Variable Stiffness Mechanism Using Mode-3 Buckling Beams
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Solution Overview
Problem
Conventional negative stiffness mechanisms are limited to two states and cannot switch or change between multiple negative stiffness states, restricting their ability to exhibit multiple values of negative stiffness, which is essential for applications like vibration isolation and shock mitigation.
Innovation Solution
The introduction of a variable stiffness structure comprising mode-3 buckling beams with an actuator system that allows for the controlled buckling and unbuckling of negative stiffness elements, enabling the system to switch between multiple negative stiffness states by using a cam with non-sinusoidal or irregular cam surfaces to compress or relax the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher-order mode buckled beams are used to achieve high isolation travel and nearly linear negative stiffness, then the negative stiffness is stable, but the ability to change the negative stiffness and create multiple states is limited
Solution Approach 1:
The system divides the negative stiffness mechanism into multiple independent first-order beam elements that can be individually controlled. Each beam can be independently buckled or unbuckled, allowing the system to achieve multiple discrete negative stiffness states by selectively activating different combinations of beams, rather than relying on a single higher-order mode beam that is limited to one state.
Solution Approach 2:
The system transitions from a static higher-order mode beam configuration to a dynamic system where first-order beams can be actively controlled between buckled and unbuckled states. This dynamic control enables real-time adjustment of negative stiffness values, allowing the mechanism to adapt between multiple states based on operational requirements.
2Device complexity
If conventional negative stiffness mechanisms are designed with fixed beam configurations, then the structure is simple, but the mechanism is limited to at most two states and cannot switch between multiple negative stiffness values
Solution Approach 1:
The mechanism is segmented into multiple independent first-order beam elements, each capable of being individually controlled. This segmentation allows the system to achieve multiple negative stiffness states through selective activation of different beam combinations, expanding functionality while maintaining relatively simple individual component designs.
Solution Approach 2:
The system uses universal first-order beam elements that can serve multiple functions - each beam can contribute to negative stiffness when buckled or provide positive stiffness when unbuckled. By selectively controlling different combinations of these universal elements, the system achieves multiple negative stiffness states without requiring complex specialized structures for each state.
3Adaptability or versatility
If first-order beam bending is used instead of higher-order mode buckling, then the ability to create adjustable positive spring component improves, but the negative stiffness characteristics become less stable
Solution Approach 1:
The system merges multiple first-order beam elements into a unified negative stiffness mechanism. By combining the effects of multiple beams that can be independently controlled, the system achieves both the adaptability of first-order bending and enhanced stability through the cumulative effect of multiple elements working together to provide consistent negative stiffness characteristics.
Solution Approach 2:
The system changes the operational parameters of first-order beams by controlling their buckling state through applied loads. By adjusting the compression force on each beam, the system can transition between buckled and unbuckled states, thereby changing the overall stiffness characteristics while maintaining the stability benefits of first-order beam theory.
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 solution allows for adjustable negative stiffness responses, enhancing the system's ability to isolate vibrations and mitigate shocks by enabling discrete changes in stiffness, reducing power and energy requirements compared to fully active systems.
Implementation Method 1
mode-3 buckling beams with an actuator system that allows for the controlled buckling and unbuckling of negative stiffness elements
Implementation Method 2
an actuator operatively coupled to ends of the first and second negative stiffness elements to control a stiffness of the variable stiffness structure
Data Source
AI summary
A variable stiffness structure includes a first negative stiffness element configured to buckle in a first direction, a second negative stiffness element configured to buckle in a second direction opposite to the first direction, and an actuator operatively coupled to ends of the first and second negative stiffness elements to control a stiffness of the variable stiffness structure. The first negative stiffness element and the second negative stiffness element are mode-3 buckling beams.