Steering Angle Sensor Multipole Magnet Interference Compensation
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Solution Overview
Problem
Current angle sensors in motor vehicles are prone to interference from external magnetic fields, particularly in electric vehicles, which can affect the accuracy of steering angle measurements and the robustness of the steering system.
Innovation Solution
An angle sensor unit featuring a multipole magnetic ring with two magnetic field sensors arranged offset in the circumferential direction, allowing for differential measurements to eliminate leakage field interference and determine an interference-free rotational angle, utilizing an evaluation unit to process signals from these sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If magnetic sensors are used to measure steering angle, then the measurement is easy to implement, but the measurement accuracy is reduced due to external magnetic field interference
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the external magnetic interference field itself as a reference signal. The method measures the magnetic field vector with the sensor, determines the interference field component, and subtracts it vectorially from the total magnetic field vector to obtain the true steering angle. This transforms the harmful interference into a usable reference that enables accurate measurement despite the presence of external magnetic fields.
2Measurement precision
If compensation for magnetic interference is implemented by determining and subtracting the interference field vectorially, then the measurement accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies the self-service principle by using the existing magnetic sensor to measure both the useful magnetic field signal and the interfering magnetic field. The evaluation unit processes these measurements to automatically determine and compensate for the interference without requiring additional dedicated compensation sensors or complex hardware modifications. The system serves itself by utilizing its own measurement capabilities to eliminate the interference.
3Adaptability or versatility
If cables conducting high currents are located in the vicinity of the steering system, then the electrical system functionality is improved, but the magnetic interference on angle sensors increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a mathematical processing step as a mediator between the magnetic sensor and the steering angle determination. The evaluation unit acts as an intermediary that receives the raw magnetic field vector containing both useful signal and interference, processes it through vectorial subtraction of the determined interference field, and outputs the corrected steering angle. This intermediary processing eliminates the harmful effect of the magnetic interference while preserving the electrical system functionality.
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 increased accuracy and reduced influence of external magnetic interference, enabling precise determination of rotational angles independent of external magnetic fields, enhancing the reliability of steering systems in electric vehicles.
Implementation Method 1
having a multipole magnetic ring (2) which has a number of pole pairs and can be connected in a torque-proof manner to the steering shaft (10), at least two magnetic field sensors (4, 5) which are assigned to the multipole magnetic ring (2)
Data Source
AI summary
An angle sensor unit for measuring a rotational angle of a rotational position of a steering shaft of a motor vehicle may include a multipole magnetic ring that has a number of pole pairs and can be connected in a torque-proof manner to the steering shaft, at least two magnetic field sensors that are assigned to the multipole magnetic ring, and an evaluation unit that is configured to determine a rotational angle on the basis of the signals of the at least two magnetic field sensors. The at least two magnetic field sensors may be offset in a circumferential direction on an outside of the multipole magnetic ring such that a magnetic field that originates from the multipole magnetic ring, in a region of the two magnetic field sensors, has an approximate equal absolute value with opposite signs.