CVG Angular Sensor Phase Locking for Bias Drift Stability
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Solution Overview
Problem
Gyroscopes face limitations due to bias drift, which affects their accuracy and usefulness in applications like aircraft and spacecraft guidance, especially when other sensors with better low-frequency performance are not available.
Innovation Solution
A high stability angular sensor system utilizing a Coriolis vibratory gyroscope with a frequency reference and phase/amplitude control circuits to reduce phase and amplitude differences between oscillations and a reference signal, employing an atomic frequency reference to stabilize the gyroscope's natural frequencies and minimize bias drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional gyroscope is used, then the device can measure angular rate, but bias drift occurs leading to reduced measurement precision over time
Solution Approach 1:
The patent applies parameter changes by precisely controlling the drive frequency of the resonator to match its natural frequency, and by controlling the phase relationship between drive and sense modes. This frequency and phase control stabilizes the bias drift, improving measurement precision over time while maintaining reliable angular rate measurement capability
Solution Approach 2:
The patent implements feedback control through phase-locked loops that continuously monitor and adjust the drive frequency to maintain synchronization with the resonator's natural frequency. This feedback mechanism corrects frequency deviations that would otherwise cause bias drift, thereby improving both measurement precision and long-term reliability
2Measurement precision
If the gyroscope operates without frequency stabilization, then the device complexity is lower, but bias drift increases reducing measurement precision
Solution Approach 1:
The patent replaces mechanical frequency stabilization methods with electronic control systems. Phase-locked loops and electronic frequency synthesis circuits substitute for mechanical tuning mechanisms, reducing moving parts while achieving precise frequency control. This electronic substitution improves measurement precision without proportionally increasing device complexity
Solution Approach 2:
The frequency control system serves multiple functions: it stabilizes the drive frequency, locks the phase relationship between modes, and provides a reference for bias drift compensation. This multi-functionality reduces the need for separate control circuits, thereby improving measurement precision while limiting the increase in device 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 gyroscope's output, enhancing its performance in guidance applications and reducing the impact of bias drift over time.
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.