| Large die-forging hydraulic press is mainly used to produce the heavy forgings of difficult-to-form materials,including titanium alloy,high temperature alloy and so on.In order to achieve near-net forming,the forgings require to be formed by single die forging with high dimensional accuracy.Because of uneven forging material,non-uniform heating,asymmetric shape,non-linear hydraulic system,uncertain parameter and deflection moment produced by eccentric force of die forging,the moving beam can deflect in forming process and low pressure causes incomplete filling of forging,which influences the machining accuracy of forging and the safety of hydraulic press frame.Therefore,each large die-forging hydraulic press needs the passive leveling control system to keep the horizontal attitude of the moving beam in a high accuracy range,which can ensures the accurate pressing of upper and lower forging dies and the dimensional accuracy of forgings.Moreover,this passive leveling control system improves the stress state of each component for the hydraulic press and extends the working life.In view of the practical problems on the appearance of deflection and leveling difficulty of the moving beam in forming process,the frames of large hydraulic press,the leveling working principles of hydraulic system and the influence factors of leveling control are analyzed in this paper to optimize the structures of the frames with the moving beam leveling control as the research object.Meanwhile,the independent metering control technology and fuzzy PID control algortithm are adopted to design the new leveling control system,which improves the leveling accuracy of the moving beam.In paper,these main research works are summarized as following:(1)The frame of 100 MN die-forging hydraulic press was designed and analyzed by finite element method.According to the analysis of stress and strain,the positions of the maximum deformation and stress concentration in the frame were obtained.Then,the thickness and fillet radius of C-shaped plate,and the structure of upper partition beam were optimized.Finally,the levelness of the moving beam in forging process was guaranteed from the mechanical body.(2)Through the stress analysis of the moving beam,the leveling control law was studied,and the relationship between the flow and pressure of the leveling cylinder and the leveling of the moving beam was analyzed.Combined with the independent metering control technology,the passive leveling hydraulic system was designed based on the independent metering control.In order to improve the dynamic response of leveling system to nonlinearity and uncertain parameters of large press,the fuzzy control rule and fuzzy PID controller were established.(3)The leveling hydraulic system model and leveling control system model were established in AMESim and Simulink,respectively.By using the fuzzy logic toolbox in MATLAB,the fuzzy PID controller was established.Then,the joint simulation of the passive leveling control system for 100 MN die-forging hydraulic press was carried out to obtain the deflection angle change curve of the moving beam and the velocity change curve of the leveling cylinder piston.According to the simulation verification of the designed leveling control system.The simulation results showed that: the passive leveling control system of100 MN die-forging hydraulic press has good leveling accuracy and speed control characteristics,which verifies the rationality of the design and control strategy of the passive leveling control system,and also provides a theoretical basis for the design of the leveling system of die-forging hydraulic press.In this work,the simulation research has important theoretical value and practical engineering significance for improving the leveling control performance of the moving beam of the die-forging hydraulic press. |
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