Surface Unwinding And Fuzzy Control For An Intermittent WEB Transport

High-speed inkjet continuous feed-printing is the fastest-growing sector in the digital printing field,which consists of cutter unit or puncher unit that requires the web transport system periodically switching on and off with high frequency.In the process of the unwinding,the diameter and rotational inertia of the unwinding roll are time-variant,so that the speed and tension control are nonlinear and strong coupling.Discontinuous unwinding will add more external disturbances into the system,i.e.,high frequency 300–600 times/min on and off representing 5–10 g acceleration,which makes the system control extremely complex.The main achievements in this thesis are as follows:1.A mathematical model has been established to analyze the advantages and disadvantages of the different combinations of motor torque mode and motor speed mode in the driver of unwinding unit over speed control and tension control.The passive unwinding control is replaced with positive unwinding decoupled tension control and speed control.At the same time,the center drive is replaced with the surface drive decoupled speed control and roll radius in order to deal with the time-varying problem.The system has been simplified greatly by reducing the associated variables and input variables,thus achieving improved dynamic response ability and energy consumption reduction;2.A non-contact free paper loop is used to connect the unwinding unit and the back-end equipment which can accommodate the motors speed difference with the paper buffer,and a fuzzy PD speed control system with the feedback of the paper loop position is designed to filter the disturbances of the discontinuous unwinding such as the intermittent on and off or the acceleration variation.The proposed control system can smooth and stabilize the speed and the tension,while no overshoot and better dynamic response can be achieved for the unwinding system,with simplified requirements of the driving motor,less control code and investment.It is difficult to establish the mathematical model of tension and paper leveling so paper leveling control is solved by curve fitting to obtain a simplified mathematical expressions with the data from experimental method;3.The prototype is installed and debugged,and the initial design goal is achieved.In this thesis,a control method is designed for the unwinding unit connected with a discontinuous transport system in the digital printing line to achieve stable speed and tension control.