Yarn Feeder Drum Stock Control via Feedback Estimation
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Solution Overview
Problem
Conventional stock-controlling methods for storage yarn feeders with rotary drums face inaccuracies due to binary sensor information and are vulnerable to detection errors and power interruptions, leading to uncontrolled yarn stock fluctuations and quality issues in textile production.
Innovation Solution
A method that estimates yarn stock based on both unwound and wound loops, using a PID controller for feedback control, and incorporates a correction routine to align estimated stock with absolute binary sensor data, eliminating the need for an initial loading procedure and addressing drift phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If binary sensor information is used to control drum rotation, then the control system is simple, but the yarn tension control is only approximate and stock oscillates with high amplitude
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors the estimated yarn stock amount and adjusts the drum rotation speed accordingly. The feedback loop compares the estimated stock with reference values and modifies the motor command to maintain optimal stock levels, thereby stabilizing yarn tension and eliminating high-amplitude oscillations.
Solution Approach 2:
The patent replaces simple binary optical sensors with a sophisticated estimation system that calculates yarn stock based on motor rotation counts and unwound/wound loop information. This substitution transforms the control approach from direct binary detection to indirect calculation, enabling continuous stock estimation and precise tension control.
2Measurement precision
If stock control is based on relative information from optical sensors, then the amount of yarn can be controlled accurately, but the system is vulnerable to detection errors and drift phenomenon
Solution Approach 1:
The control unit continuously monitors the estimated yarn stock and compares it with reference values, adjusting the drum rotation in real-time. This closed-loop feedback mechanism detects and compensates for drift phenomena by constantly correcting deviations from the optimal stock level, preventing uncontrolled stock changes even when sensor errors occur.
Solution Approach 2:
The patent establishes reference values for yarn stock amount before the feeding process begins. These pre-established references serve as a baseline for continuous comparison and correction, enabling the system to anticipate and prevent drift accumulation by regularly comparing current stock estimates against known good values.
3Duration of action of moving object
If the drum rotates by inertia after power interruption, then the drum continues to wind loops, but the control system does not detect this causing uncontrolled stock increase
Solution Approach 1:
The control unit continuously monitors motor rotation and yarn stock estimates, comparing them against expected values. During power interruptions, the feedback mechanism detects discrepancies between actual and expected stock changes, allowing the system to identify and compensate for unwound loops that occurred during inertia rotation, thereby maintaining stock control reliability.
Data Source
AI summary
A yarn feeder is provided with a drum which is driven to rotate by a motor controlled by a control unit for drawing yarn from a reel and winding it upon itself in the shape of loops forming a stock. The control unit estimates the stock on the drum on the basis of an information indicative of the amount of yarn which is unwound from the drum upon request from a downstream machine, and of an information indicative of the amount of yarn which is wound on the drum, and retroactively controls the motor to substantially stabilize the stock on a reference value. The control unit also performs a parallel correction routine in which compares the stock with the reference value to estimate a stock status RES<REF_RES or RES≧REF_RES, wherein RES is the estimated stock and REF_RES is the reference value.