Digital MEMS Gyroscope Control for Low-Power Error Compensation
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Solution Overview
Problem
MEMS gyroscopes face challenges with analog signal processing, including inaccuracy due to component parameter variations, high power consumption, and large circuit area requirements, particularly in compensating for non-idealities and quadrature errors, which are exacerbated by the need for high clock frequencies and complex PLLs in digital control circuits.
Innovation Solution
A fully digital control circuitry for MEMS gyroscopes is introduced, featuring a digital primary loop with a first analog-to-digital converter and an infinite impulse filter for phase shifting, and a digital secondary loop with phase shifting filters and coherent detection, which reduces the need for PLLs and minimizes clock frequency, thereby improving precision and reducing power consumption and circuit area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog signal processing is used for compensating non-idealities and quadrature errors, then compensation accuracy is improved, but power consumption and circuit area increase
Solution Approach 1:
The patent replaces analog signal processing circuits with a digital control circuit that uses digital signal processing to compensate for non-idealities and quadrature errors. The digital controller reads output signals from the MEMS gyroscope, processes them digitally to eliminate quadrature error and non-idealities, and generates compensation signals, thereby reducing power consumption and circuit area while maintaining compensation accuracy.
2Measurement precision
If digital control circuits use high clock frequencies and complex PLLs, then detection precision is improved, but circuit area and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the digital control circuit by using a relatively low clock frequency (e.g., 1 MHz or lower) compared to conventional high-frequency digital controllers. The digital controller achieves accurate detection and compensation at this lower frequency, thereby reducing circuit area and power consumption while maintaining detection precision through efficient digital signal processing algorithms.
3Measurement precision
If electrostatic quadrature cancellation is applied, then quadrature error is reduced, but sensitivity to component parameter variations increases
Solution Approach 1:
The patent implements a feedback-based digital compensation mechanism where the digital controller continuously reads the output signals from the MEMS gyroscope, processes them to detect quadrature error and non-idealities, and generates compensation signals that are fed back to the gyroscope. This closed-loop feedback approach dynamically compensates for quadrature error and non-idealities while being less sensitive to component parameter variations compared to static electrostatic cancellation methods.
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 digital control circuitry enables precise detection of angular velocity, robust compensation of non-idealities, and low sensitivity to component variations, while reducing power consumption and circuit area, thus enhancing the accuracy and efficiency of MEMS gyroscope operations.
Implementation Method 1
MEMS gyroscopes use the Coriolis Effect to measure the angular rate. When a mass is driven in one direction and rotational angular velocity is applied about axis orthogonal to driven axis, the mass experiences a force in orthogonal direction with respect to both driven and rotated axes as a result of the Coriolis force.
Implementation Method 2
a first infinite impulse filter configured to cause a -90-degree phase shift of the digitized primary signal on a resonance frequency of a mechanical resonator of the MEMS gyroscope
Implementation Method 3
A mass-spring structure typically exhibits a resonance or a resonant behavior by naturally oscillating at some frequencies, called as its resonant frequencies, with greater amplitude than on other frequencies.
Data Source
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AI summary
A digital control circuitry for a MEMS gyroscope is provided. The digital control circuitry comprises a digital primary loop circuitry configured to process a digitized primary signal, a digital secondary loop circuitry configured to process a digitized secondary signal and a digital phase shifting filter circuitry configured to generate two phase shifted demodulation signals from the digitized primary signal. The digital secondary loop is configured to demodulate the digitized secondary signal using the two phase shifted demodulation signals.