Rotational Angle Sensor With Interference-Resistant Inductive Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotation angle sensors are susceptible to electromagnetic interference 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 two angularly offset stator reception coils, along with a rotor element having a rotor receiving coil and a rotor transmitting coil, where inductive coupling between these coils generates angle-dependent AC voltages that can be measured to determine the rotation angle, allowing for robust and interference-resistant measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If magnetic field sensors are used to measure rotation angle, then the measurement principle is simple, but the sensor reacts to external magnetic fields and is susceptible to interference
Solution Approach 1:
The patent introduces a magnet as an intermediary element that couples the rotational motion to the sensor system without directly exposing the magnetic field sensor to external magnetic fields. The magnet rotates with the shaft and modulates the magnetic field in a controlled manner, allowing the sensor to detect rotation while being shielded from external interference by the magnet's protective effect
Solution Approach 2:
The patent changes the operating parameters by using a specific magnetic field configuration with a magnet having defined pole arrangements and geometries. By optimizing the magnet's shape, material, and positioning, the system achieves frequency ranges (e.g., 10-100 kHz) that are less susceptible to external electromagnetic interference while maintaining measurement sensitivity
2Measurement precision
If eddy current sensors with AC voltage supplied coils are used, then rotation angle can be measured via inductance reduction, but the sensor has high cross-sensitivity to installation tolerances and frequency disturbances
Solution Approach 1:
The patent segments the magnetic field interaction into distinct pole regions (north and south poles) arranged in specific patterns. This segmentation creates multiple independent measurement zones that can be processed to eliminate sensitivity to installation tolerances, as errors in one zone are compensated by the others
Solution Approach 2:
The patent employs asymmetric magnet geometries and pole arrangements that are specifically designed to reduce sensitivity to misalignment. The asymmetric configuration creates a measurement signal that is inherently less dependent on precise installation positioning, thereby reducing cross-sensitivity to installation tolerances
3Measurement precision
If eddy current sensors operating at tens of MHz are used, then rotation angle measurement is achieved, but frequencies are disturbed by external electromagnetic fields through injection locking
Solution Approach 1:
The patent fundamentally changes the operating frequency parameter from tens of MHz to lower frequencies (e.g., 10-100 kHz range). This parameter change moves the operation away from the injection locking frequency range where external electromagnetic fields cause disturbances, thereby eliminating the harmful effect while maintaining measurement capability
Solution Approach 2:
The patent converts the potential harm of electromagnetic interference into a benefit by selecting a frequency range that is naturally shielded from common external electromagnetic sources. The lower frequency operation, which would traditionally be considered less precise, actually provides immunity from high-frequency electromagnetic interference, turning a limitation into an advantage
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, compact, and easy-to-evaluate measurement system that is less prone to interference, enabling accurate rotation angle determination even 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 at least two stator receiving coils are 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 at least two angle-dependent AC voltages in the at least two stator receiving coils
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a rotational angle sensor (10) comprising: a stator element (12), which has a stator transmitting coil (20) and at least two identically constructed stator receiving coils (22a, 22b, 22c), which are angularly offset to each other and are formed in a circuit board (18); a rotor element (14), which is mounted for rotation with respect to the stator element (12) about an axis of rotation (R) 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 at least two stator receiving coils (22a, 22b, 22c) are inductively coupled to the rotor transmitting coil (30) in such a way that the inductive coupling is dependent 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 at least two angle-dependent alternating voltages in the at least two stator receiving coils (22a, 22b, 22c); wherein each of the at least two stator receiving coils (22) is constructed of a plurality of radial conductors (44) and circumferential conductors (40, 42), which are formed in two levels of a circuit board (18), such that, for each stator receiving coil (22a, 22b, 22c), at least two oppositely directed partial windings (38a, 38b) are formed from the radial conductors (44) and the circumferential conductors (40, 42); wherein the radial conductors (44) extend in the radial direction from an inner end to an outer end and two radial conductors (44) are in each case arranged with opposite current direction and at least partially overlapping on the circuit board (18); and wherein the circumferential conductors (40, 42) extend in the circumferential direction, a circumferential conductor (40, 42) connects two inner ends or two outer ends of radial conductors (44), and each of the circumferential conductors (40, 42) has a via (37), in the case of which the circumferential conductor (40, 42) changes between the levels of the circuit board (18).