Rotating Field Sensor Noise Cancellation via Phase Detection
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Solution Overview
Problem
Rotating field sensors face errors in detected angles due to noise fields, such as leakage magnetic fields and the Earth's magnetism, which are not effectively mitigated by existing solutions, and require complex designs and increased costs for magnetic shielding.
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 specific phase relationships between their output signals to cancel noise components, reducing errors and simplifying installation locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic shielding means are added to reduce noise field effects, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful noise field into a beneficial signal by detecting the noise field's effect on the rotating magnetic field and using phase detection to extract the angle information. The noise field that was previously harmful is now utilized as part of the detection mechanism, eliminating the need for magnetic shielding while maintaining or improving measurement precision.
Solution Approach 2:
The patent replaces the mechanical/physical magnetic shielding system with an electrical/electronic signal processing system. Instead of using physical barriers to block noise fields, the invention uses phase detection and signal processing methods to identify and measure the angle despite the presence of noise fields, thereby reducing device complexity and cost.
2Measurement precision
If magnetic shielding means are added to reduce noise field effects, then measurement precision improves, but manufacturing cost increases
Solution Approach 1:
The patent converts the harmful noise field into a beneficial signal by detecting the noise field's effect on the rotating magnetic field and using phase detection to extract the angle information. The noise field that was previously harmful is now utilized as part of the detection mechanism, eliminating the need for magnetic shielding while maintaining or improving measurement precision.
Solution Approach 2:
The patent replaces the mechanical/physical magnetic shielding system with an electrical/electronic signal processing system. Instead of using physical barriers to block noise fields, the invention uses phase detection and signal processing methods to identify and measure the angle despite the presence of noise fields, thereby reducing device complexity and cost.
3Measurement precision
If multiple detection units with specific phase relationships are used, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent segments the detection function into multiple detection units, each responsible for detecting the phase of the rotating magnetic field at different orientations. By dividing the detection task into segments and combining the results through phase comparison, the system achieves high measurement precision while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent inverts the traditional approach by having detection units detect the phase of the rotating magnetic field and then calculating the angle from the phase relationships, rather than directly measuring the angle. This inversion allows for high precision angle detection using simple phase-sensitive detection circuits.
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 errors in detected angles caused by noise fields while minimizing the complexity and cost of the sensor design by using phase-related signal processing to cancel noise components, thereby improving accuracy and installation simplicity.
Implementation Method 1
Each of the bridge circuits includes four magnetoresistive elements (hereinafter referred to as MR elements) serving as magnetic detection elements
Implementation Method 2
The rotating magnetic field generated by the field generation unit includes a first partial magnetic field in a first position and a second partial magnetic field in a second position. The first partial magnetic field and the second partial magnetic field differ in direction by 180° and rotate in the same direction of rotation.
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 located in the first position has first and second detection circuits whose output signals differ in phase by ¼ the period. A second detection unit located in the second position has third and fourth detection circuits whose output signals differ in phase by ¼ the period. 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 a first signal generated from the output signals of the first and third detection circuits and a second signal generated from the output signals of the second and fourth detection circuits.