Angle Measuring Device Eccentricity Correction
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Solution Overview
Problem
High-precision angle measurement devices face accuracy issues due to manufacturing tolerances leading to eccentricity and wobble errors, especially when aligning the center of the coded disc with the shaft axis, which affects the distance and position of the measuring scale relative to the scanning unit.
Innovation Solution
An absolute angle measuring device with a code disk featuring both absolutely coded and incremental graduation tracks, utilizing at least two scanning units offset over the circumference to generate absolute and incremental position signals, and a control unit that processes these signals to form corrected absolute position values for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the center of the coded disc is aligned with the axis of rotation of the shaft to be measured, then measurement accuracy is improved, but manufacturing precision and assembly complexity increase due to the requirement for precise alignment
Solution Approach 1:
The patent converts the harmful effect of eccentricity (misalignment between coded disc center and shaft axis) into a beneficial correction process. By deliberately allowing eccentricity to exist and then measuring and correcting for it through the control unit, the system achieves high measurement accuracy without requiring extremely precise manufacturing and assembly. The eccentricity values are determined and used to correct the measured angular positions, transforming a source of error into a correctable parameter.
Solution Approach 2:
The patent replaces the mechanical approach of achieving precision through perfect physical alignment with a computational approach. Instead of relying on mechanical precision to align the coded disc center with the shaft axis, the system uses electronic determination of eccentricity values and computational correction of measurement data. This substitution of mechanical precision requirements with electronic measurement and calculation reduces manufacturing and assembly complexity.
2Measurement precision
If multiple scanning units are used to correct eccentricity and wobble errors, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the measurement function across multiple scanning units positioned at different locations around the coded disc. Each scanning unit independently measures the angular position and generates eccentricity values. This segmentation allows the system to capture eccentricity and wobble errors from multiple perspectives, enabling more accurate correction calculations while distributing the measurement workload across multiple simpler components rather than requiring a single complex scanning unit.
Solution Approach 2:
The control unit serves as an intermediary that receives measurement data from multiple scanning units, determines eccentricity values, and performs correction calculations. This intermediary component coordinates the data from multiple scanning units and transforms the raw measurements into corrected angular positions, managing the complexity of processing data from multiple sources through a centralized computational approach.
3Measurement precision
If incremental graduations with high line density are used to increase angular resolution, then measurement precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent implements feedback through the determination and correction of eccentricity values. The scanning units continuously measure angular positions and generate eccentricity data, which is fed back to the control unit for correction calculations. This feedback mechanism allows the system to compensate for manufacturing imperfections in the coded disc graduations, maintaining high measurement precision without requiring extremely precise graduation application. The feedback loop continuously adjusts for deviations caused by eccentricity and wobble.
Data Source
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AI summary
The present invention relates to a device for angle measurement in the form of an angle measuring device (10), comprising: • a code disk (20) having a code track (25) with an absolutely coded division track (26) and an incremental division track (27); • at least two scanning units (30, 31) arranged offset over the circumference of the code disk (20) for determining absolute position values (PA_1, PA_2) and for generating incremental position signals (P0_1, P90_1, P0_2, P90_2); • a control unit (40) to which the absolute position values (PA_1, PA_2) and the incremental position signals (P0_1, P90_1, P0_2, P90_2) can be supplied for forming a corrected absolute position value (PK) and which has a device interface (42) for communication with a subsequent electronics unit (100).The control unit (40) comprises a processing unit (41) with a counter unit (60, 61) for each scanning unit (30, 31), each of which can be initialized with the absolute position values (PA_1, PA_2) and with which state changes of the incremental position signals (P0_1, P90_1, P0_2, P90_2) can be counted. The counter values of the counter units (60, 61) are supplied as absolute position values (PZ_1, PZ_2) to a correction unit (65), which processes them to the corrected position value (PK). (Figure 1).