Dual-Track Magnetic Encoder for Reliable Position Sensing
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Solution Overview
Problem
Existing systems for determining the position of rotating members in electric motors, such as those in electric vehicles, face reliability issues due to the probability of complete sensor failure and diagnosing partial failures, which can lead to incorrect power supply and potentially serious vehicle movements.
Innovation Solution
A position determination system comprising a rotating encoder with multipolar magnetic tracks and a sensor with two patterns of sensitive elements using different technologies, arranged at a constant reading distance to detect magnetic signals, allowing for absolute angular position measurement without requiring initial movement, and featuring a processing device that utilizes the vernier principle for precise position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor is used to detect position, then the device complexity is reduced, but the reliability decreases due to the probability of complete sensor failure
Solution Approach 1:
The sensor is segmented into two independent patterns of sensitive elements (first pattern and second pattern) that read different magnetic tracks. Each pattern can independently detect position, so if one fails, the other can still provide position information, thereby improving reliability while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent changes the parameter of detection technology by using two different technologies (e.g., magnetoresistive and Hall effect) for the two patterns. This diversity in detection parameters ensures that a failure mode affecting one technology does not necessarily affect the other, thus improving reliability without significantly increasing complexity.
2Measurement precision
If patterns are arranged along the same reading surface at constant distance, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent arranges the two patterns along the same reading surface (adding a lateral dimension) rather than stacking them radially. This dimensional arrangement allows both patterns to read at the same constant distance from the magnetic tracks, improving measurement precision while the constant distance design compensates for manufacturing tolerances.
Solution Approach 2:
The magnetic tracks are designed with a constant reading distance from the reading surface, which preliminarily establishes the geometric relationship between the tracks and patterns. This pre-established geometry reduces the sensitivity to manufacturing variations in pattern placement, as the constant distance relationship is built into the track design itself.
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 enhances reliability by reducing the likelihood of simultaneous failure of both patterns, improving operational safety and enabling immediate accurate position determination upon power-up, thus ensuring safe motor control and reducing the risk of untimely movements.
Implementation Method 1
each sensitive element of the patterns having at least one sensitive layer based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track to be detected
Implementation Method 2
with signals from a third Hall effect sensing element for the magnetic poles around another half of one of the rings
Data Source
Figure 1a~1c
Figure 2a~2b
AI summary
The invention relates to an assembly comprising an encoder (1) rotationally fixed to the member, said encoder comprising a main magnetic track (2) and a secondary magnetic track (3) and a sensor (4) having two patterns (5) of sensitive elements which are capable of detecting the signals delivered by the tracks (2, 3) of the encoder (1), each pattern (5) being arranged at a reading distance from a track (2, 3) to form a signal representative of the position of said track, the sensitive elements of the first pattern (5) being based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track (2, 3) to be detected, said first pattern being arranged at a reading distance from a secondary track (3) having 2N-1 pairs of magnetic poles, the sensitive elements of the second pattern (5) being based on an anisotropic magnetoresistive material,said second motif being arranged at a reading distance from a main track (2) having N pairs of magnetic poles.