Dual Linear Angle Sensor Layout for Stray Field Cancellation
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Solution Overview
Problem
Stray magnetic fields interfere with the accuracy of magnetic-field angle sensors, causing increased angle errors by distorting the measured position of a magnet.
Innovation Solution
The use of two-dimensional linear sensors aligned vertically with a magnet target, cosine and sine coils, and strategically positioned magnetized pole magnets to detect and mitigate the effects of stray magnetic fields, allowing for accurate angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single linear sensor is used to measure magnetic field direction, then the device complexity is low, but the angle error increases due to stray magnetic fields
Solution Approach 1:
The patent divides the measurement system into multiple linear sensors (first linear sensor and second linear sensor) positioned at different locations. Each sensor measures the magnetic field direction independently, and the system processes these segmented measurements to eliminate stray field effects while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces a processing system that acts as an intermediary between the linear sensors and the final angle measurement. This processing system compares the magnetic field direction measurements from multiple sensors and calculates the angle while compensating for stray field effects, thereby improving measurement precision without requiring complex hardware modifications.
2Reliability
If multiple linear sensors are used to reduce stray field effects, then the angle error decreases, but the device complexity increases
Solution Approach 1:
The system segments the measurement function across multiple linear sensors positioned at different locations relative to the target magnet. By distributing the measurement task, the system can compare and contrast the measurements to identify and eliminate stray field interference, thereby improving reliability while keeping each individual sensor simple.
Solution Approach 2:
The patent merges the outputs of multiple linear sensors into a unified angle measurement through a processing system. By combining the information from the first linear sensor and second linear sensor, the system achieves more reliable angle measurement that is resistant to stray field effects, while the combined system remains integrated and manageable.
3Use of energy by moving object
If the angle sensor is positioned close to the target magnet, then the magnetic field detection is stronger, but the sensor is more vulnerable to stray magnetic fields
Solution Approach 1:
The patent positions multiple linear sensors at different distances and orientations relative to the target magnet. By segmenting the measurement locations, the system can distinguish between the strong magnetic field signal from the target magnet and the weaker stray field interference, allowing the sensor to operate close to the target while maintaining immunity to stray fields through comparative measurement.
Solution Approach 2:
The patent exploits the fact that stray magnetic fields affect multiple sensors in a predictable pattern. By measuring the magnetic field direction at multiple locations and comparing the differences, the system converts the harmful stray field effect into a useful signal for identification and elimination. The stray field, which would normally cause error, becomes a characteristic that can be recognized and compensated for through the multi-sensor measurement geometry.
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
Reduces angle errors by effectively canceling out stray magnetic field interference, enhancing the precision of angle sensors in the presence of external magnetic disturbances.
Implementation Method 1
magnetic-field sensing elements like Hall Effect and magnetoresistance elements
Implementation Method 2
magnetic-field sensing elements like Hall Effect and magnetoresistance elements
Implementation Method 3
cosine and sine coils
Data Source
AI summary
In one aspect, an angle sensor includes a first linear sensor and a second linear sensor. A first magnetic-field direction of a target magnet measured by the first linear sensor is substantially equal to a second magnetic-field direction of the target magnet measured by the second linear sensor. The first linear sensor, the second linear sensor and the target magnet are on an axis. The angle sensor determines an angle of a magnetic field.