Single Inertial Mass MEMS Accelerometer for Compact Three-Axis Detection
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Solution Overview
Problem
Existing MEMS three-axis accelerometers have large dimensions due to the need for separate inertial masses and elastic coupling elements for each detection axis, which limits their optimization and integration in compact devices.
Innovation Solution
A MEMS three-axis capacitive accelerometer design featuring a single inertial mass suspended above a substrate, with elastic coupling elements allowing movement along three orthogonal axes, reducing the overall dimensions and enabling efficient detection of accelerations along x, y, and z axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate inertial masses and elastic coupling elements are used for each detection axis, then detection functionality along three orthogonal axes is achieved, but device dimensions become large (1000-1200 μm)
Solution Approach 1:
The patent merges multiple inertial masses into a single shared inertial mass that serves all three detection axes (x, y, z). This single mass is suspended by elastic coupling elements that enable movement detection along all three orthogonal axes simultaneously, eliminating the need for separate inertial masses for each axis and reducing the overall device footprint from 1000-1200 μm to a more compact size.
Solution Approach 2:
The single inertial mass performs multiple functions by detecting accelerations along three orthogonal axes. The elastic coupling elements are designed to enable this single mass to respond to external accelerations along x, y, and z directions, making the inertial mass a universal sensing element for all three detection axes rather than requiring dedicated masses for each direction.
2Measurement precision
If multiple inertial masses are integrated for three-axis detection, then detection precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple inertial masses into one shared mass that is coupled to the substrate through elastic coupling elements. This single mass structure maintains detection precision by properly coupling to the substrate while eliminating the complexity of integrating multiple separate inertial masses and their respective elastic coupling elements for each axis.
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 design achieves reduced dimensions, improved performance by minimizing thermal drift and cross-sensitivity, and enhanced linearity in acceleration detection, with a maximum encumbrance of 500-600 μm in the horizontal plane, suitable for integration in electronic devices like smartphones and cameras.
Implementation Method 1
a frame element, elastically coupled to said inertial mass by coupling elastic elements, and coupled to anchorages, fixed with respect to said substrate, by anchorage elastic elements, wherein said coupling elastic elements and said anchorage elastic elements are configured so as to enable a first inertial movement of said inertial mass in response to a first external acceleration in a first direction lying in said plane, and to enable a second inertial movement of said inertial mass in response to a second external acceleration in a second direction transverse to said plane
Implementation Method 2
Capacitive detection techniques are commonly used to determine the external acceleration acting on the sensor, as a function of the variation of capacitance defined by the capacitive coupling between the mobile regions and the fixed regions of the sensor, which form with one another capacitors with plane and parallel plates
Data Source
AI summary
A micromechanical structure for a MEMS structure is provided with: a substrate; a single inertial mass having a main extension in a plane and arranged suspended above the substrate; and a frame element, elastically coupled to the inertial mass by coupling elastic elements and to anchorages, which are fixed with respect to the substrate by anchorage elastic elements. The coupling elastic elements and the anchorage elastic elements are configured so as to enable a first inertial movement of the inertial mass in response to a first external acceleration acting in a direction lying in the plane and also a second inertial movement of the inertial mass in response to a second external acceleration acting in a direction transverse to the plane.