Design Of Automatic Control System For Stenter Frame Based On PROFIBUS-DP

The stenter frame is the very macnine used for keeping the dimensional stability of fabric in its afer-treatment-process. The paper,which is entrusted by Qing Dao Belle Maille Knitting Garments CO.,LTD, aims to design the automatic control system for the stenter frame production line, basing on its physical construction. The paper here divides the production line into five pars:the draw-in unit, the speed loop unit, the dying chamber, the cooling zoom and the take-off unit. A distrubuted control system is built in this paper, adopting the PROFIBUS fieldbus which is used in industrial control applications worldwidely.The stenter farme automatic control system takes the S7-300PLC as master station, takes the twelve MM440inverter and ten ET200L/ET200M as slave stations, also a SIMATIC operator panel OP270is connected to the syetem. The PROFIBUS fileldbus guarantees the real-time, fast, accurate convey of control command and fieldbus data. With the friendly interactive interface of OP270, the input of process parameters and the real-time monitoring of process data are achieved easily, therefore, real-time and effective management of production process is possible.Taking the requirements of regulating process parameters into account, a Common DC Bus technology is adopted in the speed loop control system, which is constituted by chain, traction roller, overfeed roller, left/right shrink roller, take-off roller and plaiter roller. A rectifier unit named ESM96is used to provide a stable DC voltage for the common bus, where the twelve MM440inverters are attached to, therefore, the feedback energy generated in the process of motor speed control can be converyed to the motors that are in electric state. This multi-motor regeneration system can not only improve energy efficiency, but also reduce the incidence fo equipment failure and the production costs.The speed control of nine circulation fan in dying chamber is another keypoint of this system. According to the characteristics of square torque load, the speed control of circulation fan are the combination of frequency control and pole-changing control. When the need of air flow is small, frequency control is used(in this case, the motor is6-pole)and meanwhile one inverter is used to drag three motors. When the need of air flow is large, pole-changing control is ued instead(in this case, the motor is4-pole), all the circulation fan motors are attached to the grid directly. In electromechanics, the power of square torque load is in proportion to the cube of its speed. Thus, the using of inverter to decrease motor speed can achieve big energy saving while the need of air flow is decreased. As the speed control of circulation fan relates to the switch between power frequency and variable frequency, the current rush problem needs to be solved, so the paper makes a analysis and programm design.In order to ease the pressure of communication, the control system uses the Siemens communication module CP342-5, through that the inverters in speed loop and operator panel OP270exchange data with PLC. Therefore, the paper makes study on the communication between CP342-5and PLC, meanwhile communication programm FC1and FC2are designed.In addition, the production process of stenter frame, the hardware architecture and network configuration of the automatic control system are introduced. At the end of the thesis, the debugging process of automatic control system and the processes of resolving problems encountered are describled.