Undulating Variable Airgap Reluctance Actuator Design
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Solution Overview
Problem
Variable airgap reluctance actuators face limitations in achieving medium displacement strokes due to the inverse square relationship between force and displacement distance, resulting in increased actuator mass and size, which restricts their use in applications like aerospace where larger displacement ranges are required.
Innovation Solution
Incorporating undulations on the opposed surfaces of the armature and stator core, allowing for a more efficient distribution and phasing of magnetic forces, which enhances the displacement range without significantly increasing the actuator's mass by optimizing the design of slots and projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the airgap width is increased to achieve medium displacement strokes, then the displacement range is improved, but the actuator mass increases significantly due to the inverse square relationship between force and displacement distance
Solution Approach 1:
The opposed surfaces of the armature and stator are segmented into multiple undulating profiles with peaks and valleys. This segmentation creates multiple localized magnetic interaction zones that collectively produce the required force over a larger displacement range without proportionally increasing actuator mass
Solution Approach 2:
The undulating profiles create local variations in airgap width across the surface area, with some regions having smaller airgaps for higher force density and other regions contributing to extended displacement range. This local quality variation optimizes the force-displacement characteristics
2Length of moving object
If the airgap width is increased to achieve medium displacement strokes, then the displacement range is improved, but the actuator size increases
Solution Approach 1:
The segmented undulating profiles allow the actuator to achieve extended displacement stroke through the relative movement of peaks and valleys rather than requiring a proportionally larger overall actuator volume
Solution Approach 2:
The undulating profiles introduce surface topology variations that effectively utilize the surface area dimension to achieve displacement range extension without linearly increasing the actuator's volumetric dimensions
3Adaptability or versatility
If conventional flat opposed surfaces are used, then the actuator construction is simple, but the displacement range is limited to below 1 mm for practical force levels
Solution Approach 1:
The undulating profiles introduce controlled curvatures and surface variations to the otherwise flat opposed surfaces. These geometric modifications enable extended displacement range while maintaining manufacturing feasibility through standard machining or molding processes
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 solution extends the displacement range while maintaining a consistent rated force, reducing the actuator's mass by approximately two-thirds compared to conventional designs, making it more suitable for weight-conscious applications like aerospace.
Implementation Method 1
an armature attracted to a stator core... when the coil or coils are energised, relative movement in the direction of arrowheads is provided in an antagonistic relationship with magnetic attraction
Implementation Method 2
the magnitude of the reluctance force at a given current varies approximately with the square of airgap width between opposed surfaces dependent upon such effects as saturation
Implementation Method 3
variable airgap reluctance actuators... the magnitude of the reluctance force at a given current varies approximately with the square of airgap width
Data Source
AI summary
With variable airgap reluctance actuators problems arise due to the relationship between actuator mass and displacement range. By providing opposed surfaces in the actuator stator core and armature which have undulations typically in the form of grooves, slots and projections, a greater displacement range can be achieved whilst maintaining performance above a rated displacement force characteristic. In such circumstances by establishing a necessary rated displacement force characteristic, an actuator can be tailored and designed to meet that characteristic over a desired displacement range which has significantly less mass in comparison with a prior actuator arrangement having flat surfaces.