Magnetic Sensor Offset Estimation Using Temperature Gradient Lookup
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Solution Overview
Problem
Magnetic balance type current sensors face significant errors in current detection due to temperature-induced changes in magnetic field detection value offsets, which existing methods inadequately address, especially as they require inefficient processing to generate offset characteristic curves for each magnetic sensor across a wide temperature range.
Innovation Solution
An offset estimation apparatus and method that uses an initial function storing unit, function settlement unit, and estimate determination unit to determine an offset estimate based on temperature changes, expressed as OSes(T)=OSst+A(OSst)×(T−Tst), where OSst is the reference offset and A(OSst) is determined by the reference offset, allowing for simple and effective offset correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If offset correction is performed using constant offset amount subtraction, then the device complexity is reduced, but the measurement precision deteriorates due to temperature-induced offset variations
Solution Approach 1:
The patent pre-calculates and stores gradient values representing offset changes per degree Celsius at the factory, based on measurements taken across a temperature range. These gradient values are stored in a lookup table. During operation, the system retrieves the appropriate gradient value corresponding to the current temperature and applies it to correct the offset, eliminating the need for complex real-time calculations while maintaining high precision across varying temperatures.
2Measurement precision
If offset characteristic curves are generated for each magnetic sensor across a wide temperature range, then the measurement precision is improved, but the productivity deteriorates due to inefficient processing requirements
Solution Approach 1:
The patent divides the temperature range into multiple discrete temperature points, and for each temperature point, pre-calculates the offset gradient value. Instead of generating complete characteristic curves for every sensor, the system segments the problem into individual gradient values that can be stored in a compact lookup table. During operation, only the gradient value corresponding to the current temperature is retrieved and applied, dramatically reducing processing requirements while maintaining accuracy.
3Productivity
If temperature compensation is implemented using gradient values stored in lookup tables, then the productivity is improved through efficient processing, but the device complexity increases due to additional storage requirements
Solution Approach 1:
The patent creates a simplified digital representation of the offset characteristics by storing only the gradient values (rate of change per degree Celsius) in a lookup table, rather than storing complete offset characteristic curves or complex compensation algorithms. This copied representation captures the essential temperature dependence information in a compact form that requires minimal storage space while enabling rapid retrieval and application during operation.
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 enables accurate offset estimation and correction across varying temperatures, reducing errors in current detection values by using a gradient-based estimate that is specific to each magnetic sensor, thus improving the reliability of magnetic balance type current sensors.
Implementation Method 1
The magnetic sensor detects a residual magnetic field between the first and second magnetic fields as a magnetic field to be detected, and generates a magnetic field detection value dependent on the strength of the magnetic field to be detected
Implementation Method 2
The feedback coil is intended to generate a second magnetic field that cancels out a first magnetic field generated by the current to be detected flowing through the conductor
Data Source
AI summary
An offset estimation unit determines an estimate of an offset of a detection value to be output from a magnetic sensor. The offset estimation unit includes an initial function storing unit, a function settlement unit, and an estimate determination unit. The initial function storing unit stores an initial function for determining the estimate according to a first variable and a second variable, with a reference offset as the first variable and temperature as the second variable, the reference offset being the offset at a reference temperature. The function settlement unit settles a value of the first variable of the initial function by the reference offset, and turns the initial function into an estimate determination function for determining the estimate according to a value of the second variable. The estimate determination unit determines the estimate by settling the value of the second variable of the estimate determination function by temperature information.