Variable Stiffness Structure with Clutch for Load-Adaptive Vibration Isolation

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Solution Overview

Problem

Conventional quasi-zero stiffness structures are unstable and unable to maintain low to zero stiffness in the presence of large static load changes, leading to ineffective vibration isolation and requiring frequent tuning or disengagement of negative stiffness elements.

Innovation Solution

A variable stiffness structure with a clutch mechanism that adjusts the connectivity between negative and positive stiffness elements, allowing for re-centering without disengagement, maintaining constant stiffness and isolating vibrations under varying loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a conventional quasi-zero stiffness structure is used, then vibration isolation is achieved, but the structure becomes unstable under large static load changes

Engineering Contradiction:

Improvevibration transmissionVSAvoidstructural stability

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent implements a dynamic adjustment mechanism that allows the system to adapt its stiffness characteristics in real-time. A motor-driven actuator adjusts the pre-compression force on the negative stiffness element based on detected static load conditions, enabling the structure to maintain stability across varying loads while preserving vibration isolation capabilities.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system incorporates a feedback control mechanism where a sensor detects changes in static load, and this information is used to automatically adjust the pre-compression force on the negative stiffness element. This closed-loop control ensures the structure remains stable under varying loads while maintaining effective vibration isolation.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If a motor is used to adjust the positive spring, then small force changes can be compensated, but the system cannot handle large static load changes

Engineering Contradiction:

Improveforce adjustment capabilityVSAvoidstatic load capacity

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

The patent changes the adjustment parameter from the positive spring force to the negative stiffness element's pre-compression force. This parameter change enables the system to handle large static load variations because the negative stiffness element can provide substantial force compensation through its non-linear characteristics, far exceeding the capability of conventional positive springs.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system performs preliminary action by pre-compressing the negative stiffness element before vibration isolation is needed. This pre-compression is adjusted based on the static load conditions, allowing the element to operate in its optimal non-linear range and provide the necessary force compensation for large load changes.

Inventive Principle:

Principle #10Preliminary action

3Force

If a passive negative stiffness system allows large motion, then the negative stiffness element can disengage, but the system cannot reset to minimum stiffness

Engineering Contradiction:

Improvestiffness rangeVSAvoidstiffness reset capability

Core Design Contradiction:

ForceVSEase of operation

Solution Approach 1:

The patent replaces the passive mechanical disengagement mechanism with an active motor-driven adjustment system. Instead of relying on large motions to disengage and slip the negative stiffness element, the motor actively controls the pre-compression force, enabling precise and reversible adjustment of the stiffness characteristics without requiring disengagement or large displacements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Manufacturing precision

If manufacturing techniques are not accurate enough, then QZS structures require frequent tuning, but higher precision manufacturing increases cost

Engineering Contradiction:

ImproveQZS structure accuracyVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The system incorporates a self-adjustment capability where the motor-driven mechanism automatically compensates for manufacturing tolerances and wear over time. The control system monitors the static load conditions and adjusts the pre-compression force accordingly, eliminating the need for frequent manual tuning and reducing dependence on high-precision manufacturing.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS9920793B1Negative stiffness system with variable preload adjustment

Publication Date: 2018.03.20 HRL LAB

AI summary

A variable stiffness structure configured to support a variable load, the variable stiffness structure including a shaft coupled to the variable load, a negative stiffness element, a clutch coupled to the negative stiffness element and configured to disengage and to engage the shaft, in response to a change in the variable load, while the structure supports the variable load.