MEMS Gyroscope Timing Synchronized to Resonant Frequency Drift
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Solution Overview
Problem
MEMS gyroscopes face performance limitations due to temperature-induced variations in resonant frequency, leading to timing errors and bias shifts in measurement signals, as existing signal processing systems do not account for these variations effectively.
Innovation Solution
A signal processing system that utilizes a voltage controlled oscillator (VCO) and phase locked loops to generate periodic signals at multiples of the resonant frequency, allowing for synchronous sampling and drive signal generation, thereby compensating for frequency variations and reducing phase errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an external oscillator of fixed frequency is used to derive sampling timing, then the device complexity is reduced, but timing errors and phase errors increase due to resonant frequency variations with temperature
Solution Approach 1:
The patent uses a phase-locked loop (PLL) that continuously monitors the resonant frequency of the MEMS resonator and adjusts the sampling clock frequency accordingly. The PLL compares the resonant frequency signal with a reference and generates a feedback signal to maintain synchronous sampling, thereby eliminating phase errors caused by temperature-induced frequency variations while keeping the system relatively simple.
Solution Approach 2:
The sampling clock frequency is made dynamic by deriving it from the resonant frequency of the MEMS resonator itself rather than using a fixed external oscillator. The system automatically adapts the sampling rate to match the resonant frequency variations, ensuring accurate timing without requiring complex external frequency synthesis equipment.
2Measurement precision
If the sampling rate is increased to capture more signal details, then the measurement precision improves, but the device complexity and processing requirements increase
Solution Approach 1:
The patent samples the resonant frequency signal at exactly the resonant frequency rate rather than using a much higher oversampling rate. This partial action approach captures sufficient signal information for accurate measurement without the excessive processing burden of high-rate sampling, thereby maintaining measurement precision while limiting system 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 ensures accurate sampling and drive signal generation, reducing phase errors and bias shifts, and maintaining synchronization with the resonant frequency, even with temperature changes, thereby improving the stability and accuracy of MEMS gyroscope measurements.
Implementation Method 1
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 2
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 3
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 4
a primary drive transducer for causing the vibrating structure angular rate sensor to oscillate at a resonant frequency
Implementation Method 5
a primary pick off transducer for detecting oscillation of the vibrating structure angular rate sensor at the resonant frequency
Implementation Method 6
a vibrating structure, a primary drive transducer for causing the vibrating structure angular rate sensor to oscillate at a resonant frequency
Data Source
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AI summary
A signal processing system (100) for a vibrating structure angular rate sensor (101) having a vibrating structure (102) and primary drive (103) and pickoff (105) transducers for causing the vibrating structure angular rate sensor to oscillate at a resonant frequency, for detecting oscillation of the vibrating structure angular rate sensor (101). The signal processing system comprises a digital signal processing system (109) configured to set a drive signal frequency for the primary drive transducer (103), a voltage controlled oscillator (111) 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 (113), 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) (115) configured to sample the primary pick off signal and a digital-to-analog converter (DAC) (118) configured to generate a drive signal waveform applied to the primary drive transducer (103).