Motorized Positive Yarn Feeder Self-Calibration for Tension Control
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Solution Overview
Problem
Existing methods for controlling yarn tension in motorized positive feeders are complex, requiring manual parameter entry and are not feasible for older knitting machines, leading to suboptimal performance due to factors like yarn type, speed variations, and distance from the feeder.
Innovation Solution
A self-calibrating method using a PID regulator with an iteratively updated integrative constant, combined with a black-box optimization algorithm and a Kalman filter, to automatically adjust yarn tension based on variance minimization, ensuring precise and reliable control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual parameter entry or electronic connection is used to optimize control loop performance, then yarn tension control precision is improved, but device complexity and setup difficulty increase
Solution Approach 1:
The control unit automatically detects knitting machine speed variations and self-adjusts feeder parameters without requiring manual intervention or external electronic connections. The system serves itself by monitoring its own operational context and adapting control parameters autonomously, eliminating the need for complex setup procedures while maintaining high tension control precision.
Solution Approach 2:
The control unit continuously monitors yarn tension through sensors and uses this feedback to automatically adjust feeder operations. By closing the control loop with real-time tension monitoring and automatic parameter adjustment, the system achieves high precision without requiring manual parameter entry or complex external connections.
2Stability of the object's composition
If speed information transmission from knitting machine to feeder is implemented, then yarn tension stability is improved, but adaptability to older knitting machines is reduced
Solution Approach 1:
The control unit acts as an intermediary that detects speed variations indirectly through yarn tension measurements rather than requiring direct speed information transmission from the knitting machine. By using tension as a mediator to infer speed variations, the system achieves tension stability while maintaining compatibility with older knitting machines that lack external speed signal capabilities.
Solution Approach 2:
The system replaces the need for mechanical or electronic speed signal transmission with a sensor-based tension measurement approach. By substituting direct speed information with indirect tension-based speed detection, the system achieves the same control objective while being compatible with older knitting machines.
3Ease of operation
If fixed control parameters are used, then ease of operation is improved, but manufacturing precision deteriorates due to varying yarn types and distances
Solution Approach 1:
The control parameters are made dynamic rather than fixed, automatically adapting to different yarn types, distances, and operating conditions. The control unit continuously adjusts parameters based on real-time feedback from tension sensors and detection of speed variations, maintaining high precision across varying conditions while requiring no manual setup intervention.
Solution Approach 2:
The system automatically changes control parameters based on detected operating conditions such as yarn stiffness, distance from feeder to knitting machine, and speed variations. By dynamically modifying parameters like proportional and integral gains in the PID controller, the system maintains high precision without requiring manual parameter entry or fixed settings.
Data Source
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AI summary
A yarn (Y) is wound on the motorized reel (12) of a feeder which draws the yarn (Y) from a spool (S) and feeds it to a knitting machine (KM). A control unit (CU) adjusts the rotation rate of the reel (12) by closed loop on the basis of the signal received from a tension sensor (14), in order to stabilize the tension of the yarn (Y) on a desired value (Tdes). The tension (T) measured by the tension sensor (14) is compared with the desired value (Tdes) in order to obtain an error (Terr) which, by means of a proportional-integral-derivative regulator (PID), generates a reference angular speed (ωRref) to be sent to a reel speed control loop (RSL). The proportional-integral-derivative regulator (PID) has an integrative constant KI which is updated iteratively by means of a self-calibration procedure (18) adapted to minimize a performance index of the signal generated by the tension sensor (14).