Monolithic 6-Axis Inertial Sensor with Partitioned Flexure
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Solution Overview
Problem
Existing 6-axis inertial sensor systems are costly and complex due to the need for separate drive and sense electronics for each axis, and they often suffer from cross-axis interference, making them unsuitable for compact and cost-effective applications.
Innovation Solution
A micromachined monolithic 6-axis inertial sensor utilizing a single center-anchored proof-mass with a partitioned flexure bearing structure that decouples response modes for each axis, allowing simultaneous accelerometer and gyroscope functionality with a single drive-mode oscillation and reduced control electronics complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate sensors are used for each axis to achieve 6-axis motion sensing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines six separate sensing functions (3-axis acceleration and 3-axis angular rate) into a single integrated sensor device. The device uses one proof mass with multiple sensing mechanisms that simultaneously detect linear acceleration along x, y, z axes and angular velocity around these axes, eliminating the need for separate sensor clusters and reducing overall system complexity.
Solution Approach 2:
The single proof mass structure serves multiple functions: it detects linear acceleration through capacitive sensing in three orthogonal directions while simultaneously detecting angular velocity through torsional oscillation modes. This multi-functional design allows one component to replace what would traditionally require six separate sensors.
2Measurement precision
If separate drive and sense electronics are used for each sensor to achieve accurate measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent integrates drive and sense electronics into shared circuits that serve all six sensing functions. The capacitive sensing mechanism uses common electrode structures and signal processing paths for both acceleration and angular rate detection, reducing the number of separate electronic channels required compared to using six independent sensors.
Solution Approach 2:
The electronic system is designed with multi-functional circuits that can process signals from the single proof mass for all six degrees of freedom. The drive electronics generate oscillation modes that enable both acceleration and gyroscope measurements, while the sense electronics process capacitive signals to extract all six measurement parameters through unified signal processing.
3Device complexity
If a single proof-mass structure is used to reduce device complexity, then device complexity is reduced, but cross-axis interference increases
Solution Approach 1:
The patent segments the sensing functions by using distinct oscillation modes and electrode configurations for different measurement types. The proof mass is designed with specific geometric features that enable separate drive modes for acceleration sensing and torsional modes for gyroscope sensing, with corresponding segmented electrode structures that minimize coupling between axes during signal detection.
Solution Approach 2:
The device employs local quality variations in the proof mass structure, such as asymmetric mass distribution or strategically placed structural features, to enhance sensitivity to specific axes while reducing cross-axis coupling. The electrode configurations are optimized locally to detect signals from particular directions with minimal interference from orthogonal axes.
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 solution significantly reduces the complexity and cost of control electronics while minimizing cross-axis interference, enabling efficient detection of 3-axis acceleration and 3-axis angular rate with improved sensitivity and reduced thermal stress, thus enhancing the performance and cost-effectiveness of 6-axis inertial sensors.
Implementation Method 1
a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the radial portion, wherein the drive electrode and the central suspension system are configured to oscillate the 6-axis inertial sensor about a z-axis normal to the x-y plane
Data Source
AI summary
The device layer of a 6-degrees-of-freedom (6-DOF) inertial measurement system can include a single proof-mass 6-axis inertial sensor formed in an x-y plane, the inertial sensor including: a main proof-mass section suspended about a single, central anchor; a central suspension system configured to suspend the 6-axis inertial sensor from the single, central anchor; and a drive electrode including a moving portion and a stationary portion, the moving portion coupled to the radial portion. The drive electrode and the central suspension system are configured to oscillate the 6-axis inertial sensor about a z-axis normal to the x-y plane.