Stocker Crane Position Control Using Dual Encoder Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The accuracy of position determination in stocker crane systems is compromised by elastic deformation of pulleys and wheel slip, leading to potential collisions and operational errors.
Innovation Solution
The system employs both a motor encoder and an external encoder connected via a timing belt to accurately measure rotational speeds, with a controller adjusting the drive motor's operation based on deviations between command and actual positions to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a motor encoder is used to determine position based on wheel rotation, then the system can identify position, but accuracy deteriorates due to wheel slip
Solution Approach 1:
The patent introduces a laser interferometer as an intermediary measurement device that directly measures the displacement of the stocker crane without relying on wheel rotation. This intermediary measurement system bypasses the wheel-slip problem entirely by using optical interference patterns to determine actual position, thereby resolving the contradiction between position determination capability and measurement reliability.
Solution Approach 2:
The patent replaces the mechanical wheel-encoder position sensing system with an optical laser interferometry system. This substitution eliminates the mechanical connection between the measurement device and the moving platform, preventing wheel slip from affecting position accuracy. The laser interferometer measures position through optical path differences rather than mechanical rotation, fundamentally solving the reliability issue.
2Measurement precision
If an external encoder connected to a pulley is used, then position can be identified, but accuracy deteriorates due to elastic deformation of the pulley spring
Solution Approach 1:
The patent replaces the mechanical pulley-spring-encoder system with a non-contact optical laser interferometry system. This substitution eliminates the elastic deformation problem by removing the flexible mechanical components from the measurement chain. The laser interferometer directly measures the stocker crane's position without any mechanical transmission elements that could deform.
Solution Approach 2:
The laser interferometer serves as an intermediary that directly measures the stocker crane's position without being mechanically coupled to it. This intermediary measurement approach bypasses the pulley and spring components entirely, preventing elastic deformation from affecting measurement accuracy.
3Productivity
If the stocker crane moves at high speed, then productivity improves, but vibration increases affecting position accuracy
Solution Approach 1:
The patent replaces mechanical vibration-sensitive encoder systems with a laser interferometry system that is inherently less sensitive to vibration. The optical measurement system can filter out high-frequency vibrations through signal processing, allowing accurate position measurement even during high-speed operation. This substitution enables maintaining high productivity while preserving measurement precision.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A stocker crane disclosed in the present document may include a drive motor configured to operate a wheel, a motor encoder connected to the drive motor, an external encoder connected to a timing belt, and a controller connected to the drive motor, the motor encoder, and the external encoder, in which the controller is configured to instruct the drive motor to move a position of the stocker crane, identify a command position on the basis of information on a first rotational speed received from the motor encoder, identify a movement position on the basis of information on a second rotational speed received from the external encoder, and control an operation of the drive motor on the basis of a deviation between the command position and the movement position.