Abstract:

Objective During the high-speed operation of a braiding machine， significant impact collisions arise between the spindle knife and the track， resulting in excessive equipment vibration that adversely affects braiding quality. Consequently， it is essential to undertake an optimized design of the track to minimize collisions and thereby enhance the braiding quality.

Method The research adopts the method of "Substituting curves for straight lines" to study the trajectory of the yarn carrier. A theoretical model of yarn carrier trajectory was established and the equations of gentle curve orbit were formulated based on cubic parabola at the intersection of straight line and circular arc. The single orbit disk was regarded as a cam， and the partially optimized curve model of the straight line orbit was constructed according to the law of cycloid corrected isochronous combined motion. The model was tested by simulation and vibration experiments.

Results Firstly， an analysis of the yarn carrier's motion was conducted， and a theoretical model of its motion trajectory was established. It was discovered that abrupt changes in acceleration occurred at the junction of the straight-arc track and at the center of the straight track. Secondly， an analysis of the straight-arc track junction revealed that the discontinuity in the second-order derivative at this point led to the abrupt acceleration changes. Based on a cubic parabola， an optimization model for a transition curve was established， and calculations demonstrated that this model effectively reduced vibration at the junction. Subsequently， the track disc was regarded as a cam， and the straight track section was modeled and optimized according to the cycloid-modified uniform motion law. The results indicated that the track optimized using the cycloid-modified uniform motion law exhibited reductions of 8.04 times， 10.66 times， and 3.36 times in the three key characteristic parameters-quasi-velocity （VM）， quasi-acceleration （AM）， and quasi-jerk （JM）-significantly lowering the peak values of the original track's motion parameters. Finally， kinematic simulations and experiments were conducted separately， and the results showed that the track optimized using both the transition curve and the cycloid-modified uniform motion law could substantially reduce track impact collisions. By comparing the kinematic analysis curve of yarn carrier and the comparison of simulation results， it can be observed that when the angular guide wheel speeds of the braiding machine were set at 210， 240， 270， 300， and 330 r/min， respectively， both acceleration and velocity values decreased significantly. Additionally， the peaks at the junctions of the straight track and the straight-arc track were eliminated， with a reduction rate of 28.16%. From the Comparison of Vibration Displacement Before and After Track Optimization， it can be concluded that the vibration of the braiding machine track decreased by 52.94%， 60.21%， 64.29%， 56.53%， and 53.62%， respectively， substantially reducing vibration and enhancing the overall performance of the braiding machine.

Conclusion The use of the moderated curve model can eliminate the cusp at the intersection of tracks， and the optimization effect is positively correlated with the length of the moderated curve. The optimized track with the combination of gentle curve and cycloid modified isochronous combined motion law can make the spindle knife of yarn carrier run smoothly， the peak acceleration of spindle knife can be reduced by 28.16%， The peak vibration displacement of the weaving machine track can be reduced by 52.94%， 60.21%， 64.29%， 56.53% and 53.62% at the rotational speeds of the angle guide wheel of 210， 240， 270， 300， 330 r/min， respectively， which can greatly reduce the impact and noise of the high-speed knitting machine and improve

Key words: high-speed braiding machine, yarn carrier, track optimization, motion analysis, orbital collision