Hall Sensor Angle Measurement Interference Compensation
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Solution Overview
Problem
Existing contactless rotation angle measurement devices face challenges with magnetic interference fields from current-carrying conductors, which are difficult to completely shield, leading to inaccuracies in measurements.
Innovation Solution
The use of a permanent magnet with an even number of poles, greater than four and not divisible by three, combined with at least three equiangularly arranged lateral Hall sensors, allows for the compensation of magnetic interference fields by calculating and eliminating field gradients, resulting in improved precision and signal-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Hall sensors are used for contactless measurement of rotation angle, then the measurement can be performed without mechanical contact, but magnetic interference fields from current-carrying conductors cause measurement inaccuracies
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the magnetic interference fields themselves as measurement information. Instead of merely compensating for the interference, the invention measures the interference field gradients and uses them to calculate and remove their own effect from the measurement, thereby converting the harmful interference into a useful correction signal that improves measurement accuracy
Solution Approach 2:
The patent implements feedback by measuring the magnetic interference field with additional Hall sensors and using this measurement to generate correction signals that are fed back to compensate for the interference in the final angle calculation. This closed-loop approach continuously eliminates the effect of magnetic interference fields on the measurement
2Measurement precision
If magnetic shielding is applied to protect Hall sensors from interference fields, then measurement accuracy may improve, but complete shielding is impossible and device complexity increases
Solution Approach 1:
The patent replaces the mechanical/physical approach of magnetic shielding with a signal processing approach. Instead of using magnetic shields to physically block interference fields, the invention uses additional Hall sensors to detect the interference and mathematical processing to eliminate its effect, substituting a complex physical shielding system with a simpler sensor array and calculation method
Solution Approach 2:
The patent changes the measurement parameters by measuring not only the magnetic field strength but also its spatial gradients through multiple sensors positioned at different locations. By measuring field gradients and using these parameters in calculations, the system can eliminate interference effects without requiring physical shielding
3Measurement precision
If compensation for magnetic interference fields is performed, then measurement accuracy improves, but the compensation process becomes more extensive and complex
Solution Approach 1:
The patent applies segmentation by separating the measurement into distinct components: the useful magnetic field from the permanent magnet and the interference field from current-carrying conductors. By using additional Hall sensors positioned specifically to detect only the interference field gradients, the system segments the total magnetic field measurement into separable components that can be independently processed and combined
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 precise contactless measurement of rotation angles by effectively eliminating inaccuracies caused by magnetic interference fields, including those from current-carrying conductors, and simplifies digital signal processing.
Implementation Method 1
The contactless measurement of a rotation angle with the aid of the Hall effect is known
Implementation Method 2
at least three first lateral Hall sensors arranged in a plane below the permanent magnet
Data Source
AI summary
An apparatus 10 for the contactless measurement of a rotation angle 15 is described. A permanent magnet 60 having a number of poles, wherein the number of poles amounts to four or more and cannot be divided by three, is mounted on the front of an axle. In a plane below the permanent magnet 16 at least three first lateral Hall sensors 40a-c are located in a circular path 50. A method for calculation the rotation angle 15 with the aid of the lateral Hall sensors 40a-40c is also described.