Tunable Vibration Isolator Using Linear Inductance Motor
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Solution Overview
Problem
Existing vibration isolation systems in aircraft, particularly rotary wing aircraft, face challenges in effectively isolating harmonic vibrations from the propulsion system, as they often rely on toxic fluids like mercury and require tunable frequency responses to adapt to varying operational conditions.
Innovation Solution
A tunable vibration isolator system utilizing a high-density, low-viscosity fluid and a linear inductance motor assembly to actively adjust the isolation frequency, ensuring that oscillatory vibrations from the propulsion system are canceled, even when the vibratory frequency changes, by modifying the inertial force of the fluid through a conical flow diverter and elastomer members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mercury is used as the tuning fluid in the vibration isolator, then the isolator achieves effective vibration cancellation, but the system becomes toxic and highly corrosive
Solution Approach 1:
The patent replaces the toxic but effective mercury with a non-toxic alternative fluid that can be easily replaced if needed. The system uses a disposable or replaceable fluid reservoir design where the tuning fluid can be changed without replacing the entire isolator assembly, thereby eliminating the harmful effects of mercury while maintaining vibration cancellation performance.
Solution Approach 2:
The patent converts the harmful property of mercury (its effectiveness as a tuning fluid) into a benefit by identifying and using alternative fluids that achieve the same inertial effect without toxicity. The high density property essential for vibration cancellation is preserved in alternative fluids like brominated hydrocarbons or metal alloys, turning the search for a safer fluid into a beneficial design opportunity.
2Device complexity
If the isolator uses a fixed frequency response, then the design is simpler, but it cannot adapt to varying operational conditions and rotor RPMs
Solution Approach 1:
The patent implements a dynamic tuning mechanism where the isolator's frequency response can be adjusted during operation. This is achieved through a variable geometry tuning passage or adjustable mass distribution system that allows the isolation frequency to be changed based on operating conditions, transforming a static device into an adaptive system that maintains effectiveness across varying RPMs.
Solution Approach 2:
The patent enables frequency tuning by changing physical parameters of the isolator system, such as the length or cross-sectional area of the tuning passage, or the position of the tuning mass. These parameter changes allow the isolator to adapt its natural frequency to match varying excitation frequencies from the propulsion system, providing versatility without requiring a completely complex active control system.
3Ease of manufacture
If the tuning passage has a constant cross-sectional area, then the manufacturing is easier, but the fluid acceleration and vibration cancellation effectiveness are reduced
Solution Approach 1:
The patent employs curved or conical geometry in the tuning passage instead of a straight cylindrical shape. The conical expansion or curved profile of the passage increases the fluid acceleration for a given piston displacement, improving the inertial effect and vibration cancellation performance. This curved geometry, while slightly more complex to manufacture, provides significant performance benefits and can be produced using standard machining or casting processes.
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 effectively isolates fuselage vibrations from rotorcraft, maintaining efficient vibration cancellation across varying rotor RPMs and accounting for temperature and material aging effects, while avoiding the use of toxic fluids and minimizing damping losses.
Implementation Method 1
A vibration isolator utilizes inertial forces (m{"umlaut over (x)}") to cancel elastic forces (kx)
Implementation Method 2
The elastomer members can be any type known in the art, including but not limited to, rubber, silicone, fluorosilicone, polyurethane, and the like
Implementation Method 3
modifying the inertial force of the fluid through a conical flow diverter
Data Source
AI summary
A vibration isolator includes a housing having an upper fluid chamber, a lower fluid chamber, a piston, a tuning passage, and a linear inductance motor assembly for changing the isolation frequency of the vibration isolator. The piston is resiliently disposed within the housing. A vibration tuning fluid is located in the upper fluid chamber, the lower fluid chamber, and the tuning passage. The linear inductance motor assembly includes a magnet member and an inductance coil at least partially surrounding the magnet member. A control system is configured to selectively actuate the magnet member; wherein selective actuation of the magnet member selectively imparts a pumping force on the tuning fluid, thereby changing the isolation frequency.