| Heat setting process is an important part of textile dyeing and finishing process,and fabric weight is an important index to evaluate the quality of products in the heat setting process.For a long time,manual detection and off-line control have been used for the fabric weight,which leads to low qualified rate of fabric weight and unstable quality of product.In order to solve this problem,the product quality and efficiency of the heat setting process are improved by establishing the model of fabric weight,designing the fabric weight on-line control system and compensating this control system's time-delay.The specific contents of this dissertation are as follows:(1)In order to realize the on-line control system of fabric weight,the model of fabric weight is established in this dissertation.According to the characteristic that the area of fabric changes but the mass,a modeling idea named “mass transfer” is proposed.Based on this idea,the mathematical model between fabric weight and the overfeed roller speed,lathe speed and fabric width is established,and the validity of the model is verified by actual production data.From the model,it can be seen that the fabric weight is related to the ratio of overfeed roller speed to lathe speed,and then the on-line control system of fabric weight is designed by using the method of double closed-up variable ratio control.The results provide theoretical support for the quantitative design of heat setting process parameters and accurate control of the fabric weight.(2)The model above has wide applicability,but the precision is relatively insufficient due to neglects the fabric internal structure.In order to improve the precision of the model,this dissertation also analyzes the internal mechanism of the fabric weight changing process for woven fabric with a wide application.And this process can be divided into three phases: speed difference to tension,tension to strain and strain to fabric weight.The corresponding relationship between the input and output of each phase is analyzed and the model of woven fabric weight is established.This study is of guiding significance for improving the precision of the model of fabric weight.(3)In heat setting process,the fabric needs a long transmission and heating process,which leads to a large time-delay in the control action.Therefore,in this dissertation,the Smith predictive control method is used to compensate the time-delay of control system of fabric weight.In view of the deficiency of Smith predictive method relying on the precise model of object,a multi-mode self-tuning Smith predictive control system is designed to detect the model parameters mismatched in the system,and the control structure of the system is adjusted on-line to improve the compensation effect of time-delay.The designed system can effectively shorten the settling time,reduce the overshoot,improve the stability and robustness of the control system of fabric weight,and thus provide an effective scheme for the heat setting process to improve the production efficiency and product quality. |
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