Dual Stator Absolute Encoder Abnormality Detection
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Solution Overview
Problem
Existing rotary type absolute encoder systems face challenges in precision and reliability due to backlash, limited rotational speed, and the difficulty in handling a wide range of rotor diameters with a single stator portion design, which leads to increased costs and installation space requirements.
Innovation Solution
The use of two stator portions positioned 180 degrees apart allows for reliable abnormality detection by comparing absolute positions, reducing the need for redundant code reading and accommodating various rotor diameters with a single stator design, while compensating for eccentricity-induced precision issues by averaging detected positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant bits are added to detect absolute position abnormalities, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the stator portion into multiple independent reading units (first reading unit and second reading unit), each capable of reading the same N-bit absolute code from the rotor. This segmentation allows parallel reading of the same code through different paths, enabling abnormality detection by comparing results from multiple independent readings without requiring redundant code bits on the rotor.
Solution Approach 2:
The patent combines multiple reading results through a synthesis unit that integrates the absolute positions detected by different reading units. By merging the outputs of parallel reading paths and comparing them, the system achieves abnormality detection functionality while maintaining the original N-bit code structure, avoiding the need for 2N-bit redundant codes.
2Reliability
If 2N bits absolute code is read for error detection, then reliability is improved, but sensor arrangement complexity increases
Solution Approach 1:
The stator portion is segmented into multiple independent reading units, each equipped with sensors that read the same N-bit absolute code from the rotor. Instead of arranging sensors to read 2N distinct code bits, the system uses multiple sensor sets reading the same N bits through different spatial paths, simplifying sensor arrangement while maintaining error detection capability.
3Reliability
If multiple stator portions are used for abnormality detection, then reliability is improved, but installation space increases
Solution Approach 1:
The patent merges multiple reading functions into a single stator portion by integrating first and second reading units within the same stator structure. This allows the system to achieve the reliability benefits of multiple readings without requiring multiple separate stator portions, thereby reducing installation space while maintaining detection reliability.
4Manufacturing precision
If reduction gears are used for precision control, then manufacturing precision is improved, but rotational speed is limited
Solution Approach 1:
The patent replaces mechanical reduction gears with a direct motor drive system equipped with a high-precision absolute encoder. The encoder uses an N-bit absolute code with continuous differentiation capability, allowing the system to achieve high position precision through electronic control and code interpretation rather than mechanical gear reduction, thereby enabling higher rotational speeds without sacrificing precision.
Data Source
AI summary
In order to cope with many rotor diameters using a single type of stator portion, two stator portions, each having a built-in signal processing circuit for detecting absolute positions independently, are disposed in opposition at positions which differ from each other with respect to a rotational center of a rotor portion. When one of the stator portions receives a request command RX from an external device, it transmits a detected serial communication signal. The other stator portion receives the transmitted serial communication signal, determines a position detection abnormality, and notifies the abnormality to the external device when a difference between the received absolute position and the absolute position detected by the other stator portion exceeds a deviation previously set for 180 degrees.