Magnetic Position Sensor External Field Compensation
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Solution Overview
Problem
Existing magnetic field sensors are susceptible to interference from external fields, which affects their measurement accuracy and reliability, particularly in applications requiring precise position determination in user input interfaces like joysticks and rotary switches.
Innovation Solution
A method and device that generate a magnetic field around a rotation point, with three-dimensional Hall sensors recording the near-field at two locations, allowing position determination through differential vector analysis, effectively compensating for external field interference by maintaining a consistent magnetic axis orientation and using cylindrical magnets with arbitrary polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic field sensors are used for position determination, then position detection capability is enabled, but measurement accuracy deteriorates due to external field interference
Solution Approach 1:
The measurement system is segmented into multiple independent measurement locations (first and second measurement locations) along the magnetic field measurement axis. Each location has its own sensor that independently measures the magnetic field, allowing differential processing to eliminate common-mode external field interference while preserving the position-dependent signal.
Solution Approach 2:
The system uses feedback by continuously measuring the magnetic field at multiple locations and using these measurements to calculate position through differential processing. The measured values from both locations are fed into the evaluation unit which computes the position based on the difference, creating a closed-loop measurement system that compensates for external field variations.
2Device complexity
If three-dimensional magnetic field sensors are used, then functional integration and compactness are improved, but susceptibility to external field interference increases
Solution Approach 1:
The integrated 3D magnetic field sensor is segmented into multiple measurement locations along the measurement axis. By distributing sensors at different positions (first and second measurement locations), the system maintains the benefits of integration while enabling differential measurement to reject external field interference.
Solution Approach 2:
The system transitions from single-point measurement to multi-point measurement along the magnetic field measurement axis. This dimensional extension allows the system to capture spatial variations in the magnetic field and use differential processing to eliminate external field interference while maintaining compact integration.
3Reliability
If single-point magnetic field measurement is used, then device simplicity is maintained, but position determination reliability deteriorates due to external field influence
Solution Approach 1:
The measurement system is divided into multiple measurement locations (first and second measurement locations) with separate sensors at each location. This segmentation enables differential measurement that cancels external field interference, significantly improving position determination reliability while adding only minimal structural complexity.
Solution Approach 2:
The system uses partial measurement information from multiple locations to achieve the desired reliability. By measuring at two specific locations along the axis and using differential processing, the system obtains sufficient information for accurate position determination without requiring complete spatial mapping, balancing reliability improvement with acceptable 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
This approach enhances position detection accuracy and reliability by minimizing external field influence, enabling precise position determination in user input interfaces with improved robustness against field strength fluctuations.
Implementation Method 1
three-dimensional measuring Hall elements
Data Source
Figure 1~2
Figure 3A~4B
Figure 5A~6B
AI summary
The present invention relates to a device and a method for determining position, wherein the position of a first mechanical element relative to a second mechanical element is determined based on a magnetic field generated by a magnet (10), which, during relative movement between the first and second mechanical elements, essentially migrates about a point of rotation (25) and whose main direction during migration always points essentially towards the point of rotation (25). The near field of the magnetic field is detected at two different locations between which the point of rotation (25) is located, and the position is determined based on the difference in the measured values at the two different locations.