Twist-Insensitive Magnetic Sensor for Wheel Speed Detection
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Solution Overview
Problem
Existing magnetic sensors for wheel speed measurement face challenges with stray-field robustness and twist sensitivity, where Hall monocell sensors are susceptible to external magnetic fields and differential Hall sensors are not twist-insensitive, leading to assembly and calibration issues.
Innovation Solution
A magnetic sensor module with multiple sensor elements arranged in a circular plane, grouped into pairs, generates differential measurement signals that are robust to homogeneous stray fields and insensitive to twist orientations, allowing for accurate rotational speed detection and direction determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a Hall monocell sensor is used, then the sensor is twist-insensitive and assembly tolerances are relaxed, but the sensor is susceptible to stray-field disturbances
Solution Approach 1:
The sensor is divided into multiple sensor elements (at least two) arranged in a specific geometric pattern, where each element contributes to the overall measurement. This segmentation allows the sensor to achieve both twist-insensitivity through geometric arrangement and stray-field rejection through differential measurement techniques.
Solution Approach 2:
The patent changes the measurement parameters by using differential measurements between multiple sensor elements and applying specific geometric arrangements. This transforms the sensor's response characteristics to simultaneously achieve twist-insensitivity and stray-field rejection without requiring external calibration.
2Object-affected harmful factors
If a differential Hall sensor is used, then stray-field robustness is improved, but the sensor becomes sensitive to twist orientations requiring reconfiguration
Solution Approach 1:
The patent employs asymmetric geometric arrangements of sensor elements relative to the rotation axis, combined with asymmetric evaluation functions. This asymmetric design inherently compensates for twist orientations without requiring active reconfiguration, while maintaining differential measurement capabilities for stray-field rejection.
Solution Approach 2:
The sensor geometry and evaluation algorithm are pre-configured to automatically compensate for potential twist orientations. This preliminary design approach eliminates the need for runtime reconfiguration or calibration, making the sensor robust against both stray fields and twist variations from the outset.
3Measurement precision
If multiple sensor elements are used to achieve both twist-insensitivity and stray-field robustness, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The multiple sensor elements serve multiple functions simultaneously: they provide differential measurements for stray-field rejection, geometric arrangement for twist-insensitivity, and redundant data for improved measurement accuracy. This multi-functionality achieves enhanced precision without proportionally increasing complexity.
Solution Approach 2:
The sensor elements and their geometric arrangement automatically compensate for each other's limitations. The differential measurement between elements self-cancels stray-field effects, while the geometric pattern self-compensates for twist orientations, eliminating the need for external calibration or complex control systems.
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 provides enhanced robustness against stray fields and maintains accuracy across various twist angles, ensuring reliable wheel speed measurement and direction detection without the need for reconfiguration of the electronic control unit.
Implementation Method 1
The plurality of sensor elements is configured to generate a plurality of sensor signals in response to sensing an oscillating magnetic field modulated by the rotation of the object
Implementation Method 2
The sensor circuit is configured to generate a plurality of differential measurement signals, one for each of the plurality of pairs of sensor elements, using the plurality of sensor signals, wherein each of the plurality of differential measurement signals is derived from sensor signals generated by a corresponding pair of sensor elements
Data Source
AI summary
A magnetic sensor includes a plurality of pairs of sensor elements, with each pair of sensor elements including two sensor elements that are oppositely disposed on a circumference of a circle arranged in a sensor plane of the magnetic sensor; and a sensor circuit configured to generate a first pulsed output signal based on a selected differential measurement signal that is indicative of a rotational speed of an object. The sensor circuit is configured to generate a plurality of differential measurement signals, one for each of the plurality of pairs of sensor elements, where each of the plurality of differential measurement signals is derived from sensor signals generated by a corresponding pair of sensor elements. The sensor circuit is further configured to select a differential measurement signal having a greatest magnitude from among the plurality of differential measurement signals as the selected differential measurement signal.