Flux Coupling Sensor Offset Invariant Positioning
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Solution Overview
Problem
Inductive magnetic sensors are not offset invariant, leading to inaccurate position determination due to sensitivity to alternating magnetic stray fields and limited by the size of sensor elements, which makes it difficult to correct for target offsets that are significant compared to the sensor size.
Innovation Solution
A position sensor system using at least three sensor elements, where one generates a magnetic field and two receive the affected field, allowing for differential or common mode signal processing to determine the target's position invariant to offsets, by measuring the impact of the target's shape on the magnetic field lines and canceling stray field influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If inductive magnetic sensors are used for position measurement, then the sensors are not affected by static disturbing magnetic fields, but they are sensitive to alternating disturbing magnetic fields and not offset invariant
Solution Approach 1:
The sensor is divided into multiple sensor elements (at least three elements) that are spatially distributed. This segmentation allows the system to differentiate between signals caused by target position and signals caused by stray fields, enabling offset-invariant position determination while maintaining immunity to alternating magnetic stray fields through differential measurement techniques.
Solution Approach 2:
The patent introduces an intermediary evaluation process that separates the useful signal from interfering signals. By using multiple sensor elements and evaluating the magnetic field properties at different locations, the system creates an intermediary representation that filters out stray field influences while preserving target position information.
2Area of stationary object
If the size of sensor elements is reduced for small packaging, then the packaging size decreases, but the tolerances for target position remain unchanged leading to substantial offsets
Solution Approach 1:
The patent transitions from single-point measurement to multi-point spatial measurement. By distributing sensor elements across a larger area and evaluating magnetic field properties at multiple locations, the system achieves offset-invariant position determination even with small individual sensor elements. The spatial distribution of sensor elements creates a dimensional advantage that compensates for the reduced size of each element.
Solution Approach 2:
The system replaces mechanical alignment requirements with magnetic field-based measurement. Instead of requiring precise mechanical alignment between target and sensor, the patent uses magnetic flux coupling and differential measurement to achieve position determination that is invariant to offsets, eliminating the need for tight mechanical tolerances.
3Measurement precision
If target offsets are corrected using complex algorithms, then position accuracy improves for small offsets, but the complexity of the system increases and corrections are limited to small offsets
Solution Approach 1:
The patent performs preliminary measurement of magnetic field properties at multiple sensor element locations before final position determination. By pre-evaluating the magnetic field distribution and using this information in the differential measurement process, the system inherently compensates for offsets without requiring complex post-processing algorithms. This preliminary action is built into the fundamental measurement architecture.
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
Enables accurate and offset-invariant position determination of targets, even when the target is significantly offset from the expected axis or path, by effectively canceling common mode signals and enhancing the usable signal, thus reducing the need for highly rotational invariant targets.
Implementation Method 1
at least one sensor element (120, 130, 140) is configured to generate a first magnetic field, at least two sensor elements (120, 130, 140) are configured to receive a second magnetic field which is associated with the first magnetic field
Implementation Method 2
The magnetic flux coupling between the at least one sensor element (120, 130, 140) and the at least two sensor elements (120, 130, 140) via the target (250) is affected by the shape or form of the target (250)
Data Source
AI summary
An apparatus for sensing a position of a target, in particular for offset invariant sensing of the position of the target, is described as well as a corresponding method. The apparatus comprises at least three sensor elements. At least one sensor element of the at least three sensor elements generates a first magnetic field. At least two sensor elements of the at least three sensor elements receive a second magnetic field associated with the first magnetic field. The at least two sensor elements of the at least three sensor elements form at least one sensor element pair and provide a signal indicative of the position of the target.