Research On Unwinding Tension Control System For AC Rewinder

Rewinding process is the last step of the papermaking processes, as the main controlled variable, unwinding web tension is the significant factor which affects the finished paper roll form in the rewinding process, the effects of unwinding web tension control directly determine the quality index of finished paper roll. In the paper industry, it has become a development trend that the AC drive will replace the DC drive. Compared with DC drive mode, the tension control system with AC drive has more obvious advantages. This paper takes the unwinding tension as the research object, aiming at the problems of multi-disturbance and nonlinear in the control system of unwinding tension, a complete set of control scheme is proposed, the fuzzy PID algorithm of rewinder tension control is studied and its simulation is carried out; the hardware structure of the main circuit of the system was designed to solve the problem of energy feedback from the AC drive system. The system was designed by taking the original data of a paper rewinding project in Ningxia as an example. The main work could be summarized as the following four aspects:(1) Control requirements were proposed for unwinding tension, some common methods for tension control was summarized. By the introduction of rewinding process, web tension as the main factor which affects the quality of finished paper roll from, the control requirement of unwinding web tension was summarized. Two common methods of tension control were analyzed, including the realization based on DC inventer and the realization based on configuring instructions T400.(2) The control scheme of unwinding tension was put forward. The model was established and the simulation was made of the unwinding tension according to the characteristics of the paper web in the rewinding process. The concrete expression of the tension was obtained by the analysis of the model, combined with operating characteristics of the drum and got indirect control scheme for unwinding tension. A close loop control system was established in the use of tension detection device and the direct control scheme of the unwinding tension was obtained. Comprehensive analysis of the advantages and disadvantages of the two control schemes, tension control system took a complex combination of both as a control scheme that combines the advantages of both.(3)Tension controller was designed and its simulation was carried out. For conventional PID control algorithm used in the traditional tension in the face of changes in system parameters due to environmental disturbances and process changes could not change controller parameters which result in poor control effect, fuzzy PID control algorithm was put forward, the tension controller was designed based on this algorithm and the simulation. Simulation results showed that the proposed algorithm can adjust the PID parameters in order to achieve a better control effect which is better than the traditional PID algorithm.(4) The hardware and software of the unwinding tension control system was designed. In view of the feedback energy processing problem of the unwinding roll motor during the braking power generation, to deal with the problem, the hardware structure of the main circuit of the control system is designed and the power supply mode of common DC bus was constructed based on the analysis of energy flow of the system in which mean the feedback energy could be return to the grid. The hardware system is designed by taking the original data and technical agreement of a paper factory in Ningxia as an example. The parameters of the motor were calculated based on original data and the motor selection was completed.6SE70 inverter was adopted as the unwinding roller motor drive unit and PROFIBUS-DP bus was applied as communication mode. In hardware PLC as the core, a given operation screen for data and process value display was used to achieve human-computer interaction. It was expected to sum up the PLC programming control tasks that should be completed and obtain the main steps for tension control, completing the tension control program using STEP7 and meanwhile giving part of the program.