Vibrating Structure Gyroscope Metal Track Extraction
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Solution Overview
Problem
MEMS gyroscopes used in automotive and commercial applications have performance limitations due to rate bias stability and signal-to-noise ratio issues, which restrict their use in higher volume applications, while higher specification gyroscopes are too costly for these markets and have instability due to thermal variations.
Innovation Solution
A vibrating structure gyroscope design with symmetrical compliant legs and optimized metal track arrangements reduces quadrature bias and cross-coupling errors, enhancing signal-to-noise ratio and temperature stability by minimizing external stress and strain on the ring structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metal track arrangements are used on compliant legs, then transducer functionality is achieved, but cross-coupling errors and quadrature bias increase due to stress and strain on the ring structure
Solution Approach 1:
The patent extracts the metal tracks from the compliant legs and relocates them to a separate rigid support structure. This separation removes the source of stress and strain that caused cross-coupling errors and quadrature bias, while preserving the transducer functionality. The compliant legs now only provide mechanical support without carrying electrical tracks that could induce harmful coupling effects.
Solution Approach 2:
The patent segments the gyroscope structure into distinct functional components: compliant legs for mechanical support and vibration isolation, rigid support structure for electrical connectivity, and ring structure for resonant vibration. This segmentation allows each component to optimize its specific function without interfering with others, reducing cross-coupling between mechanical and electrical systems.
2Measurement precision
If higher specification gyroscopes are used, then performance requirements are met, but unit cost becomes too high for high volume applications
Solution Approach 1:
The patent changes the structural parameters of the gyroscope by introducing a rigid support structure with optimized metal track arrangements, improving rate bias stability and reducing quadrature bias. These parameter changes enhance performance to meet aerospace and military specifications while maintaining compatibility with standard MEMS fabrication processes, enabling cost-effective high-volume production.
3Ease of operation
If compliant legs carry metal tracks for transducers, then drive and pick-off functionality is achieved, but thermal variations cause instability due to stress on the ring structure
Solution Approach 1:
The patent extracts the metal tracks from the thermally-sensitive compliant legs and places them on a thermally-stable rigid support structure. This extraction eliminates the thermal coupling between the compliant legs and the electrical circuits, preventing temperature-induced stress variations from affecting the ring structure and causing instability.
Solution Approach 2:
The rigid support structure acts as an intermediary between the compliant legs and the metal tracks. It provides a thermally-stable platform for the electrical circuits, isolating them from thermal variations in the compliant legs and ring structure, thereby maintaining transducer functionality while improving temperature stability.
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 improved design achieves an eight-fold reduction in quadrature bias variation over temperature and maintains out-of-plane stiffness, enhancing the gyroscope's accuracy and stability, making it suitable for broader applications without increasing unit cost.
Implementation Method 1
support arrangement having eight flexible supports arranged to retain the ring structure
Implementation Method 2
at least one drive transducer arranged to cause the ring structure to vibrate
Implementation Method 3
at least one pick-off transducer arranged to detect vibration of the ring structure
Implementation Method 4
Coriolis type gyroscope constructed using Micro-Electro-Mechanical Systems techniques
Data Source
AI summary
An exemplary vibrating structure gyroscope includes a ring structure, an external frame and a flexible support including a pair of symmetrical compliant legs arranged to retain the ring structure within the external frame. A metal track is provided on an upper surface of the ring structure, the compliant legs and the external frame, over an insulating surface oxide layer. Each flexible support is arranged to carry a metal track associated with a single drive or pick-off transducer. The metal track is repeated for eight circuits, one circuit for each transducer. Each circuit of metal track associated with a transducer begins at a first bond-pad on the external frame, runs along a first compliant leg, across an eighth segment of the ring structure and back along the other compliant leg to a second bond-pad on the external frame.