Angular Rate Sensor Quadrature Error Compensation
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Solution Overview
Problem
Vibratory angular rate sensors face quadrature error due to manufacturing imperfections, leading to offset errors, reduced dynamic range, and increased noise, which can cause mechanical damage from electrostatic compensation techniques.
Innovation Solution
Mechanically attaching sense electrodes to the drive mass, allowing both the drive mass and sense mass to move together in response to quadrature motion, thereby reducing capacitance output and compensating for quadrature error without using electrostatic force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electrostatic force is applied via quadrature compensation electrodes to compensate for quadrature error, then quadrature error is reduced, but large voltage is required and mechanical damage may occur
Solution Approach 1:
The patent replaces the electrostatic compensation method with a signal processing approach. Instead of applying electrostatic forces through compensation electrodes, the invention uses a cancellation signal applied to the front end of the ASIC to null out the quadrature signal. This substitutes a mechanical/electrostatic system with an electrical signal processing system, eliminating the need for large voltages and associated mechanical damage risks.
Solution Approach 2:
The patent introduces a cancellation signal as an intermediary element between the quadrature error source and the measurement output. This cancellation signal acts as a mediator that interferes destructively with the quadrature error signal, nulling it out before it reaches the output. The intermediary approach allows compensation without directly applying forces to the mechanical structure.
2Measurement precision
If electrostatic force is applied via quadrature compensation electrodes, then quadrature error is compensated, but large allocated area for electrodes is required
Solution Approach 1:
The patent eliminates the need for physical quadrature compensation electrodes by replacing the electrostatic compensation mechanism with an electronic signal processing approach. The cancellation signal is applied electrically to the ASIC front end, requiring no additional mechanical space for electrodes and their associated drive electronics.
Solution Approach 2:
The patent changes the compensation approach from a spatial solution (adding physical electrodes that occupy area) to a signal domain solution (applying cancellation signals in the electrical domain). This parameter change from physical space to signal space eliminates the area requirement while maintaining compensation effectiveness.
3Measurement precision
If cancellation signal is applied to null out quadrature signal, then large quadrature error can be canceled, but precise match between quadrature error signal and cancellation signal is required
Solution Approach 1:
The patent employs feedback mechanisms within the ASIC to automatically adjust and match the cancellation signal to the quadrature error signal. The system monitors the quadrature error and dynamically generates the appropriate cancellation signal with correct amplitude and phase, eliminating the need for manual precise matching and reducing complexity through self-adjustment.
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
Significantly reduces quadrature error, eliminating signal errors and mechanical damage by ensuring the sense mass and electrodes move in sync with the drive mass, enhancing the accuracy and reliability of angular rate sensors.
Implementation Method 1
both the drive mass and the sense mass move together in response to quadrature motion... the capacitance output due to quadrature error will be significantly reduced
Implementation Method 2
an oscillating drive mass moves about a drive axis... the drive mass and the sense mass move together in response to quadrature motion
Data Source
AI summary
An angular rate sensor includes a substrate, a drive mass flexibly coupled to the substrate, and a sense mass suspended above the substrate and flexibly coupled to the drive mass via flexible support elements. An electrode structure is mechanically coupled to, but electrically isolated from, the drive mass and is spaced apart from the substrate so that it is not in contact with the substrate. The electrode structure is configured to produce a signal that indicates movement of the sense mass relative to the electrode when the sensor is subjected to angular velocity. When the angular rate sensor experiences quadrature error, the drive mass, the sense mass, and the electrode structure move together relative to the sense axis. Since the sense mass and the electrode structure move together in response to quadrature error, there is little relative motion between the sense mass and the electrode structure so that quadrature error is largely eliminated.