Stepped Sinusoidal Drive for Vibratory Gyroscope Noise Reduction
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Solution Overview
Problem
Existing gyroscopic sensors face challenges in accurately detecting rotation due to parasitic modes and feed-through noise, which are exacerbated by the generation of multiple frequency harmonics from square wave signals used to maintain oscillation, making it difficult to distinguish between the drive and sensing signals.
Innovation Solution
A MEMS gyroscopic sensor that employs a stepped sinusoidal waveform to drive the vibratory gyroscopic sensor element, reducing parasitic modes and feed-through noise by generating a discrete-time periodic signal with fixed time duration steps, thereby minimizing harmonic oscillations and maintaining oscillation at a predetermined frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a square wave signal is used to drive the vibratory sensor element, then feed-through noise is reduced because the drive signal magnitude only changes at rising and falling edges, but multiple frequency harmonics are generated that induce parasitic modes of oscillation
Solution Approach 1:
The square wave drive signal is segmented into multiple discrete sinusoidal frequency components (e.g., fundamental frequency and selected harmonics). By selectively combining these segmented frequency components with different amplitudes and phases, the drive signal excites only the desired resonant mode of the vibratory sensor element while avoiding parasitic modes, thus resolving the contradiction between reducing feed-through noise and preventing parasitic oscillations.
Solution Approach 2:
The drive signal is tailored to have different amplitude qualities at different frequency components. The fundamental frequency component has maximum amplitude to drive the sensor at its resonant frequency, while parasitic frequency components have zero or minimal amplitude. This localized quality control in the frequency domain eliminates parasitic modes while maintaining effective drive signal performance.
2Object-generated harmful factors
If a continuously varying drive signal is used to avoid square wave harmonics, then parasitic modes are reduced, but feed-through noise increases because the signal does not settle to a constant value
Solution Approach 1:
The drive signal employs periodic sinusoidal oscillation at the fundamental resonant frequency of the vibratory sensor element, with the amplitude modulated according to a predetermined waveform. This periodic action ensures the drive signal settles to constant amplitude levels during each cycle, minimizing feed-through noise while the sinusoidal nature avoids generating the harsh harmonics of a square wave that cause parasitic modes.
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 stepped sinusoidal waveform effectively reduces parasitic modes and feed-through noise, allowing for more accurate detection of rotation by minimizing harmonic oscillations and maintaining the sensor at the resonant frequency, thus improving the accuracy of output signals.
Implementation Method 1
maintaining oscillation at a predetermined frequency... maintaining the sensor at the resonant frequency
Implementation Method 2
the motion of the vibratory sensor element along the sense axis changes the capacitance between the sensor element and the capacitive sensor electrodes. A sensing circuit detects the changes in capacitance to identify rotation
Implementation Method 3
If the MEMS gyroscope experiences rotation, the angular acceleration of the rotation acts upon the MEMS gyroscope to change the position of the proof mass relative to the anchored frame of the MEMS along a sense axis that is perpendicular to the axis of oscillation
Data Source
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AI summary
A gyroscopic sensor includes a vibratory gyroscopic sensor element, first and second drive electrodes positioned proximate to the vibratory gyroscopic sensor element, and a drive circuit operatively connected to the first and second drive electrodes. The drive circuit is configured to generate a stepped sinusoidal waveform having a plurality of steps, each step having a predetermined duration and each step having an output level in a plurality of predetermined output levels for the stepped sinusoidal waveform including at least three positive output levels and at least three negative output levels to generate oscillation of the vibratory gyroscopic sensor element at a predetermined frequency.