| Leveler is absolutely necessary for modern steel industry. It is necessary to control the plate profile. Now the straightening theory is already perfect. So in the modern time, the straightening precision is concentrated on. The screwdown mechanism is mechanical which drives by worm gears. In this way, the straightening force is small, straightening precision is lower and the speed of screw down is slower. So it is hard to control. Hydraulic servo control makes the straightening technology flies. Its respond speed is so fast, control precision is so high and the straightening force is so big that it can repair a lot of defects of the plate shape.This passage researches on the hydraulic control system of the leveler. The hydraulic control system is a typical system of the valve controlling cylinder which uses unsymmetrical valve to control unsymmetrical cylinder instead to eliminate the shock produced by the unsymmetrical cylinder, at the same time, uses force feedback to make up for deficiency of the position feedback. This passage builds the model of this system considering the nonlinear factors such as the flow characteristics of the valve port, builds the force feedback system block diagram by solving the servo valve’s transfer function in a new way and according to the leveler in laboratory to estimate some parameters. Then designs the controller with PID control, analyzing how each PID parameter affects the control effects, by PID parameter tuning to get the appropriate controller. It is nice to control a single cylinder. At last, this passage builds the model of four cylinders and confirms that they are coupled by the synchronous error curve.The results of simulation indicate that the precision of four-cylinder synchronously meet industry demands. The simulation is successful. This passage not only challenges the traditional screw down in leveler, but also contributes to promote the force synchronous hydraulic control system. |
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