Non-Concentric Revolving Masses for Rotor Vibration Control
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Solution Overview
Problem
Current vibration attenuation systems for rotor hubs in rotary-wing aircraft are not effective enough, requiring significant weight, power, and are prone to severe failure modes, while struggling to accurately predict and mitigate rotor-induced vibrations.
Innovation Solution
An active vibration control system is implemented, featuring a force generating device attached to the rotor hub with rotating unbalanced weights that create centrifugal shear forces to cancel rotor-induced vibrations, controlled by a microprocessor-based system using feedback from vibration sensors to minimize vibrations transmitted to the airframe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional active vibration control systems are implemented, then vibration reduction is achieved, but weight increases and device complexity increases
Solution Approach 1:
The patent employs non-concentric revolving masses where the counterweight axes are offset from the rotor mast axis by a distance 'e'. This asymmetric configuration creates centrifugal forces that are proportional to the offset distance, enabling effective vibration cancellation with reduced mass compared to conventional concentric systems. The asymmetric geometry transforms the vibration control mechanism into a more efficient force-generating system.
Solution Approach 2:
The system utilizes adjustable parameters including the offset distance 'e' between the rotor mast axis and counterweight axes, the rotational speed ratio between counterweights and rotor, and the phase angles of counterweight rotation. By optimizing these parameters, the system achieves effective vibration reduction while minimizing the required mass and system complexity.
2Object-affected harmful factors
If conventional active vibration control systems are implemented, then vibration reduction is achieved, but device complexity and power consumption increase
Solution Approach 1:
The counterweight assembly serves multiple functions simultaneously: it generates centrifugal forces for vibration cancellation, provides structural support, and enables phase and amplitude control through geometric configuration. This multi-functionality reduces the need for separate control mechanisms and actuators, thereby simplifying the overall system architecture and reducing device complexity.
3Object-affected harmful factors
If conventional active vibration control systems are implemented, then vibration reduction is achieved, but failure modes become more severe
Solution Approach 1:
The system incorporates passive vibration attenuation characteristics through the non-concentric mass configuration, which provides inherent stability and fail-safe operation. If active control fails, the geometric configuration ensures that the counterweights continue to provide some level of vibration reduction through their offset rotation, cushioning against complete system failure and maintaining basic operational safety.
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
This solution provides improved vibration reduction, extending the life of critical structural components, reducing avionics and engine vibration, and enhancing passenger comfort by effectively canceling source vibratory loads, while being lighter, more compact, and offering a fail-safe mode of operation.
Implementation Method 1
rotating unbalanced weights that create centrifugal shear forces to cancel rotor-induced vibrations
Data Source
AI summary
A vibration control system for a rotor hub provides vibration attenuation in an aircraft by reducing the magnitude of rotor induced vibratory. The system can include a force generating device attached to a rotor hub which rotates along with the rotor at the rotational speed of the rotor. Vibratory shear force is generated by rotating unbalanced weights each about an axis non-concentric with the rotor hub axis at high speed to create large centrifugal forces. The rotational speed of the weights can be a multiple of the rotor rotational speed to create shear forces for canceling rotor induced vibrations. The amplitude of the generated shear force is controlled by indexing the positions of the unbalanced weights relative to each other, while the phase of the shear force is adjusted by equally phasing each weight relative to the rotor.