Magnetic Sensor Threshold Update Immunity to Disturbances
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Solution Overview
Problem
Magnetic-field sensors in internal combustion engines face precision issues due to sensitivity to target position, geometry, temperature variations, and external magnetic disturbances, leading to incorrect switching threshold updates and decreased precision in engine synchronization.
Innovation Solution
A method to update the switching threshold of magnetic-field sensors based on oscillation frequency, suspending updates when frequencies exceed a maximum computed from engine speed and number of teeth, ensuring only engine-related oscillations are considered for threshold recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching threshold is updated based on all detected oscillations, then the sensor adapts to target position and geometry variations, but the sensor becomes vulnerable to magnetic disturbances causing false updates
Solution Approach 1:
The patent changes the parameter used for threshold updates from raw oscillation amplitude to oscillation frequency. By filtering based on frequency threshold (comparing detected frequency against expected frequency ranges for engine operations), the system maintains adaptation capability while rejecting high-frequency magnetic disturbances as spurious signals.
Solution Approach 2:
The patent introduces an intermediary filtering mechanism that processes detected oscillations before using them for threshold updates. This intermediary step involves computing oscillation frequency and comparing it against expected ranges, acting as a mediator that prevents direct influence of magnetic disturbances on threshold calibration.
2Measurement precision
If the switching threshold is updated frequently to adapt to changing conditions, then the sensor maintains accuracy under varying target positions, but the system becomes more complex with additional processing requirements
Solution Approach 1:
The patent simplifies the update mechanism by changing from amplitude-based to frequency-based filtering. This parameter change reduces processing complexity compared to complex signal processing methods, as frequency threshold comparison is computationally lighter than comprehensive signal analysis while maintaining effective filtering.
3Speed
If high-frequency oscillations are included in threshold updates, then the sensor responds quickly to changes, but magnetic disturbances cause false signals to be interpreted as valid oscillations
Solution Approach 1:
The patent changes the filtering parameter from time-domain amplitude analysis to frequency-domain analysis. By computing oscillation frequency and comparing against expected ranges, the system maintains rapid response to legitimate target position changes while automatically rejecting high-frequency magnetic disturbances as invalid signals.
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 enhances the immunity of magnetic-field sensors to high-frequency magnetic disturbances, maintaining precision and preventing false output signals, thus optimizing engine synchronization without additional hardware costs.
Implementation Method 1
A magnetic-field sensor detects magnetic-field variations induced by a passage of the teeth of the target in proximity to the sensor by generating, from said variations, a magnetic signal exhibiting oscillations
Data Source
AI summary
A method for authorizing an update of a switching threshold of a magnetic-field sensor for an internal combustion engine of a motor vehicle, in order to ensure an immunity of the sensor to external magnetic disturbances. The sensor detects magnetic-field variations induced by a passage of the teeth of a target in proximity to the sensor, by generating a magnetic signal exhibiting oscillations, certain of which may be due to magnetic disturbances and be not to be taken into account in the update by the sensor of the switching threshold, which is recomputed depending on a detected amplitude of at least two consecutive oscillations of the magnetic field. An update of the switching threshold is suspended when an oscillation frequency computed between the at least two consecutive oscillations is higher than a maximum oscillation frequency computed from a predetermined speed of rotation of the engine and from the number of teeth on the target.