Reflection Grating Angle Measurement With Eccentricity Compensation
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Solution Overview
Problem
Optical position-measuring devices face significant accuracy issues due to eccentricity and tumbling errors when measuring rotational angles, particularly in incident-light scanning, as existing solutions do not adequately address these errors.
Innovation Solution
An optical position-measuring device with a grating measuring standard that includes both radial and annular graduations, using a signal processing unit to correct rotational-angle-dependent errors by storing and applying correction values obtained during calibration, ensuring the neutral pivot points for scanning are in the same plane as the grating measuring standard, allowing for simultaneous compensation of eccentricity and tumbling errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the graduated disk is assembled separately at the customer site, then the device becomes easier to transport and assemble, but the measurement precision deteriorates due to eccentricity errors from imprecise mounting
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements during the assembly process itself. The system automatically measures the actual axis of rotation and calculates correction values before normal operation begins, eliminating the need for precise pre-alignment while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the parameter reference frame by introducing correction values that transform measurements from the actual axis of rotation to the ideal axis of rotation. This parameter transformation allows the system to compensate for mounting eccentricity and achieve accurate measurements despite imprecise assembly.
2Device complexity
If conventional scanning methods are used, then the device structure remains simple, but the measurement precision deteriorates due to uncorrected eccentricity and tumbling errors
Solution Approach 1:
The patent applies self-service by enabling the measurement system to automatically calibrate itself during assembly. The system performs self-diagnosis of mounting errors and self-correction through calculated compensation values, eliminating the need for external alignment tools or complex adjustment mechanisms.
Solution Approach 2:
The patent implements feedback by using the initial calibration measurements to generate correction values that are applied during normal operation. The system continuously uses the relationship between actual and ideal axis positions to compensate for errors, creating a closed-loop error correction mechanism.
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 solution effectively corrects both eccentricity and tumbling-related errors in rotational angle measurements, enhancing the accuracy and reliability of optical position-measuring devices, especially in incident-light scanning scenarios.
Implementation Method 1
a grating measuring standard (11), which rotates about an axis of rotation and is arranged as a reflection grating
Data Source
AI summary
In an optical position-measuring device for acquiring the rotational angle between two objects that are rotationally moveable relative to each other, a grating measuring standard rotating about an axis of rotation is arranged as a reflection grating. Position information both about an azimuthal rotary movement about the axis of rotation and about a radial displacement of the grating measuring standard is able to be obtained. At least one detection unit is used for scanning the rotating grating measuring standard in order to determine the azimuthal rotational angle as well as a radial displacement of the grating measuring standard. The neutral pivot points of the scanning of the grating measuring standard for the determination of the rotational angle and the displacement are situated in the same plane, with this plane being situated in parallel with the grating measuring standard. The neutral pivot point denotes the particular location about which the grating measuring standard or the detection unit is able to be tilted without a position offset.