Nested Seismic Masses for Dual-Axis Yaw Rate Sensing
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Solution Overview
Problem
Existing micromechanical yaw rate sensors face challenges in detecting yaw rates around multiple axes while being robust against disturbances, as they can be easily excited by linear vibrations, leading to impaired operation and increased sensitivity to environmental interference.
Innovation Solution
A micromechanical yaw rate sensor design featuring a substrate aligned with the x-y plane, with at least two seismic masses connected via drive and coupling devices that oscillate in antiphase for one axis and in phase opposition for another, utilizing capacitive comb structures for electrostatic excitation and detection, and torsion spring elements to suppress unwanted deflections, allowing precise detection of yaw rates around two orthogonal axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two seismic masses are coupled via springs to enable multi-axis detection, then the sensor can detect yaw rates around multiple axes, but the in-phase modes can be easily excited by linear vibrations, leading to impaired operation
Solution Approach 1:
The patent introduces asymmetric coupling between the two seismic masses using non-uniform spring elements. The first and second spring elements have different stiffness characteristics, creating asymmetric coupling that suppresses in-phase modes while preserving anti-phase mode excitation. This asymmetric design prevents linear vibrations from exciting unwanted modes, resolving the contradiction between multi-axis detection capability and operational stability.
Solution Approach 2:
The patent modifies the coupling parameters by using spring elements with specific stiffness ratios and damping characteristics. By carefully selecting the stiffness values of the first and second spring elements, the system achieves mode separation where only anti-phase oscillations are permitted. This parameter optimization ensures that linear vibrations cannot excite in-phase modes, maintaining reliable operation while enabling multi-axis detection.
2Object-affected harmful factors
If the sensor uses a mass balance with centers of gravity on top of each other to prevent direct excitation, then rotational disturbances are suppressed, but in-phase modes still exist and can be excited by linear vibrations
Solution Approach 1:
The patent applies asymmetric spring coupling to break the symmetry of the system. While the masses remain balanced with coinciding centers of gravity to reject rotational disturbances, the asymmetric spring elements prevent linear vibrations from exciting in-phase modes. This asymmetric coupling creates a situation where the system is immune to both rotational and linear vibration disturbances simultaneously.
Solution Approach 2:
The spring elements act as intermediaries between the seismic masses and the external environment. These coupled spring elements mediate the interaction between linear vibrations and the seismic masses, blocking the transmission of linear vibration energy that would otherwise excite in-phase modes. The springs serve as a protective intermediary layer that maintains mass balance while preventing unwanted mode excitation.
3Stability of the object's composition
If the spring concept is used to couple seismic masses, then mode separation is achieved, but the in-phase modes are not suppressed and remain susceptible to linear vibrations
Solution Approach 1:
The patent enhances mode separation by introducing asymmetric spring coupling. The non-uniform spring elements create different stiffness characteristics that selectively permit anti-phase modes while suppressing in-phase modes. This asymmetric design transforms the spring concept from a simple connector into a mode-selective element that actively prevents unwanted mode excitation, achieving both mode separation and suppression.
Solution Approach 2:
The patent optimizes the spring parameters including stiffness values, damping coefficients, and geometric dimensions to achieve complete suppression of in-phase modes. By carefully tuning these parameters, the system creates a stable configuration where only anti-phase oscillations occur. The parameter optimization ensures that linear vibrations cannot excite in-phase modes, providing reliable operation while maintaining mode separation.
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 sensor effectively detects yaw rates around two sensitive axes with enhanced robustness against disturbances, reducing control effort and costs, and providing high accuracy and stability under external influences like mechanical vibrations and shocks.
Implementation Method 1
utilizing capacitive comb structures for electrostatic excitation and detection
Implementation Method 2
torsion spring elements to suppress unwanted deflections
Implementation Method 3
In the case of a Coriolis force due to a rotational movement around the x or y axis, oscillations with movement components in the z direction are excited
Data Source
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AI summary
A micromechanical rotation rate sensor has at least one first and one second seismic mass coupled to at least one first drive device and are suspended such that the first and second seismic masses are driven such that they are deflected in antiphase in one drive mode, with the rotation rate sensor being designed such that it can detect rotation rates about at least two mutually essentially orthogonal sensitive axes, wherein at least the first and second seismic masses are designed and suspended such that they oscillate in antiphase in a first read mode when a first rotation rate about the first sensitive axis is detected, and the first and second seismic masses and/or additional seismic masses are designed and suspended such that they oscillate in antiphase in a second read mode when a second rotation rate about the second sensitive axis is detected.