Research On Control Characteristics Of Pump And Valve Joint Speed Control Of Electric Hydrostatic Transmission Forklift

The development of the warehousing industry and the logistics industry has led to an increasing demand for handling vehicles,and the electricization and energy-saving technologies of handling vehicles have gradually become hot topics in the research and development of the logistics and warehousing industry.Electric forklifts are gradually replacing internal combustion forklifts with their unique advantages,and are widely used in warehouses,ports,airports and other places.Therefore,the market share of electric forklifts continues to increase and is becoming a trend in the industry.The motor control system and the hydraulic control system are the core technologies of the electric forklift,which can directly affect the working performance of the forklift.This paper mainly studies the frequency conversion speed regulation technology and electro-hydraulic control system of electric forklift motor.The specific research contents are as follows:(1)Analyzed the current state of technological development of the electric forklift industry and the research situation of the application of variable frequency hydraulic technology.In order to verify the feasibility of the high-voltage motor scheme,a forklift was experimentally modified by means of the internal combustion forklift,and the forklift control system and hydraulic system and energy-saving control method were carried out in the form of electric hydrostatic transmission for the problems of the experimental forklift.the study.(2)The system structure of the electric hydrostatic transmission forklift is introduced.The system conditions and the main parameters of the forklift are analyzed and calculated.The hydraulic system of the forklift under the static pressure transmission is proposed.Then according to the structure of the electric hydrostatic transmission forklift and the hydraulic system principle,the control system is analyzed and the design scheme of the control system is proposed,including hardware system,software system,host computer and control strategy.(3)In order to solve the problem of slow response speed of the electric hydrostatic transmission forklift during start-up and position adjustment,the control mode of the pumpvalve joint speed regulation is proposed for the working characteristics of the electric hydrostatic transmission forklift.In the pump control section,fuzzy control is introduced as an operator function to adjust the PID parameters in real time to improve the self-adaptive ability and response speed of the motor under different working conditions.In the valve control section,PID control proportional speed control valve opening is used to ensure the output.The stability of the flow.(4)According to the theoretical analysis of the electro-hydraulic control system of vector frequency conversion speed regulation of electric forklift,the simulation software Matlab/Simulink is used to simulate the AC asynchronous motor electronic control system,and AMEsim is used to simulate the hydraulic system simulation.Combining the respective advantages of the software,the co-simulation is used to simulate and analyze the actual working conditions of the forklift operation.The hydraulic system is improved based on the simulation results.The research shows that the fuzzy PID vector speed control method is used to drive the forklift motor,combined with the pump and valve joint speed control method,which not only overcomes the shortcomings of the simple frequency conversion speed response hysteresis,but also has good adaptability to complex working conditions.At the same time,the improved hydraulic system can effectively reduce the system overflow and throttling loss,reduce the mechanical transmission torque without affecting the speed regulation accuracy,reduce the wear of the mechanical system and improve the working efficiency of the forklift.