Angular Position Sensor Error Correction via Diametrical Photodetector Averaging
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Solution Overview
Problem
Existing angular position sensors, such as optical and magnetic encoders, face challenges in effectively correcting both low and high frequency errors, with existing solutions often favoring correction of one type of error over the other, leading to ineffective or even amplified errors when installed by end users due to differing mounting conditions.
Innovation Solution
A method involving multiple photodetectors placed diametrically opposed on the sensor, where two known angular positions are measured, and their respective theoretical values are used to calculate corrected angles, averaging these to minimize both low and high frequency errors without affecting high frequency errors, allowing for independent correction of each type of error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard error correction curve is applied at the manufacturer's premises, then low-frequency errors are corrected, but the correction becomes ineffective or amplifies errors when the encoder is installed at the user's premises due to different mounting conditions
Solution Approach 1:
The patent implements dynamic error correction by performing measurements at multiple known angular positions (including 0° and 180°) and adapting the correction values based on the actual measured deviations. This allows the correction to automatically adjust to the specific mounting conditions at the user's premises, transforming the static factory calibration into a dynamic, site-specific correction process that maintains accuracy across different installation environments.
2Measurement precision
If photo-detectors are placed diametrically opposed to measure angular positions, then both low and high frequency errors can be corrected, but the device complexity increases
Solution Approach 1:
The patent makes the existing photo-detectors serve multiple functions: they not only detect angular position but also enable error correction by measuring at specific known angles (0° and 180°). This multi-functionality allows the same hardware components to perform both measurement and calibration/correction operations, avoiding the need for separate dedicated correction devices and thereby limiting the increase in overall system complexity.
3Measurement precision
If existing error correction methods are used, then low-frequency errors are corrected, but high-frequency errors remain or are amplified
Solution Approach 1:
The patent segments the error correction process into distinct components: measuring low-frequency errors at 0° and 180° positions, measuring high-frequency errors at other known angular positions, and then combining these corrections. This segmentation allows independent correction of different error types without interference, ensuring that both low-frequency and high-frequency errors are addressed effectively without amplifying either type.
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 allows for optimal correction of both low and high frequency errors without structural modifications to the sensor, ensuring effective error reduction regardless of mounting conditions, thus improving sensor performance and usability across various applications.
Implementation Method 1
In an optical encoder, a disk with opaque and transparent areas is rotated by the encoder's rotation shaft. An optical beam emitted by infrared diodes passes through the transparent areas of the rotating disk and strikes photo-detectors, creating an analog signal
Implementation Method 2
In the case of a magnetic encoder, a permanent magnet, at least bipolar, is attached to a rotation shaft and generates a magnetic field. This magnetic field varies according to the displacement of the magnet, therefore according to its rotation
Implementation Method 3
An optical beam emitted by infrared diodes passes through the transparent areas of the rotating disk and strikes photo-detectors, creating an analog signal that is amplified and transformed into a digital signal
Data Source
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AI summary
[The invention relates to a method for correcting low and high frequency errors generated by an angular position sensor, characterized in that it comprises at least the following steps: a) measuring a first known angular position (θ1), said measurement being provided by an angular position sensor (C) of an object using a set of at least two photodetectors (P, P1) the number of which is a multiple of two; b) performing a measurement of at least a second known angular position (θ2), said measurement being provided by the same sensor (C) as in step a) using the same set of photodetectors (P, P1) placed in the same location as in step a) and the number of which is the same multiple of two as in step a); c) obtaining, for each of the measurements of the first (θ1) and second (θ2) angular positions obtained in steps a) and b), a first (θ'1) and second (θ'2) angular position corrected by a correction (E1,E2) measurements of each angular position (θ1, θ2) by comparison with the values of the first and second known angular positions respectively and - d) calculate the average (θ3) of the first and second angular positions obtained (θ'1, θ'2) after correction in step c).