Electric Control System Of BOPP Film Thickness

A filme thickness control system plays an important role in the plastic film product lines.Its control performance determines the products' quality. The main function of this system is measuring film thickness.The thickness value is used as a feedback signal to control the die temperature and extruder speed. So the film thickness is regulated by the control system. Bcause of film tension fluctuating, motor speed changing, the quality and quantity of film may be impacted by those factors greatly. So for inproving product quality and increasing production rate, a new advanced control system of thickness gauge is developed which is a significant subject.Although the control system of thickness gauge in our country is widely applied, our technology level is very backward. Compared with foreign application, we still have a great gap. In our country, the conventional PID controller is the predominant types in the control system. The PID control algorithm has become one of the most universal control strategies in the industrial control system, for its simpleness, stability and reliability. However, as a result of the nonlinearity and time-varying system in the industry process, the conventional PID controller cannot bring well effect.In this paper, the technology of film gauge control system is first to be illustrated. Then, the control method of system is analyzed.Finally the general scheme of electric control system is carried out. In the process fo hardware designing, We use the Proammable Logic Controller (PLC) as the central control unit. We mainly design the servo system, detection system and temperature control system.We also complete the control system configuration based on the MELSECNET bus network. In the software design of the system, the process control program and the parameter setting of the function module are completed by PLC's software GX Developer, which is easy to read and achieve.In this paper, we analyze the shortcomings of PID controller. We propose the auto disturbance rejection controller (ADRC), which has become a new control technique instead of PID controller. The method does not depend on object model, the technical core is that both the internal dynamics and the external disturbances of control equipments are treated as unknown overall disturbances that can be estimated by the unique extended state observer (ESO). The simulation studies of temperature controller based on ADRC are carried out. The results show that, compare with PID controller, ADRC controller has better performance in respect of delay, external interference, parameter perturbation and soon, it has powerful robustness and anti-disturbances capability.