Research On Real-Time Weft Detection System For Electronic Weft Feeder

Along with shuttle less and high speed development trend of looms, yarn tension balancing problem becoming more prominent, electronic weft feeder has a rapid development, which serves as a key equipment for weft active supply and tension balancing. The accurate detection and real time control of weft circle event is a key issue of weft feeder performance, as well as an important precondition for the coordinating with fabrication process of weaving room. Leakage detection of the weft causes waste of weft, while miss detection causes defects in fabric surface, or even leads to a frequent suspend of the weaving process. That’s weft detection and circle counting system is not only the premise of weft feeder normal operation, but also the guarantee of a smooth weaving process. Therefore, the performance in enhancement research of weft detection system has important practical significance.Hence a design of the weft detection unit base on infrared photoelectric sensor and reflection type light path is carried out in this research. The characteristics of weft infrared photoelectric detection is experimental researched during weaving process, in which phenomenon of sensing signal drift, the adaptability of weaving conditions, and the noises is observed. Furthermore, the mechanism of the phenomenon is analyzed with both the experiment data and theoretical model, and the solutions are put forward as following.(1) A closed-loop current control strategy is designed for the infrared emitter driving, hence to achieve a stable DC intensity of the infrared sensing signal in long term, and the sensing signal drift caused by reflector pollution and emitter degradation can be reduced obviously.(2) An adaptive gain adjustment strategy is introduced for the amplifier conditioning circuit, hence to keep the consistency of signal amplitude in different weft specifications and fabric width. That’s high reliability of weft detection can be ensured.(3) A digital filter combining with sliding mean and sliding peak-to-peak algorithms is developed to solve the noise interferences introduced by AC Power source and the PWM motor driving signal, hence the signal to noise ratio of weft detection signal can be enhanced significantly.Finally, a prototype of real time weft detection is designed basing on a DSP platform (TMS320F28027), with the previous mentioned unit and algorithms. Considering the control logic of electronic weft feeder, the detection program is designed and long-term practice is performed on a brushless DC weft feeder. The achieved results in practice environment indicate that the proposed weft detection scheme for electronic weft feeder shows good performance.