MEMS Inertial Sensor Decoupling Acceleration and Rotation
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Solution Overview
Problem
Conventional MEMS inertial measurement units require multiple gyroscopes and accelerometers, leading to increased complexity, cost, and power consumption due to the need for precise assembly and separate processing of six units, which complicates independent measurement of linear acceleration and rotational movement.
Innovation Solution
A MEMS inertial sensor design that uses two proof masses and four electrode pairs to apply rebalancing forces, allowing for independent determination of linear acceleration and rotation by sensing changes in capacitance, thereby decoupling acceleration and rotation sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three gyroscopes and three accelerometers are mounted on separate orthogonal axes, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines acceleration and rotation sensing functions into a single MEMS device structure. The proof mass structure integrates both linear acceleration sensing (via capacitance changes in first electrode pairs) and rotational sensing (via Coriolis forces detected by second electrode pairs), eliminating the need for separate accelerometers and gyroscopes while maintaining measurement precision through coupled sensing mechanisms.
Solution Approach 2:
The single MEMS device performs multiple functions: it measures both linear acceleration and rotational movement simultaneously. The proof mass structure serves dual purposes - responding to linear acceleration forces and to Coriolis forces induced by rotation, thereby providing universal sensing capability that replaces multiple specialized devices.
2Measurement precision
If three gyroscopes and three accelerometers are used, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent merges the power requirements of multiple separate devices into a single power supply system. By integrating both acceleration and rotation sensing in one MEMS device with shared proof mass structure and electrode systems, the total power consumption is reduced compared to powering three separate gyroscopes and three separate accelerometers, while maintaining the measurement precision of the combined sensing functions.
3Measurement precision
If three gyroscopes and three accelerometers are assembled, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent consolidates six separate sensing devices (three gyroscopes and three accelerometers) into a single integrated MEMS device. This merging reduces the number of components that need to be manufactured, assembled, and calibrated, thereby lowering manufacturing costs while preserving measurement precision through the integrated proof mass structure that simultaneously senses both linear acceleration and rotation.
Solution Approach 2:
The single MEMS device provides universal sensing functionality for both acceleration and rotation, replacing the need for multiple specialized devices. This multi-functionality approach simplifies the supply chain, reduces assembly complexity, and lowers overall manufacturing cost while maintaining the measurement capabilities of the original six-device system.
4Device complexity
If acceleration sensing and rotation sensing are coupled, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent segments the sensing functions within the single MEMS device by using distinct electrode pairs for different measurement purposes. First electrode pairs are dedicated to detecting linear acceleration through capacitance changes, while second electrode pairs detect rotation through Coriolis force-induced capacitance changes. This segmentation allows independent processing of acceleration and rotation signals, maintaining measurement precision despite the integrated device structure.
Solution Approach 2:
Different regions of the proof mass structure and electrode system are optimized for specific sensing functions. The first electrode pairs are positioned and configured to maximize sensitivity to linear acceleration, while the second electrode pairs are configured for maximum sensitivity to rotational Coriolis forces. This local optimization ensures that each sensing function maintains high precision despite the coupled nature of the overall device.
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 design reduces the number of sensing devices needed, enabling independent measurement of linear acceleration and rotation while reducing size, computational requirements, and cost, and allowing for more efficient power usage.
Implementation Method 1
the drive elements may include a number of interdigitated vertical comb fingers configured to convert electrical energy into mechanical energy using electrostatic actuation
Implementation Method 2
A conventional MEMS gyroscope may be used to determine angular rotation by measuring Coriolis forces exerted on resonating proof masses
Implementation Method 3
senses a change in a first capacitance between a first electrode of a first electrode pair and a first proof mass
Data Source
AI summary
A Micro-Electro-Mechanical Systems (MEMS) inertial sensor systems and methods are operable to determine linear acceleration and rotation. An exemplary embodiment applies a first linear acceleration rebalancing force via a first electrode pair to a first proof mass, applies a second linear acceleration rebalancing force via a second electrode pair to a second proof mass, applies a first Coriolis rebalancing force via a third electrode pair to the first proof mass, applies a second Coriolis rebalancing force via a fourth electrode pair to the second proof mass, determines a linear acceleration corresponding to the applied first and second linear acceleration rebalancing forces, and determines a rotation corresponding to the applied first and second Coriolis rebalancing forces.