Circular Magnet Sensor for Large Angular Range Measurement
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Solution Overview
Problem
Current rotation angle sensor arrangements that use magneto-sensitive principles, such as Hall probes, are complex and costly when attempting to measure large angular ranges like 270 degrees, often requiring multiple sensors.
Innovation Solution
A circular magnet with a continuously changing cross-section is embedded in a magnetic field transmitter made of injection-molded plastic, allowing a single sensor to detect up to 360 degrees of rotation with a simple and inexpensive setup, where the magnet can be integrated into the measurement object or attached as a separate unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors or complex rotary angle systems are used to measure large angular ranges (e.g., 270 degrees), then the measurement precision and angular range are improved, but the device complexity and cost increase
Solution Approach 1:
The magnet is segmented in terms of its cross-sectional area along the circumferential direction, creating distinct magnetic field zones (first, second, and third magnetic fields) that correspond to different angular ranges. This segmentation allows a single sensor to detect multiple angular positions by identifying which magnetic field zone the magnet currently occupies, thereby achieving large angular range measurement without requiring multiple sensors.
Solution Approach 2:
Different regions of the magnet have different local qualities - specifically, different cross-sectional areas that generate different magnetic field strengths. The first region has a larger cross-section producing a stronger first magnetic field, the second region has a smaller cross-section producing a weaker second magnetic field, and the third region has an intermediate cross-section producing an intermediate third magnetic field. This local variation in magnetic field quality enables the single sensor to distinguish between different angular positions.
2Measurement precision
If multiple sensors are used to cover large angular ranges, then the measurement capability is improved, but the manufacturing cost increases
Solution Approach 1:
The single magneto-sensitive sensor performs multiple functions by detecting different magnetic field zones generated by the magnet's varying cross-section. Instead of requiring separate sensors for different angular ranges, this one sensor universally covers the entire angular range (e.g., 270 degrees or more) by identifying which of the three magnetic field zones is currently active, thereby reducing component count and manufacturing cost.
Solution Approach 2:
The magnet's cross-sectional area parameter is changed along the circumferential direction to create distinct magnetic field zones. By varying this geometric parameter, the system generates different magnetic field strengths (first, second, and third magnetic fields) that can be detected by a single sensor, eliminating the need for multiple sensors and reducing manufacturing costs.
3Measurement precision
If a magnet with continuously changing cross-section is used, then the angular range measurement capability is improved, but the manufacturing complexity of the magnet increases
Solution Approach 1:
The magnet features a curved or rounded corner design at its transition regions, rather than sharp angular transitions. This curvature creates smooth variations in the cross-sectional area along the circumferential direction, generating the distinct magnetic field zones needed for multi-range detection. The rounded geometry is both functionally effective for creating the three magnetic fields and manufacturable using standard molding techniques.
Solution Approach 2:
The magnet's effective cross-sectional area is dynamically varied along the circumferential direction to create different magnetic field zones. This dynamic variation in geometry (larger cross-section in the first region, smaller in the second region, intermediate in the third region) enables the magnet to generate multiple distinct magnetic fields that a single sensor can detect across different angular positions.
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 solution enables the measurement of large angular ranges with a straightforward and cost-effective sensor arrangement, suitable for applications like automotive angle measurement, allowing detection of tailgate positions including pre-locking states with reduced complexity.
Implementation Method 1
Rotation angle sensor arrangements which function on a magneto-sensitive basis, in particular by means of Hall probes
Data Source
Figure 1~2
AI summary
The arrangement has a magnet (1) and a magneto-sensitive sensor (3) e.g. Hall sensor, where the magnet is embedded in a magnetic field generator (2) and formed in a circular manner. The magnet has a cross section, which constantly changes in a circumferential direction. The sensor is arranged at a front surface of the magnet, which points in a direction parallel to a rotation axis of the magnet. The field generator is formed as a separate component, and is made of plastic material.