Dynamic Analysis Of Knitting Process And Its Control Strategy Study Of Weft Knitting Machine

There are quantities of contacts and impacts between knitting needle or guide needle andcam, especially when weft-knitting machine is running at high speed. It leads to knitting needle’sdisplacement departure comparing with its theory track, and it makes system instabilityinefficient as well as fatigue fracture due to the abrasion of knitting needle and guide needle. Withthe development of weft-knitting machine towards high-speed and high-performance, it isbecoming increasingly important to analyze the modeling and dynamic of knitting mechanismssystem and control strategy.The domestic and international research actualities of circular weft-knitting machine’sdynamic characteristics between knitting needle and cam have been summarized; the theoreticalanalysis and experimental testing of impact properties have been discussed. Weft-knittingmachines, such as the knitting system mechanism of the flat knitting machine, glove machine,circular knitting machine, seamless underwear machine and hosiery machine, have beenanalyzed. The impact and contact of the triangle, knitting needle and guide needle is the core ofthe weft-knitting machine.The theory models of looping, tuck and loop transfer technology, as well as the theoreticaldisplacement curve of the knitting needle movement theory displacement, have been proposed.As one follower and form-closed cam mechanisms for weft knitting machine knitting systemtheory model with a single degree of freedom system; focus on the force, contacts and impactsbetween knitting needle or guide needle and cams. The kinematic equations and dynamicequations of the system model have been proposed, and then solve the equations with the Fourierseries method and mode superposition method.Across impact has been analyzed between guide needle-butt and working surface of thetriangular cam wheel groove. Impact velocity increases with the increase of the cam wheelgroove gap. The velocity of traversed impact and acceleration change point is proportional to thecube root of the jerk. Dynamic models of knitting needle, guide needle, needle bed and camshave been proposed. Transient dynamics simulation result is in accord with the theoretical curvein the trend using finite element software.On the basis of experimental study, the displacement photographs of needle in the directionof knit have been obtained. Experimental results, displacement, velocity, acceleration, etc, havebeen processed by the image processing software. Finally, the displacement, velocity,acceleration and jerk movement characteristic curve in the knitting direction of the needles hookshave been obtained by the MATLAB software. The analysis of experimental results, the impactof the needles and the cam repeatedly occur at the initial point and the point of maximum lift. The model has been improved validity by comparative analysis of the motion characteristics ofthe key points.With the continuous improvement of the weft knitting machine intelligence level, the controlstrategy has become the core topic of the high performance knitting machines. Taking intoaccount the dynamic characteristics of the weft knitting machine needles and triangular cam, theproposed location of the real-time needle tracking algorithm and look-ahead control theory havebeen proposed. The control strategy compensate for the theoretical design requirements cannotbe achieved due to the dynamic response caused by mechanical processing, installation and other defects. The core control algorithms will play a decisive role in the stability and reliability of theweft knitting machine.The study has a certain reference value on the weft knitting machine weaving theoreticalanalysis, cam trajectory optimization and stress analysis of the guide needle and knitting needles,weaving system dynamics analysis and the core of the weft knitting machine control algorithm.