Rotary Encoder Self-Calibration Using Multi-Element Light Source
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Solution Overview
Problem
Rotary encoders for surveying apparatuses face challenges in achieving high precision due to errors caused by the deflection of the rotary disk during rotation, which are not adequately addressed in existing calibration methods.
Innovation Solution
The rotary encoder employs a light source with multiple light-emitting elements positioned to account for deflection errors, allowing for the calculation and self-calibration of reading values by comparing readings from different light-emitting elements, thereby reflecting and averaging errors to achieve accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light source is used for reading the angle code, then the device structure is simple, but deflection errors during rotation cannot be detected or corrected
Solution Approach 1:
The light source is segmented into multiple light-emitting elements (first light-emitting element, second light-emitting element, and third light-emitting element) positioned at different locations. Each element serves a specific function: the first element reads the angle code at the current position, while the second and third elements read codes at positions offset by +φ and -φ respectively. This segmentation enables detection of deflection errors through comparison of readings from different elements, thereby improving measurement precision without overwhelming complexity.
Solution Approach 2:
The patent introduces an intermediary calibration process that uses the multiple light-emitting elements to detect and correct deflection errors. The reading value error ΔφI due to deflection is calculated based on differences between readings from the first light-emitting element and the second light-emitting element. This intermediary error calculation serves as a mediator that bridges the gap between simple reading and accurate calibration, enabling high-precision self-calibration.
2Measurement precision
If conventional self-calibration is performed without considering deflection, then the calibration process is simple, but calibration accuracy is insufficient for high precision measurement
Solution Approach 1:
The patent implements a feedback mechanism where the reading value error ΔφI due to deflection is calculated based on the difference h(θ+φ) between readings from the first light-emitting element and the second light-emitting element. This error feedback is then used to correct the reading value fI(θ) through self-calibration. The feedback loop continuously refines the calibration by comparing readings from multiple light-emitting elements and adjusting for deflection errors, thereby achieving high calibration accuracy.
Solution Approach 2:
The patent performs preliminary error calculation before final calibration. The reading value error ΔφI due to deflection is calculated in advance using readings from the first and second light-emitting elements. This preliminary error assessment is then incorporated into the self-calibration process, allowing the system to pre-compensate for deflection effects before finalizing the calibration. This preliminary action ensures that the calibration process accounts for deflection errors from the outset, improving overall calibration accuracy.
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 enables highly accurate self-calibration of the rotary encoder, effectively addressing deflection-induced errors and enhancing measurement precision.
Implementation Method 1
a light source with multiple light-emitting elements positioned to account for deflection errors
Data Source
AI summary
A rotary encoder includes: a rotary disk with an angle code; a light source; a detector reading the angle code; and a processing unit acquiring a reading value. The light source includes at least two light-emitting elements spaced from each other. Every time the rotary disk is rotated by a predetermined angle, where an arbitrary angle from a rotation angle θ within a reading range on the detector is provided as φ, the processing unit acquires reading values fI(θ+φ) and fI(θ) with a first light-emitting element and a reading value fII(θ+φ) with a second light-emitting element, to calculate a reading value error due to deflection at an angle θ+φ based on the difference between the reading values fII(θ+φ) and fI(θ+φ), to obtain a difference gI(θ,φ) between the reading values fI(θ+φ) and fI(θ) such that the error is reflected, and to self-calibrate based on a change in the difference gI(θ,φ).