Dual Magnetic Sensor Triangulation for Airgap-Insensitive Positioning
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Solution Overview
Problem
Magnetic-field-based position determination systems are susceptible to inaccuracies due to variations in the airgap between the magnet and the magnetic field sensor, leading to unreliable measurements.
Innovation Solution
A magnetic-field-based position determination device using two magnetic field sensors spaced apart to measure magnetic field vector angles in different spatial directions, allowing for triangulation to determine the magnet's position independently of the airgap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single magnetic field sensor is used to determine position based on magnetic field vector angle, then the measurement is robust against magnetic field strength fluctuations, but the position determination becomes sensitive to airgap variations
Solution Approach 1:
The single magnetic field sensor is segmented into two separate magnetic field sensors arranged at a distance d from each other. Each sensor independently measures the magnetic field vector angle, and both measurements are combined to determine the magnet's position. This segmentation allows the system to maintain robustness against magnetic field fluctuations while eliminating sensitivity to airgap variations, as the position can be calculated from the angular difference between the two sensors regardless of the absolute airgap distance.
2Measurement precision
If the airgap between magnet and sensor is kept invariable, then position determination accuracy is maintained, but the device becomes sensitive to installation errors and user reinsertion inaccuracies
Solution Approach 1:
The system changes the measurement parameters from relying on absolute airgap distance to relying on the angular difference between two sensors. By measuring magnetic field vector angles at two different positions and calculating the position from the angular relationship rather than absolute distance, the system becomes insensitive to airgap variations caused by installation tolerances or user reinsertion inaccuracies, while maintaining high measurement precision.
3Reliability
If two magnetic field sensors are arranged at a distance to enable triangulation, then the system becomes robust against airgap variations, but the device complexity increases
Solution Approach 1:
The system transitions from one-dimensional position measurement (single sensor) to two-dimensional angular measurement (two sensors). By arranging sensors at a distance and measuring angular relationships in addition to field strength, the system gains a new dimensional parameter (angular difference) that enables robust position determination independent of airgap variations. The position calculation uses the angular difference and sensor spacing to triangulate the magnet's position, providing robustness without excessive complexity.
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 accurate position determination with minimal deviation from the actual position, regardless of airgap variations, enhancing measurement robustness and reliability.
Implementation Method 1
Each of the two magnetic field sensors is configured to measure the magnetic field emanating from the magnet in at least a first spatial direction (e.g., z-direction) and a different second spatial direction (e.g., x-direction)
Data Source
AI summary
A magnetic-field-based position determination device includes a sensor device with at least two magnetic field sensors arranged spaced apart from each other by a distance and with a magnet movable relative to the sensor device. Each of the two magnetic field sensors is configured to measure the magnetic field emanating from the magnet in at least a first spatial direction and a different second spatial direction and, based thereon, to determine a magnetic field vector angle, respectively, wherein the first magnetic field sensor determines a first magnetic field vector angle, and wherein the second magnetic field sensor determines a second magnetic field vector angle. The sensor device is configured to determine the current position of the magnet relative to the sensor device based on the determined magnetic field vector angles and the distance of the two magnetic field sensors from each other.