MEMS Gyroscope Timing Synchronization for Resonant Frequency Drift
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Solution Overview
Problem
MEMS gyroscopes face timing errors due to variations in resonant frequency with temperature, leading to phase errors and bias shifts in measured signals, as existing systems rely on external oscillators that do not account for temperature-induced frequency changes.
Innovation Solution
A signal processing system that uses a voltage controlled oscillator and phase locked loops to generate periodic signals synchronized with the resonant frequency of the vibrating structure, allowing for synchronous sampling and drive signal generation, thereby compensating for temperature-induced frequency variations and reducing phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an external oscillator of fixed frequency is used to set the timing for sampling the output signal, then the device complexity is reduced and ease of operation is improved, but timing errors and phase errors occur due to variations in the MEMS resonant frequency with temperature
Solution Approach 1:
The system uses a phase-locked loop (PLL) that continuously monitors the actual resonant frequency of the MEMS resonator and adjusts the oscillator frequency to maintain synchronization. This feedback mechanism ensures that the sampling timing remains aligned with the resonant frequency despite temperature variations, thereby maintaining measurement precision while keeping the system easy to operate.
Solution Approach 2:
The oscillator frequency is made dynamic rather than fixed, allowing it to automatically track and adjust to the varying resonant frequency of the MEMS resonator. This dynamic adjustment ensures that the sampling timing remains synchronized with the resonant frequency across different temperature conditions, resolving the contradiction between ease of operation and measurement precision.
2Device complexity
If the sampling rate is set using an external oscillator, then the device complexity is reduced, but bias shifts occur due to phase errors from misaligned sampling points
Solution Approach 1:
The phase-locked loop provides continuous feedback to adjust the oscillator frequency, ensuring that the sampling points remain precisely aligned with the resonant frequency cycles. This feedback mechanism eliminates phase errors and bias shifts while maintaining relatively simple device architecture, thus improving reliability without significantly increasing complexity.
Solution Approach 2:
The system replaces a simple fixed-frequency electronic oscillator with a phase-locked loop system that electronically tracks the resonant frequency. This substitution maintains electronic simplicity while achieving precise timing alignment, thereby improving reliability without requiring complex mechanical adjustment mechanisms.
3Manufacturing precision
If a fixed frequency oscillator is used for drive signal timing, then manufacturing precision requirements are reduced, but timing errors increase with temperature variations
Solution Approach 1:
The drive signal timing is made dynamic through the phase-locked loop, which automatically adjusts the oscillator frequency to match the resonant frequency at any given temperature. This dynamic tracking eliminates the need for extremely precise fixed-frequency manufacturing while maintaining high measurement precision across temperature variations.
Solution Approach 2:
The system changes the operating parameter (oscillator frequency) dynamically to track the resonant frequency variations with temperature. This parameter adjustment allows the system to maintain measurement precision without requiring the oscillator to be manufactured with extremely high precision for a fixed frequency, thus resolving the contradiction between manufacturing precision and measurement precision.
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 approach ensures that the signal processing system remains synchronized with the resonant frequency, reducing timing errors and improving bias stability by automatically adjusting sampling times and clock signals in response to temperature changes, leading to more accurate angular rate measurements.
Implementation Method 1
a voltage controlled oscillator (VCO) configured to receive an input indicative of the resonant frequency and to generate a first periodic signal at a first multiple of the resonant frequency
Implementation Method 2
a first phase locked loop, configured to receive the first periodic signal, and to generate a second periodic signal at a second multiple of the resonant frequency
Implementation Method 3
an analog-to-digital converter (ADC) configured to sample a primary pick off signal from the primary pick off transducer at a first rate set by the first periodic signal
Implementation Method 4
a digital-to-analog converter (DAC) configured to receive the drive signal frequency from the digital signal processing system at a second rate set by the second periodic signal and to generate a drive signal waveform to be applied to the primary drive transducer
Implementation Method 5
a primary drive transducer for causing the vibrating structure angular rate sensor to oscillate at a resonant frequency
Implementation Method 6
a primary drive transducer for causing the vibrating structure angular rate sensor to oscillate at a resonant frequency
Implementation Method 7
a primary pick off transducer for detecting oscillation of the vibrating structure angular rate sensor at the resonant frequency
Implementation Method 8
Coriolis-type MEMS gyroscopes, which utilise vibrating structures in the form of planar silicon ring resonators
Data Source
AI summary
A signal processing system for a sensor. The system comprises a digital signal processing system configured to set a drive signal frequency for the primary drive transducer, a voltage controlled oscillator configured to receive an input indicative of the resonant frequency and to generate a first periodic signal at a first multiple of the resonant frequency, and a first phase locked loop, configured to receive the first periodic signal, and to generate a second periodic signal at a second multiple of the resonant frequency. The first and second periodic signals are used to control the operation of an analog-to-digital converter (ADC) configured to sample the primary pick off signal and a digital-to-analog converter (DAC) configured to generate a drive signal waveform applied to the primary drive transducer.