The Research Of Tension Control For High-accuracy Winding Vacuum Film Coating Machine

Tension control technology is one of the common technologies exclusively used in the engineering industry such as coating, IC manufacture, printing equipment, fibre wind and ect. Along with the modem wind machine developing to higher speed and precision, tension control technology becomes more important. Due to the fact that tension system can be affected by many facts and its structures are complex, as well as its deep coupling, nonlinearity, time-variability, and indeterminacy of its parameters, there are still many problems on its basic theoretics, checking and measuring technology and control technology to be solved. It is one of the problems of significance research for the technician to study.High vacuum film coating machine is designed for the one side coating of flexible film materials such as PET, OPR BOPP with metallic layers. The metallised films are used for the production of dielectric film capacitors and packaging, applied widely in industry of electronic, packaging, and tobacco.Tension control in winding/unwinding system is the key technology, the precision and stability of tension control can make a direct impact on the final quality and the suitability to raw film. For the purpose of study, the main task is design winding/unwinding tension control system to suit the production of metallised film for high quality capacitor. This tension control mode is well suitable for the extreme condition of high speed and low tension when coating Aluminum/Zinc on extra thin film.The tension and the speed of film should be maintained at a reference value. If the delivery speed fluctuates, then the treatment on the film becomes non-uniform. On the other hand inappropriate tension may cause wrinkles or even a web break. And if the tension is not sufficient for the drive roll to capture the web, the drive roll loses control of the web, leading to web slip. Accordingly the web tension control system should have enough control performance for both of speed and tension at the same time.It has in general a decentralized information structure, which is composed of as many subsystems as the drive rolls. The strong interactions among subsystems make the controller design task complex. A change in tension force value in one section could cause neighbouring tension variation and subsequently would make the speed fluctuate and vice versa.This paper is concerned with the system uncertainty that includes variation of material constants in a process. And we study here the application of fuzzy logic Controller(FLC) with self-tuning function to cope with the robustness. The FLC's parameters that are tuned on-line are scaling factors for the output signals of tension control subsystems.Based on the models, this paper designs a closed loop tension control system with compensation technology with PLC as controller, servo motors as drivers, tension sensors feedbacking film tension change real-timely. We adopt radii calculator to compensate for tension change caused by radii change. We adopt acceleration compensation to solve tension change caused by winding velocity change. And we adopt inertia compensation to solve inertia change caused by winding/unwinding roller. Because winding system is a complex control object, its dynamic characteristic of winding/unwinding equipment changes a lot especially during winding/unwinding process. Common PID controller is difficult to assure dynamic performace of winding process. Aimed at these problems, the paper put forward a control strategy, which is fuzzy self-tuned PID controller. The results show that the self-adjusted fuzzy PID controller has a better performance than common PID controller.