Electronic Shogging System For Warp Knitting Machine Based On Linear Servo

High speed warp knitting machine has the characteristics of few guide bars, fine gauge, high production speed, and its products are widely used in clothing, decorative and technical fields. The motion law of shogging of guide bars on high speed warp knitting machine is the most important factor that affects the motion smoothness and shog accuracy of guide bars and is related to the working performance of the machine directly. Traditional high speed warp knitting machine mainly uses cam as pattern drive mechanism, making guide bars accomplish overlap and underlap. Warp knitting machines with cam pattern drive mechanisms can run at a very high speed of, but changing pattern is inconvenience, which is not conducive to product development. This paper researches and develops a new kind of electronic shogging system based on linear servo control, in order to enhance the patterning performance of high speed warp knitting machine.Firstly, starting from pattern structures of fabric knitted by this machine, the characteristics of high speed warp knitting machine with electronic shogging system was summed up. It analyzed the allowable time for shogging based on shogging requirements of guide bar. By measuring rotational angle of mainshaft which corresponds to shogging movement of various high speed warp knitting machines, the shogging time has been calculated, and it is proved that the front guide bar has a very short time to overlap, generally only a few milliseconds to dozen milliseconds depend on the speed of mainshaft of the machine.Secondly, the motion law of shogging has been studied. High speed, high precision, high frequency, intermittent characteristics of shogging movement of warp knitting machine were integrated, and the characteristic value of common curve was analyzed by cam follower movement theory. The motion law of modified trapezoidal acceleration curve was chosen as the driving law of linear servo in electronic shogging system by using Mathematical Fuzzy Comprehensive Evaluation Method. Further work was carried out based on the result of former research on guide bar shogging movement. It showed that allowed shogging period, lapping needle, machine gauge and running speed of mainshaft of machine are the four factors that affecting the motion characteristic value of guide bar. By optimizing the shogging motion like this, the overlay time was effectively extends much under the premise of ensuring the safety of shogging. The maximum value of the shogging speed, acceleration and jerk could be deduced down respectively. Thus, the performances of motion smoothness and shog accuracy of guide bars are improved obviously.Next, it is studied that a kind of electronic shogging system based on linear servo control for high speed warp knitting machine, and constitutes the three-level distributed control system composed of upper-bit computer, under-bit controller and linear servo implementing agencies. An industrial computer which has a strong ability in program execution, friendly control interface and easy to operate was used as upper-bit computer. It facilitated the realization of electronic let-off, electronic take-up, electronic jacquard and so on to control integrated and network-based production management. Under-bit controller uses a strong PLC with control stability and reliability, and control functions of an electronic cam curve to create a smooth shogging motion without any shock. Linear servo implementing agencies selects a kind of servo drives with short executing period, and a permanent magnet synchronous linear motor with strong thrust, good dynamics and simple frame. Under-bit controller communicates with upper-bit computer via internet network and with servo drives via EtherCAT network. This control system obtains characteristics of real-time processing, high dynamic responsiveness and driving smoothly.Finally, the performance of electronic shogging system based on linear servo control for high speed warp knitting machine was tested at the speed range of 600-1200r/min of machine. The command signal curve and the actual movement curve of linear motor are obtained on monitor. The difference between them become bigger while machine speed going up. A kind of dynamic model is set up to analyze the vibration of guide bar during or/and after shogging, and it is indicated that the vibration of guide bar after overlapping is the main factor which makes a limit speed of machine. Further research focused on performance and the factors which affects the shogging accuracy.The research on the performance of electronic shogging system based on linear servo control should be helpful to improve the technological level of high speed warp knitting machine and be useful to develop high quality warp knitting pattern products.