Optical Sensor Bi-Stable Spring Negative Stiffness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical sensor devices face a trade-off between size reduction and sensitivity, with the minimum achievable diameter of glass fibers limiting the stiffness and sensitivity of intrinsic fiber optic sensors, particularly in small-sized sensors, which restricts their dynamic operational frequency range and response to variations.
Innovation Solution
Incorporating a bi-stable spring with a negative stiffness range into the optical sensor design, where the optical fiber acts as a positive spring counteracting the bi-stable spring, effectively reducing the system's spring constant and enhancing sensitivity without increasing size, allowing the sensor to operate within a negative stiffness range that prevents unstable equilibrium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the optical sensor device is reduced, then the device can be implemented in compact applications, but the sensitivity of the sensor deteriorates
Solution Approach 1:
The patent introduces a bi-stable spring mechanism that dynamically changes the stiffness characteristics of the sensor system. The spring transitions between two stable states, enabling the sensor to operate in a negative stiffness range that amplifies the response to external actions. This dynamic behavior allows compact sensor design while maintaining high sensitivity through state-dependent stiffness modulation.
Solution Approach 2:
The patent changes the physical parameter of spring stiffness by utilizing the bi-stable spring's ability to operate in a negative stiffness range. By pre-stressing the optical fiber and positioning the bi-stable spring in its negative stiffness operational range, the system achieves enhanced sensitivity without increasing size. The parameter change from positive to negative stiffness is the key mechanism resolving the size-sensitivity trade-off.
2Length of moving object
If the diameter of the optical fiber is reduced, then the device size is minimized, but the stiffness and sensitivity of the sensor are limited
Solution Approach 1:
The patent applies the counterweight principle by using the bi-stable spring to counteract the limited stiffness of thin optical fibers. The negative stiffness characteristic of the bi-stable spring compensates for the reduced stiffness of smaller diameter fibers, allowing the use of minimally sized fibers while maintaining adequate sensor sensitivity and performance.
Solution Approach 2:
The patent creates a composite sensing system combining the optical fiber with the bi-stable spring mechanism. This composite structure leverages the advantages of both components: the miniaturization capability of thin optical fibers and the stiffness amplification provided by the bi-stable spring's negative stiffness behavior, achieving both small size and adequate strength.
3Volume of moving object
If the sensor size is reduced for cable implementation, then the sensor can be used in exploration and geological survey applications, but the dynamic operational frequency range is limited by resonance frequency
Solution Approach 1:
The bi-stable spring mechanism provides dynamic stiffness modulation that extends the operational frequency range of the compact sensor. By operating in the negative stiffness range, the system can respond to higher frequency variations without being constrained by the resonance frequency limitations that would affect a conventional rigid compact sensor design.
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 configuration increases the sensitivity of the optical sensor device by amplifying its response to input actions, enabling a broader operational frequency range and faster response to variations without modifying the optical fiber, while maintaining tension and preventing the bi-stable spring from reaching unstable equilibrium.
Implementation Method 1
the transmission structure comprises a bi-stable spring having a first and a second stable deflection position and a negative stiffness range around an unstable equilibrium position between the first and second stable deflection position
Implementation Method 2
the optical fiber between the transmission structure and the reference body is pre-stressed such as to be tensed, said optical fiber thereby acting as a spring having a first spring constant of positive value
Implementation Method 3
An FBG comprises a fiber having a core including therein, over a certain distance, a periodic variation of the refractive index. This periodic variation forms a wavelength-specific dielectric mirror, wherein light in a specific (narrow) range around and including a certain wavelength is reflected
Implementation Method 4
The FBG is based on the principle that a difference in strain of the optical fiber causes the geometric periodicity of the variations to change. This results in a change of the reflected wavelength, such change can be detected
Data Source
AI summary
The invention is directed at an optical sensor device, comprising a sensing element for receiving an input action, an optical fiber comprising an intrinsic fiber optic sensor, and a transmission structure arranged for exerting a sensing action on the optical fiber in response to the input action received by the sensing element, wherein the optical fiber in a first connecting part thereof is connected to a reference body and wherein the optical fiber in a second connecting part thereof is to the transmission structure for receiving the sensing action, the first connecting part and the second connecting part of the optical fiber being located on either side of the intrinsic fiber optic sensor, wherein the transmission structure comprises a bi-stable spring having a first and a second stable deflection position and a negative stiffness range around an unstable equilibrium position between the first and second stable deflection position, and wherein the optical fiber between the transmission structure and the reference body is pre-stressed such as to be tensed, said optical fiber thereby acting as a spring having a first spring constant of positive value, wherein the optical fiber thereby counteracts a spring action of the bi-stable spring such as to operate the bi-stable spring in a deflection position range within the negative stiffness range, the deflection position range not including the unstable equilibrium position of the bi-stable spring.