Micromechanical Sensor Electrostatic Torque Compensation
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Solution Overview
Problem
Existing micromechanical acceleration sensors face challenges with deflection limitations and electrostatic interactions affecting the behavior of the seismic mass, particularly due to one-sided electrostatic interactions between the seismic mass and stop devices, which can distort measurements and increase manufacturing complexity.
Innovation Solution
The sensor design incorporates two stops with overlapping areas of equal size on the cap, arranged on the substrate, ensuring that electrostatic interactions between the stops and the seismic mass compensate each other, minimizing torque and allowing for precise positioning without significant influence on the seismic mass's behavior, thus maintaining accurate acceleration measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a one-sided electrostatic interaction between the flywheel and the stop device is used to limit deflection, then the deflection of the seismic mass is limited, but the behavior of the seismic mass is distorted due to uneven electrostatic forces
Solution Approach 1:
The patent applies asymmetry by designing the seismic mass with asymmetric mass distribution relative to the pivot axis, creating intentional unevenness that allows the center of mass to shift in a controlled manner during operation, thereby maintaining measurement accuracy while still limiting deflection through the stop device
Solution Approach 2:
The patent uses the counterweight principle by introducing a second stop device on the opposite side of the seismic mass that provides a compensating electrostatic interaction, effectively counterbalancing the asymmetric forces and preventing distortion of the seismic mass behavior while maintaining deflection limits
2Measurement precision
If the cap is positioned precisely on the substrate to ensure accurate measurements, then measurement precision is maintained, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the overlapping areas between the stops and the seismic mass, specifically designing them to have different sizes that compensate for positional variations, thereby maintaining measurement accuracy across a range of cap positions without requiring precise manufacturing tolerances
Solution Approach 2:
The patent uses beforehand cushioning by designing the overlapping areas to provide a built-in compensation mechanism that anticipates and counteracts the effects of positional variations, ensuring that even if the cap is not precisely positioned, the measurement accuracy is maintained through the pre-engineered geometric relationship between the stops and seismic mass
3Measurement precision
If the first and second overlapping areas are made essentially the same size to compensate electrostatic interactions, then the seismic mass behavior is not influenced, but the manufacturing tolerances are considerably increased
Solution Approach 1:
The patent applies parameter changes by intentionally designing the overlapping areas to have different sizes rather than making them equal, and uses the resulting asymmetric electrostatic interactions to compensate for cap positioning variations, thereby maintaining measurement accuracy while actually relaxing the manufacturing tolerance requirements
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
This design effectively limits deflection, prevents distortion, and increases manufacturing tolerances, allowing for precise and cost-effective production while maintaining accurate measurements of accelerations perpendicular and parallel to the main extension plane.
Implementation Method 1
the first and second electrostatic interactions on the seismic mass are compensated and no or only an insignificant resulting torque acts on the seismic mass with an axis of rotation parallel to the main extension plane
Implementation Method 2
Electrodes on the substrate and corresponding counter-electrodes on the seismic mass are preferably arranged between the seismic mass and the substrate, so that a deflection of the seismic mass relative to the substrate and perpendicular to the main extension plane causes a change in the electrical capacitance between the electrodes and counter-electrodes and can therefore be quantified
Data Source
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AI summary
The invention relates to a sensor having a substrate, a cap and a seismic mass, wherein the substrate has a main extension plane, wherein the seismic mass is provided in a displaceable manner perpendicular to the main extension plane, wherein in a first coverage region a first stop of the cap covers a first region of the seismic mass perpendicular to the main extension plane, and wherein in a second coverage region a second stop of the cap covers a second region of the seismic mass perpendicular to the main extension plane, and wherein further the first and the second coverage regions parallel to the main extension plane are provided at substantially the same size. The distances of the coverage regions from a pivot axis of the mass configured as a rocker are the same such that the torques caused by electronic forces offset each other.