The Development Of Constant Tension Electronic Yarn Feeder

yarn feeder is one of the main components of knitting machines,and also the most important yarn inputting device,classified as positive feeding and negative feeding according to the function of yarn feeding.The passive yarn feeders cannot guarantee the tension magnitude of the yarn because they input yarn passively,and positive yarn carriers can only be used on machines,consuming yarn in a relatively equal quantity,though they can input yarn positively.For jacquard knitting machine and seamless knitting machine,as they have special requirement for yarn tension,the traditional yarn feeders cannot satisfy the requirement.Thus the development of constant tension electronic yarn feeder is proposed in this paper.This feeder can realize inputting yarn accurately and quickly based on actual yarn consumption through controlling the motor,guaranteeing the tension is fixed within a certain scale,thus improving the quality of the fabric.In this paper,the magnitude of the yarn tension is measured by sensors using FPGA(Field-Programmable Gate Array)technology,the tension data is input into the FPGA and converted to control variables by A/D conversion to control the speed volume of brushless DC motor,and regulate the output yarn tension through the motor rotation speed.The tension control system of the yarn feeder mainly includes three modules:the yarn tension measuring module,the yarn tension adjusting module and control system.The yarn tension measuring module consists of yarn tension sensor,amplifier,filter circuit and A/D conversion circuit from FPGA.Yarn tension regulating module mainly includes the yarn guide and motor.To meet the requirement of high-speed data acquisition and processing,a smart mixed-signal field-programmable gate array(FPGA)is chosen.FPGA and an ARM core is integrated on a single chip.The ARM core is used to sample the sensor signal,control keys and the LCD,and communicate with other networks,etc.While FPGA is used to send orders to the motor control chip to adjust the speed of the motor.For ARM core programming,C language is used.For FPGA programming,the specialized language,provided by the manufacturer of the chip,is used according to control strategy of the hardware circuit.Software design mainly includes:tension drive module,temperature alarms module,interactive interface module etc.Finally,the system of constant tension electronic yarn feeder is applied on computerized flat knitting machine,it turns out the yarn tension is under control,which is within our expectation.51 figures,10 tables and 72 references are included in this paper.