Radial Rotation Sensor Layout for Magnetic Interference Rejection
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Solution Overview
Problem
Existing rotational property detection devices in the automotive industry face challenges in immunity to magnetic stray or interference fields, particularly in radial reading configurations, which can lead to incorrect readings and malfunctions.
Innovation Solution
A radial magnetic field-sensitive sensor arrangement with two two-dimensional sensor elements spaced apart and at equal radial distance from the axis of rotation, calculating difference values from magnetic field components in orthogonal directions to eliminate interference field influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a radial reading direction sensor device is used, then axial installation space is reduced, but immunity to magnetic stray or interference fields deteriorates
Solution Approach 1:
The sensor device is segmented into two separate sensor elements arranged radially offset from each other. Each sensor element detects magnetic field components independently, and their signals are processed separately before being combined through differencing to eliminate interference fields while maintaining radial compactness
Solution Approach 2:
The evaluation circuit acts as an intermediary that processes the magnetic field signals from both sensor elements. By calculating the difference between corresponding components from the two sensors, the evaluation circuit eliminates magnetic interference fields while preserving the rotational position information, thus mediating between the compact radial design and interference immunity requirements
2Reliability
If two two-dimensional sensor elements are used with difference value calculation, then immunity to magnetic interference fields is improved, but device complexity increases
Solution Approach 1:
Each two-dimensional sensor element serves multiple functions: it detects both radial and axial magnetic field components simultaneously, and each element's output contributes to both the rotational position measurement and the interference field rejection through the differencing process. This multi-functionality reduces the need for additional dedicated components
Solution Approach 2:
The evaluation circuit merges the outputs from both sensor elements by calculating difference values for corresponding magnetic field components. This combining approach eliminates interference fields while deriving rotational position information from the same sensor data, reducing overall system complexity by using a single integrated processing approach
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
The solution effectively eliminates the impact of magnetic stray or interference fields, enabling accurate detection of rotational properties by calculating difference values, thus ensuring reliable operation in environments with external magnetic interference.
Implementation Method 1
each of the two sensor elements is designed as a two-dimensional sensor element that enables the detection of a magnetic field component in the x-direction as well as a magnetic field component in the y-direction
Data Source
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AI summary
The invention relates to a device for detecting a rotational property of an object rotating about an axis of rotation, comprising: a magnet (1) rotatably mounted about the axis of rotation (10) with a cylindrical circumferential wall (11) surrounding the axis of rotation (10), wherein a magnetic north pole (N) and a magnetic south pole (S) of the magnet (1) are diametrically opposed with respect to the axis of rotation (10), a magnetic field-sensitive sensor device (2) configured to detect the magnetic field of the magnet (1) when the magnet rotates, and an evaluation circuit (3) which calculates the rotational property from the detected magnetic field.To eliminate an external magnetic interference field, it is proposed that the magnetic field-sensitive sensor device (2) has two sensor elements (21; 22) each, which each enable the detection of a magnetic field component (Bx1; Bx2) in an x-direction as well as the detection of a magnetic field component (By1; By2) in a y-direction, wherein the evaluation circuit (3) is configured to calculate a first difference value (ΔBx) from the magnetic field components (Bx1, Bx2) detected by the two sensor elements (21, 22) in the x-direction and a second difference value (ΔBy) from the magnetic field components (By1, By2) detected by the two sensor elements (21, 22) in the y-direction.