Study On Autoleveller System Modeling And Control Theory Of Drawing Frame

The degree of yarn unevenness is directly related to the quality, and also indirectly affects the quality of manufactured goods. The yarn unevenness, especially for the long fragment, mainly is caused by the spinning process. Therefore, how to minimize the yarn unevenness has been an urgent research problem of textile industry.In order to ensure the quality of spinning, it's necessary to improve the autoleveller performance of draw frame under a high speed. Based on the strengths and weaknesses of current autoleveller control systems, a new autoleveller control system is put forward: dual open-loop system. This paper presents a mathematical model of the new control system, analyzes its mathematical theory, and explains the theoretical basis of dual open-loop autoleveller control system. By compared with the open-loop control system, closed-loop control system and mixed-loop control system, the paper arrives at a conclusion that the new control system could shorten the blind area, eliminate the dead area, and autoleveller cotton sliver twice.By analyzing the characteristics of the process of drawing frame autoleveller, the dual open-loop control system combines both generalized predictive control theory (GPC) and fuzzy control theory. The GPC used in this paper predicts the process output based on the experimental model, and then corrects the value with the compare of actual and predictive output of process. After that, comparing the corrected results as feedback with setting values, and make the control effect based on compare can track well the specified path. The optimization algorithms of GPC can continue to optimize the calculation, and correct the control value in time, so make all uncertainties which are caused by time-varying and interference to be compensated. Through analyzing the actual operating conditions and control parameters, the second open-loop takes fuzzy control as the ideal method. As a imitation control method, the fuzzy control can be used to autolevel yarn effectively and timely through turning the actual value to fuzzy data and setting reasonable fuzzy rules. In this paper, the simulation based on PID fuzzy control vividly demonstrates the effectiveness of fuzzy control used in autoleveller control system. As the superiority of GPC and fuzzy control theory matching the control environmental, the dual open-loop system can curb delays,strong random perturbations and time-varying of parameters, and respond quickly so as to reduce the error, and improve the autoleveller effect in the case of high-speed operation. Further more, by the superposition of two open-loops, the dual open-loop can eliminate the dead area, and targeted auto-level on real time which further optimizes the autoleveller.After simulation and summary analysis, the paper shows that, the dual-loop control system has a stable control performance, can level yarns with more extensive wavelength, also has no dead-area and blind area, and autolevellers yarn twice. All those improvement means putting the autoleveller technology to a higher level, and promotes the further development of autoleveller.