Multi-Turn Rotation Sensor Using Longitudinal Magnet Shift
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Solution Overview
Problem
Existing sensor systems are inadequate for determining absolute rotation angles beyond one full rotation, particularly for multi-turn rotatable systems like steering wheels, which require accurate angle measurement without mechanical and electronic overcomplication.
Innovation Solution
A sensor system comprising a rotatable axis, a bipolar ring magnet, and shifting means translates rotational movement into longitudinal movement, using two sensor elements to detect multi-dimensional magnetic fields and calculate absolute rotation angles through relative angle determination and longitudinal position evaluation, allowing for a range exceeding one full rotation with minimal mechanical and electronic effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field evaluation is used to determine rotation, then measurement is simple, but only relative rotation within one full rotation can be determined
Solution Approach 1:
The patent transforms the rotational measurement problem into a combination of rotational and longitudinal dimensions. The ring magnet's longitudinal position along the rotation axis encodes the number of full rotations, while the magnetic field pattern encodes the angular position within each rotation. This dimensional transformation enables multi-turn measurement while preserving the simplicity of magnetic field evaluation.
2Measurement precision
If mechanical encoding mechanisms are added for multi-turn measurement, then absolute rotation angle can be determined, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical encoding mechanisms with a magnetic field-based solution. Instead of using mechanical counters or encoders to track full rotations, the system uses the magnetic field's spatial pattern combined with the ring magnet's longitudinal position to encode absolute rotation information, significantly reducing mechanical and electronic complexity.
Solution Approach 2:
The ring magnet serves as an intermediary that couples rotational movement with longitudinal displacement through the shifting means. This intermediary mechanism translates rotational information into a form that can be read by simple magnetic field sensors, avoiding the need for complex direct measurement mechanisms.
3Measurement precision
If prior position storage is implemented, then absolute rotation can be tracked, but system reliability decreases in safety-critical applications
Solution Approach 1:
The patent implements a self-contained absolute position measurement system that does not require external memory storage or power-dependent position tracking. The ring magnet's longitudinal position and the magnetic field pattern together provide inherent absolute position information that is continuously available and independent of prior states, ensuring reliability in safety-critical applications where position loss could occur.
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 precise determination of absolute rotation angles for multi-turn systems with reduced complexity, suitable for applications like steering control systems, where accurate angle measurement is critical without the need for prior position storage, ensuring reliability in safety-critical applications.
Implementation Method 1
a ring magnet that is mounted to the rotatable axis for co-rotation and longitudinally shiftable... evaluating the magnetic field of a bipolar ring magnetic rotating with the rotatable axis
Implementation Method 2
a first sensor element and a second sensor element, each for detecting a multi-dimensional magnetic field intensity
Data Source
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AI summary
A sensor system is to be used with an arrangement comprising a rotatable axis (AX) that is arranged rotatable within a stator (ST), a ring magnet (RM) that is mounted to the rotatable axis (AX) for co-rotation and longitudinally shiftable, and shifting means (SM) for translating a rotational movement of the rotatable axis (AX) into a longitudinal movement of the ring magnet (RM). The sensor system comprises at least two sensor elements (HS1, HS2) for detecting a multidimensional magnetic field intensity, each configured to provide respective sensor values for at least two spatial dimensions, and an evaluation circuit (EV). The sensor elements (HS1, HS2) are arranged spaced apart from each other. The evaluation circuit (EV) is configured to determine a relative rotation angle (RR) based on the sensor values of at least one of the sensor elements, to determine a longitudinal position information (LP) based on the sensor values of both sensor elements (HS1, HS2), and to determine an absolute rotation angle (AR) based on a relative rotation angle (RR) and the longitudinal position information (LP).