Steering Torque Sensor Stray Magnetic Field Cancellation
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Solution Overview
Problem
Electric power steering systems face measurement errors due to stray magnetic fields, which current sensor designs fail to adequately account for or mitigate, leading to inaccurate torque readings and system performance issues.
Innovation Solution
A system and method that utilize both magnetic sensors within a torque sensing region and stray region sensors to detect and cancel out stray magnetic fields, generating a corrected torque signal to control the EPS system, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are used to detect torque in the torque sensing region, then torque measurement capability is achieved, but measurement precision deteriorates due to stray magnetic fields
Solution Approach 1:
The patent introduces stray region sensors as intermediary devices that detect stray magnetic fields separately. These sensors act as mediators between the torque sensing system and the harmful stray fields, enabling the controller to measure and compensate for interference without affecting the primary torque measurement function.
Solution Approach 2:
The system implements a feedback mechanism where stray region sensors continuously monitor stray magnetic field levels, and the controller uses this feedback information to dynamically adjust or compensate for interference in the torque measurement signals, improving measurement accuracy under varying electromagnetic conditions.
2Measurement precision
If stray region sensors are added to detect stray magnetic fields, then measurement precision improves through error cancellation, but device complexity increases
Solution Approach 1:
The patent segments the sensing function into two distinct parts: magnetic sensors for primary torque detection and stray region sensors for interference detection. This segmentation allows each sensor type to be optimized for its specific function and enables independent processing of measurement and compensation signals.
Solution Approach 2:
The controller performs multiple functions: it processes signals from both magnetic sensors and stray region sensors, calculates compensation values, and outputs corrected torque signals. This multi-functionality consolidates what could be separate systems into a single integrated control unit, reducing overall system complexity.
3Reliability
If torque signal compensation is implemented based on stray field detection, then reliability improves, but device complexity increases due to additional signal processing
Solution Approach 1:
The system performs preliminary detection of stray magnetic fields using dedicated stray region sensors before the stray fields can significantly corrupt the torque measurement. This preliminary action enables proactive compensation rather than reactive correction, improving reliability while keeping processing requirements manageable.
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 effectively cancels torque sensor errors caused by stray magnetic fields, improving the accuracy and reliability of electric power steering systems by dynamically adjusting torque signals based on detected stray field measurements.
Implementation Method 1
at least one magnetic sensor disposed within a torque sensing region to detect a magnetic field within the torque sensing region
Implementation Method 2
magnetic sensors (such as Hall effect sensors) to create an electric signal proportional to the applied torque
Implementation Method 3
The upper shaft rotor typically includes permanent magnets that act as a magnetic source, while the lower shaft rotor typically includes a pair of ferromagnetic ring structures that act as a magnetic flux path
Data Source
AI summary
A method for steering torque sensor stray magnetic field cancellation includes receiving, from at least one magnetic sensor disposed within a torque sensing region, a detected magnetic field corresponding to an angular displacement between an upper steering shaft and a lower steering shaft of an electronic power steering system. The method also includes generating a first torque signal based on the detected magnetic field and receiving, from at least one stray region sensor disposed outside of the torque sensing region, a detected stray magnetic field. The method also includes determining a torque signal error based on the detected stray magnetic field and generating a second torque signal based on the first torque signal and the torque signal error. The method also includes selectively controlling at least a portion of the electronic power steering system using the second torque signal.