MEMS Accelerometer Planar Coil Flux Angle
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Solution Overview
Problem
Traditional force balance MEMS accelerometers with a coil configuration experience high reluctance in their magnetic circuit, leading to high power requirements and nonlinearities due to heating effects, which degrade performance.
Innovation Solution
A MEMS accelerometer design featuring a planar coil with a magnetic flux angle between 30 and 60 degrees relative to the coil plane, utilizing a magnetic circuit with pole pieces and magnets positioned on either side of the proof mass, reducing the magnetic reluctance by minimizing the gap between pole pieces, and employing a method to sense capacitance for rebalancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional coil configuration with magnetic field parallel to coil plane is used, then the magnetic circuit can be simplified, but the reluctance value becomes large resulting in high power requirements
Solution Approach 1:
The patent changes the flux angle parameter from parallel (0 degrees) to perpendicular (90 degrees) relative to the coil plane, which fundamentally alters the magnetic circuit characteristics and reduces reluctance, thereby lowering power requirements while maintaining device simplicity
2Ease of manufacture
If a traditional coil configuration with large gap in magnetic return path is used, then the structure is easier to manufacture, but the reluctance value increases leading to heating effects and nonlinearities
Solution Approach 1:
The patent repositions the coil in a different spatial dimension relative to the magnetic flux path, creating a perpendicular configuration that reduces the effective gap distance in the magnetic return path, thereby reducing reluctance and minimizing heating effects while preserving manufacturing ease
3Force
If high current is used to servo the accelerometer with traditional configuration, then the magnetic force is sufficient, but heating effects increase causing nonlinearities
Solution Approach 1:
By changing the flux angle to perpendicular orientation, the patent increases magnetic coupling efficiency, allowing the same magnetic force to be achieved with lower current, thereby reducing Joule heating and associated nonlinearities
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 enhances sensitivity, increases the signal-to-noise ratio, and reduces power consumption by lowering the magnetic reluctance and minimizing heating effects, thereby improving the overall performance of the MEMS accelerometer.
Implementation Method 1
rebalancing the MEMS accelerometer by sending a current through the planar coil
Implementation Method 2
A magnetic flux field passes from at least one of the at least one magnets, through the first pole piece, through the planar coil at a flux angle between approximately 30 degrees and approximately 60 degrees relative to the coil plane
Implementation Method 3
sensing a capacitance of a pickoff in the MEMS accelerometer
Data Source
AI summary
Microelectromechanical (MEMS) accelerometer and acceleration sensing methods. A MEMS accelerometer includes a proof mass, a planar coil on the proof mass, a magnet, a first pole piece positioned proximate a first side of the proof mass, and a second pole piece positioned proximate a second side of the proof mass. A magnetic flux field passes from the magnet, through the first pole piece, through the planar coil at an angle between approximately 30 degrees and approximately 60 degrees relative to the coil plane, and into the second pole piece. The first pole piece may extend into a first recessed area of a first housing layer and the second pole piece may extend into a second recessed area of a second housing layer. A method includes sensing a capacitance of a pickoff in the MEMS accelerometer and rebalancing the MEMS accelerometer by sending a current through the planar coil.