Research On Non-contact Yarn Tension Detection Technology

In the production of knitted weft knitting,the tension of the yarn delivery is affected by the yarn feeding method and the weaving form,As tension increases,the shrinkage of the braided interface will increase correspondingly,and it is easy to break the yarn;on the contrary,tension The reduction will affect the fabric forming effect and reduce the production efficiency.Therefore,it is necessary to detect the yarn feeding tension in real time,and adjust the yarn feeding amount according to the tension fluctuation.The current yarn tension detection method can be divided into contact type and non-contact type according to whether the yarn directly touches the detector.The first type of yarn is in direct contact with the detector,and it is easy to wear the detection instrument after longterm use.At the same time,the contact type is easy to change the movement state of the yarn,thereby affecting the detection accuracy.The second type of yarn does not come into direct contact with the detector,which can avoid errors caused by direct contact with the detector and improve the accuracy of the experiment.In this paper,according to the characteristics of yarn conveying tension change during the knitting weft knitting production process,using the principle of photoelectric induction,design of new noncontact yarn tension detection system for dynamic detection.First of all,this article analyzes the yarn transport process and its tension variation characteristics in knitting weft knitting production,designs a binocular photoelectric yarn transport status detection method,uses a double-way positive and negative photoelectric induction circuit,extracts the dynamic differential signal of yarn passing through the photoelectric induction area,analyzing differential signal characteristics to realize the transformation of analog and pulse signals,and summarizes the pulse signals statistically to finally discover the law of yarn tension and the number of pulses,and then realizes the dynamic detection and real-time alarm of yarn status in the knitting process of knitting machinery production.Secondly,according to the detection scheme,the software and hardware of the noncontact yarn tension detection system are developed.Hardware design consists of photoelectric detector and centralized controller,The photodetector mainly realizes the collection of the yarn relative center fluctuation signal through the amplifying and filtering circuit,and a hysteresis comparison circuit is set to exchange the signal to a pulse signal that can be processed by the single-chip microcomputer;The central controller is responsible for the unified management of the photoelectric detectors and the transmission of the knitting machine feed control signals to the photoelectric detectors.Through the design of hardware and software and the development of communication protocols,the communication between the collector and the photodetector is completed.Finally,this article accomplishs the design and builds the experimental station,and obtains the signal characteristics of the photodetector under different yarn tensions through the method of experimental comparison and analysis,and a positive correlation between yarn tension and the number of pulses output from the photoelectric detector is obtained.During the field scene test,the centralized controller first controls the photoelectric detector to complete the sampling of the fabric.After the sampling phase is over,it starts to monitor the yarn tension of each path of the knitting equipment.When there is an abnormality in the monitoring stage,the central controller will alarm and send an alarm signal to the knitting equipment for shutdown operation.The detection system has been tested experimentally and in the field,and has shown good stability and accuracy,and the technology has broad engineering application prospects.