Triaxial Accelerometer Elastic Beam Asymmetry
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Solution Overview
Problem
Current triaxial accelerometers face reduced detection accuracy due to structural eccentricity, which causes swinging movements instead of linear movements, increasing axis coupling and reducing capacitor displacement, especially in X-axis and Y-axis measurements.
Innovation Solution
A micro-electromechanical inertial measurement module with a substrate, a mass block suspended by elastic beams, and movable electrodes, where the elastic beams are cross-connected and deviated from the mass block's center, forming differential capacitors to measure X-axis, Y-axis, and Z-axis accelerations without structural eccentricity affecting linear movement, thus improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an eccentric structure is used to measure z-axis acceleration, then the structure can detect z-axis movement, but the detection movement becomes a swinging movement rather than linear movement, increasing axis coupling and reducing capacitor displacement
Solution Approach 1:
The accelerometer is divided into three independent detection systems: an eccentric structure for z-axis detection and two symmetric elastic beams for x-y plane detection. This segmentation allows each subsystem to specialize in its designated axis without interfering with others, eliminating the swinging movement problem that occurred when a single eccentric structure attempted to detect all three axes.
Solution Approach 2:
The invention transitions from using a single eccentric structure for all axes to using the eccentricity principle only for the z-axis (vertical dimension), while the x-y plane detection uses a separate symmetric beam structure. This dimensional separation allows the eccentric structure to fulfill its z-axis function without causing swinging movements that would degrade x-y axis measurement precision.
2Device complexity
If a single eccentric structure is used for all three axes, then the device complexity is reduced, but the coupling between axes increases and detection accuracy is greatly reduced
Solution Approach 1:
The detection system is segmented into two parts: an eccentric mass block for z-axis detection and two symmetric elastic beams for x-y axis detection. This segmentation increases structural complexity slightly but dramatically improves detection accuracy by eliminating axis coupling and swinging movements, making the trade-off worthwhile.
3Measurement precision
If the elastic beams are cross-connected with deviation from the mass block center, then linear movement is maintained and axis coupling is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The elastic beams are designed with intentional asymmetric positioning relative to the mass block center, with their centers deviated from the gravity center. This asymmetric design is carefully controlled to maintain linear movement and reduce axis coupling, improving detection accuracy while the manufacturing process incorporates precise alignment requirements to ensure proper function.
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 ensures linear movement of the mass block in the X-axis and Y-axis directions, reducing axis coupling and enhancing detection accuracy by maintaining displacement and improving the overall measurement precision of the triaxial accelerometer.
Implementation Method 1
elastic beams configured to connect the substrate with the mass block, wherein the elastic beams comprise a first elastic beam located in the X-axis direction and a second elastic beam located in the Y-axis direction
Implementation Method 2
an upper electrode for forming a Z-axis detection capacitor with the first pole piece is arranged on the mass block; the substrate is provided with a first fixed electrode configured to form a Y-axis detection capacitor with the first movable electrode, and a second fixed electrode configured to form an X-axis detection capacitor with the second movable electrode
Data Source
AI summary
An inertia measurement module and three-axis accelerometer, comprising a first pole piece (4) located on a substrate and a mass block (1) suspendingly connected above the substrate via elastic beams (11, 12); the elastic beams (11, 12) includes a first elastic beam (12) and a second elastic beam (11), two ends of the second elastic beams (11) being connected to an anchor point (6) of the substrate, two ends of the first elastic beam (11) being connected to the mass block (1); a center of the first elastic beam (12) and/or the second elastic beam (11) deviates from a center of gravity of the mass block (1); the mass block (1) is further provided with a first movable electrode (9) and a second movable electrode (10) in a Y-axis and an X-axis direction; the movement of one axis in a plane of the inertia measurement module cannot be affected by an eccentric structure feature, such that both X-axis movement and Y-axis movement are linear movements, thus not intensifying an inter-axis coupling, and also not reducing displacement of a mass block on the X-axis and the Y-axis, thus improving capacitance detection precision.