MEMS Rate Sensor Coupling Springs for Synchronized Multi-Axis Sensing

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Solution Overview

Problem

Existing MEMS angular rate sensors for multiple axis sensing are complex, costly, and inefficient due to the need for multiple sets of drive and monitor electrodes and frequency generators, leading to potential inaccuracies in sense signals from unsynchronized motion of rate sensor assemblies.

Innovation Solution

The use of coupling spring structures to link multiple MEMS rate sensor assemblies, allowing them to oscillate at the same drive frequency with synchronized motion, enabling common demodulation in an ASIC and reducing complexity and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple separate rate sensors are used for multiple axis sensing, then sensing capability is improved, but device complexity and cost increase due to multiple sets of drive and monitor electrodes and frequency generators

Engineering Contradiction:

Improvemultiple axis sensing capabilityVSAvoidcomplexity of drive and monitor electrodes and frequency generators

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines multiple rate sensor assemblies into a single integrated device, sharing common drive and monitor electrodes. The coupling spring structure mechanically links the assemblies, allowing them to be driven by a single frequency generator rather than requiring separate generators for each axis, thereby reducing overall device complexity while maintaining multiple axis sensing capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The common drive and monitor electrodes serve multiple rate sensor assemblies simultaneously, making these components multi-functional. A single set of electrodes performs the driving and monitoring functions for all axes, eliminating the need for separate dedicated electrodes for each sensor assembly and reducing the overall component count

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If multiple separate rate sensors are used for multiple axis sensing, then sensing capability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvemultiple axis sensing capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

By merging multiple rate sensor assemblies into one device with shared electrodes and a common frequency generator, the patent reduces the total number of components that need to be manufactured and assembled. This consolidation lowers manufacturing costs while preserving the ability to sense rotation about multiple axes

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If multiple separate rate sensors operate at different frequencies, then independent sensing is achieved, but signal accuracy decreases due to unsynchronized motion

Engineering Contradiction:

Improveindependent sensing capabilityVSAvoidaccuracy of sense signals

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The coupling spring structure creates a mechanically synchronized system where all rate sensor assemblies operate at the same drive frequency. This equipotential approach ensures that the motion of all assemblies is coordinated and synchronized, eliminating the phase differences and timing errors that would occur with independent frequency generation, thereby improving signal accuracy while maintaining independent sensing capability

Inventive Principle:

Principle #12Equipotentiality

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 enables efficient, cost-effective, and accurate multiple axis sensing by ensuring synchronized motion of rate sensor assemblies, thereby improving signal accuracy and reducing the size and complexity of MEMS devices.

Implementation Method 1

The coupling spring enables oscillation of the rate sensors at the drive frequency in a drive direction dictated by the coupling spring

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 2

An angular rate sensor senses angular speed or velocity around one or more axes

Methodology Applied

Scientific EffectCoriolis force: Coriolis Force

Data Source

PatentUS9506756B2Multiple axis rate sensor

Publication Date: 2016.11.29 STMICROELECTRONICS INT NV

AI summary

A microelectromechanical systems (MEMS) device includes at least two rate sensors (20, 50) suspended above a substrate (30), and configured to oscillate parallel to a surface (40) of the substrate (30). Drive elements (156, 158) in communication with at least one of the rate sensors (20, 50) provide a drive signal (168) exhibiting a drive frequency. One or more coupling spring structures (80, 92, 104, 120) interconnect the rate sensors (20, 50). The coupling spring structures enable oscillation of the rate sensors (20, 50) in a drive direction dictated by the coupling spring structures. The drive direction for the rate sensors (20) is a rotational drive direction (43) associated with a first axis (28), and the drive direction for the rate sensors (50) is a translational drive direction (64) associated with a second axis (24, 26) that is perpendicular to the first axis (28).