Triaxial Acceleration Sensor Using Anisotropic Elastic Springs
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Solution Overview
Problem
Existing three-dimensional acceleration sensors face challenges in achieving accurate detection of acceleration in multiple directions due to manufacturing process variations, such as weight deviation and rotation, which affects detection accuracy and production yield, and require a more flexible design to accommodate three-dimensional movement while maintaining symmetry and miniaturization.
Innovation Solution
The acceleration sensor employs a configuration with two biaxial sensors, each with elastic members that are stiff in one direction to prevent weight rotation and allow movement in two dimensions, enabling detection of acceleration in three directions with improved accuracy and reduced size, using springs with specific zigzag patterns to enhance stiffness and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a spring is configured to allow movement in three dimensions with equal spring constants in respective axial directions, then the weight can move three dimensionally according to acceleration, but manufacturing variations cause weight deviation and rotation, lowering detection accuracy
Solution Approach 1:
The spring is designed with different stiffness characteristics in different directions: it has high stiffness in the first direction (parallel to substrate plane) and high stiffness in the second direction (perpendicular to first direction), but low stiffness in the third direction (perpendicular to substrate plane). This anisotropic spring configuration prevents weight rotation while allowing controlled movement, resolving the contradiction between three-dimensional movement capability and detection accuracy.
2Measurement precision
If a spring is configured with equal spring constants in all axial directions for symmetric three-dimensional acceleration detection, then detection accuracy in respective axial directions is improved, but the device size increases when using multiple uniaxial sensors
Solution Approach 1:
A single biaxial acceleration sensor integrates the functionality of multiple uniaxial sensors by using a weight that can move in two directions (first and second directions parallel to substrate plane) with appropriate spring configurations. This universal sensor design enables detection of acceleration in three directions (including third direction perpendicular to substrate plane through electrostatic capacity changes) while reducing the overall device size compared to using separate uniaxial sensors.
3Adaptability or versatility
If a weight is made movable in three dimensions to detect acceleration in all directions, then the sensor becomes more versatile, but manufacturing variations cause center of gravity deviation and rotation, reducing production yield
Solution Approach 1:
The spring is designed with directionally dependent stiffness: high stiffness in the first direction (parallel to substrate), high stiffness in the second direction (perpendicular to first direction), and low stiffness in the third direction (perpendicular to substrate). This local quality differentiation prevents the weight from rotating due to manufacturing variations while still allowing it to move freely in the third direction for acceleration detection, thereby improving production yield while maintaining versatility.
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 enhances detection accuracy and production yield by preventing weight rotation and allowing flexible design, while miniaturizing the sensor size compared to traditional three-dimensional sensors composed of multiple uniaxial sensors.
Implementation Method 1
a first elastic member that is fixed to the substrate at one end thereof and configured to move elastically according to acceleration with respect to two different directions one of which is a first direction parallel to a plane of the substrate and other one of which is a third direction perpendicular to the plane of the substrate
Implementation Method 2
detect acceleration associated with a change of electrostatic capacity in the capacitor
Data Source
AI summary
A first sensor section installed in an acceleration sensor employs a first elastic member which is elastically movable according to acceleration in the first and third directions and is stiff against acceleration in second direction so as to restrict elasticity in second direction. Thereby, the first sensor section is provided as a biaxial acceleration sensor which detects the first and third directional acceleration according to a change of electrostatic capacity between a first weight (i.e. the first movable electrode) made movable according to acceleration and the first fixed electrode. A second sensor section installed in the acceleration sensor is structurally identical with the first sensor section and configured to detect acceleration in second and third directions. Thereby, such combination of the first sensor section and the second sensor section constitutes a three-dimensional acceleration sensor.