Dual-PLL Gyro Sensor Mode Matching and Axis Alignment
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Solution Overview
Problem
Existing vibratory gyro sensors face challenges in maintaining accurate mode matching between two oscillation modes without specialized processing, leading to deviations in resonance frequencies and angles, which affect sensor accuracy.
Innovation Solution
The gyro sensor employs two PLL circuits to independently control the frequencies of two oscillation modes and includes demodulators to calculate amplitudes and phases, with a control circuit aligning the oscillation axis with the electrode axis based on these inputs, enabling feedback control to maintain mode match even when initial deviations are present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mode matching is performed without specialized processing, then device complexity is reduced, but measurement precision deteriorates due to frequency and angle deviations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between frequency ratios and angle deviations in a lookup table during the design phase. This allows the control circuit to quickly retrieve correction values without performing complex real-time calculations, thereby achieving high measurement precision while maintaining simple device complexity.
Solution Approach 2:
The patent replaces complex mechanical or specialized processing methods with an electronic control system that uses a lookup table and simple control circuits. This substitution achieves mode matching and angle alignment through software-based correction rather than hardware complexity, resolving the contradiction between precision and device complexity.
2Measurement precision
If feedback control is implemented to maintain mode match, then measurement precision is improved, but device complexity increases due to additional control circuits
Solution Approach 1:
The patent implements feedback control by continuously monitoring the frequency ratio between the two oscillation modes and using this information to adjust the drive signals. The control circuit compares the actual frequency ratio with the target ratio and dynamically adjusts the driving frequencies to maintain mode matching, thereby improving measurement precision through closed-loop control.
Solution Approach 2:
The patent reduces control circuit complexity by pre-storing the optimal control strategies in a lookup table. Instead of implementing complex real-time optimization algorithms, the control circuit simply queries the lookup table based on the measured frequency ratio and applies the pre-determined correction, achieving effective feedback control with minimal circuit complexity.
3Measurement precision
If frequency control is performed for both oscillation modes, then measurement precision is improved, but device complexity increases due to multiple PLL circuits
Solution Approach 1:
The patent applies universality by designing the PLL circuits to serve multiple functions. The same PLL circuit structure is used for both frequency control and phase control of the two oscillation modes. The control circuit can operate in different modes (frequency locking, phase locking, or ratio control) using the same hardware components, thereby achieving high frequency accuracy without proportionally increasing 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
This configuration allows the gyro sensor to consistently maintain mode match, improving accuracy by aligning oscillation and electrode axes, even in initial states with frequency and angle deviations, without requiring special processing.
Implementation Method 1
an oscillator having a first oscillation mode and a second oscillation mode having different resonance frequencies
Implementation Method 2
a first PLL circuit that controls a frequency of a drive signal for oscillating the oscillator in the first oscillation mode, and a second PLL circuit that controls a frequency of a drive signal for oscillating the oscillator in the second oscillation mode
Implementation Method 3
A first demodulator calculates a first demodulation output on a basis of a first detection signal from the electrode that detects oscillation in the first oscillation mode among the electrodes and a first drive signal having a frequency for resonantly driving the first oscillation mode
Data Source
AI summary
A gyro sensor includes: a first PLL circuit; a second PLL circuit; a first demodulator that calculates a first demodulation output based on a first detection signal in the first oscillation mode and a first drive signal, and a second demodulation output based on a second detection signal in the second oscillation mode and a second drive signal; and a second demodulator that calculates a third demodulation output based on the first detection signal and the second drive signal, and a fourth demodulation output based on the second detection signal and the first drive signal. A control circuit outputs a control signal that causes an oscillation axis and an electrode axis to coincide with each other based on an input signal regarding an amplitude and a phase from a demodulation output calculator.