The main control requirement of the stretch leveller production line is to control the velocity difference between 2 # S roll and 3 # S roll, so that the elongation of the sheet can be set and the physical characteristics of the sheet can be changed. Therefore, it is necessary to select the appropriate devices that can meet the control requirements to constitute the control system. According to the above conditions, we choose SIEMENS S5-135U series PLC to connect the input and output slave stations in the field operation desk through PROFIBUS-DP communication bus. DC motor driver chooses MENTOR II series controller of C.T. company.
The PLC system uses 928B CPU, IP281 high-speed counter, IM308C communication processor, ET200U remote IO slave station and other switch and analog input and output modules. The control system realizes the closed-loop control of elongation by calculating the speed difference between rolls 2 and 3 through the high-speed counter connected to rolls 2 and 3