| With the rapid development of aviation,aerospace,nuclear power,petrochemical and other important industries in our country,the processing demands for those special workpieces are increasingly high,and processing facilities are also increasingly important.Among them,giant hydraulic die forging press is a significant indicator to measure the strength of a country's heavy industry.In recent years,the tonnage of hydraulic die forging press is gradually increasing in our country,but the relevant supporting facilities are still at a backward level.As a result,the designs of the whole hydraulic system and the key components of the large-tonnage hydraulic die forging press are largely depending on importing.This paper focuses on the demand of a giant hydraulic die forging press,and systematically studies the key technologies of the two core components of the ultra-high-pressure hydraulic system,i.e.the ultra-high pressure and large flow proportional relief valve and throttle valve.The outline of this thesis is as follows:In chapter 1,the current ultra-high pressure hydraulic technologies at home and abroad are summarized.The structures,performance and researches of the ultra-high pressure and large flow proportional relief valve at home and abroad are also reviewed.The feedback type of the high pressure and large flow-rate proportional throttle valve,the simulation modeling and control algorithms are reviewed.Then,the source of this issue is introduced and the main research contents of this paper are proposed based on the existing studies at home and abroad.In chapter 2,the working principle,three-stage structure and key structural parameters of the ultra-high pressure and large-flow proportional relief valve for ultra-high pressure and large-flow working conditions are designed.Thereinto,the ultra-high pressure and large-flow proportional relief valve adopt the plug-in main structure.With the design of the amplification stage,the area ratio is reduced,and the pilot stage adopts the proportional pressure reducing valve to realize the pressure degrading design requirements.Then,the static mechanical simulation analysis is carried out on the partial structure that bears the ultrahigh pressure in ANSYS.The simulation results show that the designed structure size and coordination relationship are reasonable and can satisfy the ultra-high pressure working condition.Finally,a pilot-stage proportional pressure reducing valve is designed,of which the proportional adjustment mechanism is a valve-controlled cylinder.In chapter 3,the nonlinear mathematical model and the simulation model of the high-frequency proportional valve,which are used in the pilot-stage's proportional adjustment mechanism are established.The accuracy of the model is verified by experiments.And then,the model of the ultra-high pressure and large flow rate proportional relief valve are established.According as the simulation and test results of the prototype,the problem of pressure stability is exposed.Considering the requirement of the rapid open in the ultra-high pressure and large flow rate working condition,the main-level directional damping structure is designed to ameliorate the problem,and the structure specifications are designed by the concept of equivalent damping coefficient.The effectiveness of the main-stage directional damping under high-pressure conditions is verified by simulation and experiment.In order to ameliorate the problem of pressure stability under ultra-high pressure conditions,the pilot directional damping structure is designed,and the effectiveness of the pilot directional damping under ultra-high pressure conditions is verified by simulation and experiment.The controller hardware of the ultra-high pressure and large flow rate proportional relief valve is also designed,which is based on the stm32 microprocessor.The piecewise continuous PID with saturation for the closed-loop control of the pilot displacement is proposed.And the piecewise continuous PID with saturation and feedforward compensation for the pilot pressure is also put forward.Then,both of the two algorithms are verified by ultra-high pressure test.The pressure withstand test rig is built,whose pressure can achieve 1.5 times high than the rated working pressure of the ultra-high pressure and large-flow proportional components.The pressure-tight test rig can complete the ultra-high pressure control by using servo motor to drive ultra-high pressure small flow rate pump and a bypass damping to adjust steady working flow rate.To test the ultra-high pressure and large flow rate components,the type test rig uses multigroup ultra-high pressure small flow rate pump to provide steady flow rate and multi group accumulators to provide the transient flow rate.Finally,the performance test of the designed ultra-high pressure and large flow rate proportional relief valve is carried out.It shows that under the closed-loop pressure control of the pilot pressure,the linearity of the main-stage inlet pressure is-1.59%?1.97%,the hysteresis is 2.31%,the opening rate is 99.44%,and the closing rate is 88.45%,which indicate that all aspects of the performance can meet the design requirements.In chapter 4,the working principle,basic structure and key structural parameters of the ultra-high pressure and large flow rate proportional poppet valve with three-stage power amplification structure are designed.Among the various feedback principles of large flow proportional poppet valves,the main stage position following feedback is suitable for ultra-high pressure and large flow conditions,and the working principle of the second stage and first stage is selected as displacement-electric feedback.A pilot valve stem with a spherical pair that can be self-centering is designed and the motion damping of the pilot valve stem is enhanced.The statics simulations of the ultra-high pressure and large flow rate proportional poppet valve subjected to ultra-high pressure are carried out in ANSYS.Then the feasibility of the designed structural specifications and the fit dimensions are demonstrated.In chapter 5,the nonlinear mathematical model and simulation model of the ultra-high pressure and large flow rate proportional poppet valve are established,and the correctness of the model is testified by the comparison between simulation and experimental results.Based on the simulation analysis,the key structural parameters of the ultra-high pressure and large flow proportional poppet valve are analyzed,and reasonable structural parameters are selected.In view of the traditional PID control,the performance of the ultra-high pressure and large flow rate proportional poppet valve cannot satisfy the requirements,and there is also a contradiction between the response and the overshoot as well as the dynamic tracking error is large.Therefore,a nonlinear control algorithm based on double error driving extended disturbance observer is proposed.The proposed algorithm simplifies the model under the premise that the frequency response of the pilot valve stem is much larger than that of the pilot high-response proportional solenoid valve.In the proposed algorithm,the modeling errors,external disturbances,and system uncertainties are lumped into two uncertainties,which is observed in the extended disturbance observer,and the spool velocity of the high-response proportional solenoid valve is obtained simultaneously.The proposed algorithm also combines the Lyapunov stable theory and the backstepping method.The stable tracking performance and excellent dynamic performance of the proposed algorithm are not only proved theoretically,but also verified through simulations and experiments.Finally,the performance test of the designed ultra-high pressure and large flow rate proportional poppet valve is carried out.And the experiment results show that the main valve spool opening time is 43.5ms,the closing time is 44.1ms,the linearity is-0.36%?0.74%,the hysteresis is 0.8%,and the flow capacity can also meet the design requirements.In chapter 6,a single-cylinder ultra-high pressure hydraulic system for hydraulic forging press is designed.The system uses ultra-high pressure and large flow rate proportional relief valve to adjust the pressure of the main cylinder,and uses ultra-high pressure and large flow rate proportional poppet valve to adjust the velocity of the main cylinder and decompression.By integrating the simulation model of the ultra-high pressure and large flow rate proportional relief valve and poppet valve,the simulation model of the designed single-cylinder ultra-high pressure hydraulic system is established.And then,the simulation of quick feeding,slow feeding,pressing feeding,pressure maintaining and decompression are carried out.The effectiveness of the designed ultra-high pressure and large flow rate proportional relief valve and poppet valve are demonstrated.Finally,both of the two ultra-high pressure valves,i.e.the relief valve and the poppet valve are tested on the 800MN hydraulic forging press,and the results indicate that they can satisfy the design requirements. |
PDF Full Text Request