Research And Design Of Two-roll Bar Straightening Machine Control System

Two-roll bar straightening machine is a kind of two-cross-roll straightening machine and the important auxiliary equipment of bar assembly line finishing workshop, which is applicable for accurate straightening of various round bars such as steel tubes and bars. At present, the research on two-roll straightening machine at home and abroad focuses on the design of roll shape curve, straightening accuracy and the process of deformation; however, there is a lack of depth research on the two-roll straightening machine control system. The thesis takes the two-roll bar straightening machine in bar assembly line finishing workshop in Dalian in Northeast Special Steel Group as its research object, summarizing the bar straightening process and proposing the corresponding control requirements in connection with the practical needs of production and process. The focus of the research is the design of two-roll bar straightening machine control system. The major research findings go as follows:As the rolling reduction of two-roll straightening machine and the angle of the two rolls have a great effect on the quality of bar straightening, the hydraulic transmission system complying with the control requirements is designed to accurately control the rolling reduction and the angle of the two rolls. According to the requirements of hydraulic transmission system, we can determine the working pressure of the system, formulate the schematic diagram of hydraulic system, select proper hydraulic components and motors, and finally check the performance of hydraulic system. The result shows that the designed hydraulic transmission system satisfies the control requirements of the system.Another important factor affecting bar straightening is the rotary speed of straightening rolls. The variable frequency speed control system which meets the control requirements is designed to adjust the rotary speed of the two straightening rolls as well. Speed control method adopts the vector control, which has been widely applied in AC induction motor high-performance frequency control field. The speed sensor vector control system oriented by the rotor field is designed. At last, the system is simulated under the circumstance of MATLAB/SIMULINK. The simulation result proves that this speed control system possesses excellent dynamic and static characteristics, which completely conforms to the control requirements of the system.At last, the control system based on S7-400PLC is designed to control the whole process of bar straightening and to offer manual or automatic mode for users to choose. After the selection of hardware equipment, we shall conduct hardware configuration and parameter setting in STEP7software and establish a complete PLC hardware system. On the basis of the system, structured programming is adopted to compose the ladder diagram program to control the process of bar straightening and to present the main straightening program and the procedure diagrams of various subprograms.The control system designed in the thesis has been successfully applied in the production spots and achieved good control effect, enhancing the quality and production efficiency of bar straightening, providing reliable technological base for enterprises to obtain good economic benefit and offering some references to the design of other similar straightening machine control systems.