Variable Stiffness Hydraulic System for Vibration Isolation
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Solution Overview
Problem
Existing negative stiffness structures for vibration isolation are unstable and unable to maintain low or zero stiffness in the presence of large static load changes, limiting their effectiveness in isolating unwanted vibrations.
Innovation Solution
A variable stiffness structure combining a positive stiffness element with a negative stiffness element and a hydraulic system that adjusts the relative position of these elements in response to changes in load, using fluidic pressure to maintain a constant or zero stiffness, even under varying static forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a negative stiffness element is combined with a positive stiffness element to provide quasi-zero stiffness for vibration isolation, then vibration isolation performance is improved, but the structure becomes unstable and requires frequent tuning due to manufacturing inaccuracies
Solution Approach 1:
The patent uses a hydraulic system to dynamically adjust the stiffness parameter of the isolation structure. By changing the hydraulic pressure, the system can maintain quasi-zero stiffness across varying load conditions without requiring manual retuning, thereby resolving the instability issue while preserving vibration isolation performance
Solution Approach 2:
The hydraulic system incorporates feedback mechanisms that sense the current stiffness state and automatically adjust the hydraulic pressure to maintain the desired quasi-zero stiffness condition. This closed-loop control ensures stable operation despite manufacturing variations or external disturbances
2Stability of the object's composition
If a passive negative stiffness system is used where large motion causes the negative stiffness element to disengage and slip, then the system can handle large displacements, but it is unable to reset to its minimum stiffness after slippage, limiting vibration isolation ability
Solution Approach 1:
The hydraulic system acts as an intermediary between the negative stiffness element and the positive stiffness element. It controls their relative positioning and ensures that the negative stiffness element remains properly engaged within its operational range, preventing slippage while still allowing large displacements. This mediator function enables the system to maintain vibration isolation capabilities throughout the full displacement range
Solution Approach 2:
The patent replaces the purely mechanical engagement/disengagement mechanism with a hydraulically controlled system. The hydraulic actuator provides precise control over the relative position of the stiffness elements, eliminating the uncontrolled slippage that occurs in passive mechanical systems and enabling automatic reset functionality
3Adaptability or versatility
If a motor is used to adjust a secondary softer positive spring in parallel to the main support spring, then small changes in force can be compensated, but the system can only adjust to small changes in force and cannot handle large static load variations
Solution Approach 1:
The patent employs a hydraulic system instead of a motor to adjust the spring elements. The hydraulic actuator can generate sufficient force to handle large static load variations while providing fine control for small adjustments. The incompressible nature of hydraulic fluid ensures precise force transmission and enables the system to adapt to both small and large force changes effectively
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 low-amplitude vibrations while supporting large static forces, maintaining low stiffness at mid to high frequencies and allowing large loads to pass through, with minimal power consumption and wide bandwidth isolation.
Implementation Method 1
a hydraulic system coupled to the positive and negative stiffness elements and configured to adjust a relative position of the positive and negative stiffness elements in response to a change in the variable load
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A variable stiffness structure configured to support a variable load, the variable stiffness structure including a positive stiffness element coupled to the variable load, a negative stiffness element, a hydraulic system coupled to the positive and negative stiffness elements and configured to adjust a relative position of the positive and negative stiffness elements in response to a change in the variable load, while the variable stiffness structure supports the variable load.