Micromechanical Accelerometer Stiffness Switching for Wide-Range Sensing
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Solution Overview
Problem
Existing acceleration sensors face challenges in simultaneously measuring both low and high accelerations with optimal sensitivity and full scale range due to the inverse proportionality of these parameters, leading to increased complexity, integration area, and cost when multiple sensors are used, and mechanical contacts in single sensors cause damage and sticking issues.
Innovation Solution
A micromechanical device with a movable structure and a control structure that varies the total elastic constant through capacitive control, allowing for two operating modes with different elastic constants, enabling efficient measurement of accelerations using a single sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single acceleration sensor is used to measure both low and high accelerations, then the integration area and device complexity are reduced, but the measurement precision and reliability deteriorate due to the inverse proportionality between full scale range and sensitivity
Solution Approach 1:
The patent applies the dynamics principle by making the elastic constant of the sensor variable rather than fixed. The elastic constant can be dynamically changed between a first value (for high acceleration measurement with larger full scale range) and a second value (for low acceleration measurement with higher sensitivity). This is achieved through a variable elastic constant mechanism that allows the sensor to adapt its mechanical properties based on the measurement requirements, resolving the contradiction between full scale range and sensitivity.
2Adaptability or versatility
If mechanical contacts are used to vary the elastic constant, then the full scale range and sensitivity can be adjusted, but the reliability deteriorates due to damage and sticking issues
Solution Approach 1:
The patent replaces the mechanical contact-based elastic constant variation mechanism with a different approach that avoids direct mechanical contacts between moving parts. By substituting the mechanical contact system with an alternative mechanism (such as magnetic or electrostatic actuation), the patent eliminates the sticking and damage problems associated with mechanical contacts while maintaining the ability to adjust the elastic constant for different measurement ranges.
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 device achieves enhanced acceleration measurement by optimizing sensitivity and full scale range through capacitive control, reducing sensor complexity and integration area, and minimizing mechanical contact-related issues.
Implementation Method 1
a capacitively controllable control structure to vary a total elastic constant of the micromechanical device
Implementation Method 2
an elastic assembly which has an equivalent elastic constant (Keq), is mechanically coupled to the movable structure (53) and to the semiconductor body (51) and is configured to elongate and contract along the oscillation direction (61) to allow the oscillation of the movable structure (53) as a function of a force applied to the movable structure (53) along said oscillation direction (61), said force being caused by an acceleration applied to the micromechanical device (50)
Data Source
AI summary
Micromechanical device comprising: a semiconductor body; a movable structure configured to oscillate relative to the semiconductor body along an oscillation direction; and an elastic assembly with an elastic constant, coupled to the movable structure and to the semiconductor body and configured to deform along the oscillation direction to allow the oscillation of the movable structure as a function of an acceleration applied to the micromechanical device. The movable structure and the semiconductor body comprise a control structure for the capacitive control of the oscillation of the movable structure: when the control structure is electrically controlled in a first state the micromechanical device is in a first operating mode wherein a total elastic constant of the micromechanical device has a first value, and when it is electrically controlled in a second state the micromechanical device is in a second operating mode wherein the total elastic constant has a second value lower than, or equal to, the first value.