Research On The Pressure Control Of The Electro-hydraulic Servo Pump In The Pressure Build-up Stage Of The Hydraulic Die Cushion

The hydraulic stretch pad is the key supporting equipment in the press stretch forming process.The traditional hydraulic pad adopts the servo valve control system,which has low energy utilization rate and high calorific value.With the development goal of "carbon peak,carbon neutrality" It is proposed that the electro-hydraulic servo pump controlled hydraulic stretching mat with high power-to-weight ratio,high integration,environmental friendliness and high efficiency and energy saving is the upgrading direction of stretch forming equipment.Too little or too much system pressure in the pressure building stage of the hydraulic stretching pad will cause the parts to wrinkle and tear,and if the pressure building stroke is too long,the stretching stroke of the mold pad will be shortened,so that the parts cannot be stretched enough,so the pump The research on the pressure control strategy in the pressure build-up stage of the controlled hydraulic cushion has academic significance and application value.In this paper,the following research is carried out on the pressure building control of the hydraulic tension pad controlled by the electro-hydraulic servo pump:Firstly,a mathematical model of the system is established according to the components of the pump-controlled hydraulic cushion system,and the nonlinear influencing factors of the system are analyzed—the flow pulsation of the plunger pump and the nonlinear friction of the symmetrical cylinder.Analyze the dynamic and static characteristics of the system according to the mathematical model derived from the system,and provide a theoretical basis for the design of control algorithms and the establishment of simulation models.Secondly,according to the established mathematical model including system pulsation and nonlinear friction,and the control standard of the system pressure build-up condition,a model predictive control algorithm based on the expansion state observer is proposed.The model predictive control algorithm can solve the problem of system pressure constraints very well,but the mathematical model will be affected by modeling errors,friction and pressure fluctuations.Therefore,the fusion of the expansion state observer realizes active compensation for internal and external disturbances and enhances the robustness of model predictive control.The genetic algorithm is used to optimize the parameters of the controller in the model prediction,so that the model predictive control algorithm has the best control effect.Finally,a simulation model and an experimental test platform for electro-hydraulic servo pump-controlled hydraulic pads are built.Under the simulation and test platform,the model predictive control algorithm based on the expansion state observer is compared with the traditional PID control algorithm.The results show that the designed control The algorithm has obvious advantages in the pressure building test of the pump-controlled hydraulic cushion.By reducing the pressure overshoot,it can reduce the quality problems during the stretching of the material,and at the same time increase the pressure response speed to shorten the pressure building stroke.