Surface Acoustic Wave Gyroscope Without Mechanical Stops
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Solution Overview
Problem
MEMS gyroscopes fail to measure angular rate under linear accelerations exceeding 20000g due to fragile support structures, compromising performance and necessitating mechanical stops that further degrade measurement capability.
Innovation Solution
A gyroscope design utilizing spatially orthogonal standing surface acoustic waves, with an axisymmetric construction and reflectors positioned at antinodes, enhances flexural rigidity and gyroscopic coupling, enabling robust angular rate measurement under extreme accelerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical stops are used to prevent failure under high acceleration, then structural reliability improves, but angular rate measurement precision deteriorates
Solution Approach 1:
The patent removes the mechanical stop component entirely from the gyroscope structure. By extracting this harmful element, the device achieves both high acceleration tolerance (through the robust proof mass design) and maintains angular rate measurement precision without the performance degradation caused by mechanical stops.
Solution Approach 2:
The patent replaces the mechanical stop protection mechanism with an acoustic field-based detection and protection system. Surface acoustic waves are used to sense the state of the proof mass and detect collisions, eliminating the need for mechanical contact elements that degrade measurement precision while still providing protection under extreme acceleration.
2Manufacturing precision
If fragile beam-like support structures are used in MEMS gyroscopes, then manufacturing precision is improved, but reliability under high acceleration deteriorates
Solution Approach 1:
Instead of using fragile beam-like structures that require precise manufacturing, the patent inverts the approach by using a massive, robust proof mass that is inherently tolerant of high acceleration. The design flips the traditional MEMS paradigm from small, precise, fragile structures to large, robust, acceleration-tolerant structures that happen to be manufacturable with modern techniques.
Solution Approach 2:
The patent changes the scale and physical parameters of the proof mass, transitioning from micro-scale beam structures to macro-scale massive structures. This parameter change fundamentally alters the mechanical properties, making the structure tolerant of extreme acceleration while remaining compatible with manufacturing capabilities.
3Reliability
If the proof mass is made larger to withstand high acceleration, then reliability improves, but device complexity increases
Solution Approach 1:
The patent merges the proof mass with the resonator structure into a single integrated component. The massive proof mass serves dual functions as both the inertial element for acceleration tolerance and the resonating structure for angular rate sensing, eliminating the need for separate support structures and reducing overall device complexity despite the large mass size.
Solution Approach 2:
The proof mass is designed to perform multiple functions simultaneously: it provides acceleration tolerance through its large mass, serves as the resonator for angular rate measurement, and acts as the platform for transducer placement. This multi-functionality reduces the number of separate components needed, simplifying the overall device architecture.
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 allows for accurate angular rate measurement under high accelerations without mechanical stops, maintaining structural integrity and simplifying manufacturing, making it suitable for applications like guided munitions.
Implementation Method 1
A gyroscope comprises a proof mass for bearing at least a pair of spatially orthogonal surface acoustic waves. The mass bears at least one transducer operable to produce the pair of orthogonal surface acoustic waves.
Implementation Method 2
The mass comprises a reflector arranged to reflect the at least one surface acoustic wave.
Data Source
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AI summary
Example implementations relate to gyroscopes comprising: a cyclic symmetric proof mass for bearing on a first surface degenerate, spatially orthogonal primary and secondary modes of vibration which become coupled in response to rotation about an axis of the proof mass; at least one actuator for inducing a primary surface acoustic wave of circumferential order n associated with the primary mode; and at least one sensor for sensing a secondary surface acoustic wave of circumferential order n associated with the secondary mode.