Rotating Field Sensor Angle Detection Error Reduction
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Solution Overview
Problem
Rotating field sensors face errors in detecting angles due to noise fields, such as leakage magnetic fields and the Earth's magnetism, which can exceed the desired accuracy, and existing solutions either increase sensor size and cost or limit the arrangement of magnetic detection elements.
Innovation Solution
A rotating field sensor design that includes a field generation unit producing a rotating magnetic field with partial fields differing by 180°, and detection units with circuits and arithmetic circuits to calculate angles, allowing for error reduction by canceling out noise field errors through phase differences in output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic detection elements are arranged to detect rotating magnetic field components in different directions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The sensor divides the detection function into multiple independent detection elements (first and second magnetic detection elements) that detect different components of the rotating magnetic field. Each element operates independently but contributes to the overall angle measurement, allowing the system to achieve high precision through segmented detection rather than a single complex detector.
Solution Approach 2:
The patent combines the output signals from multiple magnetic detection elements with different phase characteristics to determine the angle of the rotating magnetic field. By merging the detection results from elements with 90-degree phase differences, the system achieves accurate angle measurement while maintaining a relatively simple overall structure.
2Measurement precision
If magnetic detection elements are arranged in specific configurations to cancel noise field errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs asymmetric arrangement of magnetic detection elements where the first and second detection elements are positioned to detect magnetic field components with a 90-degree phase difference. This asymmetric configuration creates unequal detection characteristics that enable the system to distinguish between the rotating magnetic field signal and noise field errors, improving measurement precision through intentional asymmetric design.
Solution Approach 2:
The patent converts the harmful effect of noise fields into a beneficial cancellation mechanism. By arranging detection elements with specific phase relationships, the noise field errors that affect individual elements are converted into complementary errors that cancel each other out when the element outputs are processed, thereby eliminating the harmful noise effect.
3Measurement precision
If bridge circuits with multiple magnetoresistive elements are used to detect magnetic field components, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by using magnetoresistive elements with specific local characteristics - each element is optimized to detect a particular component of the magnetic field based on its position and orientation. The first detection element detects one component while the second detects another component with 90-degree phase difference, allowing precise angle measurement through locally optimized detection rather than requiring complex expensive elements throughout.
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 sensor effectively reduces angle detection errors caused by noise fields while minimizing the installation locations of magnetic detection elements, maintaining accuracy and reducing costs.
Implementation Method 1
Each of the bridge circuits includes four magnetoresistive elements (hereinafter referred to as MR elements) serving as magnetic detection elements. Each of the bridge circuits detects the intensity of a component of the rotating magnetic field in one direction
Implementation Method 2
Systems using rotating field sensors are typically provided with means (for example, a magnet) for generating a rotating magnetic field whose direction rotates in conjunction with the rotation or linear movement of the object
Data Source
AI summary
A field generation unit generates a rotating magnetic field including a first partial magnetic field in a first position and a second partial magnetic field in a second position. The first and second partial magnetic fields differ in direction by 180° and rotate in the same direction of rotation. A first detection unit detects, in the first position, a first angle that the direction of a first applied field forms with respect to a first direction. The first applied field includes the first partial magnetic field as its main component. A second detection unit detects, in the second position, a second angle that the direction of a second applied field forms with respect to a second direction. The second applied field includes the second partial magnetic field as its main component. A detected value of the angle that the direction of the rotating magnetic field in a reference position forms with respect to a reference direction is calculated based on detected values of the first and second angles.