MEMS Force Sensor Decoupling Springs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micro-electromechanical force sensors face challenges in protecting piezoresistive gauges from irreversible deformations due to mechanical stresses along the x and y axes, leading to reduced sensitivity and measurement range mismatch, with existing solutions failing to optimize both mechanical sensitivity and protection simultaneously.
Innovation Solution
A micro-electromechanical device with a mobile mass divided into a supporting structure and a main body connected by decoupling springs, which decouples in-plane movements from out-of-plane displacements, using torsionally deformable elements to increase mechanical sensitivity while protecting strain gauges from stresses, and featuring stops to absorb energy and prevent irreversible deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mobile mass is allowed to move out-of-plane to increase measurement range, then the sensitivity is improved, but the strain gauges become vulnerable to irreversible deformations from in-plane stresses
Solution Approach 1:
The mobile mass is divided into two distinct parts: a supporting structure that carries the strain gauges and remains constrained to out-of-plane movement, and a main body that can move both in-plane and out-of-plane. This segmentation isolates the sensitive gauges from damaging in-plane stresses while preserving the desired measurement capability.
Solution Approach 2:
Flexible connecting elements (springs) are introduced as intermediaries between the supporting structure and the main body. These springs allow controlled relative movement and force transmission while protecting the strain gauges from direct exposure to harmful in-plane mechanical stresses.
2Reliability
If deformable elements in torsion are used to restrict in-plane movements, then the strain gauges are protected, but the mechanical sensitivity decreases
Solution Approach 1:
Different regions of the system are assigned different mechanical properties: the connecting elements have high torsional stiffness to protect gauges from in-plane movement, while the out-of-plane flexibility is maintained through the spring design. This local differentiation allows simultaneous optimization of protection and sensitivity.
Solution Approach 2:
The solution moves the protective function from the measurement dimension (out-of-plane) to a different dimension (in-plane constraint). By restricting in-plane movements through torsional elements while allowing out-of-plane movement, the system protects gauges without compromising measurement sensitivity in the z-direction.
3Reliability
If the mobile mass is constrained to prevent in-plane displacements, then the strain gauges are protected from irreversible deformations, but the measurement range is reduced
Solution Approach 1:
The mobile mass is segmented into a supporting structure with constrained movement (protecting gauges) and a main body with freedom of movement (enabling measurement). This allows the system to simultaneously achieve gauge protection and extended measurement range.
Solution Approach 2:
The system transitions from static constraint to dynamic protection: the flexible connecting elements allow controlled in-plane movement of the main body while dynamically protecting the gauges through the elasticity of the springs, enabling both protection and extended measurement capability.
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 solution enhances mechanical sensitivity while protecting strain gauges from mechanical stresses, ensuring the force sensor's reliability and accuracy by decoupling movements and distributing external forces effectively, maintaining high sensitivity and preventing gauge damage.
Implementation Method 1
there are force sensors employing one or more piezoresistive gauges 3 sensitive in compression and in tension to the displacements of the mobile mass 1
Implementation Method 2
at least one deformable element, the deformable element connecting the mobile mass to the anchoring zone
Data Source
Figure 1A~2
Figure 3~4
Figure 5~7
AI summary
The invention relates to a micro-electromechanical device used as a force sensor, comprising a mobile mass connected to at least one securing zone by means of springs or deformable elements, and means for detecting the movement of the mobile mass, the mobile mass having an outer frame and an inner body, the outer frame and the inner body being connected by at least two flexible portions forming integral decoupling springs on two separate sides of the outer frame.