Variable Stiffness Structure for Dynamic Vibration Isolation
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Solution Overview
Problem
Conventional quasi-zero stiffness structures are unstable and require fine adjustments for moderate performance, making them labor-intensive and impractical for many applications due to manufacturing inaccuracies and size constraints, especially when trying to isolate vibrations effectively.
Innovation Solution
A variable stiffness structure incorporating a negative stiffness element and an actuator to control the stiffness, combined with a positive stiffness element, allowing for a range of stiffness values from zero to the combined stiffness, using actuators like piezoelectric materials or electro-active polymers to dynamically adjust the structure's stiffness based on detected conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional quasi-zero stiffness structures are used for vibration isolation, then vibration isolation performance is improved, but manufacturing precision and stability deteriorate due to sensitivity to manufacturing inaccuracies requiring fine adjustments
Solution Approach 1:
The patent applies dynamics by making the stiffness of the negative stiffness element可调 (adjustable) through an actuator that applies compressive force. This allows the structure to dynamically adapt its stiffness characteristics, transforming a static quasi-zero stiffness structure into a dynamic one that can maintain optimal performance without requiring precise manufacturing tolerances. The actuator compensates for manufacturing variations by actively adjusting the compressive force on the negative stiffness element.
Solution Approach 2:
The patent changes the parameter of stiffness by using an actuator to vary the compressive force applied to the negative stiffness element. This parameter change allows the structure to transition between different stiffness states, enabling it to achieve desired vibration isolation performance while compensating for manufacturing inaccuracies through active control rather than relying solely on precise passive manufacturing.
2Object-affected harmful factors
If conventional quasi-zero stiffness structures are used for vibration isolation, then vibration isolation performance is improved, but device complexity and labor intensity increase due to required fine adjustments
Solution Approach 1:
The patent applies self-service by incorporating a control system with sensors and actuators that automatically adjust the stiffness of the negative stiffness element based on detected vibration conditions. The system monitors its own performance and self-regulates without requiring manual intervention or complex adjustment mechanisms, thereby reducing device complexity and labor intensity while maintaining effective vibration isolation.
Solution Approach 2:
The patent implements feedback by using sensors to detect vibration conditions and feeding this information back to a control system that adjusts the actuator force on the negative stiffness element. This closed-loop feedback mechanism automatically optimizes the vibration isolation performance without requiring manual adjustment, simplifying the overall device complexity while maintaining effective harm reduction.
3Force
If very long linear springs are used to achieve very low stiffness, then stiffness is reduced, but device complexity and size increase making them impractical
Solution Approach 1:
The patent applies composite materials by combining a negative stiffness element (such as a buckled beam or snap-through structure) with a positive stiffness spring. This composite configuration creates a quasi-zero stiffness system where the negative stiffness element counteracts the positive stiffness of the spring, achieving very low overall stiffness with a compact structure that does not require very long springs.
Solution Approach 2:
The patent applies segmentation by dividing the stiffness function into two separate components: a positive stiffness spring and a negative stiffness element. This segmentation allows each component to be optimized independently, with the spring providing structural support and the negative stiffness element providing the softening effect, thereby achieving low stiffness without requiring an excessively long single spring.
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 variable stiffness structure effectively isolates vibrations by dynamically adjusting its stiffness to match excitation frequencies, providing improved vibration isolation and comfort in applications like vehicles and gyroscopes, while also enabling energy harvesting and storage.
Implementation Method 1
Negative stiffness can be generated by non-linear behavior. For instance, simple and widely used non-linear structures that can generative negative stiffness include snap-through beams, buckling beams
Implementation Method 2
a negative stiffness element (e.g., a buckling-type beam than can exhibit non-linear behavior) can be combined with a positive stiffness element
Implementation Method 3
snap-through beams, buckling beams, over-rotation, and rolling or sliding contact between components
Implementation Method 4
using actuators like piezoelectric materials or electro-active polymers to dynamically adjust the structure's stiffness
Implementation Method 5
using actuators like piezoelectric materials or electro-active polymers to dynamically adjust the structure's stiffness
Implementation Method 6
The variable stiffness structure effectively isolates vibrations by dynamically adjusting its stiffness to match excitation frequencies, providing improved vibration isolation and comfort
Implementation Method 7
dynamically adjusting its stiffness to match excitation frequencies
Data Source
AI summary
A variable stiffness structure configured to isolate a mass from unwanted vibrations includes a negative stiffness element and an actuator operatively coupled to the negative stiffness element. The actuator is configured to be actuated to control a stiffness of the negative stiffness element. The variable stiffness structure may also include a positive stiffness element coupled to the negative stiffness element.