Co-prime Grating Angle Sensor for High Pole Count Motors
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Solution Overview
Problem
Existing angle sensors in bearing environments, particularly those using magnetic encoders, face challenges in accurately determining absolute and electrical angle signals due to limitations in the difference between the number of magnetic poles, leading to errors especially in greasy conditions and when dealing with electrical motors with high magnetic pole pairs.
Innovation Solution
The use of co-prime numbered grating elements in a dual grating ring configuration allows for a simple linear relationship to calculate absolute and electrical angle signals, enabling accurate determination without the need for additional magnetic encoders, even in greasy environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnetic encoders with a difference of 1 magnetic pole are used, then the calculation of absolute angle signal is simple, but the accuracy deteriorates when dealing with electrical motors with high magnetic pole pairs
Solution Approach 1:
The patent changes the fundamental parameter from the difference between magnetic pole numbers to the greatest common divisor (GCD) of the magnetic pole numbers. By using co-prime numbers (GCD = 1), the system achieves both simple linear calculation and high measurement precision, even for motors with high magnetic pole pairs. The angle calculation uses the formula: angle = (N1 * signal1 - N2 * signal2) / (N1 - N2), where N1 and N2 are co-prime magnetic pole numbers.
Solution Approach 2:
The angle sensor with co-prime magnetic pole configurations serves multiple functions: it accurately measures absolute angle positions and simultaneously provides accurate electrical angle signals for motor control. This multi-functionality eliminates the need for separate sensors for different measurement purposes, maintaining simplicity while achieving high precision across multiple applications.
2Measurement precision
If additional magnetic encoders are added to improve accuracy for high magnetic pole pairs, then the angle signal determination accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent makes a single angle sensor with co-prime magnetic pole configurations perform multiple functions: measuring absolute angle positions and providing electrical angle signals for motor control. This eliminates the need for additional magnetic encoders that would otherwise be required for high-precision measurements in motors with high magnetic pole pairs, maintaining device simplicity while achieving high accuracy.
Solution Approach 2:
By changing the magnetic pole configuration to use co-prime numbers, the system achieves high measurement accuracy without adding more sensors. The mathematical relationship between co-prime numbers allows the same sensor to accurately track both absolute positions and electrical angles, even for motors with many magnetic pole pairs.
3Measurement precision
If optical encoders are used, then the measurement precision is high, but the reliability deteriorates in greasy bearing environments
Solution Approach 1:
The patent replaces optical detection mechanisms with magnetic field-based detection. Magnetic fields penetrate grease and contaminants that block optical signals, allowing the sensor to maintain high measurement precision in greasy bearing environments where optical encoders would fail. The magnetic poles and Hall sensors create a detection system immune to optical obstruction.
Solution Approach 2:
The magnetic field acts as an intermediary between the rotating component and the sensor, transmitting angular position information through the grease and bearing environment without being blocked by contaminants. This intermediary mechanism allows reliable detection despite the presence of grease, unlike direct optical paths.
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 enhances the accuracy of angle signal determination, reduces errors, and allows for the use of the same sensor to calculate both absolute and electrical angle signals with improved precision, especially in environments with high magnetic pole pairs, while maintaining robustness in greasy conditions.
Implementation Method 1
each first grating element interacting with a first sensor for generating a first signal representative of a relative position of the first sensor along the corresponding ring segment
Implementation Method 2
each second grating element interacting with a second sensor for generating a second signal representative of a relative position of the second sensor along the corresponding ring segment
Data Source
AI summary
An angle sensor is provided for determining an absolute angle signal of a first part rotated with respect to a second part. The angle sensor comprises a first grating ring for generating a first signal representative of a relative position of a first sensor along a corresponding ring segment of the first grating ring. The angle sensor further comprises a second grating ring for generating a second signal representative of a relative position of a second sensor along the corresponding ring segment of the second grating ring. The first plurality and the second plurality are co-prime numbers and a difference between the first plurality and the second plurality being larger than 1. The angle sensor also comprises a calculator configured for calculating the absolute angle signal using a first linear combination of the first signal and the second signal.