Research On Position Tracking Control Strategy Of Electro-hydraulic Proportional System For Internal High Pressure Forming

Internal high pressure forming is a process of forming hollow parts by applying liquid pressure inside metal pipes.It is widely used in automotive,aviation,aerospace and other fields because of its characteristics such as saving materials and reducing weight.However,due to the influence of uncertain factors such as installation precision and hydraulic parameter perturbation,the traditional control method can not meet the precision requirements of the electromechanical hydraulic control system of the internal high pressure forming,which leads to unqualified components in production.Therefore,the electromechanical hydraulic control technology of the internal high pressure forming has been deeply studied in this paper.This paper mainly includes the following research work:Firstly,according to the relevant literature,the process of internal high pressure forming technology and the research progress of electro-hydraulic control technology are analyzed.In order to verify the effectiveness and practicability of the proposed method in engineering application,an electro-hydraulic proportional comprehensive test simulation platform was designed and built.The control system of the test platform adopts the structure of "industrial computer + data acquisition board card",which mainly includes the acquisition of displacement signal and the output of control quantity.Aiming at the electromechanical hydraulic proportional position control system of internal high pressure forming,the mathematical model of the system is established based on the analysis of its mechanism,which mainly is composed of industrial computer,electro-hydraulic proportional valve,hydraulic cylinder,proportional amplifier and displacement sensor modules.Secondly,aiming at the repetitive motion of electro-hydraulic proportional position control system for internal high pressure forming,an iterative learning control algorithm is designed.The proposed algorithm can use the historical deviation information to calculate the control input of the current desired output trajectory,which is suitable for nonlinear uncertain strongly coupled dynamic systems.At the same time,in order to eliminate the jitter and the spike burr in the process of error convergence,the input compensation and error compensation are added into the algorithm.Simulation and experimental results show that,compared with PID,the proposed iterative learning control algorithm improves the tracking control accuracy and reduces the tracking error.Finally,aiming at the problem that the position of the subsystems on both sides of the hydraulic cylinder is not synchronized,a control strategy based on "equal + master-slave" structure is proposed.At the same time,an improved Oustaloup filtering algorithm is adopted to design a fractional order PID algorithm which is not strictly dependent on the exact model of the system.In order to solve the complexity of fractional order PID parameter tuning,a particle swarm optimization algorithm is adopted.Combined with the superiority of fractional order control theory,a fractional order iterative learning control algorithm is designed.The simulation and test results show that the fractional order PID control strategy based on "equivalent + master-slave" structure can effectively accelerate the convergence speed of the system and reduce the position synchronization error of the system.