| The hydraulic transmission system is widely used in industrial automation equipment,non-road mobile machinery,heavy machinery and other fields due to its advantages of high power density,long service life,and flexible layout.According to the control mode,the hydraulic transmission system can be divided into valve control(throttle control)and pump control(volumetric control).The valve control system has fast dynamic response and high control accuracy,but the fatal disadvantage is that there is large throttling loss,which leads to low energy efficiency of the system and energy waste.The pump control system eliminates the throttling loss of the system,so the energy efficiency is high,but the deficiency is that the dynamic response is slow,and because the actuators are mostly single out rod hydraulic cylinders with different areas of two cavities,and the flow at the inlet and outlet of the existing hydraulic pump is equal,additional compensation measures are needed to balance the flow,which increases the system cost and control complexity.In response to the above problems,and around the goal of energy-saving and efficient operation of hydraulic transmission systems,supported by the National Natural Science Foundation of China,“Theory and method of energy-efficient conversion and utilization of speed variable separate chamber volumetric direct drive electro-hydraulic system(51575374)”,this subject studies the key technology of the speed variable separate chamber volumetric direct drive electrohydraulic system.Adopt high energy efficient and fast response speed variable servo motor to drive quantitative hydraulic pump as the power source,use separate chamber volumetric direct drive to completely eliminate the throttling loss of the system,and adopt the position-total pressure composite control strategy to improve the control accuracy,and obtain the effect of similar valve control system,and the application of the system in injection molding machine and excavator is studied.Mainly completed the following content:The characteristics of various electro-hydraulic power source configurations are compared and analyzed firstly,and the configuration of the servo motor driven quantitative hydraulic pump is determined as the power source used in this subject.Two such power sources are used to control the two chambers of the hydraulic actuator respectively,forming a speed variable separate chamber volumetric direct drive electro-hydraulic system.By controlling the speed of the servo motor to change the output flow and pressure of the hydraulic pump,the actuator is directly driven to run,completely eliminating the throttling loss of the system and improving the energy efficiency of the system.And establish the mathematical model of the system,put forward the position-total pressure control strategy,analyze the control mode and energy efficiency characteristics of the system under different working conditions.On the basis of theoretical analysis,build a simulation model containing the control system-electrical system-hydraulic system in Simulation X software,and conduct simulation research on the system operating characteristics and energy efficiency characteristics.And further build a test platform to test the feasibility of the proposed system and control strategy,as well as the dynamic characteristics and four-quadrant operating characteristics of the system.The speed variable separate chamber volumetric direct drive electrohydraulic system is applied to the injection molding machine.The structure and working principle of the existing injection molding machine are analyzed.Five different electro-hydraulic power sources were used to drive the injection molding machine and test its energy consumption.It shows that the electro-hydraulic power source,which is a servo motor driven quantitative hydraulic pump,has the best energy-saving effect,can reduce the energy consumption of the whole machine by 87 %.In order to further improve the energy efficiency of injection molding machine,the scheme of speed variable separate chamber volumetric direct drive injection molding machine is designed.The speed variable separate chamber volumetric direct drive electrohydraulic system is applied to the excavator.The structure and working principle of the existing excavator are analyzed.Design the scheme and control strategy of the speed variable separate chamber volumetric direct drive the whole machine of the excavator.Taking the existing 6-ton hydraulic excavator in the laboratory as the research object,a test prototype was built to test the entire system,and a machine-electro-hydraulic joint simulation model was built in the multidisciplinary simulation software Simulation X.The single-actuator action and compound action of the speed variable separate chamber volumetric direct drive excavator are simulated and analyzed respectively.The energy recovery efficiency is in the range of 40-75%,and good control characteristics and energy saving effect are obtainedThe research results of this subject show that the speed variable separate chamber volumetric direct drive electro-hydraulic system has good operating characteristics and significant energy saving effects.The use of a combined position-total pressure control strategy can make the system obtain a control effect similar to the valve control system.The application of this system to injection molding machines and excavators can improve the energy efficiency of the machine.The research results of this subject can be further applied to other industries and construction machinery,providing theoretical basis and new ideas for energy-saving and efficient operation of hydraulic transmission system and energy-saving and emission reduction of hydraulic machinery. |
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