| Walking beam furnace the key equipment of billet rolling. Compared with pusher reheating furnace, because the walking beam furnace has many advantages, it is widely used lots of steel rolling enterprises at home and abroad. Driven by the hydraulic control system, stepping mechanism make steel billet step movement in the furnace. The hydraulic control system realize it by adopting the strategy of asymmetric electro-hydraulic proportional valve controlling asymmetrical hydraulic cylinder structure. The walking beam is composed of a fixed beam and a moving beam, which is the core component of the billet heating furnace. The moving beam is driven by the hydraulic cylinder to do the rectangular movement, which makes the steel billet in hundreds of tons of steel in the heating process step by step from the furnace side to the side of the furnace. The velocity of walking beam should be ensured the production rhythm as well as the gently handle of the billet in order to avoid the damage of moving beam and the fixed beam. So it is very important to control the moving speed of moving beam. Moving beam itself is large and heavy, in large heating furnace, the full load of billet is usually up to hundreds of tons, so the beam system has the characteristics of large inertia. Due to the flow, pressure change and leakage and other factors, makes the hydraulic transmission mechanism with nonlinear characteristics. How to control the smooth, accurate and fast movement of the walking beam in each stage of the operation period is a prominent problem in engineering. In order to avoid the overshoot and oscillation of the system.At present most of the steel rolling mill in the heating furnace in the speed of the PLC as the core of the open loop control. But the open loop control can cause the speed control to be not allowed to produce the error accumulation to affect the production cycle.On the basis of studying the structure characteristics and working principle of the walking beam system, the mathematical model of electro hydraulic proportional directional valve and hydraulic cylinder is established in this paper. Nonlinear PID control has the characteristics of strong adaptability, good robustness and so on. Due to the structure of nonlinear PID controller, the saturation function is used to solve the nonlinear problems in engineering. While the step beam exist the nonlinear problem as the hydraulic cylinder dead area, in order to solve the problem, put forward the nonlinear PID control of walking beam motion system. Write the relevant procedures and simulation research has been made by using the Matlab/Simulink. The results show that the method can realize the precise tracking of speed and accurately control the displacement in the walking beam system. |
