Magnetic Encoder Signal Processing for Runout Error Reduction
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Solution Overview
Problem
Magnetic encoders using multi-pole magnets face precision issues due to fluctuations in magnetic flux density caused by rotational runout and nonuniformity, leading to reduced detection accuracy, especially when combined with bipolarly or multi-polarized magnetic rings.
Innovation Solution
A magnetic encoder design featuring a multi-pole magnet with alternating N-poles and S-poles, paired with first and second magnetic detecting elements outputting 90° phase sinusoidal signals, and third and fourth elements similarly arranged, with signal processing to generate rotational position signals, effectively suppressing error components from rotational runout and turbulence by using sum or differential signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-pole magnet is used to detect rotational position, then the resolution of rotational position detection is improved, but the precision is reduced due to fluctuations in magnetic flux density caused by rotational runout and nonuniformity
Solution Approach 1:
The patent combines the output signals from multiple magnetic detecting elements (including both two-pole and multi-pole magnet systems) through signal processing circuits. By merging these signals and performing synthetic processing, the system achieves high-resolution absolute position detection while compensating for the instability and fluctuations inherent in individual multi-pole magnet signals.
Solution Approach 2:
The patent employs signal processing that incorporates feedback mechanisms where the detected signals from multiple elements are continuously processed and refined. The system uses the combined information from multiple detecting elements to correct and stabilize the final position detection output, compensating for runout and nonuniformity effects.
2Measurement precision
If a two-pole magnetic encoder and a 64-pole magnetic encoder are combined to obtain 12-bit absolute value output, then the resolution is improved to 4096, but the precision is reduced due to magnetic flux interference between adjacent magnets
Solution Approach 1:
The patent extracts and processes signals from multiple magnetic detecting elements separately before combining them. By taking the output from each element (including the two-pole and multi-pole systems) and processing them independently through signal processing circuits, the system can combine the useful information while filtering out the harmful magnetic flux interference between adjacent magnets.
Solution Approach 2:
The patent introduces signal processing circuits as intermediaries between the magnetic detecting elements and the final position output. These circuits act as mediators that process the raw signals from multiple elements, combining them in a way that achieves high resolution (4096 positions) while eliminating the adverse effects of magnetic flux interference between adjacent two-pole and multi-pole magnets.
3Measurement precision
If the precision of the two-pole magnetic encoder is increased to match the 64-pole encoder precision, then the overall output precision is improved, but the device complexity and adjustment time increase
Solution Approach 1:
The patent changes the approach from adjusting mechanical precision parameters to using signal processing parameters. Instead of increasing the physical precision of the two-pole encoder to match the 64-pole encoder, the system uses signal processing circuits to combine outputs from elements with different precisions, achieving high overall precision without the complexity of precise mechanical alignment and adjustment.
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 configuration enhances the precision of rotational position detection using a multi-pole magnet, reducing errors caused by magnetic flux density fluctuations and allowing for accurate absolute rotational position measurement.
Implementation Method 1
first and second magnetic detecting elements adjacently arranged so as to output a sinusoidal signal having a mutual phase difference of 90° in accompaniment with the rotation of the multi-pole magnet
Implementation Method 2
a signal processing circuit for generating a signal representing the rotational position on the basis of a sum signal or a differential signal of the output signal of the first magnetic detecting element and the output signal of the third magnetic detecting element, and on the basis of a sum signal or a differential signal of the output signal of the second magnetic detecting element and the output signal of the fourth magnetic detecting element
Data Source
AI summary
A magnetic encoder includes a multi-pole magnetic detecting unit having a multi-pole magnet. In the multi-pole magnetic detecting unit, first and second magnetic detecting elements that output sinusoidal signals having a 90° phase difference are arranged apart from third and fourth magnetic detecting elements at a mechanical angle of 180° . The first and third magnetic detecting elements are disposed at the same position represented by an electrical angle and output sinusoidal signals of a same phase. The second and fourth magnetic detecting elements are arranged at the same position represented by an electrical angle and output sinusoidal signals of a same phase. A sum signal of the output signals of the first and third magnetic detecting elements and that of the output signals of the second and fourth magnetic detecting elements are obtained, thereby eliminating or remarkably reducing error components of detection signals of the first to fourth magnetic detecting elements caused by the magnetic flux of a two-pole magnet and those of the detection signals caused by rotational run out of the multi-pole magnet. A rotational angle can be detected with high accuracy.