Inductive Position Sensing With a Screening Layer for Misalignment
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Solution Overview
Problem
Inductive position sensors face challenges in accurately measuring relative positions between members due to sensitivity to geometric changes and misalignment, particularly in applications like hydraulic cylinders or dampers, where integrating target systems are prone to measurement errors and require longer sensors.
Innovation Solution
The use of a screening layer, such as ferrite, is applied over a portion of a conductive member to 'cloak' the underlying material, reducing its influence on the inductive sensor and allowing an exposed portion to act as a spot target, thereby minimizing errors caused by geometric tolerances and misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an inductive sensor element is used to detect relative position between members, then position detection capability is provided, but the sensor becomes sensitive to geometric changes and misalignment causing measurement errors
Solution Approach 1:
The patent applies a screening layer to specific portions of the target member surface, creating local differentiation between screened and unscreened areas. This local quality change allows the sensor to distinguish position based on electromagnetic property variations rather than relying on precise geometric alignment, thereby reducing sensitivity to geometric changes while maintaining position detection accuracy.
Solution Approach 2:
The screening layer acts as an intermediary between the inductive sensor element and the target member surface. By introducing this intermediate layer with specific electromagnetic properties, the system transforms the sensor's interaction with the target, making position detection less dependent on precise geometric relationships and more robust against misalignment and geometric variations.
2Measurement precision
If a screening layer is applied over a portion of the target member surface, then measurement precision is improved by reducing sensitivity to geometric changes, but device complexity increases
Solution Approach 1:
Rather than modifying the entire target member or sensor assembly, the patent applies the screening layer only to specific portions of the target surface. This localized approach achieves the desired measurement precision improvement while minimizing the added complexity, as only selected areas require the additional layer rather than the entire system.
Solution Approach 2:
The screening layer can be applied as a coating or deposited layer that replicates the necessary electromagnetic properties without requiring complex mechanical structures. This approach simplifies the overall device complexity compared to alternative solutions that might require mechanical linkages, multiple sensor elements, or complex positioning mechanisms.
3Length of moving object
If the entire target member surface is exposed to the sensor, then the sensor length can be shorter, but geometric tolerances and misalignment cause measurement errors
Solution Approach 1:
By creating local differentiation through the screening layer on specific portions of the target surface, the patent enables shorter sensor lengths while maintaining measurement accuracy. The screened and unscreened areas create distinct electromagnetic signatures that provide precise position information even with reduced sensor-to-target distance, eliminating the need for longer sensors required by traditional integrating target systems.
Solution Approach 2:
The target member surface is effectively segmented into screened and unscreened portions, each interacting differently with the sensor's electromagnetic field. This segmentation creates distinct measurement zones that provide accurate position detection with shorter sensor lengths, as the differentiated regions provide clear positional cues without requiring the sensor to span the entire target surface.
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 configuration enhances positional accuracy by reducing electromagnetic interference, allowing for more compact and cost-effective sensors that are less sensitive to geometric changes and misalignment, while maintaining measurement precision.
Implementation Method 1
The screening layer may be configured to reduce an effect on induced signals in the inductive sensor element caused by the screened portion of the second member
Implementation Method 2
The inductive sensor element can be configured to detect relative position of the two members by detecting the position of the soft magnetic or conductive target relative to the inductive sensor element
Data Source
AI summary
An inductive position sensor may be configured to detect relative position between a first member and a second member. The inductive position sensor may include an inductive sensor element configured to be coupled to the first member and a screening layer formed over a screened portion of a member surface of the second member such that an exposed portion of the member surface is free of the screening layer. The screening layer may be configured to reduce an effect on induced signals in the inductive sensor element caused by the screened portion of the second member.