Multi-Detector Encoder Layout for Wide-Range Mover Position Sensing
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Solution Overview
Problem
Existing transport apparatuses using incremental encoders face challenges in detecting the position and attitude of a mover over a wide range with high accuracy due to issues with sensor detection range and resolution, particularly when switching detectors.
Innovation Solution
A transport apparatus is designed with a stator and a mover equipped with a first scale and multiple detectors arranged at intervals, utilizing an incremental encoder system where a control unit corrects position information based on detection values from multiple detectors to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single detector is used to detect the mover position, then the sensor size remains small, but the detection range is limited and resolution decreases when detection range is increased
Solution Approach 1:
The patent divides the detection system into multiple detectors (first detector and second detector) arranged at different positions along the first direction. Each detector has a limited detection range, but together they cover a wide overall detection range. The control unit selects which detector to use based on the mover's current position, ensuring high resolution detection throughout the entire range without requiring a single large sensor.
2Area of stationary object
If the detection range of the mover is increased using eddy current sensor or laser displacement meter, then the detection range expands, but the sensor size increases and resolution decreases
Solution Approach 1:
Instead of using a single detector with large detection range that sacrifices resolution, the patent segments the detection function across multiple detectors with smaller individual ranges. The first detector detects position in a first range, and the second detector detects position in a second range, collectively providing wide coverage while maintaining high resolution at each detection point.
3Measurement precision
If an incremental encoder is used to detect position and attitude, then detection capability improves, but when the detector is switched the initial value becomes indefinite and detection accuracy may be lowered
Solution Approach 1:
The control unit continuously monitors the mover's position and determines which detector should be active based on current position feedback. When switching between detectors, the system uses feedback from the scale and detector arrangement to calculate and maintain continuous position values, preventing loss of initial value and ensuring detection accuracy is maintained across detector transitions.
Data Source
AI summary
A transport apparatus includes: a stator; a mover that includes a first scale and is movable along the stator in a first direction; a plurality of first detectors each of which is provided to be able to face the first scale and detects a position of the mover in a second direction crossing the first direction; and a control unit that controls position and/or attitude of the mover, the first scale and the first detector constitute an incremental encoder, wherein the plurality of first detectors are arranged at a predetermined interval along the first direction in the stator, and the control unit corrects position information of the mover by a detection value of one of the first detectors based on position information of the mover by a detection value of another of the first detectors.