Asymmetric Encoder Wheel Assembly for Absolute Angular Position
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Solution Overview
Problem
Existing encoder technologies for determining absolute angular position and rotational direction in electric machines are cumbersome, require complex assembly, and have limitations in mechanical tolerances, cost, and real-time signal processing capabilities, especially in high-speed applications.
Innovation Solution
An encoder arrangement comprising two non-rotatably connected encoder wheels with asymmetrically offset teeth, where one wheel has teeth equally spaced and the other has teeth offset by a consistent angular magnitude, allowing binary signal derivation for determining absolute angular position and rotational direction using sensors and a controller for digital output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic resolvers are used to determine absolute angular position and rotational direction, then measurement capability is provided, but installation space requirement increases and assembly complexity increases
Solution Approach 1:
The encoder wheel is divided into multiple segments with different tooth patterns (first encoder wheel with evenly spaced teeth, second encoder wheel with asymmetrically offset teeth). Each segment provides specific measurement information, and the combination enables absolute position determination with simplified assembly compared to traditional resolvers.
Solution Approach 2:
The patent replaces the complex electromagnetic resolver system with a mechanical encoder wheel system that uses tooth patterns and optical/magnetic sensors. This substitution eliminates the need for complex electromagnetic fields and winding phases, significantly reducing assembly complexity while maintaining measurement capability.
2Measurement precision
If optical resolvers are used to determine absolute angular position, then measurement capability is provided, but cost increases and sensitivity to soiling increases
Solution Approach 1:
The patent uses cost-effective encoder wheels with asymmetric tooth patterns that can be manufactured inexpensively. The system is designed to be robust against environmental factors like soiling, and the encoder wheels can be replaced as a simple unit if needed, reducing overall system cost while maintaining measurement capability.
3Measurement precision
If inductive absolute angle sensors based on eddy current effect are used, then absolute angular position measurement is provided, but cross-sensitivity to mechanical installation tolerances increases
Solution Approach 1:
The second encoder wheel features asymmetrically offset teeth relative to the first encoder wheel. This asymmetric pattern creates a unique measurement signature that is less sensitive to mechanical installation tolerances and tilting, as the asymmetric pattern provides reference information that compensates for misalignment errors.
Solution Approach 2:
The patent uses two different tooth patterns on two concentric encoder wheels, adding a dimensional aspect to the measurement. This dual-pattern approach provides redundant measurement information that reduces sensitivity to mechanical tolerances in the radial and axial directions.
4Measurement precision
If phase encoders with three Hall elements are used to measure absolute angular position, then measurement capability is provided, but sensor cost increases and assembly complexity increases
Solution Approach 1:
The patent extracts the essential measurement function from complex multi-sensor arrangements and implements it using a simpler dual-encoder-wheel system with asymmetric tooth patterns. This extraction reduces the number of required sensors and simplifies the assembly process while maintaining absolute position measurement capability.
Data Source
AI summary
An encoder wheel assembly comprising: a first encoder wheel rotationally fixed to a rotor and having a number n of teeth arranged along the circumference of the encoder wheel; a second encoder wheel rotationally fixed to the first encoder wheel, and having the same number n of teeth as the first encoder wheel along the circumference of the encoder wheel, wherein the teeth of the second encoder wheel have an asymmetrical angular offset relative to the teeth of the first encoder wheel; a first sensor designed to scan the first encoder wheel; a second sensor designed to scan the second encoder wheel; and a controller connected to the first sensor and the second sensor and designed to ascertain the absolute angular position and the rotational direction based on a binary signal derived from a first signal of the first sensor and a second signal of the second sensor.