(College of Mechanical and Industrial System Engineering, Kyunghee University)
As high-speed weaving technologies are developed, the control of the warp tension during weaving process becomes one of the most important issues in weaving industry. In innovatory looms, many types of warp tension control methods were introduced. An active negative type of let-off mechanism is one of the most advanced methods. In this study, the active negative type of let-off mechanism was used to control the warp tension and the take-up speed of the weaving system was regarded as a mechanical disturbance of the system because this could cause an excessive variation of warp tension when the loom started up. Usually, the take-up speed goes to the final value after some transient state when used an on/off switch that can be regard as a step type of the input of the system. Thus an excessive take-up speed causes a variation of warp tension. To reduce this variation, take-up speed was changed in "ramp type" that had a slope until it reached the final warp tension value, which can be comparable with the on/off switch. Then the slopes of ramp type of take-up speed were optimized. The optimum slope was found by simulation and confirmed by experiments. From the results of this study, it can be concluded that 1) it is valuable to change the behavior of the main motor speed by "ramp type" and 2) although this new type of take-up speed behavior could not reduce all of the variation of the warp tension, it could control this variation well enough to reduce the stop marks.top marks.