Differential Angle Sensor Using Asymmetric Magnetic Field Segmentation
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Solution Overview
Problem
Existing differential angle sensors in Electrical Power Steering systems face challenges in accurately measuring the differential angle between input and output shafts, which is crucial for precise vehicle operation, often resulting in inaccuracies across varying operating ranges.
Innovation Solution
A differential angle sensor system comprising a target assembly with radially extending teeth and a ring magnet, utilizing magnetic field sensors to measure magnetic field strengths, allowing for accurate determination of the differential angle between input and output shafts through calculated ratios and calibration methods, achieving ±0.1 degrees accuracy across ±6.0 degrees operating range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic field sensing methods are used, then the device complexity is reduced, but the measurement precision deteriorates due to inaccuracies across varying operating ranges
Solution Approach 1:
The target assembly is divided into multiple targets (first target, second target, third target, fourth target) with teeth extending radially. Each target interacts with the ring magnet to generate distinct magnetic field patterns. This segmentation allows the sensor to measure differential angle through multiple magnetic field interactions, improving measurement precision while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent introduces magnetic field sensors as intermediaries between the mechanical rotation (input/output shafts) and the electrical signal processing. The magnetic field sensors detect changes in magnetic field strength caused by the relative motion between the ring magnet and toothed targets, converting mechanical differential angle into measurable electrical signals with high precision.
2Measurement precision
If the number of magnetic field sensors is increased, then the measurement precision improves through multiple measurement points, but the device complexity increases
Solution Approach 1:
The patent employs an asymmetric arrangement where the first and second targets are positioned at different angular locations relative to the ring magnet, as are the third and fourth targets. This asymmetric positioning creates distinct magnetic field strength variations that are measured by the magnetic field sensors, enabling precise differential angle measurement through the asymmetric magnetic field patterns rather than requiring symmetric multiple sensors.
3Measurement precision
If the angular spacing between teeth is decreased, then the measurement resolution improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes changes in magnetic field strength parameters as the primary measurement mechanism rather than relying solely on precise mechanical tooth spacing. The magnetic field sensors detect variations in magnetic field strength caused by the relative angular positions of the ring magnet and toothed targets. This approach converts mechanical positioning requirements into magnetic field detection, reducing the impact of manufacturing tolerances on measurement resolution.
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 system provides precise measurement of the differential angle with high accuracy, ensuring reliable operation of Electrical Power Steering systems by effectively determining the angle using measured magnetic field strengths and calibration data, enhancing vehicle control and performance.
Implementation Method 1
A ring magnet is fixed to rotate with the other one of the input shaft or the output shaft opposite from the shaft with the target assembly. The ring magnet includes a plurality of magnetic segments with alternating magnetic polarities
Implementation Method 2
a first magnetic field sensor disposed therebetween for measuring a first magnetic field strength therebetween. The third and fourth targets also extend parallel and spaced apart from one another with a second magnetic field sensor disposed therebetween for measuring a second magnetic field strength therebetween
Data Source
AI summary
A differential angle sensor for measuring a differential angle between an input shaft and an output shaft includes a target assembly fixed to rotate with one of the shafts and a ring magnet with equidistantly spaced magnet segments fixed to rotate with the other one of the shafts. The target assembly includes four identical targets extending about the common axis parallel and axially spaced apart from one another, and each having a plurality of wedge-shaped teeth extending radially toward the ring magnet. A first magnetic field sensor is disposed between first and second targets for measuring a first magnetic field strength therebetween. A second magnetic field sensor is disposed between third and fourth targets for measuring a second magnetic field strength. The targets are all circumferentially offset relative to one another such that the magnetic field strengths each vary with the differential angle between the shafts and differently from one-another.