Magnetic Field Sensor Adaptive Threshold for Airgap Wobble
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Solution Overview
Problem
High precision applications, such as automobile engine control systems, face accuracy variations in detecting motion due to irregularities in sensed target profiles, particularly due to rotational wobble and airgap variations between magnetic field sensors and targets, leading to errors in ignition timing and fuel injection.
Innovation Solution
A magnetic field sensor with a magnetoresistance element, a detector responsive to a threshold level, and a threshold generator that sets rising and falling threshold level limits to accurately control transitions and minimize errors over airgap variations, using an analog-to-digital converter to digitize the magnetic field signal and track peak values and baseline for precise sensor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor is used to detect motion of a target object, then motion detection capability is provided, but accuracy variations occur due to airgap variations and rotational wobble
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the threshold level based on detected peak values and baseline measurements. The threshold is calculated as a percentage of the peak-to-peak amplitude, allowing the sensor to adapt to varying airgap conditions and maintain consistent detection accuracy despite mechanical variations in the target profile or airgap distance
Solution Approach 2:
The patent implements feedback by continuously monitoring the magnetic field signal to detect peak values and baseline levels, then using this information to adjust the threshold level for transition detection. This closed-loop approach ensures that the sensor maintains accurate motion detection by compensating for airgap variations and target profile irregularities through real-time threshold adaptation
2Productivity
If threshold level is used for transition detection, then output signal transitions are generated, but errors occur due to airgap variations between sensor and target
Solution Approach 1:
The patent applies dynamics by making the threshold level adaptive rather than fixed. The threshold dynamically adjusts based on the detected signal characteristics (peak values and baseline), allowing the system to maintain both fast transition detection and high accuracy across varying airgap conditions. This dynamic adaptation enables the sensor to respond quickly while preserving measurement precision
Solution Approach 2:
The patent changes the threshold parameter based on measured signal characteristics. By calculating the threshold as a percentage of the peak-to-peak amplitude and adjusting it according to detected baseline and peak values, the system maintains accurate transition detection despite variations in airgap distance or target profile, thereby preserving both productivity and measurement precision
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 effectively minimizes errors in detecting mechanical features by generating threshold levels with rising and falling limits, ensuring accurate sensor output signals even under varying airgap conditions, thus improving the reliability of motion detection in high precision applications.
Implementation Method 1
at least one magnetoresistance element configured to generate a magnetic field signal indicative of a magnetic field associated with a target
Data Source
AI summary
A magnetic field sensor including at least one magnetoresistance element configured to generate a magnetic field signal indicative of a magnetic field associated with a target having features and spaced from the at least one magnetoresistance element by an airgap. The sensor includes a detector responsive to the magnetic field signal and to a threshold level to generate a sensor output signal containing transitions, each transition associated with a feature of the target and occurring in response to the magnetic field signal crossing the threshold level. The sensor includes a threshold generator configured to generate the threshold level having a rising threshold level limit and a falling threshold level limit.