CVG Angular Sensor Phase Control for Bias Drift Stability
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Solution Overview
Problem
Gyroscopes face limitations due to bias drift, which affects their accuracy, especially in guidance applications where low-frequency performance is crucial and other sensors are not available to complement them.
Innovation Solution
A high stability angular sensor system utilizing a Coriolis vibratory gyroscope (CVG) with dual normal modes, frequency and phase control circuits, and amplitude control mechanisms, driven by a stable frequency reference like a rubidium atomic clock, to minimize phase and amplitude differences and reduce bias drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gyroscope is used to measure angular rate, then it can provide guidance data, but it exhibits bias drift which limits its usefulness
Solution Approach 1:
The gyroscope measures angular rate along three orthogonal axes separately, with each axis having its own resonator and measurement circuitry. This segmentation allows independent optimization and error correction for each axis, improving overall measurement precision while maintaining reliability through diverse error sources that can be individually compensated
Solution Approach 2:
The system employs feedback mechanisms where the measured angular rate data is continuously processed to detect and correct bias drift. The bias estimation module uses historical data and statistical methods to identify drift patterns, and the system adjusts measurements in real-time to compensate for detected bias, thereby maintaining measurement precision over time despite the inherent bias drift problem
2Measurement precision
If the amplitude of the first normal mode is increased to improve signal strength, then the measurement sensitivity improves, but the phase control becomes more difficult
Solution Approach 1:
The system combines the phase measurement and control functions into an integrated phase-locked loop (PLL) architecture that simultaneously handles multiple normal modes. By merging the control of different modes through a unified feedback system, the complexity is managed while maintaining high measurement sensitivity through coordinated phase control of all modes
Solution Approach 2:
The system introduces an intermediary reference signal at a known frequency that mediates between the resonator oscillations and the measurement system. This reference signal acts as a stable intermediary that simplifies phase measurement by providing a consistent comparison point, reducing the complexity of direct phase control while improving measurement sensitivity through precise phase difference detection
3Reliability
If a stable frequency reference is used to reduce phase noise, then the bias stability improves, but the device complexity increases
Solution Approach 1:
The stable frequency reference system is designed to serve multiple functions simultaneously: it provides the primary frequency standard for phase measurement, enables calibration of the resonator frequencies, and serves as a reference for bias drift detection and correction. This multi-functionality reduces the need for separate systems for each purpose, thereby improving bias stability without proportionally increasing device complexity
Solution Approach 2:
The system dynamically adjusts operating parameters such as the drive frequency and detection frequency based on the reference signal to optimize performance. By changing these parameters adaptively, the system maintains high bias stability across varying conditions without requiring an overly complex fixed-frequency reference system, achieving reliability through flexible parameter optimization rather than rigid complexity
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 system achieves reduced bias instability and improved accuracy by stabilizing the frequency reference, controlling phase and amplitude errors, and coupling energy between modes, resulting in lower Allan deviation and enhanced performance over traditional systems.
Implementation Method 1
a Coriolis vibratory gyroscope (CVG) resonator, configured to oscillate in a first normal mode and in a second normal mode
Data Source
AI summary
An angular rate sensor. The sensor includes a Coriolis vibratory gyroscope (CVG) resonator, configured to oscillate in a first normal mode and in a second normal mode; a frequency reference configured to generate a reference signal; and a first phase control circuit. The first phase control circuit is configured to: measure a first phase difference between: a first phase target, and the difference between: a phase of an oscillation of the first normal mode and a phase of the reference signal. The first phase control circuit is further configured to apply a first phase correction signal to the CVG resonator, to reduce the first phase difference. A second phase control circuit is similarly configured to apply a second phase correction signal to the CVG resonator, to reduce a corresponding, second phase difference.