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Weft feeler is one of important accessories in air-jet loom. Weft feeler is used to probe whether the weft arrived at the appoint location in the set time. In this paper, the working principle of optical weft feeler testing system is analyzed, study the un-even characteristic of the light intensity caused by the LED in the weft feeler, combined with the wave dynamic characteristics of weft drag by airflow, a new weft detection method was proposed, the features of the method is only probe the wave weft , through real-time recognition of this dynamic yarn to achieve the purpose of detect weft, thus reducing false judgment caused by various types of static interferences.Paper describes the following aspects:1. Describes the development of the current domestic and foreign weft detection technology, introduces several weft feeler control devices in the air-jet loom, principles and testing methods of feeler were analyzed and compared, identify their own priorities and shortcomings, on this basis, a new detection method was proposed, and discusses the methods, proposed theoretical and technical means to detect weft .2. Combined with the practical application of weft detection characteristics, discuss theoretical knowledge of electro-optical which relate to detection technology of weft. This includes the characteristics of LED and photoelectric light-emitting, and gives the design method of the optical signal processing circuit.3. According to the weft detection method proposed by the paper, designed signal processing circuit and feeler, LED was driven with the pulsed signal, photoelectric silicon PIN photodiode is used. Preamplifier input circuit, automatic gain control circuit, peak detector circuit and comparing the output circuit was included in the signal processing circuit, circuit schematics are given and discussed. Application circuit design software design weft signal processing circuit schematics, PCB layout was designed and welding the components in the system board. 4. Discusses the structures of the experimental platform and study the processing and analyzing experimental results, weft feeler was fixed on the air-jet loom , weft feeler and signal processing board were connected, then the signal processing board will connect with the control system .In the process of debugging, with a data acquisition platform to acquire the experiment data ,the experimental data was collection and analysis , the analysis and appraisal of experimental data presented in this paper prove feasibility and superiority of the weft feeler.5. Analysis and demonstration the feasibility of digital weft feeler, given some solutions of the technical difficulties. The hardware design and software of system were described, digital filter and peak detection algorithms were designed by using MATLAB software, and use MATLAB to simulate theoretical process.
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