Stacked Lateral Overlap Transducer for Three-Axis Accelerometer
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Solution Overview
Problem
Current small-scale gyroscopes and accelerometers, while incorporated into mobile devices, lack improved performance and efficiency, particularly in terms of reduced quadrature and bias errors, and are limited by conventional tuning-fork structures that suffer from drive interference and parasitic resonant modes.
Innovation Solution
The development of micromachined piezoelectric gyroscopes and accelerometers with torsionally oscillating proof masses and decoupled drive and sense modes, utilizing piezoelectric films and flexible beams to minimize drive interference and enhance sensitivity, and the integration of capacitive stacked lateral overlap transducers for three-axis sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional tuning-fork structures are used in gyroscopes and accelerometers, then device complexity is reduced and ease of manufacture is improved, but drive interference and parasitic resonant modes increase, degrading measurement precision
Solution Approach 1:
The device is segmented into distinct functional components: a proof mass for sensing, separate drive beams for actuation, and separate sense beams for detection. This segmentation isolates the drive and sense modes, eliminating drive interference and parasitic resonant modes that occur in conventional integrated tuning-fork structures, thereby improving measurement precision.
Solution Approach 2:
Flexible beams serve as intermediary elements connecting the proof mass to the substrate. These beams are specifically designed to provide mechanical coupling while isolating drive and sense pathways, acting as mediators that transfer motion for sensing without allowing drive interference to contaminate the sense signal.
2Measurement precision
If piezoelectric films and flexible beams are used to decouple drive and sense modes, then sensitivity is improved and quadrature errors are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The design optimizes the geometric parameters of the flexible beams, including width, length, and thickness, to achieve uniform stress distribution during torsional oscillation. By carefully controlling these parameters, the beams maintain consistent mechanical properties that improve sensitivity while managing manufacturing precision requirements through design rather than process complexity.
3Measurement precision
If electrostatic actuators are integrated to fine-tune mechanical mode shapes, then quadrature error suppression is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The electrostatic actuators are merged with the existing flexible beam structure, using the same fabrication layers and processes where possible. The actuators are integrated into the beam architecture rather than added as separate components, allowing fine-tuning of mechanical mode shapes through a unified fabrication process that minimizes additional manufacturing steps.
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
These designs significantly reduce quadrature and bias errors, improve sensitivity, and enable efficient three-axis sensing, suitable for consumer electronics like smartphones and navigation devices, by decoupling drive and sense motions and optimizing flexure types for each axis.
Implementation Method 1
utilize piezoelectric films and flexible beams to minimize drive interference and enhance sensitivity
Implementation Method 2
A lateral movement of the proof mass in response to an applied lateral acceleration along the first axis may result in a first change in capacitance at the second plurality of electrodes
Implementation Method 3
The frame may include a first plurality of slots extending along the first axis and a second plurality of slots extending along the second axis
Data Source
AI summary
This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for making and using accelerometers. Some such accelerometers include a substrate, a first plurality of electrodes, a second plurality of electrodes, a first anchor attached to the substrate, a frame and a proof mass. The substrate may extend substantially in a first plane. The proof mass may be attached to the frame, may extend substantially in a second plane and may be substantially constrained for motion along first and second axes. The frame may be attached to the first anchor, may extend substantially in a second plane and may be substantially constrained for motion along the second axis. A lateral movement of the proof mass in response to an applied lateral acceleration along the first or second axes may result in a change in capacitance at the first or second plurality of electrodes.