Characteristics And Its Application Of Separating Metering Electro-Hydraulic Servo System With Heavy Load

Electro-hydraulic servo system has the characteristics of high power-density ratio,excellent dynamic characteristics and huge output force,etc.It has been widely used in metallurgical equipment,mining equipment,fatigue test,robot and other fields.In a typical electro-hydraulic servo system,each actuator is driven by a four-sided spool valve,and the actuator is controlled by the throttling orifice of the control side.The efficiency is low and the valve orifice can only be adjusted with mechanical linkage,which brings challenges to the application under heavy load and complex working conditions.With the development of modern microelectronic technology,multi-axis control technology which integrates intelligent digital control technology has been widely used in many engineering fields.Based on the background of low carbon energy saving requirements and better adaptability to the complex working conditions,in order to achieve high control performance,reduce energy consumption and the pressure drop loss,separating metering technology is proposed for electro-hydraulic servo system.This research is funded by "the Coordinative Creation Center of Taiyuan Heavy Machinery Equipment(1331 project)".In order to improve the tracking precision of the separating metering electro-hydraulic servo system,research works are carried out along two aspects: the damping characteristic of the system and the closed-loop control algorithm of the system.Firstly,the composition and the working principle of the separating metering electrohydraulic servo system is introduced.In order to analyze and verify the characteristics of the system,a test platform is built and a computer measurement and control system is designed.Moreover,the experimental platform is modeled mathematically to lay a foundation for the subsequent research.Secondly,on the one hand,the damping characteristics of the separating metering electrohydraulic servo system are studied.With the benefit that the outlet servo valve can be controlled independently,the back pressure of the hydraulic cylinder can produce damping effect for the system,so as to reduce the disturbance of the system.Theoretical analysis,simulation and experiments show that the active damping control strategy based on acceleration feedback can improve the damping ratio of the system and reduce the disturbance.On the other hand,considering the disturbs exists in the separating metering electro-hydraulic servo system,the dynamic surface control algorithm combining with nonlinear tracking differentiator and nonlinear disturbance observer are studied.The nonlinear disturbance observer is utilized to solve the disturbance caused by the parameter perturbation,nonlinear factors and load disturbance to the system.Thirdly,since the proposed dynamic surface control algorithm needs the accurate model during the design process,in different engineering applications,the structure and order of the model are different,so the dynamic surface control algorithm is not the same.Therefore,aiming at the engineering applications,the active disturbance rejection algorithm with piecewise linear saturated function are studied,which does not rely on mathematical model.The extended state observer is utilized to restrain the disturbance caused by the parameter perturbation,nonlinear factors and the load disturbance of the system.The piecewise linear saturation function is used in the algorithm,so as to further reduce the time complexity of the algorithm and is convenient for engineering application.In addition,due to the need to control the two valves for the separating metering electrohydraulic servo system,the hardware and the software of the smart controller for the separating metering electro-hydraulic servo system are designed.LUA script interpreter is integrated in the controller,which can extend the function of the controller through the script.The script interpreter increases the flexibility and reflects the intelligence of the proposed controller.The controller prototype is made and tested.The test results show that the controller has high control accuracy,stable operation,and reaches the certain level of intelligence.Finally,the application of the separating metering electro-hydraulic servo system of the rolling shear is studied.In order to ensure the accuracy of the system while solving the problem of heat,a variable supply pressure electro-hydraulic servo system with separating metering technology is proposed.The dynamic surface control algorithm with nonlinear tracking differentiator and nonlinear disturbance observer is used during the controller design process.In addition,the energy-saving characteristics of the system are studied.The experimental results show that the control accuracy of the proposed electro-hydraulic servo system is improved,and the purpose of energy saving is achieved.