Rotating Mass Damping System for Structural Oscillation Control

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Solution Overview

Problem

Existing structures, such as wind turbine towers and bridges, experience mechanical stress and discomfort due to oscillations, which can lead to damage and malfunction, and current damping systems are inadequate for effectively addressing these issues.

Innovation Solution

A system utilizing two solid masses with controllable moments of inertia, rotating in opposite directions at the frequency of oscillation, generates a harmonic force to dampen oscillations, with phase and amplitude control to align the resulting motion with the oscillation direction, using sensors and controllers to adjust the masses' positions and phases for optimal damping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a movable mass is set into simple linear oscillations to dampen structure oscillations, then oscillation damping is achieved, but the system complexity and control limitations increase

Engineering Contradiction:
Improveoscillation damping effectivenessVSAvoiddamping system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies the dynamics principle by transitioning from simple linear oscillation to controlled rotational oscillation of two masses. The masses rotate in opposite directions about axes transverse to the oscillation direction, with individually controllable frequencies and phases. This dynamic control approach allows the system to adapt to varying oscillation conditions while maintaining effectiveness, resolving the contradiction between damping reliability and system complexity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent implements parameter changes by allowing individual control of the rotating masses' frequencies, phases, and moments of inertia. The moments of inertia can be adjusted by shifting the centres of gravity of the masses relative to their rotation axes. This parametric control enables optimization of damping performance for different oscillation scenarios without requiring overly complex system architecture.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If two masses rotate at the frequency of oscillation in opposite directions to generate harmonic force, then oscillation damping improves, but the control system complexity increases

Engineering Contradiction:
Improvedamping performanceVSAvoidcontrol system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies periodic action by rotating the two masses at the oscillation frequency in opposite directions. This periodic rotational motion generates a harmonic force that counteracts the structure's oscillations. The synchronized periodic rotation simplifies the control strategy compared to arbitrary motion control, as the frequencies are locked to the oscillation frequency, reducing control system complexity while maintaining high damping performance.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent uses the anti-weight principle by having two masses rotate in opposite directions. The counter-rotation creates balanced harmonic forces that effectively counteract the oscillation without requiring excessive control intervention. This symmetric counter-rotation approach simplifies control while achieving reliable damping.

Inventive Principle:
Principle #8Anti-weight (Counterweight)

3Measurement precision

If the moments of inertia of rotating masses are individually controlled to optimize damping, then oscillation control precision improves, but the system complexity and manufacturing difficulty increase

Engineering Contradiction:
Improveoscillation control precisionVSAvoidmass adjustment mechanism complexity
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent extracts the moment of inertia control function into a separate adjustable mechanism. The centres of gravity of the masses can be shifted relative to the rotation axes through dedicated adjustment mechanisms, separating this control function from the basic rotation mechanism. This modular approach allows precise moment of inertia control without overly complicating the overall manufacturing process.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies dynamics by making the moments of inertia adjustable rather than fixed. The ability to shift centres of gravity allows the system to adapt to different oscillation conditions, improving control precision. This dynamic adjustability is implemented through practical mechanisms that balance precision requirements with manufacturing feasibility.

Inventive Principle:
Principle #15Dynamics

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 system effectively reduces oscillations in structures by generating a harmonic force that counteracts the oscillations, minimizing mechanical stress and discomfort, and can be adapted to various structures, including wind turbine towers, by continuously monitoring and adjusting the masses' moments of inertia and phases.

Implementation Method 1

When two masses of equal moments of inertia are rotated at the same frequency in opposite directions, the resulting equivalent force will be a harmonic force

Methodology Applied
Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP2167748B2A system for damping oscillations in a structure
Publication Date: 2015.03.25 VESTAS WIND SYSTEMS AS
  • EP2167748B2 patent drawingFigure 1~2

AI summary

The system for damping oscillations in a structure according to the invention provides two masses that can be controlled to rotate at the frequency of oscillation of the structure and in opposite directions about axes of rotation transverse to the direction of the oscillations. The masses have individually controllable moments of inertia, and when their moments of inertia are equal a harmonic linear force is generated. The phases of the rotating masses can be individually controlled whereby the direction of the resulting harmonic linear force can be controlled. The moments of inertia can be controlled by shifting their centres of gravity relative to the respective axes of rotation.