Mechanical Oscillator Control Electronics for Zero-Phase MEMS Gyros
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Solution Overview
Problem
MEMS gyroscopes face challenges in achieving navigation-grade performance due to errors in digital control systems, including phase errors and data latency, which are not effectively addressed by existing control electronics.
Innovation Solution
A digital signal processor (DSP) is used to generate a synthetic sinusoidal motor drive signal synchronized with the motor pickoff signal, employing a voltage-controlled oscillator (VCO) to ensure zero phase error and compensate for switch delays, while analog signal processing adjusts the motor drive signal to maintain proper amplitude and frequency alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital signal processor is used to generate motor drive signals, then navigation-grade performance can be achieved, but phase errors and data latency occur due to digital system limitations
Solution Approach 1:
A voltage-controlled oscillator (VCO) is introduced as an intermediary component between the digital signal processor and the mechanical oscillator. The VCO receives a control voltage from the DSP and generates a continuous-frequency clock signal that drives the mechanical oscillator, thereby eliminating the phase errors and data latency inherent in purely digital timing systems while maintaining the precision benefits of digital control.
Solution Approach 2:
The patent replaces the purely digital timing mechanism with an analog VCO-based timing system. Instead of using digital counters and software timing loops that introduce latency, the system uses an analog VCO whose frequency is continuously adjusted by the DSP output voltage, providing real-time phase-accurate synchronization without digital sampling delays.
2Reliability
If the clock frequency is locked to the motor pickoff signal, then phase errors are eliminated, but the system complexity increases due to additional control circuitry
Solution Approach 1:
The system implements a feedback mechanism where the motor pickoff signal is used to control the frequency of the VCO. The DSP reads the pickoff signal, processes it to determine the required frequency adjustment, and outputs a control voltage to the VCO that locks its output frequency to match the mechanical oscillator's actual frequency, thereby eliminating phase errors through continuous feedback adjustment.
Solution Approach 2:
The patent combines multiple functions into the VCO component: it serves as both the clock source for the DSP and the drive signal generator for the mechanical oscillator. By locking the VCO frequency to the pickoff signal, the system merges the timing function and the drive function into a single synchronized system, reducing the need for separate phase-correction circuitry.
3Ease of operation
If transitions occur only at clock signal edges in digital systems, then digital control is simplified, but phase errors and timing inaccuracies occur
Solution Approach 1:
The system transitions from a static digital clocking system to a dynamic analog VCO-based system. The VCO's frequency and phase can continuously adjust in response to control voltage changes from the DSP, allowing the system to dynamically compensate for timing variations and maintain precise synchronization without being constrained to fixed clock edge transitions.
Data Source
AI summary
A control system for a mechanical oscillator having a sinusoidal drive signal with a frequency that is a fractional multiple of a frequency of a signal of the mechanical oscillator. The drive signal may be in phase and in registration with the signal from the mechanical oscillator. A sense signal may be picked off from the oscillator and be demodulated to obtain a parameter sensed by the oscillator. The drive signal to the oscillator may be selected or blanked out while receiving and demodulating the sense signal.