Rotating Mass Damper for Low-Frequency Vibration in Elongated Structures
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Solution Overview
Problem
Existing vibration control methods for elongated structures like wind turbines fail to effectively address the technical challenge of vibrations at very low frequencies and require significant mass or are complex and costly, and they often fail to address unpredictable vibrations effectively, particularly those involving unpredictable or changing vibrations, especially in unpredictable or varying loads, such as unpredictable or unpredictable vibrations, and they often fail to dampen vibrations efficiently at very low frequencies.
Innovation Solution
A vibration control device comprising a support structure with a rotating frame and a linear spring dashpot, which exerts a non-linear force to oscillate a mass around a rest position, effectively damping vibrations across a wide frequency range, including very low frequencies, and is simple, cost-effective, and adaptable to existing structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear resonators are used for vibration mitigation, then vibration reduction performance is improved when the system is well-tuned, but the device requires heavy mass (about 10% of the mass of the system to be damped) and is sensitive to detuning
Solution Approach 1:
The patent changes the fundamental parameter of the damping mechanism from linear spring-based to gravity-based nonlinear restoring force. This allows the device to achieve effective vibration damping with significantly reduced mass compared to linear resonators, as the gravity-based mechanism does not require heavy masses for structural support and can operate effectively across varying frequency conditions.
Solution Approach 2:
The patent employs a dynamically adjustable mechanism where the restoring force changes with the amplitude of oscillation. The nonlinear gravity-based restoring force automatically adapts to varying vibration amplitudes and frequencies, making the device less sensitive to detuning while maintaining effective vibration reduction performance.
2Reliability
If linear resonators are used for vibration mitigation, then vibration reduction is achieved under known dynamics properties, but the device is not applicable to floating wind turbines subject to varying loads
Solution Approach 1:
The patent utilizes parameter changes through the nonlinear gravity-based restoring force that naturally adapts to varying vibration amplitudes and frequencies. As the oscillation amplitude changes, the restoring force parameter changes accordingly, allowing the device to maintain effectiveness under varying load conditions without requiring retuning.
Solution Approach 2:
The device employs dynamic characteristics where the restoring force is not constant but varies with the position and velocity of the oscillating mass. This dynamic behavior enables the system to automatically adapt to changing operating conditions, making it suitable for floating wind turbines with varying loads.
3Reliability
If existing NES mechanisms are used for vibration control, then energy dissipation over large frequency band is achieved, but the mechanisms are complex and behave poorly at very low frequencies below 10Hz
Solution Approach 1:
The patent extracts the essential function of energy dissipation from complex NES mechanisms and implements it through a simplified gravity-based system. By removing unnecessary mechanical linkages and using direct gravitational force, the device achieves energy dissipation with minimal complexity while maintaining effectiveness at very low frequencies.
Solution Approach 2:
The patent substitutes complex mechanical NES mechanisms with a simpler gravity-based system. Instead of using intricate nonlinear spring mechanisms, the invention uses the straightforward gravitational force acting on an oscillating mass, which naturally provides the required nonlinear restoring force without mechanical complexity.
4Reliability
If structure size is increased to avoid resonance with environmental loads, then natural frequency distance from environmental loads is improved, but mechanical constraints and environmental impact worsen
Solution Approach 1:
The patent converts the harmful effect of vibrations into a beneficial control mechanism. Instead of trying to avoid resonance by increasing structure size, the invention uses the vibrational energy itself to drive a damping mechanism that dissipates the energy, turning the problem of vibration into the solution for vibration control.
Solution Approach 2:
The patent inverts the conventional approach by not trying to avoid vibration through structural changes but rather by actively managing and dissipating vibrational energy through a controlled damping mechanism. This inversion allows maintaining original structure dimensions while achieving vibration control.
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 device efficiently reduces vibration amplitude, tolerates tuning variations, and can be easily installed and maintained, providing rapid damping of vibrations, including rotational and translational modes, with reduced friction and increased lifetime.
Implementation Method 1
the linear spring dashpot is configured to exert a force to bring said mass to a rest position such that the mass oscillates around the rest position when the vibration control device is biased by a vibration
Implementation Method 2
it features considerably reduced friction between moving parts due to the use of rotational connections
Implementation Method 3
a rotating frame rotatably mounted on the support structure around a first axis
Implementation Method 4
linear spring dashpot comprising a first end that is pivotably attached to the support structure around a second axis and a second end pivotably attached to the rotating frame around a third axis
Data Source
Figure 1~2B
Figure 3~4
Figure 5~6
AI summary
Vibration control device (1) configured to dampen vibrations in an elongated structure, the vibration control device (1) comprising: - a support structure (2) configured to be anchored to the elongated structure, - a rotating frame (3) rotatably mounted on the support structure (2) around a first axis A1, and - a linear spring dashpot (6) comprising a first end (61) that is pivotably attached to the support structure (2) around a second axis A2 and a second end (62) pivotably attached to the rotating frame (3) around a third axis A3, wherein the rotating frame (3) comprises a mass (M) distant from said first axis A1, said linear spring dashpot (6) is configured to exert a force to bring said mass to a rest position such that the mass oscillates around the rest position about the first axis A1 when the vibration control device is biased by a vibration.