This method consists of a SM velocity controller and two SM tension controllers. In, a sliding-mode (SM) feedback linearization control system is designed for a multimotor web-winding system. As this scheme directly controls torque current of motors, faster dynamic response can be obtained in case of linear speed acceleration or deceleration. Song and Sul proposed a tension control method with tension observer, which is used in continuous strip processing line, including the acceleration torque.
Exponential stability of the error dynamics is also demonstrated in this method, and the performance of the estimator is experimentally compared with two competing designs on real web-handing machine. Lynch from the University of Alberta in Canada exploited linear time-varying error dynamics to design a reduced-order, nonlinear tension observer. Two new tension estimators are developed for a two-drum electric-braking-generator production winder that are based on unwinding and rewinding variables, respectively, with the essential dynamic, friction, and inertial variation effects considered in the scheme. at the University of Concepcion, Chile, proposed a control scheme without tension sensor in papermaking system. Therefore, if a tension observer can be designed to replace the tension sensor and the same control performance can be obtained compared with the direct closed-loop control method, it will be of great significance in tension control field.ĭomestic and foreign scholars have put forward a variety of implementations about tension control without tension sensor in winding systems. Besides the high price and the existing delay, the signal of the tension sensor is also very weak, which is easily interfered by the environment, so this method cannot be applied in some special occasions. However, tension sensors need to be installed in direct closed-loop control method. Since the precision is lower in open-loop control method, the direct closed-loop control methods are commonly used in actual industry. Currently, there are three ways to control the tension in industrial application: open-loop control, direct closed-loop control, and indirect closed-loop control. Improper control of tension will result in the winding material fracture, wrinkle, deviation, and so on. Tension control system is widely applied in industrial fields where high precision and productivity are required, including printing, textile, chemical fiber, and metallurgy. At last, the feasibility and effectiveness of the proposed method are verified by the experimental results. In addition, the proposed sensorless tension control method is simple and easy to implement, which only uses the current and speed signals of the motors without any additional hardware needed. As the tension control system has the ability to adapt to the change of inertia, its dynamic performance is improved to some extent. Moreover, the estimated inertias are used to adjust the PI parameters of the speed controllers.
For the time-variable inertia, Landau discrete-time recursive algorithm is used to estimate the inertias of the rewind and unwind motors. Then the measurement delay caused by tension sensor is reduced. According to the principle of torque balance, a tension observer is designed to replace the tension sensor, and the observed value instead of the measured value of tension is used as feedback.
Based on the process of rewinding and unwinding, a sensorless tension control method with PI parameters of adaptive speed controllers is proposed in this paper. In a winding system, it is very important to control the tension precisely.
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