Predictive Thresholds for Magnetic Field Sensors
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Solution Overview
Problem
Conventional magnetic field sensors in automobile engine management applications suffer from sub-optimal phase accuracy and parasitic switching due to reactive output switching thresholds that are dependent on relative positioning and slow adaptation.
Innovation Solution
A predictive output switching threshold determination system for magnetic field sensors that calculates individual optimal thresholds for each tooth or pole during a rotation and applies them in subsequent rotations, using maximum and minimum signal values to improve phase accuracy and compensate for manufacturing and positioning tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single threshold is set over the entire pattern with slow adaptation, then robustness is improved, but phase accuracy deteriorates
Solution Approach 1:
The patent segments the single threshold into multiple individual thresholds, one for each tooth or pole of the target wheel. This segmentation allows each threshold to be optimized independently for its specific tooth or pole, improving phase accuracy while maintaining the robustness benefits of adaptive thresholding.
Solution Approach 2:
The patent applies local quality by determining individual thresholds based on the specific signal characteristics of each tooth or pole. Each threshold is locally optimized using the maximum and minimum signal values associated with that specific tooth or pole, rather than applying a global threshold that averages out local variations.
2Measurement precision
If output switching threshold adapts continuously to signal characteristics, then phase repeatability is improved, but parasitic switching increases
Solution Approach 1:
The patent applies preliminary action by determining the individual thresholds in advance during a first rotation of the target wheel. These pre-determined thresholds are then stored and reused for subsequent rotations, avoiding the need for continuous adaptation that causes parasitic switching while maintaining the benefits of customized thresholding for each tooth or pole.
Solution Approach 2:
The patent implements periodic action by determining thresholds during a first rotation and then reusing them for a predetermined number of subsequent rotations. This periodic approach balances the need for accurate thresholds with the need to avoid excessive updates that cause parasitic switching, updating thresholds only when necessary rather than continuously.
3Measurement precision
If offset regulation loop updates frequently, then phase accuracy is improved, but system response speed deteriorates due to anti-aliasing filter constraints
Solution Approach 1:
The patent determines the individual thresholds in advance during a calibration phase (first rotation) before normal operation begins. This preliminary determination eliminates the need for frequent updates during operation, achieving high phase accuracy without the speed penalty of continuous adaptation constrained by anti-aliasing filters.
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 system achieves improved phase accuracy and reduces parasitic switching by determining and applying predictive optimal switching thresholds for each tooth or pole, enhancing the robustness and precision of engine control.
Implementation Method 1
magnetic field sensors associated with rotating tooth or pole wheels and a back bias magnet can be used to sense rotation and/or positioning of the camshaft
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
Embodiments relate to predictive output switching threshold determination systems and methods for sensors, for example magnetic field sensors. In embodiments, at least one individual switching threshold is determined predictively, rather than reactively, for each tooth or pole of a ferromagnetic tooth or pole wheel, respectively. For example, in one embodiment, the number of teeth or poles is programmed, and an optimal threshold for each tooth or pole is determined during a rotation of the wheel. The determined optimal threshold for each tooth is then used for that tooth in at least one subsequent rotation of the wheel, with calibration optionally taking place in future subsequent rotations. Thus, in embodiments, thresholds are predictive for each individual tooth or pole rather than reactive to an adjacent tooth or pole.