Adjustable Negative Stiffness Mechanism for Wide-Range Vibration Isolation
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Solution Overview
Problem
Existing negative stiffness mechanisms lack the ability to support significant loads when soft and are limited in isolating both low and large amplitude vibrations, with pneumatic components requiring large volume air springs and high-friction seals, and voice coil or piezoelectric components failing to isolate larger amplitude vibrations effectively.
Innovation Solution
An adjustable negative stiffness mechanism featuring a central shaft, outer annular member, and negative stiffness elements with an actuator that compresses and expands to adjust mechanical response, utilizing hydraulic or pneumatic bladders, wedge-shaped members, and motors to rotate the annular member and align cam surfaces with the negative stiffness elements, allowing for varying stiffness and isolation of vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pneumatic components are used in negative stiffness mechanisms, then the mechanism can provide adjustable stiffness, but the mechanism requires large volume air springs and high-friction seals which prevent isolation of low amplitude vibrations
Solution Approach 1:
The patent removes the pneumatic components (air springs and seals) from the negative stiffness mechanism, replacing them with a purely mechanical actuation system. This extraction eliminates the friction and volume issues associated with pneumatic components while maintaining the adjustable stiffness capability through mechanical means such as variable stiffness springs and leveraged mechanisms.
Solution Approach 2:
The patent replaces the pneumatic actuation system with a mechanical actuation system. Instead of using air springs and seals to adjust stiffness, the invention employs mechanical components such as variable stiffness springs, leveraged mechanisms, and mechanical actuators that can adjust the negative stiffness without introducing friction or volume constraints.
2Adaptability or versatility
If voice coil or piezoelectric components are used in negative stiffness mechanisms, then the mechanism can provide adjustable stiffness, but the mechanism is not capable of isolating larger amplitude vibrations
Solution Approach 1:
The patent implements a dynamic system where the negative stiffness mechanism can adapt its mechanical properties in real-time. The variable stiffness springs and leveraged mechanisms allow the system to dynamically adjust its stiffness characteristics, enabling it to effectively isolate both low and large amplitude vibrations by changing its mechanical response to match the vibration conditions.
Solution Approach 2:
The patent changes the mechanical parameters of the negative stiffness mechanism through mechanical actuation. By adjusting the pre-compression of variable stiffness springs, changing the leverage ratio through mechanical linkages, or modifying the geometric configuration of the mechanism, the system can alter its stiffness parameters to maintain effective isolation across different vibration amplitudes.
3Adaptability or versatility
If related art negative stiffness mechanisms are used, then the mechanism can exhibit negative stiffness, but the mechanism is incapable of supporting a significant load when soft
Solution Approach 1:
The patent applies preliminary compression to the variable stiffness springs to establish a pre-load condition. This preliminary action ensures that the mechanism can support significant loads even when operating in the soft negative stiffness regime. The pre-compression creates a baseline force that prevents the mechanism from becoming too compliant under load.
Solution Approach 2:
The patent employs a composite structure combining negative stiffness elements with positive stiffness elements. The variable stiffness springs work in conjunction with leveraged mechanisms and supporting structural elements to create a composite system that maintains both negative stiffness characteristics and adequate load support capability. The combination of different mechanical elements allows the system to achieve both softness for isolation and strength for load bearing.
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 mechanism effectively isolates vibrations across a range of amplitudes by adjusting its stiffness, supporting loads while minimizing friction and volume requirements, enhancing the usability of negative stiffness in vibration isolation and shock mitigation applications.
Implementation Method 1
A variety of non-linear structures exhibit negative mechanical stiffness, such as snap-through beams and buckling beams. Negative stiffness may also be exhibited by various combinations and arrangements of springs and/or beams with pinned or clamped boundaries.
Implementation Method 2
The actuator may include a hydraulic or pneumatic bladder configured to move between an inflated state to compress the at least two negative stiffness elements and a deflated state to expand the at least two negative stiffness elements.
Implementation Method 3
The actuator may include an inner cam surface on the annular member configured to engage the outer ends of the at least two negative stiffness elements and a motor operatively coupled to the annular member to rotate the annular member around the central shaft. The rotation of the annular member around the central shaft alternately aligns the at least one peak on the cam surface with the negative stiffness elements to compress the negative stiffness elements and aligns the at least one recess on the cam surface to expand the negative stiffness elements.
Implementation Method 4
The actuator may also include a flexure coupled to the outer end of each of the at least two negative stiffness members. Each of the flexures is configured permit movement of the outer ends of the negative stiffness members in a first direction and prevent movement of the outer ends of the negative stiffness members in a second direction perpendicular to the first direction.
Data Source
Figure 1A~1C
Figure 2
Figure 3A
AI summary
An adjustable negative stiffness mechanism is disclosed. The adjustable negative stiffness mechanism includes a central shaft, an outer annular member extending around the central shaft, at least two negative stiffness elements extending between the central shaft and the annular member, and an actuator coupled to the negative stiffness elements. Each of the negative stiffness elements has an inner end coupled to the central shaft and an outer end engaging the annular member. The actuator is configured to compress and expand the negative stiffness elements to adjust a negative stiffness mechanical response exhibited by the negative stiffness elements.