Rotation Angle Sensor Hall Element Saturation Correction
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Solution Overview
Problem
Existing rotation angle measurement apparatuses using magnetic flux concentrators face accuracy degradation due to magnetic saturation, which is not effectively addressed by existing technologies, and there is a need for a method to detect and correct this issue, especially in applications requiring high reliability like power steering systems in automobiles.
Innovation Solution
A rotation angle measurement apparatus comprising multiple Hall element pairs, a magnetic flux concentrator, and an angle calculation unit that calculates and corrects rotation angle information, with a failure detection unit capable of detecting magnetic saturation by comparing outputs from different Hall element pairs and reference signals, using additional coordinate systems to cancel out angle errors and detect saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic flux concentrator is used to collect and amplify magnetic fields, then measurement sensitivity is improved, but magnetic saturation occurs in strong magnetic fields causing accuracy degradation
Solution Approach 1:
The system divides the measurement function into multiple independent Hall element pairs (first pair and second pair) with different orientations. Each pair measures magnetic field components in different directions, and the results are combined to obtain the final rotation angle. This segmentation allows the system to maintain accuracy even when one pair experiences magnetic saturation, as the other pair provides compensating measurement data.
Solution Approach 2:
The invention changes the orientation parameter of Hall element pairs by introducing a rotational offset angle α between the first and second pairs. This parameter change enables the pairs to measure magnetic field components at different angles, providing redundant measurement paths that are less susceptible to magnetic saturation effects in any single orientation.
2Reliability
If multiple Hall element pairs are added to detect magnetic saturation, then reliability is improved, but device complexity increases
Solution Approach 1:
The multiple Hall element pairs serve dual functions: they simultaneously perform normal rotation angle measurement and magnetic saturation detection. The same hardware components used for measuring the rotation angle also provide the data needed to detect magnetic saturation by comparing measurements across different pairs. This multi-functionality eliminates the need for separate detection hardware, maintaining reliability improvement without proportionally increasing device complexity.
Solution Approach 2:
The system implements feedback by continuously comparing measurements from multiple Hall element pairs and using this comparison to detect magnetic saturation conditions. The angle calculation unit receives feedback from the differential measurements and can identify when magnetic saturation occurs, enabling the system to compensate for or flag accuracy issues in real-time.
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 enables accurate rotation angle measurement even in strong magnetic fields, reduces angle errors, and detects magnetic saturation, enhancing the reliability and safety of rotation angle sensors in applications like power steering systems.
Implementation Method 1
Hall elements on a silicon substrate and a magnetic flux concentrator formed on the Hall elements are provided. A magnetic field (i.e., transverse magnetic field) parallel to a plane of the silicon substrate generated by the rotating magnet is detected by using the magnetic flux concentrator and the Hall elements
Implementation Method 2
a magnetic flux concentrator for collecting and amplifying surrounding magnetic fields
Implementation Method 3
a rotating magnet attached to a rotor... A magnetic field (i.e., transverse magnetic field) parallel to a plane of the silicon substrate generated by the rotating magnet
Data Source
AI summary
A rotation angle measurement apparatus includes: a first Hall element pair for detecting a magnetic component in a first direction; a second Hall element pair for detecting a magnetic component in a second direction different from the first direction; a third Hall element pair for detecting a magnetic component in a third direction different from the first direction and the second direction; and a fourth Hall element pair for detecting a magnetic component in a fourth direction different from the first to third directions. An angle calculation unit calculates a first rotation angle θ of a rotating magnet based upon the strengths of the output signals from the first Hall element pair and the second Hall element pair, and calculates a second rotation angle θc of the rotating magnet based upon the strengths of the output signals from the third Hall element pair and the fourth Hall element pair.