Rotary Encoder Eccentricity Detection via Sensor Differential
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Solution Overview
Problem
Existing rotary encoders face challenges in accurately determining the rotation angle when the eccentricity of the scale from the rotational axis exceeds allowable ranges, leading to deviations in the determined rotation angle, and require additional detectors for eccentricity checking, which increases cost and complexity.
Innovation Solution
A method using a pair of sensor units arranged symmetrically with respect to the rotational axis to determine eccentricity information by acquiring output signals at multiple rotation angles, calculating differential values between phase information from each sensor unit, and determining eccentricity based on these values, allowing for accurate eccentricity checking without additional detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pair of sensor units are used to determine rotation angle with eccentricity error removed, then measurement precision is improved, but the system cannot accurately determine rotation angle when eccentricity exceeds allowable range
Solution Approach 1:
The patent introduces an intermediary calculation process that uses both sensor units to compute differential values representing eccentricity components. By processing the relationship between the two sensor outputs through differential calculation, the system can accurately determine both the rotation angle and eccentricity state even when eccentricity exceeds traditional allowable ranges, thereby improving reliability without sacrificing measurement precision.
2Reliability
If an additional detector for eccentricity detection is provided, then reliability of eccentricity checking is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing pair of sensor units serve multiple functions: they simultaneously perform rotation angle detection and eccentricity state checking. By processing the differential values from these sensors, the system can determine both the rotation angle (with eccentricity error removed) and the eccentricity quantity, eliminating the need for additional dedicated eccentricity detectors and thereby reducing device complexity while maintaining reliability.
Solution Approach 2:
The system uses its own sensor units to self-diagnose the eccentricity state. The differential values obtained from the two sensor units provide information about the eccentricity components, allowing the system to self-check and determine whether the eccentricity is within allowable ranges without requiring external or additional detection devices, thus simplifying the overall system configuration.
3Ease of operation
If previously stored eccentricity factor is used for correction, then ease of operation is improved, but measurement precision deteriorates when eccentricity varies with service period
Solution Approach 1:
The patent transitions from using fixed, previously stored eccentricity factors to a dynamic calculation approach. The system continuously calculates differential values from the two sensor units to determine current eccentricity components, allowing the eccentricity information to dynamically adapt to changes in the actual eccentricity state due to service period or usage conditions, thereby maintaining measurement precision while keeping the operation simple through automated calculation.
Data Source
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Figure 3A~3B
AI summary
The present invention provides: a rotary encoder checking an eccentricity state of a scale by sensor units; and related matters. The scale moves, relatively to the sensor units, around a rotational axis line. The pair of sensor units are arranged opposite to each other sandwiching the rotational axis line C0 therebetween. A processing system acquires output signals from each of the sensor units, at a plurality of rotation angles at which the scale has moved relatively to the sensor units. The processing system determines first phase information based on the output signal obtained from the sensor unit, and second phase information based on the output signal obtained from the sensor unit. The processing system determines eccentricity information based on a differential value between any one of the first phase information and the second phase information and an average value of the first phase information and the second phase information.