Rotational Angle Measurement with Pin-Angle Error Correction
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Solution Overview
Problem
Existing rotational angle measurement apparatuses face challenges in correcting pin-angle errors with high accuracy due to the complexity of calculation operations and the need for precise angle settings, which often require expensive microcontrollers and encoders.
Innovation Solution
A rotational angle measurement apparatus with a signal processing unit that calculates the ratio of output signals from COS and SIN bridges, applies a correction parameter to correct pin-angle errors, and uses averaging and window function processing to reduce calculation complexity, allowing for accurate angle determination without the need for an encoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correction methods are used to correct pin-angle errors, then measurement precision is improved, but device complexity increases due to expensive microcontrollers and encoders
Solution Approach 1:
The patent extracts the essential correction functionality from complex microcontroller-based systems and implements it through simple signal processing operations. By taking out only the necessary calculation elements (ratio calculation, parameter subtraction, and arctangent processing) and eliminating unnecessary components like encoders and expensive microcontrollers, the invention achieves pin-angle error correction with reduced device complexity.
Solution Approach 2:
The patent replaces expensive, complex components (microcontrollers and encoders) with simple, inexpensive signal processing operations. The correction is achieved through basic mathematical operations on bridge output signals rather than requiring costly hardware, effectively substituting cheap computational methods for expensive physical components.
2Measurement precision
If precise angle settings are required to reduce pin-angle errors, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary correction by calculating a correction parameter from the bridge output signals and applying it through simple subtraction before arctangent processing. This preliminary correction action compensates for pin-angle setting errors, allowing the system to achieve high measurement precision even when manufacturing precision of the pin-angle settings is limited.
Solution Approach 2:
The patent changes the parameter representation by working with the ratio of bridge outputs and applying a correction parameter through subtraction rather than requiring precise physical angle settings. This parameter transformation approach allows correction of manufacturing errors through software-based parameter adjustment rather than requiring high-precision physical alignment.
3Measurement precision
If complex calculation operations are used for error correction, then measurement precision is improved, but productivity decreases due to increased calculation time
Solution Approach 1:
The patent applies partial correction by using a single correction parameter derived from the bridge output ratio, rather than performing exhaustive multi-parameter optimization. This partial correction approach achieves sufficient measurement precision with minimal calculation operations, avoiding excessive computation while maintaining adequate correction accuracy for practical applications.
Solution Approach 2:
The patent substitutes complex mechanical correction systems with simple mathematical operations. By replacing what would traditionally require complex mechanical alignment and multiple correction steps with straightforward ratio calculation, parameter subtraction, and arctangent processing, the system achieves both high precision and fast calculation speed.
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 apparatus effectively corrects pin-angle errors with a reduced amount of calculation operations, enabling accurate rotational angle measurement even with errors in pin-angle settings, and facilitates manufacturing by increasing tolerance for pin-angle settings.
Implementation Method 1
The GMR element has a first magnetic layer 13 (pinned magnetic layer) and a second magnetic layer 11 (free magnetic layer) in which a non-magnetic layer 12 (spacer layer) is sandwiched between both of the magnetic layers. When an external magnetic field is applied to the GMR element, while the magnetization direction of the pinned magnetic layer does not change and remains fixed as it is, the magnetization direction 20 of the free magnetic layer changes in accordance with the direction of the external magnetic field.
Data Source
Figure 1~2B
Figure 3A~4
Figure 5
AI summary
This invention relates to a rotational angle measurement apparatus that is capable of correcting an error due to pin-angle error with a small amount of calculation operation. The rotational angle measurement apparatus includes a magnetic sensor 301 and a signal processing unit 303M. The magnetic sensor includes two bridges comprising magneto-resistance elements each having a pinned magnetic layer. A ratio-calculation unit 381 of the signal processing unit 303M calculates a ratio Vy/Vx of output signals Vx and Vy. A parameter correction unit 382 subtracts a predetermined correction parameter β from the ratio Vy/Vx calculated by the ratio-calculation unit. An atan-processing unit 383 conducts arctangent processing on the value calculated by the parameter correction unit and calculates an angle of magnetic field θ.