Design And Simulation Of Electro-hydraulic Servo System For Continuous Flat Hot-press

Production of wood based panel is mainly determined by hot-pressing. It can no longermeet the development of production by using traditional multi-layer press. Instead continuouspress adapts the market for its good properties. Facing the obstacle of technical blockade abroad,this research will build electro-hydraulic servo system to control pressure and thickness to helpmanufacture continuous press in our country.First this study introduces the configuration of continuous press and analyses processingtask and parameters. Control object is pressure and displacement of cylinder. Servo valve servesthe closed-loop control system. Diagram of pump system and frame cylinder control system isdesigned which control the pressure, flow rate and lifting of upper hot platen.Then the mathematic model of every link in position servo system is built. Parameters aredesigned for MDF of which thickness is12mm so that we can get the closed-loop transferfunction. Based on the mathematic model, performance of system can be analyzed. If someproperties of the system don’t meet the control demand, correction is necessary. In this paperPID controller is used for system correction. There are four methods being used including stableboundary method, Ziegler-Nichols PID parameters tuning formula, Cohen-Coon tuning formulaand error integral performance index. The effect of error integral performance index is the best.After correction, peak time of the system is tpless than0.01s. Regulation time tsis0.03s. Thereis no steady-state error. Overshoot s%is14%. The performance of system is good enough.Finally software called AMESim is used for system simulation. Through the analysis ofsimulation results with kinds of loads, the control mode should be different between thebeginning of secondary pressing and outlet of the press. The simulation results of cylinderscontrol in the same side show that several cylinders controlled by one servo valve can be usedat the beginning of secondary pressing, but in the outlet of the press we’d better use onecontrolled by one. The simulation results of cylinders control in one frame suggest that inexhaust section cylinder in the middle use pressure control mode and cylinders in the left andright use position control mode, in order to keep the transverse dimension same of the mat.