Off-center GMR Sensor Angular Position Measurement
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Solution Overview
Problem
Magnetic sensing devices, such as GMR sensors, face challenges when positioned off-center from a rotating shaft due to non-uniform magnetic fields, leading to errors in angular position measurement, particularly in applications where space constraints or cost considerations prevent traditional toothwheel or polewheel setups.
Innovation Solution
An integrated circuit with adjustable magnetic sensing bridges and parameters, such as amplitude, offset, and orthogonality parameters, is used to minimize errors in signal representation, allowing for accurate angular position determination of a rotating shaft from an off-axis position by compensating for variations in the magnetic field and physical construction inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a GMR sensor is positioned off-center from the rotating shaft, then space constraints are satisfied and the device complexity is reduced, but measurement precision deteriorates due to non-uniform magnetic fields
Solution Approach 1:
The patent applies parameter changes by adjusting the output signals from the GMR sensor through calibration parameters. These parameters modify the signal characteristics to compensate for the non-uniform magnetic field effects caused by off-center positioning, thereby maintaining measurement precision while allowing flexible sensor placement
Solution Approach 2:
The patent implements feedback through a calibration process where the off-center sensor position is detected and correction parameters are applied to the output signals. This feedback mechanism compensates for positioning errors and maintains accurate angular position measurements despite the non-ideal sensor location
2Measurement precision
If traditional toothwheel or polewheel setups are used, then measurement precision is improved, but device complexity increases and cost increases
Solution Approach 1:
The patent extracts the complex mechanical components (toothwheels or polewheels) from the sensor system and replaces them with a simplified GMR-based magnetic sensing approach. By removing these mechanical elements and using only magnetic field sensing with software-based compensation, the device complexity is reduced while maintaining measurement precision
Solution Approach 2:
The patent substitutes the mechanical toothwheel or polewheel system with an electronic/magnetic sensing system. Instead of using mechanical features to encode position information, the system uses magnetic field detection combined with parameter-based signal correction, eliminating moving mechanical parts and reducing overall system complexity
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 reduces measurement errors caused by non-uniform magnetic fields and physical variations, providing accurate and continuous angular position data, even when the sensor is positioned off-center, thereby improving the reliability and precision of angular position measurement systems.
Implementation Method 1
Magnetic sensing devices, such as Giant Magnetoresistance (GMR) sensors
Implementation Method 2
a magnetic sensor (e.g. a Hall effect sensor) are positioned proximate to the wheel
Data Source
AI summary
A method for measuring an angular position of a rotating shaft, the method including providing a magnetic field which rotates with the shaft about an axis of rotation, positioning an integrated circuit having first and second magnetic sensing bridges within the magnetic field at a radially off-center position from the axis of rotation, the first and second magnetic sensing bridges respectively providing first and second signals representative of first and second magnetic field directions, the integrated circuit having a set of adjustment parameters for modifying attributes of the first and second signals, modifying values of the set of adjustment parameters until errors in the first and second signals are substantially minimized, and determining an angular position of the shaft based on the first and second signals.