Hover Rotor Eccentric Mass Assembly for Vibration Attenuation
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Solution Overview
Problem
Existing helicopter rotors experience high-frequency and low-frequency vibrations that deteriorate occupant comfort and cause structural stress, with known active attenuating devices being bulky, costly, and lacking flexibility in adjusting to rapid vibration changes.
Innovation Solution
A rotor design incorporating mass units with eccentrically rotating masses and a transmission unit to generate centrifugal forces that counteract vibrations, featuring a compact epicyclic train and reversible gear coupling for precise adjustment of attenuating forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive attenuating devices are used, then simplicity of construction is improved, but vibration attenuation performance deteriorates
Solution Approach 1:
The patent employs dynamic vibration absorbers with adjustable mass and eccentricity parameters that can be tuned to match varying vibration frequencies. The attenuating device includes movable masses that can be repositioned along the rotor shaft to adapt to different operating conditions, transforming a static system into a dynamic one that maintains effectiveness across varying speeds and loads.
Solution Approach 2:
The invention allows modification of key parameters including mass of attenuating weights, eccentricity distance, and rotational speed of counterweights. By adjusting these parameters, the system can optimize vibration cancellation for different frequency ranges and intensity levels, overcoming the fixed-performance limitation of passive devices.
2Reliability
If active attenuating devices are used, then vibration attenuation performance is improved, but device complexity and cost deteriorate
Solution Approach 1:
The system uses dynamically adjustable counterweights that can change their position and mass distribution in real-time, providing adaptive vibration cancellation without requiring complex electronic control systems. The mechanical adjustability replaces sophisticated sensors and actuators with simpler manual or automated weight positioning mechanisms.
Solution Approach 2:
By enabling parameter adjustment of mass and eccentricity, the system achieves active-like performance where the attenuating characteristics can be optimized for different conditions. This provides flexible vibration control comparable to active systems but with reduced complexity by using mechanical adjustment rather than electromagnetic actuators.
3Reliability
If existing active attenuating devices are used, then vibration attenuation is improved, but adaptability to rapid vibration changes deteriorates
Solution Approach 1:
The patent implements a dynamically reconfigurable attenuating system where masses can be rapidly repositioned along the rotor shaft in response to changing vibration conditions. This dynamic capability allows the system to track and counteract rapid frequency modulations and transient vibrations that static or slowly-adjusting systems cannot handle.
Solution Approach 2:
The system can be pre-configured with multiple mass positions and eccentricity settings optimized for anticipated operating conditions. By preparing these configurations in advance, the system can quickly switch between predetermined settings to respond to rapid changes without requiring complex real-time calculation and adjustment mechanisms.
4Object-affected harmful factors
If vibration attenuation devices are added, then occupant comfort is improved, but weight and bulk deteriorate
Solution Approach 1:
The attenuating device is integrated within the existing rotor structure, with counterweights positioned inside the rotor hub or along the rotor shaft. This nesting approach utilizes existing structural space, avoiding the need for separate external attenuation systems that would add significant weight and bulk to the helicopter.
Solution Approach 2:
The rotor structure serves dual functions: primary rotation for lift generation and secondary vibration attenuation through integrated counterweights. By making the rotor system itself multi-functional, the invention eliminates the need for dedicated attenuation hardware, thereby minimizing additional weight and spatial requirements.
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 rotor effectively attenuates vibrations by adjusting centrifugal forces to match vibration frequencies, reducing structural stress and improving comfort while minimizing weight, bulk, and cost.
Implementation Method 1
The masses are coupled to the rotation of the mast by a transmission device so that the masses of the first mass unit rotate eccentrically around the mast with a rotational speed with respect to the fixed system equal to N*Ω and in the same direction of rotation as the mast, and the masses of the second mass unit rotate with a rotational speed equal to N*Ω with respect to the fixed system and in the opposite direction of rotation to the mast. In this way, the masses generate respective radial centrifugal forces with respect to the axis of the mast.
Data Source
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AI summary
A rotor (3') for an aircraft (1) is described that has a mast (50), an attenuating device (7') to attenuate the transmission of vibrations from the mast (50) in a plane orthogonal to the first axis (A), and a transmission device (15) interposed between the mast (50) and the attenuating device (7'); the attenuating device (7') comprises a first and a second mass unit (8, 9) with a first and a second mass (10, 11) rotatable about the first axis (A) with a first and a second rotational speed ((N-1)*Q; (N+1)*Ω), two control units (40) operable to cause an additional rotation of at least one of the first and second masses (10, 11), and a first and a second support assembly (41, 42) carrying the first and second masses (10, 11); each control unit (40) controls the angle between the first and second masses (10, 11) and comprises a set of drive gear teeth (55') integral with the first support assembly (41, 42), a cogwheel (56) with a set of control gear teeth (57) meshing with the drive gear teeth (55'), and an actuator (58) to cause the rotation of the cogwheel (56) about a second axis (F) and of the first mass (10, 11) about said first axis (A).