Inductive Angular Position Sensor With Opposing Partial Windings
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Solution Overview
Problem
Existing rotation angle sensors are susceptible to interference from external magnetic fields and have high cross-sensitivity to installation tolerances, making them unreliable in environments with high electromagnetic interference, such as the engine compartment of a vehicle.
Innovation Solution
A rotation angle sensor design featuring a stator element with a stator transmission coil and a rotor element with a rotor receiving coil, where the rotor receiving coil is inductively coupled to the stator transmitting coil, generating an angle-dependent AC voltage in the stator receiving coil, reducing susceptibility to external electromagnetic fields by using oppositely oriented partial windings that cancel out induced voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a magnet and magnetic field sensor are used to measure rotation angle, then the measurement principle is simple, but the sensor is very susceptible to interference from external magnetic fields
Solution Approach 1:
The patent replaces the magnetic field-based measurement system with an inductive coupling system using sensor coils and a metallic target. Instead of detecting magnetic fields directly, the system uses electromagnetic induction through the metallic target, which eliminates susceptibility to external magnetic field interference while maintaining measurement functionality.
Solution Approach 2:
The metallic target serves as an intermediary element between the sensor coils and the measurement system. The target mediates the electromagnetic interaction, allowing angle measurement through inductive coupling while isolating the sensor from direct exposure to external magnetic fields that would otherwise interfere with measurement.
2Measurement precision
If eddy current effect with metallic target and sensor coils is used, then rotation angle can be measured via frequency change, but the sensor has high cross-sensitivity to installation tolerances
Solution Approach 1:
The sensor system is segmented into distinct functional components: excitation coils, sensor coils, and a metallic target with specific geometric features. This segmentation allows each component to be optimized independently, reducing the impact of installation tolerances on overall measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from direct frequency measurement to a ratio-based measurement using multiple sensor coils. By measuring the ratio of voltages from different coil configurations, the system becomes insensitive to absolute frequency shifts caused by installation variations, thereby reducing sensitivity to installation tolerances.
3Speed
If eddy current sensor operates at tens of MHz frequency, then angle measurement is possible, but the frequency is disturbed by external electromagnetic fields
Solution Approach 1:
The patent converts the harmful effect of external electromagnetic fields into a beneficial measurement mechanism. By using the metallic target as an intermediary, external fields that would directly interfere with high-frequency operation are blocked or shielded by the target structure, while the desired inductive coupling between sensor coils and target remains effective.
Solution Approach 2:
The metallic target acts as a protective intermediary between the high-frequency sensor coils and external electromagnetic fields. The target's geometry and material properties are designed to allow desired inductive coupling while providing shielding against external interference, enabling stable high-frequency operation.
4Adaptability or versatility
If conventional rotation angle sensors are used in engine compartment, then they can measure throttle position, rotor position, or pedal position, but they are unreliable in high electromagnetic interference environments
Solution Approach 1:
The patent replaces magnetic field-based sensing with inductive sensing using sensor coils and a metallic target. This substitution eliminates the primary vulnerability to electromagnetic interference while maintaining the ability to measure various rotational positions in diverse applications such as throttle control, motor rotor position, and pedal position sensing.
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 solution provides a cost-effective, tolerance-robust, and interference-insensitive measurement of rotation angles, allowing for larger mechanical tolerances and improved reliability in harsh electromagnetic environments.
Implementation Method 1
the rotor receiving coil is inductively coupled to the stator transmitting coil such that an electromagnetic field generated by the stator transmitting coil induces a current in the rotor receiving coil
Implementation Method 2
the stator receiving coil is inductively coupled to the rotor transmitting coil, so that the inductive coupling depends on a rotation angle between the stator element and the rotor element, and the further electromagnetic field generated by the rotor transmitting coil induces an angle-dependent AC voltage in the stator receiving coil
Data Source
Figure 1~2
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Figure 5~6
AI summary
The invention relates to a rotational angle sensor (10) comprising: a stator element (12), which has a stator transmitting coil (20) and a stator receiving coil (22); a rotor element (14), which is mounted for rotation about an axis of rotation (R) in relation to the stator element (12) and which has a rotor receiving coil (28) and a rotor transmitting coil (30), which are electrically connected to each other; wherein the rotor receiving coil (28) is inductively coupled to the stator transmitting coil (20) such that an electromagnetic field produced by the stator transmitting coil (20) induces a current in the rotor receiving coil (28), which current flows through the rotor transmitting coil (30) such that the rotor transmitting coil (30) produces a further electromagnetic field; wherein the stator receiving coil (22) is inductively coupled to the rotor transmitting coil (30) in such a way that the inductive coupling depends on a rotational angle between the stator element (12) and the rotor element (14), and the further electromagnetic field produced by the rotor transmitting coil (30) induces an angle-dependent alternating voltage in the stator receiving coil (22); wherein the stator transmitting coil (20) has a circular outer partial winding (34a) and a circular inner partial winding (34b), which is arranged within the outer partial winding (34a) and is electrically connected to the outer partial winding (34a) in such a way that the inner partial winding is oriented opposite to the outer partial winding (34a) with respect to a current flow; wherein the rotor receiving coil (28) has a circular outer partial winding (34a) and a circular inner partial winding (34b), which is arranged within the outer partial winding (34a) and is electrically connected to the outer partial winding (34a) in such a way that the inner partial winding is oriented opposite to the outer partial winding (34a) with respect to a current flow; wherein the outer partial winding (34a) of the stator transmitting coil (20) and the outer partial winding (34a) of the rotor receiving coil (28) are oriented with respect to each other; wherein the inner partial winding (34b) of the stator transmitting coil (20) and the inner partial winding (34b) of the rotor receiving coil (28) are oriented with respect to each other.