Electromagnetically Actuated MEMS Rotor Segmentation
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Solution Overview
Problem
Existing micromechanical devices with electromagnetic actuation face limitations in applying significant torsional forces along two axes of rotation due to weak and ill-defined magnetic fields within wide air gaps, leading to reduced actuation forces and efficiency, and geometric constraints that limit current intensity and rotor geometry.
Innovation Solution
A micromechanical device design featuring a rotor with a segment separated from the active element by an empty space, where the stator's magnetic poles are positioned on both sides of the segment, allowing for a localized and intense magnetic field that acts independently on each rotor segment, enabling efficient actuation along two perpendicular axes without global magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wide air gap is used in the stator, then the rotor can be positioned more freely and manufacturing is easier, but the magnetic field intensity becomes weak and ill-defined, reducing actuation force
Solution Approach 1:
The rotor is divided into two separate segments (first rotor segment and second rotor segment) that can be independently positioned in the air gap. This segmentation allows each segment to be optimally positioned for magnetic field interaction while maintaining manufacturing ease through modular assembly
Solution Approach 2:
The patent creates localized regions of intense magnetic field by positioning stator poles close to specific rotor segments while maintaining a wider overall air gap. This local quality approach concentrates magnetic flux where needed for actuation force while preserving manufacturing flexibility
2Force
If magnetic poles are positioned close to the rotor for intense magnetic field, then actuation force increases, but the air gap width is reduced, limiting rotor positioning freedom
Solution Approach 1:
The air gap space is effectively segmented into different regions: narrow regions near stator poles for intense magnetic field interaction, and wider regions for rotor positioning freedom. This is achieved by having multiple rotor segments at different positions relative to the poles
Solution Approach 2:
The patent utilizes the third dimension (depth/position along the axis) to resolve the contradiction. Rotor segments are positioned at different axial locations, allowing some segments to be close to poles for force generation while others maintain distance for positioning freedom
3Adaptability or versatility
If a single magnetic field is applied at 45 degrees to two rotation axes, then both axes can be actuated, but the force on each axis is reduced by a factor of 0.7 due to the angle
Solution Approach 1:
The rotor is segmented into first and second rotor segments, each independently interactable with magnetic fields. This allows separate magnetic field applications on each segment for actuating different axes without the 0.7 force reduction penalty
Solution Approach 2:
Different magnetic field orientations and intensities are applied locally to different rotor segments. The first stator poles create fields optimized for one axis, while second stator poles create fields optimized for the other axis, eliminating the need for compromised 45-degree field application
4Ease of operation
If the rotor geometry is constrained to rectangular turns, then current direction can be controlled, but the maximum current intensity is limited and rotor geometry flexibility is reduced
Solution Approach 1:
The rotor is divided into independent segments with separate electrical connections. This segmentation allows flexible current path design that can optimize both current direction control and current intensity without being constrained to simple rectangular geometries
Solution Approach 2:
The patent enables dynamic current distribution across different rotor segments based on operational requirements. Current can be selectively applied to different segments to optimize performance for different operating conditions, rather than being limited to fixed rectangular patterns
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 the local intensity of the magnetic field, increases actuation force without increasing current, and allows for efficient actuation along two axes with reduced power loss, resulting in a more efficient and flexible micromechanical device.
Implementation Method 1
Their operating principle is based on the exploitation of the Laplace force, i.e. the force F L exerted by a magnetic field B on a conductor of length l traversed by a current I
Data Source
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AI summary
A micromechanical device with electromagnetic actuation comprises a support (12), an active element (10) mounted for rotation about the axis (AA) on said support (12), a rotor (17) formed of at least one conductive line and rotationally fixed to the active element (10), and a stator (19) comprising at least two opposing magnetic poles (20, 21) separated by an air gap (22) from the rotor. The rotor (17) includes a segment (18) but is separated from the active element (10) by a gap (16). The stator (19) is positioned inside the support (12) so as to receive the segment (18) in its air gap (22). The poles (20, 21) of the stator are arranged on either side of the segment (18), one of them being located inside the gap (16).