MEMS Gyroscope In-Plane Actuation for Linear Pitch/Roll Sensing
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Solution Overview
Problem
Micro-electromechanical gyroscopes face challenges in managing out-of-plane sensing movements due to technological imperfections, non-linear capacitive coupling, and the risk of movable mass collapse, which affect precision and performance.
Innovation Solution
A micro-electromechanical gyroscope design with symmetrical driving and sensing structures, using skew-bending motion conversion flexures and comb finger electrodes, allows for in-plane actuation and differential operation to mitigate these challenges, ensuring linear sensing and preventing mass collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If out-of-plane sensing structures are used for pitch/roll sensing, then the gyroscope can sense rotations around axes parallel to the supporting body, but the sensing becomes more sensitive to technological imperfections such as wall angle, resulting in quadrature components and performance deterioration
Solution Approach 1:
The patent inverts the conventional out-of-plane sensing approach by using in-plane sensing structures. Instead of moving the sensing mass perpendicular to the supporting body, the mass moves parallel to the supporting body plane, thereby avoiding sensitivity to wall angle imperfections while maintaining pitch/roll sensing capability
Solution Approach 2:
The patent changes the orientation parameter of the sensing motion from out-of-plane to in-plane. This parameter change transforms the sensing mechanism to be less sensitive to manufacturing imperfections like wall angle, thereby improving measurement precision
2Device complexity
If parallel-plate capacitive coupling is used for out-of-plane sensing, then the structure is simpler, but the coupling becomes more non-linear and readings are more affected by non-linearity
Solution Approach 1:
The patent replaces the parallel-plate capacitive coupling mechanism with a comb-finger capacitive coupling mechanism. This substitution maintains structural simplicity while providing linear sensing response, as the comb-finger geometry naturally provides more linear capacitive coupling characteristics for in-plane motion
3Force
If high driving voltage is applied to overcome electrostatic forces, then the movable mass can be actuated, but the mass may collapse on the driving electrodes due to the prevalence of electrostatic forces when voltage exceeds a critical threshold
Solution Approach 1:
The patent extracts the movable mass from the region where strong electrostatic forces act on the supporting body. By positioning the mass to move in-plane rather than out-of-plane, the design removes the mass from the high-electrostatic-field zone, preventing collapse while maintaining actuation capability
Solution Approach 2:
The patent introduces motion conversion flexures as an intermediary mechanism between the driving electrodes and the movable mass. These flexures convert in-plane driving motion into out-of-plane sensing motion, allowing actuation without direct exposure to strong electrostatic collapse forces
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 improved precision and linearity in pitch and roll sensing by minimizing the impact of technological imperfections and electrostatic forces, while maintaining high sensitivity and avoiding capacitive coupling issues.
Implementation Method 1
the actuator is configured to cause the driving mass to oscillate along a second driving axis perpendicular to the first driving axis and to the sensing axis
Implementation Method 2
the motion conversion flexures are configured so as to cause movements of the transduction mass along the first driving axis in response to movements of the driving mass along the second driving axis
Implementation Method 3
When the supporting body rotates around a rotation axis perpendicular to the driving direction, with an angular velocity, the movable mass undergoes a Coriolis force along a sensing direction perpendicular to both the driving direction and the rotation axis
Implementation Method 4
A variable capacitive coupling between the movable mass and fixed electrodes on the supporting body allows the displacements of the movable mass due to the Coriolis force to be sensed
Data Source
AI summary
A micro-electromechanical gyroscope includes a supporting body and a sensor assembly. The sensor assembly includes a transduction mass, constrained to the supporting body for oscillation along a first driving axis perpendicular to the supporting body and along a sensing axis perpendicular to the first driving axis, driving structures each having an actuator, and a driving mass and motion conversion flexures connecting the driving mass to the transduction mass. The actuator causes the driving mass to oscillate along a second driving axis perpendicular to the first driving axis and the sensing axis. The motion conversion flexures cause movements of the transduction mass along the first driving axis in response to movements of the driving mass along the second driving axis. Sensing structures are mechanically coupled to the transduction mass and have a variable capacitance depending on a position of the transduction mass along the sensing axis.