Planar Coriolis Gyroscope Single Anchor Thermal Stress
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Solution Overview
Problem
Prior MEMS planar gyroscopes face issues due to mismatched resonant frequencies caused by manufacturing tolerances, multiple anchor points inducing stress from differential thermal expansion, and non-optimized springs supporting both primary and secondary resonators, leading to erroneous readings and sensitivity to external vibrations.
Innovation Solution
A planar MEMS gyroscope design featuring two counter-oscillating masses supported by flexible beams from a common frame, with a single anchor region and separate springs for excitation and Coriolis modes, achieving near 100% coupling and minimizing thermal stress, allowing for precise inertial rotation rate sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If multiple anchor regions are used to support the vibrating structure, then mechanical stability is improved, but thermal stress is induced due to differential thermal expansion between the substrate layer and the Silicon vibrating structure
Solution Approach 1:
The patent merges multiple anchor regions into a single anchor region that supports the entire vibrating structure. This consolidation eliminates the thermal stress issues caused by multiple separation points while maintaining mechanical stability through the unified support structure.
Solution Approach 2:
The patent segments the support function by using a single anchor region with multiple compliant members (springs) that are distributed throughout the structure. This allows the structure to accommodate thermal expansion differently than rigid multiple anchors would, reducing thermal stress while maintaining stability.
2Device complexity
If the same springs support both primary and secondary resonators, then device complexity is reduced, but the springs cannot be optimized separately for each resonator mode
Solution Approach 1:
The patent segments the spring functions by providing separate sets of compliant members: one set supports the primary resonator masses, and another set supports the secondary resonator frame. This allows each resonator to be independently optimized for its specific mode while maintaining overall device coherence.
Solution Approach 2:
The patent applies local quality by designing different spring configurations in different regions of the device. The springs supporting the primary resonator are optimized for mass vibration, while the springs supporting the secondary resonator are optimized for frame vibration, allowing each local region to have the properties needed for its specific function.
3Manufacturing precision
If the resonant frequencies of the two masses are not perfectly matched due to manufacturing tolerances, then manufacturing precision requirements are relaxed, but the masses respond differently to linear vibration causing erroneous readings
Solution Approach 1:
The patent merges the two mass responses through a common secondary resonator frame that is supported by compliant members. This coupling ensures that even if the individual mass frequencies differ slightly, their combined response to linear vibration remains balanced, preventing erroneous readings while allowing relaxed manufacturing tolerances.
Solution Approach 2:
The patent uses a composite structure where two masses with potentially different resonant frequencies are coupled through a common frame and support system. This composite arrangement creates a unified response characteristic that is more tolerant of manufacturing variations than individual perfectly-matched masses would be.
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 enhances accuracy and reduces thermal stress-induced errors by ensuring matched mass responses and separate optimization of resonator springs, achieving high sensitivity and robustness against external vibrations.
Implementation Method 1
a device layer substantially parallel to the lower substrate... a substantially rigid frame supported by a first plurality of compliant members... at least two masses each supported by a second plurality of compliant members
Implementation Method 2
when the excitation resonator is driven via the actuator in an oscillatory motion, the oscillatory motion combines with an inertial rotation rate around at least a first rotation axis to generate a Coriolis force acting on the at least two masses
Implementation Method 3
an actuator deployed for exciting oscillatory motion of one of the first and second resonators
Data Source
AI summary
A planar Coriolis gyroscope includes at least two counter oscillating masses attached to a common rigid frame by one or more elastic members defining an excitation axis. The frame is attached to a support region by one or more additional elastic members which together with the masses define a Coriolis resonator. The Coriolis resonator responds to inertial rotation of the gyroscope and in conjunction with a position pickoff provides a signal indicative on the gyroscope inertial rotation.