the vibration attenuating device is designed for nominal speed only, then constructional simplicity is maintained, but effectiveness at increased speeds is lost
Solution Approach 1:
The patent implements feedback by incorporating a sensor that detects the angular speed of the mast and feeds this information to a control system. The control system processes the speed signal and adjusts the stiffness of the elastic elements accordingly, creating a closed-loop system that automatically optimizes vibration attenuation for the current operating condition without requiring complex manual intervention
Solution Approach 2:
The patent applies parameter changes by dynamically modifying the stiffness parameter of the elastic elements in the vibration attenuating device based on the detected rotor speed. The control system varies the stiffness parameter to match the operating conditions, enabling the device to maintain optimal attenuation performance across different speed regimes while using relatively simple mechanical components
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 at both nominal and increased rotor speeds, enhancing passenger comfort by optimizing vibration reduction across varying operational conditions without compromising constructional simplicity.
Implementation Method 1
elastic means, arranged to support the mass in an oscillating manner along the axis of rotation
Implementation Method 2
behaving as a tuned mass absorber at both nominal and increased speeds to efficiently reduce axial vibrations
Implementation Method 3
attenuating device to attenuate the transmission of axial vibrations to the fuselage
Data Source
AI summary
A rotor for a hover-capable aircraft includes an attenuating device to attenuate the transmission of vibrations from a mast to the aircraft. The attenuating device includes a first mass free to oscillate parallel to a hub rotation axis with respect to a casing of the attenuating device and elastically connected to the casing. The attenuating device further includes a second mass free to oscillate parallel to the hub rotation axis, connection means adapted to make the first and second masses integrally movable along the hub rotation axis when the angular speed of the mast assumes a first value, and actuator means activatable to decouple the first and second masses when the angular speed of the mast assumes a second value, different from the first value.