Rotor Hub Attenuator for N/REV Vibration Reduction
Find Innovative SolutionsGenerate Solutions
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 failing to address vibrations at frequencies other than 1/rev and being susceptible to transient disturbances like gusts, due to their reliance on specific dynamic characteristics of the mast attachment point.
Innovation Solution
A rotorcraft hub-mounted vibration-reduction device featuring revolving spring masses that orbit at N/REV frequencies, allowing for self-positioning to counteract hub vibrations independently of mast dynamics, with a control system to adjust the weight's radial position and phase, ensuring effective vibration attenuation across various flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive mast-mounted rotating balancer (UREKA device) is used to reduce vibrations, then 1/rev frequency vibrations are minimized, but the device cannot oppose n/rev vibrations where n is greater than 1 and may amplify vibrations if the mast attachment point does not possess specific dynamic characteristics
Solution Approach 1:
The patent employs multiple counter-rotating weights that can independently adjust their rotational speeds and positions. This dynamic configuration allows the system to generate counter-vibrations at multiple frequencies (n/rev where n>1), unlike the single-frequency UREKA device. The weights can change their operational parameters to adapt to different vibration frequencies encountered during various flight conditions.
Solution Approach 2:
The vibration attenuation device is designed to counteract multiple types of rotor-induced vibrations simultaneously. By incorporating multiple adjustable weights that can operate at different frequencies and phases, the system achieves multi-functionality, addressing both 1/rev and n/rev vibrations across various flight regimes, making it universally applicable to different vibration scenarios.
2Reliability
If the UREKA device is used for vibration reduction, then rotor imbalance at 1/rev frequency is minimized, but the device is susceptible to gusts and transients that disturb roller position, creating vibration transients
Solution Approach 1:
The patent incorporates sensors that detect vibration levels and provide feedback to a control system. The control system continuously adjusts the position and rotational speed of the counter-weights based on real-time vibration data. This closed-loop feedback mechanism ensures stable operation by constantly correcting deviations caused by gusts and transients, preventing the creation of vibration transients.
3Reliability
If conventional vibration attenuation systems are mounted on the airframe or mast, then vibrations at specific points are reduced, but amplified vibrations occur in other locations on the airframe
Solution Approach 1:
The patent extracts the vibration counteraction mechanism from the mast or airframe mounting and relocates it to the rotor hub. By mounting the counter-weights directly on the rotor hub, the system generates counter-vibrations at the source of rotor-induced vibrations, preventing the propagation and amplification of vibrations through the mast and airframe structure.
4Reliability
If hub shear pendulums are used for vibration attenuation, then approximately 50% of n/rev vibration is canceled, but the device is heavy and only attenuates vibrations at a single frequency
Solution Approach 1:
The patent uses counter-rotating weights with adjustable rotational speeds and positions, allowing the system to dynamically adapt to different vibration frequencies. This dynamic capability enables the lighter device to cancel vibrations at multiple frequencies (n/rev where n>1), unlike the fixed-frequency shear pendulum system, achieving both weight reduction and enhanced vibration cancellation effectiveness.
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 provides comprehensive vibration attenuation without relying on specific mast dynamics, effectively reducing N/REV vibrations and minimizing the impact of transients, thereby extending component life and improving passenger comfort.
Implementation Method 1
The vibration attenuator system has a base frame that revolves with the rotor hub and a central mass that moves in a circular path at N/REV frequencies. The mass moves in response to hub vibrations and generates oscillatory forces to counteract the vibrations.
Implementation Method 2
The centrally located mass moves in a circular path that varies in radius proportionally with the N/REV vibration magnitude. The revolving spring mass system utilizes centrifugal forces generated by the rotating masses to create counter-vibrations.
Implementation Method 3
The base frame is attached to a hub and revolves with the rotor hub. Springs connect the base frame to a centrally located mass, allowing the mass to move relative to the frame while storing and releasing elastic energy during the vibration attenuation process.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A vibration attenuator (301) for attenuating vibrations in a mast of an aircraft is disclosed. The vibration attenuator comprises a first spinner (215) configured for rotation about a first axis; a first mass (307) 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 (311) coupled to the first mass for selectively controlling a radial location of the first mass relative to the axis; and a first motor for driving the first spinner in rotation about the first axis.