Position Sensor Pitch Deviation Determination via Zero-Crossing Analysis
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Solution Overview
Problem
Existing absolute position sensors, particularly those with magnetic rings, face inaccuracies due to non-perfect sine wave magnetic fields and varying period lengths, leading to challenges in determining total pitch deviation (TPD) from noisy angular signals.
Innovation Solution
A process for determining TPD involves recording angular signals, determining zero-crossing positions, filtering and interpolating to reduce noise, calculating pole pair lengths, and calculating TPD based on these lengths, without requiring a high-numbered encoder or additional interpolation stages, thus reducing errors and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods are used to determine TPD from angular signals, then measurement can be performed, but measurement precision deteriorates due to noisy signals and interpolation errors
Solution Approach 1:
The method segments the angular signal analysis into distinct steps: recording raw angular signals, determining zero-crossing positions, calculating pole pair lengths from these positions, and finally computing TPD. This segmentation allows selective application of filtering and interpolation only where necessary (in signal preprocessing) while preserving the integrity of the core measurement calculation, thereby improving measurement precision without introducing unnecessary error sources.
Solution Approach 2:
The method performs preliminary filtering and interpolation on the angular signals before TPD calculation. By pre-processing the signals to reduce noise and fill gaps, the subsequent TPD determination operates on cleaned data, improving measurement accuracy. The preliminary action includes determining zero-crossing positions from filtered signals and calculating pole pair lengths from these pre-processed positions.
2Measurement precision
If high-numbered encoders and additional interpolation stages are used to improve measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The method extracts only the essential information needed for TPD measurement: zero-crossing positions from the angular signals. By focusing solely on these critical points rather than processing the entire high-resolution encoder output, the method achieves accurate TPD measurement without requiring high-numbered encoders or multiple interpolation stages, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The method uses a simpler encoder system with lower resolution compared to traditional high-numbered encoders. Instead of relying on expensive, high-resolution encoding hardware, the invention achieves comparable or superior measurement accuracy through intelligent signal processing of lower-resolution data, effectively replacing complex hardware with simpler computational methods.
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 method effectively determines TPD with robustness against noisy signals, providing accurate pitch deviation measurements representative of the magnetic disk's actual pitch, without inducing additional errors from interpolation or needing a high-numbered encoder.
Implementation Method 1
recording, over one mechanical turn, an angular signal of an magnetic intensity measured by a magnetic detector as a function of an angle of rotation of the magnetic disk
Data Source
AI summary
A process for determining the total pitch deviation of a position sensor fitted with a magnetic disk and a magnetic detector, the magnetic disk comprising pairs of magnetic poles, the process includes recording, over one mechanical turn, an angular signal of the magnetic intensity measured by the magnetic detector as a function of the angle of rotation of the magnetic disk, determining zero-crossing positions based on the angular signal recorded and the number of zero-crossing position determined, determining the pole pair lengths based on the zero-crossing positions, and determining the total pitch deviation based on the pole pair lengths.