MEMS Spring Mass Configuration for Nonlinear Motion Reduction
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Solution Overview
Problem
Conventional angular velocity sensors face inefficiencies and increased costs due to nonlinearities in out-of-plane drive mechanisms, requiring large vertical gaps, high-voltage actuation, and multiple drive circuits for multi-axis gyroscopes, which complicate fabrication and increase power consumption.
Innovation Solution
The proposed solution involves modifying the spring mass configuration by adding a rigid element, tuning the spring system, and coupling an electrical cancellation system to minimize unwanted nonlinear motion, such as 2nd harmonic motion, in Micro-Electro-Mechanical Systems (MEMS) sensors, specifically by using a guided mass system with rotating arms and actuators that counter-rotate and eliminate erroneous signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If out-of-plane drive mechanism is used, then angular velocity sensing is achieved, but nonlinear motion increases and device performance is limited
Solution Approach 1:
The patent converts the harmful nonlinear motion (particularly 2nd harmonic motion) into a beneficial cancellation mechanism by introducing a counter-rotating structure that generates equal and opposite nonlinear motion, thereby eliminating the harmful effects while maintaining the out-of-plane drive capability
2Ease of operation
If large vertical gap or cavity is provided under proof-mass, then sufficient room for oscillation is achieved, but fabrication complexity and cost increase
Solution Approach 1:
The patent resolves the space constraint by transitioning from a vertical dimension solution (large gap or cavity) to a lateral dimension solution (counter-rotating structure positioned sideways), eliminating the need for complex cavity fabrication while providing sufficient oscillation room
3Ease of operation
If electrostatic actuator with large vertical gap is used, then proof-mass oscillation is achieved, but electrostatic force is reduced
Solution Approach 1:
The patent addresses the reduced electrostatic force by converting the oscillation requirement into a counter-rotation mechanism where the actuator drives rotational motion rather than direct linear oscillation, allowing the proof-mass to achieve the necessary motion amplitude through the counter-rotating linkage without requiring excessive force
4Ease of operation
If high-voltage actuation is applied, then large amplitude oscillation is achieved, but fabrication cost and circuit complexity increase
Solution Approach 1:
The patent employs dynamic amplification through the counter-rotating mechanism, where a small-amplitude high-frequency actuation signal is converted into large-amplitude oscillation through the mechanical leverage and resonance of the counter-rotating structure, eliminating the need for high-voltage actuation
5Adaptability or versatility
If multiple drive circuits are used for multi-axis gyroscope, then multi-axis sensing is achieved, but power consumption and cost increase
Solution Approach 1:
The patent implements a universal drive mechanism where a single drive circuit controls multiple proof-masses through a common counter-rotating structure, allowing the same actuation signal to simultaneously drive oscillation in multiple axes, thereby reducing power consumption and eliminating the need for separate drive circuits
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 approach reduces the impact of nonlinear motion, simplifies the drive mechanism, and allows for efficient sensing of angular velocity with reduced fabrication complexity and power consumption, enhancing the performance of MEMS sensors.
Implementation Method 1
Rotation of the sensor imparts a Coriolis force to the oscillating mass that is proportional to the angular velocity (or rotation rate), and depends on the orientation of the angular velocity vector with respect to the velocity vector of the proof mass
Implementation Method 2
modifying the spring mass configuration by adding a rigid element, tuning the spring system, and coupling an electrical cancellation system to minimize unwanted nonlinear motion, such as 2nd harmonic motion
Data Source
AI summary
Embodiments for modifying a spring mass configuration are disclosed that minimize the effects of unwanted nonlinear motion on a MEMS sensor. The modifications include any or any combination of providing a rigid element between rotating structures of the spring mass configuration, tuning a spring system between the rotating structures and coupling an electrical cancellation system to the rotating structures. In so doing unwanted nonlinear motion such as unwanted 2nd harmonic motion is minimized.