Quartz Vibrating Element Decoupling Vibration Modes for Gyroscope Accuracy
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Solution Overview
Problem
The chemical machining of quartz tuning forks for vibratory gyrometers results in oblique facets that cause mechanical coupling between vibration modes, leading to inaccurate measurements of angular velocity, particularly at low rotational velocities, and existing solutions either require costly trimming or are inefficient in signal processing.
Innovation Solution
A vibrating element configuration with a symmetry axis parallel to the electric crystallographic axis of the piezoelectric material, where the mass part's center of gravity is on the symmetry axis, decouples the first and second vibration modes, allowing for equal resonant frequencies and improved measurement accuracy without the need for trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical machining is used to manufacture quartz tuning forks, then manufacturing cost is reduced and dimensional definition is improved, but mechanical coupling between vibration modes is created due to oblique facets
Solution Approach 1:
The patent applies asymmetry by intentionally creating asymmetric oblique facets through chemical machining, then compensating with asymmetric electrode arrangements and asymmetric mass distribution. This asymmetric design cancels out the mechanical coupling effects while preserving the manufacturing advantages of chemical machining.
Solution Approach 2:
The patent changes geometric parameters by precisely controlling the orientation, position, and dimensions of oblique facets created during chemical machining. By adjusting these parameters and compensating with corresponding electrode and mass configurations, the mechanical coupling between vibration modes is eliminated while maintaining low manufacturing costs.
2Ease of manufacture
If chemical machining is used to manufacture quartz tuning forks, then industrial manufacturing cost is reduced, but mechanical coupling between vibration modes occurs
Solution Approach 1:
The patent applies local quality by creating localized asymmetric features (oblique facets) at specific positions on the tuning fork, then compensating with localized asymmetric electrode arrangements and mass distributions. This localized approach maintains the overall symmetry needed for reliable vibration modes while allowing the benefits of chemical machining.
Solution Approach 2:
The patent uses copying by creating symmetric pairs of asymmetric features - multiple oblique facets are created through chemical machining, then compensated by corresponding electrode and mass configurations that mirror the asymmetry. This copying approach ensures vibration mode independence while preserving manufacturing efficiency.
3Measurement precision
If trimming is performed to remove quadrature signal, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by designing the tuning fork with pre-configured asymmetric features (oblique facets) and electrode arrangements that prevent mechanical coupling from occurring in the first place. This eliminates the need for subsequent trimming operations, achieving high measurement accuracy while maintaining low manufacturing costs.
Solution Approach 2:
The patent converts the harmful effect of chemical machining (oblique facets causing mechanical coupling) into a beneficial design feature. By intentionally creating and then compensating for these facets through asymmetric electrode and mass configurations, the patent turns a manufacturing byproduct into a controlled design parameter that eliminates the need for costly trimming.
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 configuration significantly enhances the measurement accuracy of angular velocity by eliminating mechanical coupling between vibration modes and reducing manufacturing costs, while maintaining the benefits of chemical machining, such as low industrial costs and precise dimensional definition.
Implementation Method 1
a vibrating element configuration made in a piezoelectric material for such a gyrometer
Implementation Method 2
The operating principle of a vibratory gyrometer is based on the sensing of Coriolis accelerations acting on an element vibrating according to a first useful mode of vibration
Data Source
AI summary
The present disclosure relates to a vibrating element which is planar parallelly to an electrical crystallographic axis of a piezoelectric material such as quartz. The element comprises a beam holding electrodes, a stationary portion rigidly connected to one end of the beam, and a solid portion rigidly connected to the other end of the beam. The structure with facets from the chemical machining of the element has an axis of symmetry parallel to the electrical axis, and the solid portion has a center of gravity on the axis of symmetry. The useful vibration modes of the vibrating element, according to which the solid portion is reciprocatingly rotated about the axis of symmetry and reciprocatingly moved parallel to the plane of the element, are uncoupled. The measurement of an angular speed by a rate gyroscope including said vibrating elements is more precise.