Needle Detection Device On Knitting Machines

Circular knitting machine is a kind of textile machine which has been widely used in textile industry, it uses knitting needle to weave clothes. Fabric flaw will occur while the knitting needle was distorted or broken. This paper designed a real-time online detection device to find the failure knitting needle. The detection principle was to judge whether the needle was failure through a reflecting laser signal from a laser module, and the signal from a good needle was bigger than that from a broken needle. This device has three parts: laser mechanical fixture, system board and system firmware. The mechanical fixture was used to hold the laser module and a photosensitive receiving tube, and the irradiation angle of laser can be adjusted a little by tuning a nut on this mechanical fixture.The system board comprised a control board and a display board. Here STM32F0 MCU was used as the core of the control board. It was mainly used for collecting and processing the knitting needle signal, and the result would be sent to the display board through a serial port. The display board would stop the knitting machine through a relay and display the broken needle position. The relay circuit was isolated from other circuits by an optical coupling chip to improve the reliability of the system.The system firmware comprised a control program and a display program. The control program consisted of a time synchronization program, a signal sampling program and a data judging program. Firstly, the time synchronization program was used to find the needle signal. Then, the signal sampling program was used to collect the needle signal. Finally, the result processed by the data judging program would be sent to the display module. The display program comprised a digital display program and a relay program. The digital display program was used to display the broken needle position by refreshing the digital tube. The relay program was used to start or shut down the circular knitting machine by a relay.According to the testing result, even there are different roughness on different needle hook and the reflecting signal ware different, still the device could get the hook signal and detect the broken needle properly.